Soybeans:Key

KEY TO SOYBEAN PESTS AND NUTRITIONAL DISORDERS

Seed

Seed disorders are limited to disorders while in the ground and not to potential disorders inherent in the seed.

BLACK

Colletotrichum truncatum

Seeds may show no symptoms or may develop brown staining or small, irregular gray areas with black specks; infected seeds may die during germination, or if they do germinate, may produce infected seedlings

Soybean Mosaic

Leaves are mottled green and yellow and are curled; small veins turn yellow; leaves become crinkled in cool weather; entire plant becomes stunted and yellow; seeds may be mottled brown or black with reduced germination; leaves may be puckered and misshapen, resembling 2,4-D injury; diseased pods may be stunted and curved

BROWN

Colletotrichum truncatum

Seeds may show no symptoms or may develop brown staining or small, irregular gray areas with black specks; infected seeds may die during germination, or if they do germinate, may produce infected seedlings

Pythium Rot

Seedling decays before or after emergence; seed may decay in soil; roots develop a brown wet rot, causing the plant to wilt; smaller roots may decay or break away when plants are pulled from the soil; freshly invaded stem tissues are translucent and older lesions become brown producing a watery soft rot; later, if dry weather sets in, the plants appear dry and shredded; cortical tissues in the larger roots may disintegrate and slough off, exposing the central woody cylinder

Reniform Nematode

Symptoms include yellowing, stunting, and unthrifty growth, with the production of a large number of empty pods; galls are not produced on roots, but the root system is severely stunted and may dry out; most common symptom is the soil-covered egg masses on roots

Soybean Mosaic

Leaves are mottled green and yellow and are curled; small veins turn yellow; leaves become crinkled in cool weather; entire plant becomes stunted and yellow; seeds may be mottled brown or black with reduced germination; leaves may be puckered and misshapen, resembling 2,4-D injury; diseased pods may be stunted and curved

CREAM

Fusarium Pod and Collar Rot

Depressed, water-soaked, cream-colored, serrated lesions form on cotyledons and hypocotyls of emerging or slightly older seedlings; as the seedlings mature, these areas turn dark brown to black and eventually group together to form large lesions; pods may dry prematurely with the drying beginning at the pod tip and progressing toward the base; pods eventually turn dark brown to black

GRAY

Colletotrichum truncatum

Seeds may show no symptoms or may develop brown staining or small, irregular gray areas with black specks; infected seeds may die during germination, or if they do germinate, may produce infected seedlings

PINK

Purple Seed Stain

Seed is discolored pink to purple, in small spots or on the entire seed; cracks often occur in discolored areas; infected leaves have reddish purple angular, crusty, dark spots on both surfaces; veinal necrosis may also be observed

RED

Purple Seed Stain

Seed is discolored pink to purple, in small spots or on the entire seed; cracks often occur in discolored areas; infected leaves have reddish purple angular, crusty, dark spots on both surfaces; veinal necrosis may also be observed

WHITE

Phomopsis Seed Decay

Heavily infected seed are badly cracked and shriveled and are frequently covered with white mycelium; these seed will not germinate; lightly infected seed are often normal in size and appearance

YELLOW

Fusarium Root Rot

Seedlings are stunted or damp off; adult plants show root rot; cotyledons of diseased seedlings are yellow and later dry up; plants may wilt in dry weather

No Distinct Discoloration

Bacillus Seed Decay

Soft decay of seeds; bacterium produces rough or smooth, slimy, glistening colonies on seeds

Damping-Off

Seed decay, poor stand, stem rots at soil line, seedlings rot and die

Heat Canker

The hypocotyl in the seed is girdled at or just above the soil line; affected area varies in length, with the affected tissues appearing reddish brown and shriveled; hypocotyl tissue directly above or below the constriction appears normal

Phytophthora Root and Stem Rot

Seed rot and pre-emergence damping-off; root and stem rot of older seedlings; in more mature plants water-soaked lesions develop on the stem and roots, yellowing, chlorosis and wilting of leaves, with a dark brown discoloration on lower stem progressing upward from the soil line; leaves on older plants become chlorotic between the veins followed by a general wilting and death; withered leaves generally remain attached; root rot of older plants may also occur; affected plants are clustered in field

Seedling

BLACK

Fusarium Pod and Collar Rot

Depressed, water-soaked, cream-colored, serrated lesions form on cotyledons and hypocotyls of emerging or slightly older seedlings; as the seedlings mature, these areas turn dark brown to black and eventually group together to form large lesions; pods may dry prematurely with the drying beginning at the pod tip and progressing toward the base; pods eventually turn dark brown to black

BROWN

Fusarium Pod and Collar Rot

Depressed, water-soaked, cream-colored, serrated lesions form on cotyledons and hypocotyls of emerging or slightly older seedlings; as the seedlings mature, these areas turn dark brown to black and eventually group together to form large lesions; pods may dry prematurely with the drying beginning at the pod tip and progressing toward the base; pods eventually turn dark brown to black

Heat Canker

The hypocotyl in the seed is girdled at or just above the soil line; affected area varies in length, with the affected tissues appearing reddish brown and shriveled; hypocotyl tissue directly above or below the constriction appears normal

Pythium Rot

Seedling decays before or after emergence; seed may decay in soil; roots develop a brown wet rot, causing the plant to wilt; smaller roots may decay or break away when plants are pulled from the soil; freshly invaded stem tissues are translucent and older lesions become brown producing a watery soft rot; later, if dry weather sets in, the plants appear dry and shredded; cortical tissues in the larger roots may disintegrate and slough off, exposing the central woody cylinder

Rhizoctonia Stem and Root Rot

Pre-emergence or post-emergence damping off of seedlings; brown or reddish brown lesions on larger seedlings and young plant stems at the soil line and on the taproot causing the tissue to decay; infected stems may break in the lesioned area; lesions may enlarge, become sunken, and girdle the plant; lesions on freshly dug plants appear brick red but soon become brown to dark brown upon exposure to air; usually occurs on a few scattered plants or groups of plants

Rhizoctonia Stem and Root Rot

Pre-emergence or post-emergence damping off of seedlings; brown or reddish brown lesions on larger seedlings and young plant stems at the soil line and on the taproot causing the tissue to decay; infected stems may break in the lesioned area; lesions may enlarge, become sunken, and girdle the plant; lesions on freshly dug plants appear brick red but soon become brown to dark brown upon exposure to air; usually occurs on a few scattered plants or groups of plants

Rhizoctonia Stem and Root Rot

Pre-emergence or post-emergence damping off of seedlings; brown or reddish brown lesions on larger seedlings and young plant stems at the soil line and on the taproot causing the tissue to decay; infected stems may break in the lesioned area; lesions may enlarge, become sunken, and girdle the plant; lesions on freshly dug plants appear brick red but soon become brown to dark brown upon exposure to air; usually occurs on a few scattered plants or groups of plants

CREAM

Fusarium Pod and Collar Rot

Depressed, water-soaked, cream-colored, serrated lesions form on cotyledons and hypocotyls of emerging or slightly older seedlings; as the seedlings mature, these areas turn dark brown to black and eventually group together to form large lesions; pods may dry prematurely with the drying beginning at the pod tip and progressing toward the base; pods eventually turn dark brown to black

RED

Heat Canker

The hypocotyl in the seed is girdled at or just above the soil line; affected area varies in length, with the affected tissues appearing reddish brown and shriveled; hypocotyl tissue directly above or below the constriction appears normal

Pod and Stem Blight

The most characteristic symptom is the arrangement of black sclerotia in linear rows on the stems and are scattered on pods; infected seed crack and shrivel and are often covered with white mold; these seeds fail to germinate, or produce weak seedlings with brownish-red pinpoint lesions on the cotyledons; reddish-brown streaks appear on the seedling stem near or below the soil line

Rhizoctonia Stem and Root Rot

Pre-emergence or post-emergence damping off of seedlings; brown or reddish brown lesions on larger seedlings and young plant stems at the soil line and on the taproot causing the tissue to decay; infected stems may break in the lesioned area; lesions may enlarge, become sunken, and girdle the plant; lesions on freshly dug plants appear brick red but soon become brown to dark brown upon exposure to air; usually occurs on a few scattered plants or groups of plants

Rhizoctonia Stem and Root Rot

Pre-emergence or post-emergence damping off of seedlings; brown or reddish brown lesions on larger seedlings and young plant stems at the soil line and on the taproot causing the tissue to decay; infected stems may break in the lesioned area; lesions may enlarge, become sunken, and girdle the plant; lesions on freshly dug plants appear brick red but soon become brown to dark brown upon exposure to air; usually occurs on a few scattered plants or groups of plants

YELLOW

Fusarium Root Rot

Seedlings are stunted or damp off; adult plants show root rot; cotyledons of diseased seedlings are yellow and later dry up; plants may wilt in dry weather

No Distinct Discoloration

Damping-Off

Seed decay, poor stand, stem rots at soil line, seedlings rot and die

Fusarium Root Rot

Seedlings are stunted or damp off; adult plants show root rot; cotyledons of diseased seedlings are yellow and later dry up; plants may wilt in dry weather

Phytophthora Root and Stem Rot

Seed rot and pre-emergence damping-off; root and stem rot of older seedlings; in more mature plants water-soaked lesions develop on the stem and roots, yellowing, chlorosis and wilting of leaves, with a dark brown discoloration on lower stem progressing upward from the soil line; leaves on older plants become chlorotic between the veins followed by a general wilting and death; withered leaves generally remain attached; root rot of older plants may also occur; affected plants are clustered in field

Root

BLACK

Charcoal Root Rot

Loss of vigor in mature plants; leaves turn yellow and wilt but remain attached; light gray or silver discoloration in taproot and lower stem after flowering; small black sclerotia present in taproot and stem tissues just beneath the epidermis or bark; the lower stem becomes girdled causing wilting and death

Mycoleptodiscus Terrestris

A postemergence damping-off of seedlings develops as a reddish brown to black cortical decay of crown and root tissues; a dark decay of the lateral root system and taproot of older plants also develops

Thielaviopsis Root Rot

A dark brown to black drying of the cortex of hypocotyls, taproots, and fibrous roots forms below the soil line, sometimes resulting in root rot

BROWN

Fusarium Blight or Wilt

The most characteristic symptom is browning or blackening of the vascular system in roots and stems, which is evident when stems are split open; leaves of affected plants may become yellow, wither, and eventually drop

Mycoleptodiscus Terrestris

A postemergence damping-off of seedlings develops as a reddish brown to black cortical decay of crown and root tissues; a dark decay of the lateral root system and taproot of older plants also develops

Pod and Stem Blight

The most characteristic symptom is the arrangement of black sclerotia in linear rows on the stems and are scattered on pods; infected seed crack and shrivel and are often covered with white mold; these seeds fail to germinate, or produce weak seedlings with brownish-red pinpoint lesions on the cotyledons; reddish-brown streaks appear on the seedling stem near or below the soil line

