Tomatoes:Diagnostics

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TOMATO PESTS AND NUTRITIONAL DISORDERS


Contents

ACETANILIDES

‘‘‘Acetanilides: ‘‘‘ Tomatoes that are exposed to low concentrations of acetanilides may not appear to have any injury to the plants, but plants that are exposed to high rates are stunted and the leaves become crinkled, cupped and twisted. (Herbicide Damage)


ALFALFA MOSAIC (AMV)

‘‘‘Alfalfa Mosaic (AMV) ‘‘‘ This disease is characterized by terminal leaves that take on a yellow or bronze color and the leaflet veins become dry. Another identifying symptoms is a reddish brown discoloration of the phloem of the main stem, which can be see by scraping the epidermis of the stem near the soil line. The fruit may also exhibit symptoms that include varying degrees of dry spots, both external and internal, and distortion. There are no resistant cultivars available but it is possible to avoid infection by not planting tomatoes near alfalfa. (Disease Caused By Viruses)


ALTERNARIA STEM CANKER (BLACK MOLD) (ALTERNARIA ALTERNATA PV LYCOPERSICI)

‘‘‘Alternaria Stem Canker (Black Mold) (Alternaria alternata pv lycopersici) ‘‘‘ This disease is characterized by dark brown to black cankers in areas of concentric rings that can be found on stems near the soil line or aboveground. The fruit may also exhibit similar concentric rings accompanied by dark brown sunken lesions. The leaves may develop dark brown to black areas of dead tissue between the leaf veins. The best form of control is the use of resistant cultivars. (Disease Caused by Fungi)


AMIDES

‘‘‘Amides: ‘‘‘ Plants that are suffering from amide exposure are stunted, have malformed leaves with a downward and inward curling of the leaves. (Herbicide Damage)


ANTHRACNOSE (COLLETOTRICHUM SPP)

‘‘‘Anthracnose (Colletotrichum spp.) ‘‘‘ This disease is characterized by small, slightly depressed, circular lesions that appear on ripened fruit, although they may have infected the fruit before it began to ripen. The leaves also develop lesions that are small, circular, and brown surrounded by yellow halos. The plants root system becomes extremely damaged by brown lesions and no longer can support the plants needs so it shuts down. The best form of control is to control the weeds in the field, apply fungicide sprays, stake the plants and practice good mulching habits. (Disease Caused by Fungi)


APHIDS (MACROSIPHUM EUPHORBIAE AND MYZUS PERSICAE)

‘‘‘Aphids (Macrosiphum euphorbiae and Myzus persicae) ‘‘‘ Plants that are suffering from aphids have yellow spots, distorted leaves, are stunted, wilt, and the blossoms fall off. The aphids consume more plant juices than they need and excrete the excess as a sugary substance called honeydew resulting in reduced photosynthesis and fruit quality.


ARSENICALS

‘‘‘Arsenicals: ‘‘‘ Plants that have been exposed to arsenicals may have yellow, dry leaves that may take on a purplish cast. (Herbicide Damage)


ASTER YELLOWS

‘‘‘Aster Yellows: ‘‘‘ This disease is characterized by plants that are stunted and stiff. The leaves may turn yellow or purple and the upper leaflets will roll. The best form on control is the use of insecticides. (Disease Caused by Mycoplasmalike Organisms)


BACTERIAL CANKER (CLAVIBACTER MICHIGANENSIS PV MICHIGANENSIS)

‘‘‘Bacterial Canker (Clavibacter michiganensis pv michiganensis) ‘‘‘ The most characteristic symptom of this disease is that the plant will wilt. The leaves may also show characteristic symptoms that include downward turning of the lower leaves and upward curling of leaflet edges that may show drying of the margins of the leaflets. Sometimes that leaves will have pale green to creamy white blister-like spots that have dark, dry rings surrounding the spot. The fruit will develop lesions that have raised brown centers surrounded by an opaque white halo. The best form of control is to use clean seed and equipment and rotating the crop with a nonhost crop. (Disease Caused By Bacteria)


BACTERIAL SOFT ROT (ERWINIA CAROTOVORA PV CAROTOVORA)

‘‘‘Bacterial Soft Rot (Erwinia carotovora pv carotovora) ‘‘‘ This disease is characterized by the development of lesions of the fruit in soft, dark, water-soaked areas of the fruit near the stem scar or a pointed pore. These lesions may also appear as small, sunken, light to dark colored, water-soaked areas associated with injuries and natural openings. Bacterial ooze may flow from the wounds, pores, or breaks in the epidermis and spread all over the entire fruit. The best forms of control include using resistant cultivars, clean seed and soil, avoiding mechanical injuries, applying the appropriate fungicides, and controlling the postharvest environment. (Postharvest Diseases And Disorders Of Tomato Fruit)


BACTERIAL SPECK (PSEUDOMONAS SYRINGAE)

‘‘‘Bacterial Speck (Pseudomonas syringae) ‘‘‘ This disease is characterized by lesions that usually develop on the leaflets but may also affect stems, petioles, peduncles, pedicels, and sepals. The lesions are round and dark brown to black o the leaflets and oval to elongated on the other plant parts. The fruit develops small lesions or specks that are dark and are rarely larger than 1 mm in diameter. The best forms of control include avoiding planting in the same field two successive years, using disease-free transplants, and applying appropriate bactericides where recommended. (Disease Caused By Bacteria)


BACTERIAL SPOT (XANTHOMONAS CAMPESTRIS PV VESICATORIA)

‘‘‘Bacterial Spot (Xanthomonas campestris pv vesicatoria) ‘‘‘ This disease is characterized by brown, circular spots that develop on the leaves, stems, and fruit scars. Fruit lesions begin as small, slightly raised blisters and as a spot increases in size it becomes brown, scablike, and slightly raised. The best form of control is to rotating fields to avoid carryover crop residue, produce disease-free transplants, use seed treatments, and apply bactericides or fungicide-bactericide combinations where recommended. (Disease Caused By Bacteria)


BACTERIAL STEM ROT (ERWINIA CAROTOVORA PV CAROTOVORA)

‘‘‘Bacterial Stem Rot (Erwinia carotovora pv carotovora) ‘‘‘ This disease is characterized by wilting of the plants near the time of harvest. The wilting can occur on the plant for several days. The best form of control is to practice good cultural practices to avoid the disease being spread to healthy plants. (Disease Caused By Bacteria)


BACTERIAL WILT (PSEUDOMONAS SOLANACEARUM)

‘‘‘Bacterial Wilt (Pseudomonas solanacearum) ‘‘‘ This disease is characterized by wilting of the youngest leaves and if the disease progresses, the whole plant will quickly wilt. By suspending a clean section of the diseased stem in water, it is possible to detect this specific disease from other vascular diseases. After 3-5 minutes, a white, milky stream of bacterial cells and slime flow from xylem elements of the infected plant. The best forms of control include crop rotation, applying soil fumigants and using pathogen-free soil. There are only a few cultivars that offer resistance and they should be used when possible. (Disease Caused By Bacteria)


BIPYRIDYLIUMS

‘‘‘Bipyridyliums: ‘‘‘ Under optimum conditions, symptoms occur in a matter of hours and first appear as wilting and water-soaked areas develop where spray droplets have contacted the tissue. These areas darken rapidly becoming dry and desiccated. Contacted tissue dies within 24-48 hours under most conditions which excludes any control measures. (Herbicide Damage)


BLACK MOLD ROT

‘‘‘Black Mold Rot: ‘‘‘ This disease is characterized by lesions that are brown to black on the outside and slightly darkened to black on the inside. These lesions begin as sunken or slightly flattened areas that may or may not have definite margins and attack the center of the fruit. Sometimes the exterior lesions may take on a water-soaked appearance. The best forms of control include using resistant cultivars, clean seed and soil, avoiding mechanical injuries, applying the appropriate fungicides, and controlling the postharvest environment. (Postharvest Diseases And Disorders Of Tomato Fruit)


BLACK ROOT ROT (THIELAVIOPSIS BASICOLA)

‘‘‘Black Root Rot (Thielaviopsis basicola) ‘‘‘ This disease is generally a cool weather disease and causes a breakdown of the cortex and young feeder roots as thick, dark spores accumulate on the tissues. As the spores reproduce, they become resistant to control measures, allowing them to survive for long periods of time. The best form of control is to apply fumigants to the soil.