Pythium Rot

Seedling decays before or after emergence; seed may decay in soil; roots develop a brown wet rot, causing the plant to wilt; smaller roots may decay or break away when plants are pulled from the soil; freshly invaded stem tissues are translucent and older lesions become brown producing a watery soft rot; later, if dry weather sets in, the plants appear dry and shredded; cortical tissues in the larger roots may disintegrate and slough off, exposing the central woody cylinder

Reniform Nematode

Symptoms include yellowing, stunting, and unthrifty growth, with the production of a large number of empty pods; galls are not produced on roots, but the root system is severely stunted and may dry out; most common symptom is the soil-covered egg masses on roots

Root-Knot Nematode

Galls on roots; numerous galls tend to group together so that entire roots may be greatly swollen; plants severely affected are stunted and yellow; occasional wilting occurs

Soybean Cyst Nematode

Slight to severe stunting with slight to severe chlorosis of the leaves; gradual yield decline over several years; decreased nodulation and canopy slow to close; symptoms are similar to nitrogen and/or potassium deficiency; some root decay; pin-head sized cysts develop on roots first appearing white or yellow and turning dark brown with age; stunted plants develop in elliptic or lens-shaped areas in the field with the long axis parallel to the direction of major tillage

Thielaviopsis Root Rot

A dark brown to black drying of the cortex of hypocotyls, taproots, and fibrous roots forms below the soil line, sometimes resulting in root rot

DARK

Lesion Nematode

Dark lesions on roots and an overall browning of the roots, which may decrease root growth; the epidermis and cortex of severely infected roots may slough away from the stele; plants may be stunted and pod set may be reduced

Sting Nematode

Roots with nubs, occasionally long roots with few branches; plants stunted; small, dark, sunken lesions develop along the root axis or at root tips which girdle the roots or extend along the longitudinal axis of affected roots; terminal growth often ceases

GRAY

Charcoal Root Rot

Loss of vigor in mature plants; leaves turn yellow and wilt but remain attached; light gray or silver discoloration in taproot and lower stem after flowering; small black sclerotia present in taproot and stem tissues just beneath the epidermis or bark; the lower stem becomes girdled causing wilting and death

Sudden Death Syndrome

Yellow interveinal spots expand into streaks, which become necrotic leaving green tissue along the leaf veins; leaf blades drop, leaving petioles attached to the stem; foliar symptoms similar to brown stem rot; light brown or gray discoloration occurs in internal taproot tissue, while pith remains white

RED

Mycoleptodiscus Terrestris

A postemergence damping-off of seedlings develops as a reddish brown to black cortical decay of crown and root tissues; a dark decay of the lateral root system and taproot of older plants also develops

SILVER<CF 200 000 000><S18>SILVER

Charcoal_Root_Rot<S16><b>Charcoal Root Rot

Loss of vigor in mature plants; leaves turn yellow and wilt but remain attached; light gray or silver discoloration in taproot and lower stem after flowering; small black sclerotia present in taproot and stem tissues just beneath the epidermis or bark; the lower stem becomes girdled causing wilting and death

TAN

Sudden Death Syndrome

Yellow interveinal spots expand into streaks, which become necrotic leaving green tissue along the leaf veins; leaf blades drop, leaving petioles attached to the stem; foliar symptoms similar to brown stem rot; light brown or gray discoloration occurs in internal taproot tissue, while pith remains white

WHITE

Soybean Cyst Nematode

Slight to severe stunting with slight to severe chlorosis of the leaves; gradual yield decline over several years; decreased nodulation and canopy slow to close; symptoms are similar to nitrogen and/or potassium deficiency; some root decay; pin-head sized cysts develop on roots first appearing white or yellow and turning dark brown with age; stunted plants develop in elliptic or lens-shaped areas in the field with the long axis parallel to the direction of major tillage

YELLOW

Soybean Cyst Nematode

Slight to severe stunting with slight to severe chlorosis of the leaves; gradual yield decline over several years; decreased nodulation and canopy slow to close; symptoms are similar to nitrogen and/or potassium deficiency; some root decay; pin-head sized cysts develop on roots first appearing white or yellow and turning dark brown with age; stunted plants develop in elliptic or lens-shaped areas in the field with the long axis parallel to the direction of major tillage

No Distinct Discoloration

Fusarium Root Rot

Seedlings are stunted or damp off; adult plants show root rot; cotyledons of diseased seedlings are yellow and later dry up; plants may wilt in dry weather

Nematode Diseases

Stunting or suppressed growth, wilting, root lesions or dark discolored areas in roots, root swelling, injured or devitalized root tips, reduced and discolored root systems, and yield reductions

Phytophthora Root and Stem Rot

Seed rot and pre-emergence damping-off; root and stem rot of older seedlings; in more mature plants water-soaked lesions develop on the stem and roots, yellowing, chlorosis and wilting of leaves, with a dark brown discoloration on lower stem progressing upward from the soil line; leaves on older plants become chlorotic between the veins followed by a general wilting and death; withered leaves generally remain attached; root rot of older plants may also occur; affected plants are clustered in field

Crown

BLACK

Mycoleptodiscus Terrestris

A postemergence damping-off of seedlings develops as a reddish brown to black cortical decay of crown and root tissues; a dark decay of the lateral root system and taproot of older plants also develops

BROWN

Mycoleptodiscus Terrestris

A postemergence damping-off of seedlings develops as a reddish brown to black cortical decay of crown and root tissues; a dark decay of the lateral root system and taproot of older plants also develops

Pythium Rot

Seedling decays before or after emergence; seed may decay in soil; roots develop a brown wet rot, causing the plant to wilt; smaller roots may decay or break away when plants are pulled from the soil; freshly invaded stem tissues are translucent and older lesions become brown producing a watery soft rot; later, if dry weather sets in, the plants appear dry and shredded; cortical tissues in the larger roots may disintegrate and slough off, exposing the central woody cylinder

Stem Canker

First symptoms are small reddish-brown lesions at the base of branches or petioles; lesions elongate, become sunken and may girdle the stem; a brown canker forms above the soil line; plants may be girdled before the leaves mature; leaves exhibit interveinal yellowing and chlorosis which becomes necrotic; leaves on dead plants dry up but remain attached

RED

Mycoleptodiscus Terrestris

A postemergence damping-off of seedlings develops as a reddish brown to black cortical decay of crown and root tissues; a dark decay of the lateral root system and taproot of older plants also develops

WHITE

Southern Stem Blight

Symptoms usually develop during late reproductive stages of plant growth; a white cottony mold on the main stem at the soil surface develops; small brown sclerotia are associated with the mold on the stem; infected plants are often killed; girdling of stems near the soil line may occur

Stem

RED

Scab

Lesions on leaves are on both surfaces and common on the center veins; stem lesions are buff, sometimes with reddish brown margins and young lesions on pods are red to brown

No Distinct Discoloration

Neocosmospora Vasinfecta

A dark discoloration of stems and pith, with occasional chlorosis and defoliation of the lower leaves

BLACK

Anthracnose

The fungus produces an abundance of spores which infect and kill lower branches, leaves, and young pods; foliar symptoms include leaf rolling and veinal necrosis; symptoms appear on stems, pods, and petioles as red or dark brown areas; later these areas are covered with black acervuli that resemble tiny pin cushions; infection of young pods results in empty pods at maturity; pods infected later contain shriveled or moldy seed and may have dark lesions on the seed coat

Bacterial Blight

Initial symptoms are small angular yellow water-soaked spots on leaves; lesion centers dry out and turn brown to black with water-soaked margins and yellow halos; lesions may coalesce resulting in large blighted areas; affected tissue often drops out, giving a tattered appearance to the leaves; black lesions develop on the stem; small water-soaked spots develop on pods; the spots enlarge and become black; seeds are shriveled

Charcoal Root Rot

Loss of vigor in mature plants; leaves turn yellow and wilt but remain attached; light gray or silver discoloration in taproot and lower stem after flowering; small black sclerotia present in taproot and stem tissues just beneath the epidermis or bark; the lower stem becomes girdled causing wilting and death

Pod and Stem Blight

The most characteristic symptom is the arrangement of black sclerotia in linear rows on the stems and are scattered on pods; infected seed crack and shrivel and are often covered with white mold; these seeds fail to germinate, or produce weak seedlings with brownish-red pinpoint lesions on the cotyledons; reddish-brown streaks appear on the seedling stem near or below the soil line

Sclerotinia Stem Rot

Wilting and death; dead leaves remain attached to stems; tan to white lesions at nodes can girdle stems causing them to rot; cottony fungal growth may be present on diseased plant parts; tufts of white mold are common on stems and later turn into black sclerotia, which can be found inside and outside the stem; leaves wilt or are covered with mold

BRONZE

Cercospora Leaf Blight

Symptoms are first observed at the beginning of seed set; small, reddish purple, angular to irregular lesions occur on the upper leaves which become leathery and dark purplish-red with bronze highlights; this discoloration may extend to the upper stems, petioles, and pods; heavily infected leaves rapidly turn yellow and fall; lower leaves remain green

BROWN

Aerial Blight

Symptoms include leaf spots, leaf blighting, or defoliation; leaf spots are irregular water-soaked spots that develop reddish-brown margins during drier conditions; tissue in the center of lesions falls out giving the plant a ragged appearance; brown lesions may also form on the petioles, stems, and pods; severe infection causes pod blight

Anthracnose

The fungus produces an abundance of spores which infect and kill lower branches, leaves, and young pods; foliar symptoms include leaf rolling and veinal necrosis; symptoms appear on stems, pods, and petioles as red or dark brown areas; later these areas are covered with black acervuli that resemble tiny pin cushions; infection of young pods results in empty pods at maturity; pods infected later contain shriveled or moldy seed and may have dark lesions on the seed coat

Brown Spot

Irregular light-brown to red lesions, ranging in size from small specks to a few mm in diameter; lesions eventually darken to brownish black; lesions are primarily found on leaves, but can also occur on stems, petioles, and pods; infected leaves turn yellow and drop off; early season infection is restricted to unifoliate and first trifoliate leaves

Brown Stem Rot

Symptoms are usually not evident until late in the growing season; leaves may suddenly discolor, with brown tissue between veins and green tissue along veins; leaves remain attached; browning of pith inside stem of infected plants

Brown Stem Rot

Red-brown discoloration develops in the stem pith, at first near the soil line and at the nodes; infected plants turn brown just before maturing; infected plants may lodge; on leaves, brown to yellow areas occasionally develop between the veins as chlorosis and necrosis; lower part of infected stems turns dull brown and is followed by sudden blighting and drying of leaves, which may drop prematurely

Bud Blight

Stunting occurs when young plants are infected; stem terminal will curve, forming a crook which is probably the most distinguishing characteristic; lateral buds become brown and drop off; brown discoloration of stems, beginning at nodes; leaves are dwarfed and curl upward; pods often abort, or are underdeveloped and mature plants have clusters of minute pods; infected plants remain green longer than healthy plants; symptoms often develop first on plants near the edges of a field

Frogeye Leaf Spot

Leaves that expand during periods of weather unfavorable for invasion remain relatively disease free and result in layers of healthy leaves between layers of heavily diseases leaves; foliar, circular lesions measure up to 5 mm in diameter but may coalesce to form larger spots; young, fully developed lesions have a gray to brown center with a distinct purplish to reddish-brown margin; as lesions age, the center becomes tan to nearly white and the margin darkens; lesions also occur on stems and pods

Fusarium Blight or Wilt

The most characteristic symptom is browning or blackening of the vascular system in roots and stems, which is evident when stems are split open; leaves of affected plants may become yellow, wither, and eventually drop

Phytophthora Root and Stem Rot

Seed rot and pre-emergence damping-off; root and stem rot of older seedlings; in more mature plants water-soaked lesions develop on the stem and roots, yellowing, chlorosis and wilting of leaves, with a dark brown discoloration on lower stem progressing upward from the soil line; leaves on older plants become chlorotic between the veins followed by a general wilting and death; withered leaves generally remain attached; root rot of older plants may also occur; affected plants are clustered in field

Pythium Rot

Seedling decays before or after emergence; seed may decay in soil; roots develop a brown wet rot, causing the plant to wilt; smaller roots may decay or break away when plants are pulled from the soil; freshly invaded stem tissues are translucent and older lesions become brown producing a watery soft rot; later, if dry weather sets in, the plants appear dry and shredded; cortical tissues in the larger roots may disintegrate and slough off, exposing the central woody cylinder

Red Crown Rot

Earliest symptom is yellowing of leaves of individual plants or patches of plants within a field; leaves of infected plants develop yellow spots between the veins, which eventually turn light brown and may shatter; many of the leaves drop prematurely; fungus spreads from the roots, causing a grayish-brown discoloration of the internal stem; outer surface of infected stems turns red and is killed; reddish-orange pycnidia develop on the stem 1 to 3 inches above the soil surface

Red Leaf Blotch

Lesions develop on foliage, pods, and stems and the lesions are often associated with primary leaf veins; they may initially occur on unifoliolate leaves and are dark red to brown, circular to angular

Sclerotium Blight

Light brown lesions enlarge until the hypocotyl or stem is girdled; a sudden yellowing or wilting of plants is usually the first symptoms; leaves of infected plants turn brown, dry, and often cling to the dead stem; a leaf spot phase is characterized by circular, tan to brown, zonate lesions with dark brown margins

Southern Stem Blight

Symptoms usually develop during late reproductive stages of plant growth; a white cottony mold on the main stem at the soil surface develops; small brown sclerotia are associated with the mold on the stem; infected plants are often killed; girdling of stems near the soil line may occur

Sunburn

Minor sunburn appears as small, interveinal, brick red spots on both leaf surfaces; with severe sunburn the discoloration spreads over and along the leaf veins; later the spots develop brownish centers, which may crack; damage on petioles and stems appears as elongated, brink red lesions; on pods, brown spots appear, spread, and are often colonized later by fungi

Tobacco Ringspot Virus

Most significant symptom is the curving of the terminal bud; later, other buds on the plant become brown, dry and brittle; such buds may fall off at the slightest touch; the pith of stems and branches may show a brown discoloration first near the nodes and then throughout the stem; brown streaks are occasionally observed on petioles and large leaf veins

DARK

Hail

Leaves injured are torn and ragged and large areas of tissues may be beaten away; stems may be cut off or broken or may have sunken, dark areas; most damage is usually on the side of the plant facing the prevailing winds of the storm

GRAY

Charcoal Root Rot

Loss of vigor in mature plants; leaves turn yellow and wilt but remain attached; light gray or silver discoloration in taproot and lower stem after flowering; small black sclerotia present in taproot and stem tissues just beneath the epidermis or bark; the lower stem becomes girdled causing wilting and death

Frogeye Leaf Spot

Leaves that expand during periods of weather unfavorable for invasion remain relatively disease free and result in layers of healthy leaves between layers of heavily diseases leaves; foliar, circular lesions measure up to 5 mm in diameter but may coalesce to form larger spots; young, fully developed lesions have a gray to brown center with a distinct purplish to reddish-brown margin; as lesions age, the center becomes tan to nearly white and the margin darkens; lesions also occur on stems and pods

Red Crown Rot

Earliest symptom is yellowing of leaves of individual plants or patches of plants within a field; leaves of infected plants develop yellow spots between the veins, which eventually turn light brown and may shatter; many of the leaves drop prematurely; fungus spreads from the roots, causing a grayish-brown discoloration of the internal stem; outer surface of infected stems turns red and is killed; reddish-orange pycnidia develop on the stem 1 to 3 inches above the soil surface

GREEN

Soybean Dwarf Virus

Plants are severely stunted, turn deep green, become thick and brittle, and are smaller than normal

Sulfur Deficiency

Small, yellow-green leaves; stems are thin, hard, and elongated; leaf symptoms resemble those produced by deficiencies of other elements but stem elongation is characteristic

Brown Stem Rot

Symptoms are usually not evident until late in the growing season; leaves may suddenly discolor, with brown tissue between veins and green tissue along veins; leaves remain attached; browning of pith inside stem of infected plants

Stem (Additional Elements)

LIGHT

Brown Spot

Irregular light-brown to red lesions, ranging in size from small specks to a few mm in diameter; lesions eventually darken to brownish black; lesions are primarily found on leaves, but can also occur on stems, petioles, and pods; infected leaves turn yellow and drop off; early season infection is restricted to unifoliate and first trifoliate leaves

ORANGE

Red Crown Rot

Earliest symptom is yellowing of leaves of individual plants or patches of plants within a field; leaves of infected plants develop yellow spots between the veins, which eventually turn light brown and may shatter; many of the leaves drop prematurely; fungus spreads from the roots, causing a grayish-brown discoloration of the internal stem; outer surface of infected stems turns red and is killed; reddish-orange pycnidia develop on the stem 1 to 3 inches above the soil surface

Cercospora Leaf Blight

Symptoms are first observed at the beginning of seed set; small, reddish purple, angular to irregular lesions occur on the upper leaves which become leathery and dark purplish-red with bronze highlights; this discoloration may extend to the upper stems, petioles, and pods; heavily infected leaves rapidly turn yellow and fall; lower leaves remain green

Frogeye Leaf Spot

Leaves that expand during periods of weather unfavorable for invasion remain relatively disease free and result in layers of healthy leaves between layers of heavily diseases leaves; foliar, circular lesions measure up to 5 mm in diameter but may coalesce to form larger spots; young, fully developed lesions have a gray to brown center with a distinct purplish to reddish-brown margin; as lesions age, the center becomes tan to nearly white and the margin darkens; lesions also occur on stems and pods

RED

Anthracnose

The fungus produces an abundance of spores which infect and kill lower branches, leaves, and young pods; foliar symptoms include leaf rolling and veinal necrosis; symptoms appear on stems, pods, and petioles as red or dark brown areas; later these areas are covered with black acervuli that resemble tiny pin cushions; infection of young pods results in empty pods at maturity; pods infected later contain shriveled or moldy seed and may have dark lesions on the seed coat

Brown Spot

Irregular light-brown to red lesions, ranging in size from small specks to a few mm in diameter; lesions eventually darken to brownish black; lesions are primarily found on leaves, but can also occur on stems, petioles, and pods; infected leaves turn yellow and drop off; early season infection is restricted to unifoliate and first trifoliate leaves

Brown Stem Rot

Red-brown discoloration develops in the stem pith, at first near the soil line and at the nodes; infected plants turn brown just before maturing; infected plants may lodge; on leaves, brown to yellow areas occasionally develop between the veins as chlorosis and necrosis; lower part of infected stems turns dull brown and is followed by sudden blighting and drying of leaves, which may drop prematurely

Cercospora Leaf Blight

Symptoms are first observed at the beginning of seed set; small, reddish purple, angular to irregular lesions occur on the upper leaves which become leathery and dark purplish-red with bronze highlights; this discoloration may extend to the upper stems, petioles, and pods; heavily infected leaves rapidly turn yellow and fall; lower leaves remain green

Frogeye Leaf Spot

Leaves that expand during periods of weather unfavorable for invasion remain relatively disease free and result in layers of healthy leaves between layers of heavily diseases leaves; foliar, circular lesions measure up to 5 mm in diameter but may coalesce to form larger spots; young, fully developed lesions have a gray to brown center with a distinct purplish to reddish-brown margin; as lesions age, the center becomes tan to nearly white and the margin darkens; lesions also occur on stems and pods

Red Crown Rot

Earliest symptom is yellowing of leaves of individual plants or patches of plants within a field; leaves of infected plants develop yellow spots between the veins, which eventually turn light brown and may shatter; many of the leaves drop prematurely; fungus spreads from the roots, causing a grayish-brown discoloration of the internal stem; outer surface of infected stems turns red and is killed; reddish-orange pycnidia develop on the stem 1 to 3 inches above the soil surface

Red Leaf Blotch

Lesions develop on foliage, pods, and stems and the lesions are often associated with primary leaf veins; they may initially occur on unifoliolate leaves and are dark red to brown, circular to angular

Rust

Tan to dark brown or reddish brown lesions develop on petioles, pods, and stems but are most abundant on leaves; disease begins with small, water-soaked lesions, which gradually increase in size, turning from gray to tan or brown

Stem Canker

First symptoms are small reddish-brown lesions at the base of branches or petioles; lesions elongate, become sunken and may girdle the stem; a brown canker forms above the soil line; plants may be girdled before the leaves mature; leaves exhibit interveinal yellowing and chlorosis which becomes necrotic; leaves on dead plants dry up but remain attached

Target Spot

Lesions on leaves are reddish-brown, circular, and variable in size up to 15 mm in diameter; spots may also be found on petioles, stems, and pods; the largest lesions often show distinct concentric zones of dead tissue and may have a narrow, indistinct yellow-green halo; lesions which form along veins may be narrow and elongated; severe infections may cause premature leaf drop

Rhizoctonia_Stem_and_Root_Rot<S16><b>Rhizoctonia Stem and Root Rot

Pre-emergence or post-emergence damping off of seedlings; brown or reddish brown lesions on larger seedlings and young plant stems at the soil line and on the taproot causing the tissue to decay; infected stems may break in the lesioned area; lesions may enlarge, become sunken, and girdle the plant; lesions on freshly dug plants appear brick red but soon become brown to dark brown upon exposure to air; usually occurs on a few scattered plants or groups of plants