BLACK SHOULDER

‘‘‘Black Shoulder: ‘‘‘ This disease is characterized by gray spots or close grooves on the shoulders of green fruit. Later these spots develop into larger, irregular, dark gray to black areas surrounding the stem scar. As the fruit ripens, the diseased tissue shrivels and becomes tough. The best form of control is to plant cultivars that are more tolerant to shoulder cracking.


BLOSSOM DROP

‘‘‘Blossom Drop: ‘‘‘ This disease is characterized by the pedicels and calyx becoming yellow after a flower has aborted. The best form of control is to avoid any type of stress to the plant and to follow proper fertilization practices. (Physiological Disorders)


BLOSSOM-END ROT

‘‘‘Blossom-End Rot: ‘‘‘ This disease is characterized by occurring at the blossom end of the fruit as light tan water-soaked lesions. As these lesions grow, they turn black and leathery, and often become overrun with black mold. The best form of control is to use resistant cultivars and practice proper fertilization and water control. (Physiological Disorders)


BORON

‘‘‘Boron: ‘‘‘ Plants that are suffering from boron deficiency have brittle leaves, the lower leaf tips turn yellow and the terminal growing point dries up. The fruit on these plants develop corky areas around the stem end, open locules, and uneven ripening. (Nutritional disorder)


BUCKEYE ROT & PHYTOPHTHORA ROOT ROT (PYTOPHTHORA PARASITICA, CAPSICI, AND DRECHSLERI)

‘‘‘Buckeye Rot & Phytophthora Root Rot (Pytophthora Parasitica, Capsici, and Drechsleri) ‘‘‘ This disease is characterized by a brownish spot that appears where the fruit and soil become in contact with each other. The roots also develop water-soaked lesions that gradually turn dry and dark brown, reducing the vigor of the plant. The best form of control is to use fungicides and avoid planting in fields, with heavy, poorly drained soils. (Disease Caused by Fungi)


CALCIUM

‘‘‘Calcium: ‘‘‘ Plants that are suffering from calcium deficiency have undeveloped leaves at the growing point, yellow and marginal drying in between the veins, and the growing point dies. (Nutritional disorder)


CATFACE

‘‘‘Catface: ‘‘‘ This disease is characterized by large scars and holes in the blossom end of the fruit. The fruit is often in distorted into a variety of shapes with elongated blossom scars. The best form of control is to use resistant cultivars and do not over water the plants. (Physiological Disorders)


CERCOSPORA LEAF MOLD (PSEUDOCERCOSPORA FULIGENA)

‘‘‘Cercospora Leaf Mold (Pseudocercospora fuligena) ‘‘‘ This disease is characterized by small lesions that develop on the young leaflets as indistinct discolorations with no definite margins. No petiole, stem, or fruit symptoms have been observed. The best form of control is to apply fungicides or use resistant cultivars. (Disease Caused by Fungi)


CHARCOAL ROT (MACROPHOMINA PHASEOLINA)

‘‘‘Charcoal Rot (Macrophomina phaseolina) ‘‘‘ This disease is characterized by black, sunken cankers below the first leaf node at the time of emergence. Mature plants that become infected are stunted, may wilt and the lower leaves are often yellow. (Disease Caused by Fungi)


CHILLING INJURY

‘‘‘Chilling Injury: ‘‘‘ Plants that have experienced chilling injury do not ripen regularly and the fruit rarely ripens. The fruit also softens prematurely and has a lot of pits on the surface. The seeds become brown and frequently decay due to the injury. This physiological disorder appears more often on green tomatoes than on ripe tomatoes. There is little that can be done to control the problem because it is difficult to control the field weather. (Physiological Disorders)


CHLORINE

‘‘‘Chlorine: ‘‘‘ Plants that are suffering from chlorine deficiency grow slow, have dry leaf margins and the leaves fall off. (Nutritional disorder)


COPPER

‘‘‘Copper: ‘‘‘ Plants suffering from copper deficiency have young leaves that wilt and become yellow and dry. (Nutritional disorder)


CORKY ROOT ROT (PYRENOCHAETA LYCOPERSICI)

‘‘‘Corky Root Rot (Pyrenochaeta lycopersici) ‘‘‘ This disease is characterized by areas of plants that are unthrifty and not as healthy as the other plants around them. They may also experience interveinal and outside yellowing of the leaves which may fall off prematurely. The root system is also not healthy with small feeder roots, brown lesions, and corky lesions on the bigger roots. The best form of control is to use resistant cultivars and apply soil sterilants before planting. (Disease Caused by Fungi)


CUCUMBER MOSAIC (CMV)

‘‘‘Cucumber Mosaic (CMV) ‘‘‘ This disease is characterized by long, skinny leaf blades and plants that are yellow, bushy and stunted soon after they become established. The fruit on these plants is very small and late to mature if the plant even produces any tomatoes at all. The best form on control is to apply insecticides and mineral oil sprays to the plant. (Disease Caused By Viruses)


CURLY TOP (CTV)

‘‘‘Curly Top (CTV) ‘‘‘ This disease is characterized by immature, dull and wrinkled fruit. The leaves also develop dull, yellow purplish veins and become thickened and crisp and roll upward as the petioles curve downward. Only mature plants that become infected can survive the disease, but those may become yellowed and stunted and have erect terminals. The best form of control is to apply insecticides to prevent leafhoppers from invading the plant and avoid planting near overwintered beets. (Disease Caused By Viruses)


DAMPING-OFF

‘‘‘Damping-Off ‘‘‘ Damping-off affects seedling under cool, wet conditions. Seedlings that are attacked fail to emerge or fall over and die soon after emergence. Soil compaction and poor drainage add to the problem and replanting is necessary. Water management, good seedbed preparation, and the use of fungicides are the best forms of control.

DIDYMELLA STEM ROT (DIDYMELLA LYCOPERSICI)

‘‘‘Didymella Stem Rot (Didymella lycopersici) ‘‘‘ This disease is characterized by a dark brown, sunken lesion, which eventually may girdle the stem just above the soil line. The lower leaves on the plant then turn yellow and the plant wilts. The leaves may also develop lesions the are brown with round rings and the fruit develops lesions on the stem end. The best form of control is to use clean seed and apply fungicides. (Disease Caused by Fungi)


DINITROANILINES

‘‘‘Dinitroanilines: ‘‘‘ Plants that have been exposed to dinitroanilines rarely develop lateral or secondary roots and the established roots are short, thickened and stubby. (Herbicide Damage)


DIPHENYL ETHERS

‘‘‘Diphenyl Ethers: ‘‘‘ Plants that are exposed to diphenyl ethers are extremely stunted, the tissues are burned, and they become dry and crisp. Plants that are exposed to high doses may experience symptoms which include leaf crinkling and marginal leaf curl. Plants that are exposed to lower doses will usually have leaves that are cupped downward. (Herbicide Damage)


DISEASES CAUSED BY VIROIDS

‘‘‘Diseases Caused By Viroids: ‘‘‘ Plants that are exposed to Tomato Bunchy Top Virus stop growing at the terminal branches and the leaves and other foliage are closely bunched together. Plants that are exposed to Tomato Planta Macho Viroid have a quick slowing of growth but the leaves experience increased growth causing them to bend downward causing them to become crinkled and brittle along the veins shortly after the infected strikes. As the disease progresses, the plants begin slowing growing again and develop small, upright, yellow leaves. The leaflets also bend upward along the rachis but very small fruit are produced that have few or no seeds at all. Plants that are exposed to Tomato Apical Stunt Viroid have apical stunting, curling of the leaves and leaflets and the leaves are rugged. As the disesase progresses, the plant has a stunted and bushy appearance with the upper leaflets still small, yellow, and sometimes rolled upward like spoons. There are no control measures at this time for any of these viroid infections.


EARLY BLIGHT (ALTERNARIA SOLANI)

‘‘‘Early Blight (Alternaria solani) ‘‘‘ This disease is characterized by small, dark, slightly sunken stem lesions on seedlings that develop into small brownish black lesions on older foliage. The fruits also exhibit symptoms which include a leathery skin that may be covered with a velvety mass of black spores. The best form of control is to use resistant cultivars and by spraying regularly with fungicides. (Disease Caused by Fungi)


FLEA BEETLES

‘‘‘Flea Beetles: ‘‘‘ These are small beetles, about one sixth of an inch long, that mainly attack seedlings. The may be black, brown, greenish or yellow and leave small holes on the leaves of attacked plants.