SILVER

Charcoal Root Rot

Loss of vigor in mature plants; leaves turn yellow and wilt but remain attached; light gray or silver discoloration in taproot and lower stem after flowering; small black sclerotia present in taproot and stem tissues just beneath the epidermis or bark; the lower stem becomes girdled causing wilting and death

TAN

Frogeye Leaf Spot

Leaves that expand during periods of weather unfavorable for invasion remain relatively disease free and result in layers of healthy leaves between layers of heavily diseases leaves; foliar, circular lesions measure up to 5 mm in diameter but may coalesce to form larger spots; young, fully developed lesions have a gray to brown center with a distinct purplish to reddish-brown margin; as lesions age, the center becomes tan to nearly white and the margin darkens; lesions also occur on stems and pods

Rust

Tan to dark brown or reddish brown lesions develop on petioles, pods, and stems but are most abundant on leaves; disease begins with small, water-soaked lesions, which gradually increase in size, turning from gray to tan or brown

Sclerotinia Stem Rot

Wilting and death; dead leaves remain attached to stems; tan to white lesions at nodes can girdle stems causing them to rot; cottony fungal growth may be present on diseased plant parts; tufts of white mold are common on stems and later turn into black sclerotia, which can be found inside and outside the stem; leaves wilt or are covered with mold

Sclerotium Blight

Light brown lesions enlarge until the hypocotyl or stem is girdled; a sudden yellowing or wilting of plants is usually the first symptoms; leaves of infected plants turn brown, dry, and often cling to the dead stem; a leaf spot phase is characterized by circular, tan to brown, zonate lesions with dark brown margins

WHITE

Frogeye Leaf Spot

Leaves that expand during periods of weather unfavorable for invasion remain relatively disease free and result in layers of healthy leaves between layers of heavily diseases leaves; foliar, circular lesions measure up to 5 mm in diameter but may coalesce to form larger spots; young, fully developed lesions have a gray to brown center with a distinct purplish to reddish-brown margin; as lesions age, the center becomes tan to nearly white and the margin darkens; lesions also occur on stems and pods

Sclerotinia Stem Rot

Wilting and death; dead leaves remain attached to stems; tan to white lesions at nodes can girdle stems causing them to rot; cottony fungal growth may be present on diseased plant parts; tufts of white mold are common on stems and later turn into black sclerotia, which can be found inside and outside the stem; leaves wilt or are covered with mold

YELLOW

Brown Spot

Irregular light-brown to red lesions, ranging in size from small specks to a few mm in diameter; lesions eventually darken to brownish black; lesions are primarily found on leaves, but can also occur on stems, petioles, and pods; infected leaves turn yellow and drop off; early season infection is restricted to unifoliate and first trifoliate leaves

Sclerotium Blight

Light brown lesions enlarge until the hypocotyl or stem is girdled; a sudden yellowing or wilting of plants is usually the first symptoms; leaves of infected plants turn brown, dry, and often cling to the dead stem; a leaf spot phase is characterized by circular, tan to brown, zonate lesions with dark brown margins

Soybean Mosaic

Leaves are mottled green and yellow and are curled; small veins turn yellow; leaves become crinkled in cool weather; entire plant becomes stunted and yellow; seeds may be mottled brown or black with reduced germination; leaves may be puckered and misshapen, resembling 2,4-D injury; diseased pods may be stunted and curved

Sudden Death Syndrome

Yellow interveinal spots expand into streaks, which become necrotic leaving green tissue along the leaf veins; leaf blades drop, leaving petioles attached to the stem; foliar symptoms similar to brown stem rot; light brown or gray discoloration occurs in internal taproot tissue, while pith remains white

No Distinct Discoloration

Bean Pod Mottle

Diseased plants show a mild yellow mottling on young actively growing leaves; as these leaves approach maturity the mottling becomes masked; plants infected with both soybean mosaic and pod mottle are stunted, have distorted foliage, misshapen fruit, and necrotic tissue; seed from plants infected with pod mottle are smaller than normal

Damping-Off

Seed decay, poor stand, stem rots at soil line, seedlings rot and die

Lightning

Kills plants in circular patterns in the field with a wide border of damaged plants; lower parts of stems may be blackened, with many dead leaves still attached; pith of such plants appears cooked or blanched

Leaf

BLACK

Bacterial Blight

Initial symptoms are small angular yellow water-soaked spots on leaves; lesion centers dry out and turn brown to black with water-soaked margins and yellow halos; lesions may coalesce resulting in large blighted areas; affected tissue often drops out, giving a tattered appearance to the leaves; black lesions develop on the stem; small water-soaked spots develop on pods; the spots enlarge and become black; seeds are shriveled

Sclerotinia Stem Rot

Wilting and death; dead leaves remain attached to stems; tan to white lesions at nodes can girdle stems causing them to rot; cottony fungal growth may be present on diseased plant parts; tufts of white mold are common on stems and later turn into black sclerotia, which can be found inside and outside the stem; leaves wilt or are covered with mold

Wildfire

Light brown spots of variable size and shape, which are surrounded by a broad yellow halo on the leaves; smaller dark brown to black lesions sometimes form without the typical halo; during wet weather, the lesions expand to form large dead areas that eventually tear away resulting in a tattered appearance

BLUE

Phosphorus Deficiency

Affected plants are spindly and have small leaflets and growth is severely retarded; leaves turn dark green or bluish green and the leaf blade may curl up and appear pointed; blooming and maturity are delayed; the dark green of the leaves gives the impression that the plants are quite healthy

BRONZE

Cercospora Leaf Blight

Symptoms are first observed at the beginning of seed set; small, reddish purple, angular to irregular lesions occur on the upper leaves which become leathery and dark purplish-red with bronze highlights; this discoloration may extend to the upper stems, petioles, and pods; heavily infected leaves rapidly turn yellow and fall; lower leaves remain green

Magnesium Deficiency

Deficiency is recognized by pale green to yellow interveinal tissues on the leaf blade; leaves later become deep yellow, except at the base; lowest leaves show symptoms first and as the disease progresses, rusty specks and dry blotches may appear between the veins and around the edges of middle and upper leaves; leaf margins curve down, with a gradual yellowing from the margin inward, followed by bronzing of the entire leaf

BROWN

Aerial Blight

Symptoms include leaf spots, leaf blighting, or defoliation; leaf spots are irregular water-soaked spots that develop reddish-brown margins during drier conditions; tissue in the center of lesions falls out giving the plant a ragged appearance; brown lesions may also form on the petioles, stems, and pods; severe infection causes pod blight

Alternaria Leaf Spot

Lesions develop on the leaves and are nearly circular unless they are restricted by a major vein or coalesce with another lesion; single lesions range up to 25 mm in diameter, have brown concentric rings, and a well defined margin

Ammonia

Leaves that are almost fully expanded are most sensitive to ammonia; lesions develop on leaves ranging from local, reddish brown lesions to broad, cream to brown bands between veins

Bacterial Pustule

Small, yellow-green spots with reddish-brown centers develop on leaves; later a small, raised pustule develop on one or both sides of leaves which is most noticeable on the lower leaf surface; pustule formation and the absence of a water-soaked appearance in the early stages of lesion development distinguish bacterial pustule from bacterial blight; diseased leaves develop a tattered appearance as dead tissue is torn away because of weathering; leaves may fall off; severe infection often causes some defoliation of young leaves which are more susceptible than older leaves

Bacterial Tan Spot

A small lesion develops on the leaflet which becomes yellow along leaf margins, and progresses inward toward the midrib; infected tissues die, dry out, and turn brown

Boron

Deficiency will cause shortened internodes and yellowing or reddening of upper leaves; flowers fail to develop; excessive boron is toxic, especially to seedlings and affected plants are stunted; toxicity appears only on leaves as the leaf tip becomes brown eventually taking in the whole leaf

Brown Spot

Irregular light-brown to red lesions, ranging in size from small specks to a few mm in diameter; lesions eventually darken to brownish black; lesions are primarily found on leaves, but can also occur on stems, petioles, and pods; infected leaves turn yellow and drop off; early season infection is restricted to unifoliate and first trifoliate leaves

Brown Stem Rot

Red-brown discoloration develops in the stem pith, at first near the soil line and at the nodes; infected plants turn brown just before maturing; infected plants may lodge; on leaves, brown to yellow areas occasionally develop between the veins as chlorosis and necrosis; lower part of infected stems turns dull brown and is followed by sudden blighting and drying of leaves, which may drop prematurely

Downy Mildew

Pale green to yellow spots on upper leaf surface; lesions turn grayish brown to dark brown with a yellow or light green margin; tufts of gray fungal growth may be visible on lower leaf surface during moist weather; severely affected leaves turn brown and drop; whitish fungal growth may be present on interior of pods and seed coats; infected seedlings from infected seeds are stunted with mottled foliage

Frogeye Leaf Spot

Leaves that expand during periods of weather unfavorable for invasion remain relatively disease free and result in layers of healthy leaves between layers of heavily diseases leaves; foliar, circular lesions measure up to 5 mm in diameter but may coalesce to form larger spots; young, fully developed lesions have a gray to brown center with a distinct purplish to reddish-brown margin; as lesions age, the center becomes tan to nearly white and the margin darkens; lesions also occur on stems and pods

Foliage Blight

Symptoms appear first on the lower leaves and advance to the upper ones; discrete, water-soaked, orange-brown specks form on leaves and enlarge to round or irregularly shaped orange-brown lesions with definite, dark brown margins

Manganese Deficiency

Interveinal areas of leaves become light green to white while the veins remain green; dry, brown spots develop as the deficiency becomes more severe and leaves may drop prematurely

Phyllosticta Leaf Spot

Lesions form primarily on leaves; leaf spots are round to oval, irregular, or V-shaped; the spots begin as a pale green color and become dull gray to tan, with a narrow dark brown or purplish border

Powdery Mildew

The first symptom is usually a circular area of white to light-gray, superficial powdery growth on the upper leaf surface; under favorable conditions, cool humid night and mild dry days, these areas expand rapidly, coalesce and cover the entire leaf surface; all green plant parts may be covered by the powdery growth; heavily infected leaves turn yellow, then brown, and drop prematurely

Pythium Rot

Seedling decays before or after emergence; seed may decay in soil; roots develop a brown wet rot, causing the plant to wilt; smaller roots may decay or break away when plants are pulled from the soil; freshly invaded stem tissues are translucent and older lesions become brown producing a watery soft rot; later, if dry weather sets in, the plants appear dry and shredded; cortical tissues in the larger roots may disintegrate and slough off, exposing the central woody cylinder

Red Crown Rot

Earliest symptom is yellowing of leaves of individual plants or patches of plants within a field; leaves of infected plants develop yellow spots between the veins, which eventually turn light brown and may shatter; many of the leaves drop prematurely; fungus spreads from the roots, causing a grayish-brown discoloration of the internal stem; outer surface of infected stems turns red and is killed; reddish-orange pycnidia develop on the stem 1 to 3 inches above the soil surface