FUMIGANTS

‘‘‘Fumigants: ‘‘‘ Plants that have been exposed to fumigants turn yellow very quickly and the plants usually dry up and die shortly after. (Herbicide Damage)


FUSARIUM CROWN AND ROOT ROT (FUSARIUM OXYSPORUM PV RADICIS-LYCOPERSICI)

‘‘‘Fusarium Crown and Root Rot (Fusarium oxysporum pv radicis-lycopersici) ‘‘‘ This disease is characterized by yellowing along the margins of the oldest leaves when the first fruit is nearing maturity. As the disease progresses, the younger leaves are also attacked. The roots are also affected, exhibiting a dry, brown rot of the cortex and xylem. The best form of control is to steam the soil and then apply a heavy application of fungicides that are effective against Fusarium. (Disease Caused by Fungi)


FUSARIUM WILT (FUSARIUM OXYSPORUM PV LYCOPERSICI)

‘‘‘Fusarium Wilt (Fusarium oxysporum pv lycopersici) ‘‘‘ This disease is characterized by drooping and downward curling of the older leaves which turn yellow. Also, seedlings become stunted if infected. Using resistant cultivars is the best form of control. (Disease Caused by Fungi)


GRAY LEAF SPOT (STEMPHYLIUM SPP)

‘‘‘Gray Leaf Spot (Stemphylium spp.) ‘‘‘ This disease is characterized by small, barely visible, brownish black specks that develop on the lower leaves and then the leaves turn brown, die rapidly, and drop. The best form of control is to use resistant cultivars and spray with fungicides. (Disease Caused by Fungi)


GRAY MOLD (BOTRYTIS CINEREA)

‘‘‘Gray Mold (Botrytis cinerea) ‘‘‘ This disease is characterized by fuzzy, gray-brown diseased tissue that develops lesions. The lesions on the leaflets gradually grow and include the entire leaflet, then the petiole, and finally the stem. When the lesions have spread to the fruit, the tomato will have decayed white areas similar to soft rot. The best form of control is to apply appropriate fungicides. (Disease Caused by Fungi)


GRAY MOLD ROT (BOTRYTIS CINEREA)

‘‘‘Gray Mold Rot (Botrytis cinerea) ‘‘‘ This disease is characterized by lesions that develop at the point of contact between the fruit and diseased plant tissues. These lesions begin as gray-green to gray-brown, slightly water-soaked spots located most frequently near the stem end of the tomato and a grayish mold may develop at breaks in the skin or sparsely over the surface of older lesions. The best forms of control include using resistant cultivars, clean seed and soil, avoiding mechanical injuries, applying the appropriate fungicides, and controlling the postharvest environment. (Postharvest Diseases And Disorders Of Tomato Fruit)


GRAYWALL

‘‘‘Graywall: ‘‘‘ This disease is characterized by black to dark brown dry tissue on the walls of the tomato fruit, usually only affecting the outer walls. The disease is sometimes found in the cross walls of the fruit but seldom found in the center of the fruit. Usually this disease is only found on green fruit right before harvest. The best form of control is to use resistant cultivars and to regulate the fertilizer amounts of potassium and nitrogen when susceptible cultivars have been planted.


GROWTH CRACKS

‘‘‘Growth Cracks: ‘‘‘ Plants that have growth cracks either split through the epidermis in circular patterns around the stem scar or split from the stem scar in a pattern that radiates toward the blossom end of the fruit. Usually cracks do not appear until the tomatoes are near maturity. The best forms of control include planting cultivars that are tolerant to cracking practicing good cultural habits. (Physiological Disorders)


HORNWORMS

‘‘‘Hornworms ‘‘‘ Hornworms have a distinctive horn on the rear end. They will completely defoliate a plant leaving only the stems. They may eat some fruit leaving gouged areas where they were eating.


IMIDAZOLINONES

‘‘‘Imidazolinones: ‘‘‘ Plants that are exposed to imidazolinones quit growing, have shortened internodes, and usually are bunched with yellowing and drying tissues. The terminal buds are the first to develop the yellow symptom. (Herbicide Damage)


INTERNAL WHITE TISSUE

‘‘‘Internal White Tissue: ‘‘‘ Plants that suffer from internal white tissue develop white fibers that are spread throughout the pericarp. The most common location of the disease is the development in the outer wall of the fruit where the white strands group together into a solid mass. The best form of control is to ensure proper nutrition, especially with potassium, to reduce the white tissue formation. Also avoiding stress conditions, using tolerant cultivars, and controlling the sweetpotato whitefly can help to reduce the incidence of affected fruit. (Physiological Disorders)


IRON

‘‘‘Iron: ‘‘‘ Plants that are suffering from iron deficiency have areas of yellow between the veins on young leaves. These areas initially develop near the leaf base and gradually progress to the leaf tip. (Nutritional disorder)


LATE BLIGHT (PHYTOPHTHORA INFESTANS)

‘‘‘Late Blight (Phytophthora infestans) ‘‘‘ This disease is characterized by lesions that develop on the leaves that appear water-soaked and may enlarge to pale green to brown lesions that cover large areas on the leaf. As the disease progresses, a ring of moldy growth on the underside of the large brown lesions can be seen. The best form of control is to use fungicide applications. (Disease Caused by Fungi)


LEAF MOLD (FULVIA FULVA)

‘‘‘Leaf Mold (Fulvia fulva) ‘‘‘ This disease is characterized by pale green to yellowish spots located on the upper surface of leaves and will eventually develop into a distinct yellow color. Foliage is generally the only tissue affected leaving other plant parts only occasionally attacked by the fungus. The best form of control is to apply fungicides. (Disease Caused by Fungi)


MAGNESIUM

‘‘‘Magnesium: ‘‘‘ Plants that suffer from magnesium deficiency are characterized by yellowing between the veins of the oldest leaves and gradually moves to the younger leaves. (Nutritional disorder)


MANGANESE

‘‘‘Manganese: ‘‘‘ Plants that suffer from manganese deficiency show yellowing of tissue between the veins on younger leaves and is followed by the development of dry areas between the veins. The leaf veins remain their green color. (Nutritional disorder)


MOLYBDENUM

‘‘‘Molybdenum: ‘‘‘ Plants rarely suffer from molybdenum deficiency but symptoms of the deficiency include yellowing and marginal drying of older leaves that later progresses to the younger leaves. (Nutritional disorder)


NITROGEN

‘‘‘Nitrogen: ‘‘‘ Plants suffering from nitrogen deficiency appear yellow beginning with the youngest leaves and progressing to the older leaves which become yellow and drop off. If too much nitrogen is applied, there will be an excess amount of top growth with little fruit production. (Nutritional disorder)


PHENOXY & SUBSTITUTED BENZOIC ACIDS

‘‘‘Phenoxy and Substituted Benzoic Acids: ‘‘‘ This condition is characterized by light to moderate crinkling of young leaves with increased growth of the older leaves. Growth of the plant may temporarily stop for 1-2 weeks. If the plant is exposed to high concentrations, it may cause the plant to stop growing for a considerable amount of time and become distorted. The leaves may continue to grow creating a thickening and increased brittleness of stems and petioles, and the formation of adventitious roots. (Herbicide Damage)


PHENYLUREAS

‘‘‘Phenylureas: ‘‘‘ Plants exposed to phenylureas have yellow leaf veins that may spread to yellowing of the tissue between the veins. Generally the older leaves are most affected and leaf tip dieback is usually associated with the disease. (Herbicide Damage)


PHOMA ROT (PHOMA DESTRUCTIVA)

‘‘‘Phoma Rot (Phoma destructiva) ‘‘‘ This disease is characterized by small black spots that appear on both leaf surfaces which develop into dark, elongated lesions with faint round rings that develop on the stems. The fungus enters green or ripe fruit through growth cracks, stem scars, mechanical injuries, and occasionally insect punctures. Invaded injured fruit develops dark brown to black sunken spots. The best form of control is to apply registered pesticides. (Disease Caused by Fungi)


PHOSPHONO AMINO ACIDS

‘‘‘Phosphono Amino Acids: ‘‘‘ This disease is characterized by plants that may die due to temporary growth stoppage, drying, wilting, crinkling and cupping of foliage, and leaf spotting. Lethal doses of phosphono amino acids produce yellowing of terminals with symptoms slowly extending from the apical to the basal portions of plants. (Herbicide Damage)


PHOSPHORUS

‘‘‘Phosphorus: ‘‘‘ Plants that are suffering from phosphorus deficiency have a purple color on the undersides of the leaves in the veins and gradually extends out to the interveinal areas. The growth on the plant may have stopped giving it a dwarfed appearance and the upper leaves may take on a dull or light green to yellow coloration. (Nutritional disorder)