Red Leaf Blotch

Lesions develop on foliage, pods, and stems and the lesions are often associated with primary leaf veins; they may initially occur on unifoliolate leaves and are dark red to brown, circular to angular

Sclerotium Blight

Light brown lesions enlarge until the hypocotyl or stem is girdled; a sudden yellowing or wilting of plants is usually the first symptoms; leaves of infected plants turn brown, dry, and often cling to the dead stem; a leaf spot phase is characterized by circular, tan to brown, zonate lesions with dark brown margins

Stem Canker

First symptoms are small reddish-brown lesions at the base of branches or petioles; lesions elongate, become sunken and may girdle the stem; a brown canker forms above the soil line; plants may be girdled before the leaves mature; leaves exhibit interveinal yellowing and chlorosis which becomes necrotic; leaves on dead plants dry up but remain attached

Sulfur Dioxide Toxicity

Areas between leaf veins are yellow, dry and exhibit irregular cream-colored to light brown dry areas

Sunburn

Minor sunburn appears as small, interveinal, brick red spots on both leaf surfaces; with severe sunburn the discoloration spreads over and along the leaf veins; later the spots develop brownish centers, which may crack; damage on petioles and stems appears as elongated, brink red lesions; on pods, brown spots appear, spread, and are often colonized later by fungi

Tobacco Ringspot Virus

Most significant symptom is the curving of the terminal bud; later, other buds on the plant become brown, dry and brittle; such buds may fall off at the slightest touch; the pith of stems and branches may show a brown discoloration first near the nodes and then throughout the stem; brown streaks are occasionally observed on petioles and large leaf veins

Wildfire

Light brown spots of variable size and shape, which are surrounded by a broad yellow halo on the leaves; smaller dark brown to black lesions sometimes form without the typical halo; during wet weather, the lesions expand to form large dead areas that eventually tear away resulting in a tattered appearance

Zinc Deficiency

Stunted stems and leaves with yellow interveinal areas; later, entire leaves turn yellow or light green and the lower leaves may turn brown or gray and drop early; few flowers are formed, and the pods that set are abnormal and slow in maturing; yield reduction is the result of the reduced number of seeds formed

CREAM

Ammonia

Leaves that are almost fully expanded are most sensitive to ammonia; lesions develop on leaves ranging from local, reddish brown lesions to broad, cream to brown bands between veins

Sulfur Dioxide Toxicity

Areas between leaf veins are yellow, dry and exhibit irregular cream-colored to light brown dry areas

DARK

Yellow Leaf Spot

Symptoms include rapid defoliation, poor pod fill, and reduced seed size; lesions develop from pinpoint spots similar to those of bacterial pustule; later, yellow halos, larger than those of bacterial pustule, develop around the enlarging spots; young plants may have more spots than older ones and spots may be reddish brown

GRAY

Choanephora Leaf Blight

Symptoms occur in the field after two or three consecutive days of rain; first symptom of the disease appears on mature leaves and occasionally on young leaves at the top of the plant; leaves first appear grayish and then turn dark

Downy Mildew

Pale green to yellow spots on upper leaf surface; lesions turn grayish brown to dark brown with a yellow or light green margin; tufts of gray fungal growth may be visible on lower leaf surface during moist weather; severely affected leaves turn brown and drop; whitish fungal growth may be present on interior of pods and seed coats; infected seedlings from infected seeds are stunted with mottled foliage

Frogeye Leaf Spot

Leaves that expand during periods of weather unfavorable for invasion remain relatively disease free and result in layers of healthy leaves between layers of heavily diseases leaves; foliar, circular lesions measure up to 5 mm in diameter but may coalesce to form larger spots; young, fully developed lesions have a gray to brown center with a distinct purplish to reddish-brown margin; as lesions age, the center becomes tan to nearly white and the margin darkens; lesions also occur on stems and pods

Phyllosticta Leaf Spot

Lesions form primarily on leaves; leaf spots are round to oval, irregular, or V-shaped; the spots begin as a pale green color and become dull gray to tan, with a narrow dark brown or purplish border

Powdery Mildew

The first symptom is usually a circular area of white to light-gray, superficial powdery growth on the upper leaf surface; under favorable conditions, cool humid night and mild dry days, these areas expand rapidly, coalesce and cover the entire leaf surface; all green plant parts may be covered by the powdery growth; heavily infected leaves turn yellow, then brown, and drop prematurely

Zinc Deficiency

Stunted stems and leaves with yellow interveinal areas; later, entire leaves turn yellow or light green and the lower leaves may turn brown or gray and drop early; few flowers are formed, and the pods that set are abnormal and slow in maturing; yield reduction is the result of the reduced number of seeds formed

GREEN

Bacterial Induced Chlorosis

White to yellow-green band on outer edge of young foliage; band varies in width; discolored leaves may turn green again; usually only 2 or 3 leaves show symptoms

Bacterial Pustule

Small, yellow-green spots with reddish-brown centers develop on leaves; later a small, raised pustule develop on one or both sides of leaves which is most noticeable on the lower leaf surface; pustule formation and the absence of a water-soaked appearance in the early stages of lesion development distinguish bacterial pustule from bacterial blight; diseased leaves develop a tattered appearance as dead tissue is torn away because of weathering; leaves may fall off; severe infection often causes some defoliation of young leaves which are more susceptible than older leaves

Bud Blight

Stunting occurs when young plants are infected; stem terminal will curve, forming a crook which is probably the most distinguishing characteristic; lateral buds become brown and drop off; brown discoloration of stems, beginning at nodes; leaves are dwarfed and curl upward; pods often abort, or are underdeveloped and mature plants have clusters of minute pods; infected plants remain green longer than healthy plants; symptoms often develop first on plants near the edges of a field

Downy Mildew

Pale green to yellow spots on upper leaf surface; lesions turn grayish brown to dark brown with a yellow or light green margin; tufts of gray fungal growth may be visible on lower leaf surface during moist weather; severely affected leaves turn brown and drop; whitish fungal growth may be present on interior of pods and seed coats; infected seedlings from infected seeds are stunted with mottled foliage

Indonesian Soybean Dwarf Virus

Dwarfing, with shortened leaf petioles and internodes, and infected plants are often dark green; upper leaves are small and often crinkled and curled; lower leaves show rugosity and are often brittle

Iron Chlorosis

Plants are stunted with yellow leaves and green veins; a few scattered plants may be affected or large circular patches may develop; appears on highly alkaline soils

Magnesium Deficiency

Deficiency is recognized by pale green to yellow interveinal tissues on the leaf blade; leaves later become deep yellow, except at the base; lowest leaves show symptoms first and as the disease progresses, rusty specks and dry blotches may appear between the veins and around the edges of middle and upper leaves; leaf margins curve down, with a gradual yellowing from the margin inward, followed by bronzing of the entire leaf

Manganese Deficiency

Interveinal areas of leaves become light green to white while the veins remain green; dry, brown spots develop as the deficiency becomes more severe and leaves may drop prematurely

Molybdenum Deficiency

Leaves are pale green or yellow, dry, and twisted; drying is largely confined to the midribs, interveinal areas, and margins

Nitrogen Deficiency

Plants become pale green and the leaves turn distinctly and uniformly yellow; symptoms appear first on the basal leaves and quickly spread to the upper parts; plants eventually defoliate and are often stunted and spindly

Peanut Mottle

A mosaic of dark green and yellow areas is produced in older leaves; ring patterns of yellow patches develop on the third and fourth leaves following infection; infected leaves pucker and curl downward at the margins

Phosphorus Deficiency

Affected plants are spindly and have small leaflets and growth is severely retarded; leaves turn dark green or bluish green and the leaf blade may curl up and appear pointed; blooming and maturity are delayed; the dark green of the leaves gives the impression that the plants are quite healthy

Phyllosticta Leaf Spot

Lesions form primarily on leaves; leaf spots are round to oval, irregular, or V-shaped; the spots begin as a pale green color and become dull gray to tan, with a narrow dark brown or purplish border

Soybean Dwarf Virus

Plants are severely stunted, turn deep green, become thick and brittle, and are smaller than normal

LIGHT

Brown Spot

Irregular light-brown to red lesions, ranging in size from small specks to a few mm in diameter; lesions eventually darken to brownish black; lesions are primarily found on leaves, but can also occur on stems, petioles, and pods; infected leaves turn yellow and drop off; early season infection is restricted to unifoliate and first trifoliate leaves

ORANGE

Foliage Blight

Symptoms appear first on the lower leaves and advance to the upper ones; discrete, water-soaked, orange-brown specks form on leaves and enlarge to round or irregularly shaped orange-brown lesions with definite, dark brown margins

PURPLE

Cercospora Leaf Blight

Symptoms are first observed at the beginning of seed set; small, reddish purple, angular to irregular lesions occur on the upper leaves which become leathery and dark purplish-red with bronze highlights; this discoloration may extend to the upper stems, petioles, and pods; heavily infected leaves rapidly turn yellow and fall; lower leaves remain green

Frogeye Leaf Spot

Leaves that expand during periods of weather unfavorable for invasion remain relatively disease free and result in layers of healthy leaves between layers of heavily diseases leaves; foliar, circular lesions measure up to 5 mm in diameter but may coalesce to form larger spots; young, fully developed lesions have a gray to brown center with a distinct purplish to reddish-brown margin; as lesions age, the center becomes tan to nearly white and the margin darkens; lesions also occur on stems and pods

Phyllosticta Leaf Spot

Lesions form primarily on leaves; leaf spots are round to oval, irregular, or V-shaped; the spots begin as a pale green color and become dull gray to tan, with a narrow dark brown or purplish border

Purple Seed Stain

Seed is discolored pink to purple, in small spots or on the entire seed; cracks often occur in discolored areas; infected leaves have reddish purple angular, crusty, dark spots on both surfaces; veinal necrosis may also be observed

RED

Aerial Blight

Symptoms include leaf spots, leaf blighting, or defoliation; leaf spots are irregular water-soaked spots that develop reddish-brown margins during drier conditions; tissue in the center of lesions falls out giving the plant a ragged appearance; brown lesions may also form on the petioles, stems, and pods; severe infection causes pod blight

Ammonia<S16><b>Ammonia

Leaves that are almost fully expanded are most sensitive to ammonia; lesions develop on leaves ranging from local, reddish brown lesions to broad, cream to brown bands between veins

Bacterial_Pustule<S16><b>Bacterial Pustule

Small, yellow-green spots with reddish-brown centers develop on leaves; later a small, raised pustule develop on one or both sides of leaves which is most noticeable on the lower leaf surface; pustule formation and the absence of a water-soaked appearance in the early stages of lesion development distinguish bacterial pustule from bacterial blight; diseased leaves develop a tattered appearance as dead tissue is torn away because of weathering; leaves may fall off; severe infection often causes some defoliation of young leaves which are more susceptible than older leaves