POTASSIUM

‘‘‘Potassium: ‘‘‘ Plants suffering from potassium deficiency usually have marginal drying of older leaves. The drying is preceded by scattered small, yellow areas near the leaf margin, which enlarge, group together, and finally dry out. (Nutritional disorder)


POTATO VIRUS Y (PVY)

‘‘‘Potato Virus Y (PVY) ‘‘‘ This disease is characterized by slight spotting and distortion and dark green bands in the main veins. The terminal leaflets may show severe drying, and in many cases all leaflets are affected by curved petioles and leaves that are rolled downward giving the plants a drooping appearance. There are no fruit symptoms known and no resistant cultivars are available. The best form of control is to avoid planting in areas where tomato or pepper crops were previously planted, plant in areas that will not support aphid populations, and spray the plants with mineral oil. This disease affects tomato, tobacco and pepper plants. (Disease Caused By Viruses)


POWDERY MILDEW (LEVEILLULA TAURICA)

‘‘‘Powdery Mildew (Leveillula taurica) ‘‘‘ This disease is characterized by light green to bright yellow lesions that develop on the upper surface of the leaves. Leaves that are severely infected may die but generally will not drop from the plant. The best form of control is to apply fungicides. (Disease Caused by Fungi)


PUFFINESS

‘‘‘Puffiness: ‘‘‘ Puffiness is characterized by fruit that appears slab-sided or angular and is less dense than normal fruit. The best form of control is the use of tolerant cultivars and proper nutrition. (Physiological Disorders)


PYRIDAZINONES & PYRIDINONES

‘‘‘Pyridazinones and Pyridinones: ‘‘‘ Plants that have been exposed to the herbicides develop a bleached appearance within 1 week of exposure. The plants will also eventually become completely yellow due to the lack of chlorophyll in the plant. (Herbicide Damage)


PYTHIUM DISEASES (PYTHIUM SPP)

‘‘‘Pythium Diseases (Pythium spp.) ‘‘‘ Plants that have been attacked with pythium diseases develop dark brown or black water-soaked lesions very early and inhibits the germination of the seedling. If established plants become exposed, dark, water-soaked lesions begin to develop of the root and eventually moves up the stem near the soil line. The best form of control includes the use of fungicides and clean cultural practices. (Disease Caused by Fungi)


PYTHIUM RIPE FRUIT ROT (PYTHIUM ULTIMUM)

‘‘‘Pythium Ripe Fruit Rot (Pythium ultimum) ‘‘‘ This disease only occurs on ripe fruit that is near moist soil. The fruit touching the soil is soft and watery, but the proper color of fruit remains. Often the skin will break and the contents of the fruit will leak out. The best form of control is proper water management and keeping fruit away from direct contact with water.


RAIN CHECK

‘‘‘Rain Check: ‘‘‘ Rain check is characterized by numerous tiny concentric cracks that develop on the shoulder of the tomato fruit and sometimes they group together into larger cracks. The cracks feel rough or ridgy to the touch. The affected area can become leathery and remain green when the fruit ripens, or it can become blackish. Rain check is often seen under dead leaves sticking to the fruit or near adjacent flowers that have not set. The best form of control is to use tolerant cultivars and use cultural practices that reduce fruit exposure to the problem. (Physiological Disorders)


RHIZOCTONIA DISEASES (RHIZOCTONIA SOLANI)

‘‘‘Rhizoctonia Diseases (Rhizoctonia solani) ‘‘‘ This disease is characterized by seedlings that may fail to germinate or established plants that develop a fungus near the soil line with a brown, reddish brown or black lesion. The best forms of control include using good quality seed, fungicide applications, and chemical or heat pasteurized planting medium. The best way to prevent fruit rot losses is to prevent direct contact of the fruit with the soil under warm, moist conditions. (Disease Caused by Fungi)


RHIZOCTONIA FRUIT ROT (RHIZOCTONIA SOLANI)

‘‘‘Rhizoctonia Fruit Rot (Rhizoctonia solani) ‘‘‘ This disease attacks the fruit while they are still green. Rusty colored spots appear on the fruit surface that is closest to the soil. As the spots enlarge, they become dark and sunken and eventually cover much of the fruit. These lesions are firm at first, but may eventually develop star shaped cracks in the fruit and produce a watery decay.