Bean Yellow Mosaic Virus

A conspicuous yellow spotting develops on the leaves; yellow areas are either scattered or produced in indefinite bands along the major veins; rusty, dry spots appear in the yellow areas as the leaves mature; some leaves may experience crinkling

Boron

Deficiency will cause shortened internodes and yellowing or reddening of upper leaves; flowers fail to develop; excessive boron is toxic, especially to seedlings and affected plants are stunted; toxicity appears only on leaves as the leaf tip becomes brown eventually taking in the whole leaf

Brown Spot

Irregular light-brown to red lesions, ranging in size from small specks to a few mm in diameter; lesions eventually darken to brownish black; lesions are primarily found on leaves, but can also occur on stems, petioles, and pods; infected leaves turn yellow and drop off; early season infection is restricted to unifoliate and first trifoliate leaves

Cercospora Leaf Blight

Symptoms are first observed at the beginning of seed set; small, reddish purple, angular to irregular lesions occur on the upper leaves which become leathery and dark purplish-red with bronze highlights; this discoloration may extend to the upper stems, petioles, and pods; heavily infected leaves rapidly turn yellow and fall; lower leaves remain green

Frogeye Leaf Spot

Leaves that expand during periods of weather unfavorable for invasion remain relatively disease free and result in layers of healthy leaves between layers of heavily diseases leaves; foliar, circular lesions measure up to 5 mm in diameter but may coalesce to form larger spots; young, fully developed lesions have a gray to brown center with a distinct purplish to reddish-brown margin; as lesions age, the center becomes tan to nearly white and the margin darkens; lesions also occur on stems and pods

Magnesium Deficiency

Deficiency is recognized by pale green to yellow interveinal tissues on the leaf blade; leaves later become deep yellow, except at the base; lowest leaves show symptoms first and as the disease progresses, rusty specks and dry blotches may appear between the veins and around the edges of middle and upper leaves; leaf margins curve down, with a gradual yellowing from the margin inward, followed by bronzing of the entire leaf

Purple Seed Stain

Seed is discolored pink to purple, in small spots or on the entire seed; cracks often occur in discolored areas; infected leaves have reddish purple angular, crusty, dark spots on both surfaces; veinal necrosis may also be observed

Red Leaf Blotch

Lesions develop on foliage, pods, and stems and the lesions are often associated with primary leaf veins; they may initially occur on unifoliolate leaves and are dark red to brown, circular to angular

Rust

Tan to dark brown or reddish brown lesions develop on petioles, pods, and stems but are most abundant on leaves; disease begins with small, water-soaked lesions, which gradually increase in size, turning from gray to tan or brown

Scab

Lesions on leaves are on both surfaces and common on the center veins; stem lesions are buff, sometimes with reddish brown margins and young lesions on pods are red to brown

Stem Canker

First symptoms are small reddish-brown lesions at the base of branches or petioles; lesions elongate, become sunken and may girdle the stem; a brown canker forms above the soil line; plants may be girdled before the leaves mature; leaves exhibit interveinal yellowing and chlorosis which becomes necrotic; leaves on dead plants dry up but remain attached

Sunburn

Minor sunburn appears as small, interveinal, brick red spots on both leaf surfaces; with severe sunburn the discoloration spreads over and along the leaf veins; later the spots develop brownish centers, which may crack; damage on petioles and stems appears as elongated, brink red lesions; on pods, brown spots appear, spread, and are often colonized later by fungi

Target Spot

Lesions on leaves are reddish-brown, circular, and variable in size up to 15 mm in diameter; spots may also be found on petioles, stems, and pods; the largest lesions often show distinct concentric zones of dead tissue and may have a narrow, indistinct yellow-green halo; lesions which form along veins may be narrow and elongated; severe infections may cause premature leaf drop

Yellow Leaf Spot

Symptoms include rapid defoliation, poor pod fill, and reduced seed size; lesions develop from pinpoint spots similar to those of bacterial pustule; later, yellow halos, larger than those of bacterial pustule, develop around the enlarging spots; young plants may have more spots than older ones and spots may be reddish brown

TAN

Frogeye Leaf Spot

Leaves that expand during periods of weather unfavorable for invasion remain relatively disease free and result in layers of healthy leaves between layers of heavily diseases leaves; foliar, circular lesions measure up to 5 mm in diameter but may coalesce to form larger spots; young, fully developed lesions have a gray to brown center with a distinct purplish to reddish-brown margin; as lesions age, the center becomes tan to nearly white and the margin darkens; lesions also occur on stems and pods

Phyllosticta Leaf Spot

Lesions form primarily on leaves; leaf spots are round to oval, irregular, or V-shaped; the spots begin as a pale green color and become dull gray to tan, with a narrow dark brown or purplish border

Rust

Tan to dark brown or reddish brown lesions develop on petioles, pods, and stems but are most abundant on leaves; disease begins with small, water-soaked lesions, which gradually increase in size, turning from gray to tan or brown

WHITE

Bacterial Induced Chlorosis

White to yellow-green band on outer edge of young foliage; band varies in width; discolored leaves may turn green again; usually only 2 or 3 leaves show symptoms

Frogeye Leaf Spot

Leaves that expand during periods of weather unfavorable for invasion remain relatively disease free and result in layers of healthy leaves between layers of heavily diseases leaves; foliar, circular lesions measure up to 5 mm in diameter but may coalesce to form larger spots; young, fully developed lesions have a gray to brown center with a distinct purplish to reddish-brown margin; as lesions age, the center becomes tan to nearly white and the margin darkens; lesions also occur on stems and pods

Manganese Deficiency

Interveinal areas of leaves become light green to white while the veins remain green; dry, brown spots develop as the deficiency becomes more severe and leaves may drop prematurely

Powdery Mildew

The first symptom is usually a circular area of white to light-gray, superficial powdery growth on the upper leaf surface; under favorable conditions, cool humid night and mild dry days, these areas expand rapidly, coalesce and cover the entire leaf surface; all green plant parts may be covered by the powdery growth; heavily infected leaves turn yellow, then brown, and drop prematurely

YELLOW

Bacterial Blight

Initial symptoms are small angular yellow water-soaked spots on leaves; lesion centers dry out and turn brown to black with water-soaked margins and yellow halos; lesions may coalesce resulting in large blighted areas; affected tissue often drops out, giving a tattered appearance to the leaves; black lesions develop on the stem; small water-soaked spots develop on pods; the spots enlarge and become black; seeds are shriveled

Bacterial Induced Chlorosis

White to yellow-green band on outer edge of young foliage; band varies in width; discolored leaves may turn green again; usually only 2 or 3 leaves show symptoms

Bacterial Pustule

Small, yellow-green spots with reddish-brown centers develop on leaves; later a small, raised pustule develop on one or both sides of leaves which is most noticeable on the lower leaf surface; pustule formation and the absence of a water-soaked appearance in the early stages of lesion development distinguish bacterial pustule from bacterial blight; diseased leaves develop a tattered appearance as dead tissue is torn away because of weathering; leaves may fall off; severe infection often causes some defoliation of young leaves which are more susceptible than older leaves

Bacterial Tan Spot

A small lesion develops on the leaflet which becomes yellow along leaf margins, and progresses inward toward the midrib; infected tissues die, dry out, and turn brown

Bean Pod Mottle

Diseased plants show a mild yellow mottling on young actively growing leaves; as these leaves approach maturity the mottling becomes masked; plants infected with both soybean mosaic and pod mottle are stunted, have distorted foliage, misshapen fruit, and necrotic tissue; seed from plants infected with pod mottle are smaller than normal

Bean Yellow Mosaic Virus

A conspicuous yellow spotting develops on the leaves; yellow areas are either scattered or produced in indefinite bands along the major veins; rusty, dry spots appear in the yellow areas as the leaves mature; some leaves may experience crinkling

Boron

Deficiency will cause shortened internodes and yellowing or reddening of upper leaves; flowers fail to develop; excessive boron is toxic, especially to seedlings and affected plants are stunted; toxicity appears only on leaves as the leaf tip becomes brown eventually taking in the whole leaf

Brown Spot

Irregular light-brown to red lesions, ranging in size from small specks to a few mm in diameter; lesions eventually darken to brownish black; lesions are primarily found on leaves, but can also occur on stems, petioles, and pods; infected leaves turn yellow and drop off; early season infection is restricted to unifoliate and first trifoliate leaves

Brown Stem Rot

Symptoms are usually not evident until late in the growing season; leaves may suddenly discolor, with brown tissue between veins and green tissue along veins; leaves remain attached; browning of pith inside stem of infected plants

Charcoal Root Rot

Loss of vigor in mature plants; leaves turn yellow and wilt but remain attached; light gray or silver discoloration in taproot and lower stem after flowering; small black sclerotia present in taproot and stem tissues just beneath the epidermis or bark; the lower stem becomes girdled causing wilting and death

Downy Mildew

Pale green to yellow spots on upper leaf surface; lesions turn grayish brown to dark brown with a yellow or light green margin; tufts of gray fungal growth may be visible on lower leaf surface during moist weather; severely affected leaves turn brown and drop; whitish fungal growth may be present on interior of pods and seed coats; infected seedlings from infected seeds are stunted with mottled foliage

Fusarium Blight or Wilt

The most characteristic symptom is browning or blackening of the vascular system in roots and stems, which is evident when stems are split open; leaves of affected plants may become yellow, wither, and eventually drop

Chlorosis

Plants are stunted with yellow leaves and green veins; a few scattered plants may be affected or large circular patches may develop; appears on highly alkaline soils

Magnesium Deficiency

Deficiency is recognized by pale green to yellow interveinal tissues on the leaf blade; leaves later become deep yellow, except at the base; lowest leaves show symptoms first and as the disease progresses, rusty specks and dry blotches may appear between the veins and around the edges of middle and upper leaves; leaf margins curve down, with a gradual yellowing from the margin inward, followed by bronzing of the entire leaf

Molybdenum Deficiency

Leaves are pale green or yellow, dry, and twisted; drying is largely confined to the midribs, interveinal areas, and margins

Mung Bean Yellow Mosaic Virus

Initial symptom in leaves is vein yellowing along veinlets and severe yellow mosaic can develop on older infections

Neocosmospora Vasinfecta

A dark discoloration of stems and pith, with occasional chlorosis and defoliation of the lower leaves

Nitrogen Deficiency

Plants become pale green and the leaves turn distinctly and uniformly yellow; symptoms appear first on the basal leaves and quickly spread to the upper parts; plants eventually defoliate and are often stunted and spindly

Peanut Mottle

A mosaic of dark green and yellow areas is produced in older leaves; ring patterns of yellow patches develop on the third and fourth leaves following infection; infected leaves pucker and curl downward at the margins

Phytophthora Root and Stem Rot

Seed rot and pre-emergence damping-off; root and stem rot of older seedlings; in more mature plants water-soaked lesions develop on the stem and roots, yellowing, chlorosis and wilting of leaves, with a dark brown discoloration on lower stem progressing upward from the soil line; leaves on older plants become chlorotic between the veins followed by a general wilting and death; withered leaves generally remain attached; root rot of older plants may also occur; affected plants are clustered in field

Potassium Deficiency

Irregular yellow spotting appear around leaflet margins when the plant is young; the yellow areas group together to form a more or less continuous, irregular yellow border, which is followed by drying of yellowed areas and downward cupping of leaf margins

Powdery Mildew

The first symptom is usually a circular area of white to light-gray, superficial powdery growth on the upper leaf surface; under favorable conditions, cool humid night and mild dry days, these areas expand rapidly, coalesce and cover the entire leaf surface; all green plant parts may be covered by the powdery growth; heavily infected leaves turn yellow, then brown, and drop prematurely

Red Crown Rot

Earliest symptom is yellowing of leaves of individual plants or patches of plants within a field; leaves of infected plants develop yellow spots between the veins, which eventually turn light brown and may shatter; many of the leaves drop prematurely; fungus spreads from the roots, causing a grayish-brown discoloration of the internal stem; outer surface of infected stems turns red and is killed; reddish-orange pycnidia develop on the stem 1 to 3 inches above the soil surface

Reniform Nematode

Symptoms include yellowing, stunting, and unthrifty growth, with the production of a large number of empty pods; galls are not produced on roots, but the root system is severely stunted and may dry out; most common symptom is the soil-covered egg masses on roots

Root-Knot Nematode

Galls on roots; numerous galls tend to group together so that entire roots may be greatly swollen; plants severely affected are stunted and yellow; occasional wilting occurs

Sclerotium Blight

Light brown lesions enlarge until the hypocotyl or stem is girdled; a sudden yellowing or wilting of plants is usually the first symptoms; leaves of infected plants turn brown, dry, and often cling to the dead stem; a leaf spot phase is characterized by circular, tan to brown, zonate lesions with dark brown margins

Soybean Chlorotic Mottle Virus

Veinclearing and yellowing followed by spotting are characteristic; leaf size is also reduced and infected plants become stunted, with shortened internodes

Soybean Cyst Nematode

Slight to severe stunting with slight to severe chlorosis of the leaves; gradual yield decline over several years; decreased nodulation and canopy slow to close; symptoms are similar to nitrogen and/or potassium deficiency; some root decay; pin-head sized cysts develop on roots first appearing white or yellow and turning dark brown with age; stunted plants develop in elliptic or lens-shaped areas in the field with the long axis parallel to the direction of major tillage

Soybean Mosaic

Leaves are mottled green and yellow and are curled; small veins turn yellow; leaves become crinkled in cool weather; entire plant becomes stunted and yellow; seeds may be mottled brown or black with reduced germination; leaves may be puckered and misshapen, resembling 2,4-D injury; diseased pods may be stunted and curved

Soybean Yellow Vein Virus

Yellowing of the veins on the upper leaves; found only in Thailand

Stem Canker

First symptoms are small reddish-brown lesions at the base of branches or petioles; lesions elongate, become sunken and may girdle the stem; a brown canker forms above the soil line; plants may be girdled before the leaves mature; leaves exhibit interveinal yellowing and chlorosis which becomes necrotic; leaves on dead plants dry up but remain attached

Sudden Death Syndrome

Yellow interveinal spots expand into streaks, which become necrotic leaving green tissue along the leaf veins; leaf blades drop, leaving petioles attached to the stem; foliar symptoms similar to brown stem rot; light brown or gray discoloration occurs in internal taproot tissue, while pith remains white

Sulfur Deficiency

Small, yellow-green leaves; stems are thin, hard, and elongated; leaf symptoms resemble those produced by deficiencies of other elements but stem elongation is characteristic

Sulfur Dioxide Toxicity

Areas between leaf veins are yellow, dry and exhibit irregular cream-colored to light brown dry areas

Target Spot

Lesions on leaves are reddish-brown, circular, and variable in size up to 15 mm in diameter; spots may also be found on petioles, stems, and pods; the largest lesions often show distinct concentric zones of dead tissue and may have a narrow, indistinct yellow-green halo; lesions which form along veins may be narrow and elongated; severe infections may cause premature leaf drop

Tobacco Streak Virus

Irregular, yellow spots form on leaves; several axillary branches form which are stunted and produce dwarfed leaves; mosaic symptoms and dry streaks may develop at nodes

Water Stress

Symptoms include stunting, poor vigor, and yellowing of the interveinal area of leaves, which changes to a general yellowing with interveinal drying in severe situations; soybeans die if they are grown in fields that are flooded or submerged for extended periods

Wildfire

Light brown spots of variable size and shape, which are surrounded by a broad yellow halo on the leaves; smaller dark brown to black lesions sometimes form without the typical halo; during wet weather, the lesions expand to form large dead areas that eventually tear away resulting in a tattered appearance

Yellow Leaf Spot

Symptoms include rapid defoliation, poor pod fill, and reduced seed size; lesions develop from pinpoint spots similar to those of bacterial pustule; later, yellow halos, larger than those of bacterial pustule, develop around the enlarging spots; young plants may have more spots than older ones and spots may be reddish brown

Zinc Deficiency

Stunted stems and leaves with yellow interveinal areas; later, entire leaves turn yellow or light green and the lower leaves may turn brown or gray and drop early; few flowers are formed, and the pods that set are abnormal and slow in maturing; yield reduction is the result of the reduced number of seeds formed

No Distinct Discoloration

Anthracnose

The fungus produces an abundance of spores which infect and kill lower branches, leaves, and young pods; foliar symptoms include leaf rolling and veinal necrosis; symptoms appear on stems, pods, and petioles as red or dark brown areas; later these areas are covered with black acervuli that resemble tiny pin cushions; infection of young pods results in empty pods at maturity; pods infected later contain shriveled or moldy seed and may have dark lesions on the seed coat

Hail

Leaves injured are torn and ragged and large areas of tissues may be beaten away; stems may be cut off or broken or may have sunken, dark areas; most damage is usually on the side of the plant facing the prevailing winds of the storm

Lightning

Kills plants in circular patterns in the field with a wide border of damaged plants; lower parts of stems may be blackened, with many dead leaves still attached; pith of such plants appears cooked or blanched

Soybean Crinkle Leaf Virus

Leaves show crinkling, curling, cupping, and twisting and have veinal enations on the undersurface; not common

Flower

BROWN

Tobacco Ringspot Virus

Most significant symptom is the curving of the terminal bud; later, other buds on the plant become brown, dry and brittle; such buds may fall off at the slightest touch; the pith of stems and branches may show a brown discoloration first near the nodes and then throughout the stem; brown streaks are occasionally observed on petioles and large leaf veins

No Distinct Discoloration

Boron

Deficiency will cause shortened internodes and yellowing or reddening of upper leaves; flowers fail to develop; excessive boron is toxic, especially to seedlings and affected plants are stunted; toxicity appears only on leaves as the leaf tip becomes brown eventually taking in the whole leaf

Machismo

Pods may be rigid, curved, flat, and then, usually in an upright position, with no beans formed; flowers are smaller and remain closed; first symptoms usually appear about the time of flowering or after pod formation begins

Fruit

BLACK

Anthracnose

The fungus produces an abundance of spores which infect and kill lower branches, leaves, and young pods; foliar symptoms include leaf rolling and veinal necrosis; symptoms appear on stems, pods, and petioles as red or dark brown areas; later these areas are covered with black acervuli that resemble tiny pin cushions; infection of young pods results in empty pods at maturity; pods infected later contain shriveled or moldy seed and may have dark lesions on the seed coat

Bacterial Blight

Initial symptoms are small angular yellow water-soaked spots on leaves; lesion centers dry out and turn brown to black with water-soaked margins and yellow halos; lesions may coalesce resulting in large blighted areas; affected tissue often drops out, giving a tattered appearance to the leaves; black lesions develop on the stem; small water-soaked spots develop on pods; the spots enlarge and become black; seeds are shriveled

Colletotrichum truncatum

Seeds may show no symptoms or may develop brown staining or small, irregular gray areas with black specks; infected seeds may die during germination, or if they do germinate, may produce infected seedlings

Fusarium Pod and Collar Rot

Depressed, water-soaked, cream-colored, serrated lesions form on cotyledons and hypocotyls of emerging or slightly older seedlings; as the seedlings mature, these areas turn dark brown to black and eventually group together to form large lesions; pods may dry prematurely with the drying beginning at the pod tip and progressing toward the base; pods eventually turn dark brown to black

BRONZE

Cercospora Leaf Blight

Symptoms are first observed at the beginning of seed set; small, reddish purple, angular to irregular lesions occur on the upper leaves which become leathery and dark purplish-red with bronze highlights; this discoloration may extend to the upper stems, petioles, and pods; heavily infected leaves rapidly turn yellow and fall; lower leaves remain green

BROWN

Aerial Blight

Symptoms include leaf spots, leaf blighting, or defoliation; leaf spots are irregular water-soaked spots that develop reddish-brown margins during drier conditions; tissue in the center of lesions falls out giving the plant a ragged appearance; brown lesions may also form on the petioles, stems, and pods; severe infection causes pod blight

Alternaria Pod and Seed Decay

Condia on the pod are smooth and pale brown to golden, with short or long beaks with an occasional terminal beak swelling; they are formed in short, unbranching chains of eight or fewer

Anthracnose

The fungus produces an abundance of spores which infect and kill lower branches, leaves, and young pods; foliar symptoms include leaf rolling and veinal necrosis; symptoms appear on stems, pods, and petioles as red or dark brown areas; later these areas are covered with black acervuli that resemble tiny pin cushions; infection of young pods results in empty pods at maturity; pods infected later contain shriveled or moldy seed and may have dark lesions on the seed coat

Brown Spot

Irregular light-brown to red lesions, ranging in size from small specks to a few mm in diameter; lesions eventually darken to brownish black; lesions are primarily found on leaves, but can also occur on stems, petioles, and pods; infected leaves turn yellow and drop off; early season infection is restricted to unifoliate and first trifoliate leaves

Colletotrichum truncatum

Seeds may show no symptoms or may develop brown staining or small, irregular gray areas with black specks; infected seeds may die during germination, or if they do germinate, may produce infected seedlings

Frogeye Leaf Spot

Leaves that expand during periods of weather unfavorable for invasion remain relatively disease free and result in layers of healthy leaves between layers of heavily diseases leaves; foliar, circular lesions measure up to 5 mm in diameter but may coalesce to form larger spots; young, fully developed lesions have a gray to brown center with a distinct purplish to reddish-brown margin; as lesions age, the center becomes tan to nearly white and the margin darkens; lesions also occur on stems and pods

Fusarium Pod and Collar Rot

Depressed, water-soaked, cream-colored, serrated lesions form on cotyledons and hypocotyls of emerging or slightly older seedlings; as the seedlings mature, these areas turn dark brown to black and eventually group together to form large lesions; pods may dry prematurely with the drying beginning at the pod tip and progressing toward the base; pods eventually turn dark brown to black

Pythium Rot

Seedling decays before or after emergence; seed may decay in soil; roots develop a brown wet rot, causing the plant to wilt; smaller roots may decay or break away when plants are pulled from the soil; freshly invaded stem tissues are translucent and older lesions become brown producing a watery soft rot; later, if dry weather sets in, the plants appear dry and shredded; cortical tissues in the larger roots may disintegrate and slough off, exposing the central woody cylinder

Red Leaf Blotch

Lesions develop on foliage, pods, and stems and the lesions are often associated with primary leaf veins; they may initially occur on unifoliolate leaves and are dark red to brown, circular to angular

Yeast Spot

Pale yellow to grayish brown and slightly sunken areas develop on young seeds; sunken spots are light or cream-colored on more mature seeds; pods may also develop small discolored areas where they contact infected seeds; when infection occurs during pod formation, seeds fail to develop and pods drop prematurely

CREAM

Yeast Spot

Pale yellow to grayish brown and slightly sunken areas develop on young seeds; sunken spots are light or cream-colored on more mature seeds; pods may also develop small discolored areas where they contact infected seeds; when infection occurs during pod formation, seeds fail to develop and pods drop prematurely

DARK

Anthracnose

The fungus produces an abundance of spores which infect and kill lower branches, leaves, and young pods; foliar symptoms include leaf rolling and veinal necrosis; symptoms appear on stems, pods, and petioles as red or dark brown areas; later these areas are covered with black acervuli that resemble tiny pin cushions; infection of young pods results in empty pods at maturity; pods infected later contain shriveled or moldy seed and may have dark lesions on the seed coat

GRAY

Colletotrichum truncatum

Seeds may show no symptoms or may develop brown staining or small, irregular gray areas with black specks; infected seeds may die during germination, or if they do germinate, may produce infected seedlings

Frogeye Leaf Spot

Leaves that expand during periods of weather unfavorable for invasion remain relatively disease free and result in layers of healthy leaves between layers of heavily diseases leaves; foliar, circular lesions measure up to 5 mm in diameter but may coalesce to form larger spots; young, fully developed lesions have a gray to brown center with a distinct purplish to reddish-brown margin; as lesions age, the center becomes tan to nearly white and the margin darkens; lesions also occur on stems and pods

Yeast Spot

Pale yellow to grayish brown and slightly sunken areas develop on young seeds; sunken spots are light or cream-colored on more mature seeds; pods may also develop small discolored areas where they contact infected seeds; when infection occurs during pod formation, seeds fail to develop and pods drop prematurely

LIGHT

Brown Spot

Irregular light-brown to red lesions, ranging in size from small specks to a few mm in diameter; lesions eventually darken to brownish black; lesions are primarily found on leaves, but can also occur on stems, petioles, and pods; infected leaves turn yellow and drop off; early season infection is restricted to unifoliate and first trifoliate leaves

PURPLE

Cercospora Leaf Blight

Symptoms are first observed at the beginning of seed set; small, reddish purple, angular to irregular lesions occur on the upper leaves which become leathery and dark purplish-red with bronze highlights; this discoloration may extend to the upper stems, petioles, and pods; heavily infected leaves rapidly turn yellow and fall; lower leaves remain green

Frogeye Leaf Spot

Leaves that expand during periods of weather unfavorable for invasion remain relatively disease free and result in layers of healthy leaves between layers of heavily diseases leaves; foliar, circular lesions measure up to 5 mm in diameter but may coalesce to form larger spots; young, fully developed lesions have a gray to brown center with a distinct purplish to reddish-brown margin; as lesions age, the center becomes tan to nearly white and the margin darkens; lesions also occur on stems and pods

RED

Anthracnose

The fungus produces an abundance of spores which infect and kill lower branches, leaves, and young pods; foliar symptoms include leaf rolling and veinal necrosis; symptoms appear on stems, pods, and petioles as red or dark brown areas; later these areas are covered with black acervuli that resemble tiny pin cushions; infection of young pods results in empty pods at maturity; pods infected later contain shriveled or moldy seed and may have dark lesions on the seed coat

Brown Spot

Irregular light-brown to red lesions, ranging in size from small specks to a few mm in diameter; lesions eventually darken to brownish black; lesions are primarily found on leaves, but can also occur on stems, petioles, and pods; infected leaves turn yellow and drop off; early season infection is restricted to unifoliate and first trifoliate leaves

Cercospora Leaf Blight

Symptoms are first observed at the beginning of seed set; small, reddish purple, angular to irregular lesions occur on the upper leaves which become leathery and dark purplish-red with bronze highlights; this discoloration may extend to the upper stems, petioles, and pods; heavily infected leaves rapidly turn yellow and fall; lower leaves remain green

Frogeye Leaf Spot

Leaves that expand during periods of weather unfavorable for invasion remain relatively disease free and result in layers of healthy leaves between layers of heavily diseases leaves; foliar, circular lesions measure up to 5 mm in diameter but may coalesce to form larger spots; young, fully developed lesions have a gray to brown center with a distinct purplish to reddish-brown margin; as lesions age, the center becomes tan to nearly white and the margin darkens; lesions also occur on stems and pods

Red Leaf Blotch

Lesions develop on foliage, pods, and stems and the lesions are often associated with primary leaf veins; they may initially occur on unifoliolate leaves and are dark red to brown, circular to angular

Rust

Tan to dark brown or reddish brown lesions develop on petioles, pods, and stems but are most abundant on leaves; disease begins with small, water-soaked lesions, which gradually increase in size, turning from gray to tan or brown

Scab

Lesions on leaves are on both surfaces and common on the center veins; stem lesions are buff, sometimes with reddish brown margins and young lesions on pods are red to brown

Sunburn

Minor sunburn appears as small, interveinal, brick red spots on both leaf surfaces; with severe sunburn the discoloration spreads over and along the leaf veins; later the spots develop brownish centers, which may crack; damage on petioles and stems appears as elongated, brink red lesions; on pods, brown spots appear, spread, and are often colonized later by fungi

Target Spot

Lesions on leaves are reddish-brown, circular, and variable in size up to 15 mm in diameter; spots may also be found on petioles, stems, and pods; the largest lesions often show distinct concentric zones of dead tissue and may have a narrow, indistinct yellow-green halo; lesions which form along veins may be narrow and elongated; severe infections may cause premature leaf drop

TAN

Frogeye Leaf Spot

Leaves that expand during periods of weather unfavorable for invasion remain relatively disease free and result in layers of healthy leaves between layers of heavily diseases leaves; foliar, circular lesions measure up to 5 mm in diameter but may coalesce to form larger spots; young, fully developed lesions have a gray to brown center with a distinct purplish to reddish-brown margin; as lesions age, the center becomes tan to nearly white and the margin darkens; lesions also occur on stems and pods

Rust

Tan to dark brown or reddish brown lesions develop on petioles, pods, and stems but are most abundant on leaves; disease begins with small, water-soaked lesions, which gradually increase in size, turning from gray to tan or brown

WHITE

Downy Mildew

Pale green to yellow spots on upper leaf surface; lesions turn grayish brown to dark brown with a yellow or light green margin; tufts of gray fungal growth may be visible on lower leaf surface during moist weather; severely affected leaves turn brown and drop; whitish fungal growth may be present on interior of pods and seed coats; infected seedlings from infected seeds are stunted with mottled foliage

Frogeye Leaf Spot

Leaves that expand during periods of weather unfavorable for invasion remain relatively disease free and result in layers of healthy leaves between layers of heavily diseases leaves; foliar, circular lesions measure up to 5 mm in diameter but may coalesce to form larger spots; young, fully developed lesions have a gray to brown center with a distinct purplish to reddish-brown margin; as lesions age, the center becomes tan to nearly white and the margin darkens; lesions also occur on stems and pods

Pod and Stem Blight

The most characteristic symptom is the arrangement of black sclerotia in linear rows on the stems and are scattered on pods; infected seed crack and shrivel and are often covered with white mold; these seeds fail to germinate, or produce weak seedlings with brownish-red pinpoint lesions on the cotyledons; reddish-brown streaks appear on the seedling stem near or below the soil line

YELLOW

Alternaria Pod and Seed Decay

Condia on the pod are smooth and pale brown to golden, with short or long beaks with an occasional terminal beak swelling; they are formed in short, unbranching chains of eight or fewer

Brown Spot

Irregular light-brown to red lesions, ranging in size from small specks to a few mm in diameter; lesions eventually darken to brownish black; lesions are primarily found on leaves, but can also occur on stems, petioles, and pods; infected leaves turn yellow and drop off; early season infection is restricted to unifoliate and first trifoliate leaves

Cercospora Leaf Blight

Symptoms are first observed at the beginning of seed set; small, reddish purple, angular to irregular lesions occur on the upper leaves which become leathery and dark purplish-red with bronze highlights; this discoloration may extend to the upper stems, petioles, and pods; heavily infected leaves rapidly turn yellow and fall; lower leaves remain green

Reniform Nematode

Symptoms include yellowing, stunting, and unthrifty growth, with the production of a large number of empty pods; galls are not produced on roots, but the root system is severely stunted and may dry out; most common symptom is the soil-covered egg masses on roots

Yeast Spot

Pale yellow to grayish brown and slightly sunken areas develop on young seeds; sunken spots are light or cream-colored on more mature seeds; pods may also develop small discolored areas where they contact infected seeds; when infection occurs during pod formation, seeds fail to develop and pods drop prematurely

No Distinct Discoloration

Bacillus Seed Decay

Soft decay of seeds; bacterium produces rough or smooth, slimy, glistening colonies on seeds

Bean Pod Mottle

Diseased plants show a mild yellow mottling on young actively growing leaves; as these leaves approach maturity the mottling becomes masked; plants infected with both soybean mosaic and pod mottle are stunted, have distorted foliage, misshapen fruit, and necrotic tissue; seed from plants infected with pod mottle are smaller than normal

Bud Blight

Stunting occurs when young plants are infected; stem terminal will curve, forming a crook which is probably the most distinguishing characteristic; lateral buds become brown and drop off; brown discoloration of stems, beginning at nodes; leaves are dwarfed and curl upward; pods often abort, or are underdeveloped and mature plants have clusters of minute pods; infected plants remain green longer than healthy plants; symptoms often develop first on plants near the edges of a field

Machismo

Pods may be rigid, curved, flat, and then, usually in an upright position, with no beans formed; flowers are smaller and remain closed; first symptoms usually appear about the time of flowering or after pod formation begins