RHIZOPUS ROT (RHIZOPUS STOLONIFER)

‘‘‘Rhizopus Rot (Rhizopus stolonifer) ‘‘‘ This disease is characterized by lesions that rapidly enlarge and water-soaked areas that are located adjacent to wounds, stem scars, or open stylar pores. The lesions are soft and somewhat watery but usually have structure due to coarse, threadlike strands of mycelia, which branch out through the fruit tissues. The odor of Rhizopus rot is similar to that of eggs. The best forms of control include using resistant cultivars, clean seed and soil, avoiding mechanical injuries, applying the appropriate fungicides, and controlling the postharvest environment. (Postharvest Diseases And Disorders Of Tomato Fruit)


ROOT-KNOT NEMATODES (MELOIDOGYNE SPP)

‘‘‘Root-Knot Nematodes (Meloidogyne spp.) ‘‘‘ Plants that are suffering from root-knot nematodes are often wilted and lack nutrition because the normal transfer of substances from roots to the plant top is restricted. In the field, galled roots may be invaded by microorganisms, causing more drastic damage than root knot alone. The best forms of control include using resistant cultivars when available and rotating the crop with grasses and other monocots allowing a clean fallow during the off-season to decrease the root-knot nematode populations. (Disease Caused By Nematodes)


SEPTORIA LEAF SPOT (SEPTORIA LYCOPERSICI)

‘‘‘Septoria Leaf Spot (Septoria lycopersici) ‘‘‘ This disease is characterized by lesions that develop on the lower leaves, stems, petioles and calyx after the first fruit sets on the plant. Plants that have numerous lesions may turn slightly yellow and brown and then wither. The best form of control is using protective fungicide sprays and a rotating for at least 1-2 years between tomato crops. (Disease Caused by Fungi)


SOUR ROT (GEOTRICHUM CANDIDUM AND PENICILLATUM)

‘‘‘Sour Rot (Geotrichum candidum and Penicillatum) ‘‘‘ This disease is characterized by greasy, water-soaked lesions at wounds or at the edge of the stem scar in green and ripe fruit. In green fruit, the lesions remain firm until the disease is well advanced, and then they may emit a lactic acid odor. In ripe fruit, the disease progresses rapidly, particularly under warm conditions, and the epidermis covering the lesions usually cracks, allowing the watery contents to spill out. The best forms of control include using resistant cultivars, clean seed and soil, avoiding mechanical injuries, applying the appropriate fungicides, and controlling the postharvest environment. (Postharvest Diseases And Disorders Of Tomato Fruit)


SOUTHERN BLIGHT (SCLEROTIUM ROLFSII)

‘‘‘Southern Blight (Sclerotium rolfsii) ‘‘‘ This disease is characterized by a brown to black rot of the stem, which develops near the soil line. The lesions develop rapidly, completely girdling the stem and resulting in a sudden and permanent wilt of all aboveground parts. The best forms of control include crop rotations with nonsusceptible grass crops and the use of protective fungicides. (Disease Caused by Fungi)


SPIDER MITES (TETRANYCHUS SPP)

‘‘‘Spider Mites (Tetranychus spp.) ‘‘‘ Plants that have been attacked by spider mites have small, yellow spots on the upper surfaces of leaves where the mites have been feeding. The lower surfaces of the leaves are covered with silken threads which is a characteristic symptom. As the population density of the mites increase, they move to the top leaves, where they produce large amounts of silk webbing.


SPIDER TRACK

‘‘‘Spider Track: ‘‘‘ This disease is characterized by brown, dry scars that radiate from the stem scar but do not always connect with it. In addition, rays of off-colored epidermal tissue may extend from the stem scar. In green-shouldered fruit, the rays are generally lighter in color. The best form of control is to use resistant cultivars. (Physiological Disorders)


STING NEMATODE (BELONOLAIMUS SPP)

‘‘‘Sting Nematode (Belonolaimus spp.) ‘‘‘ This disease is characterized by plants that become stunted only 6-7 weeks after planting and the stem tip becomes yellow. The best form of control is the use of steam, solarization and soil fumigants. Also, proper cultivating practices, maintenance of high water tables and soil desiccation help control the nematode. (Disease Caused By Nematodes)


STUBBY-ROOT NEMATODES (PARATRICHODORUS AND TRICHODORUS SPP)

‘‘‘Stubby-Root Nematodes (Paratrichodorus and Trichodorus spp.) ‘‘‘ This disease is characterized by roots that are crisp and fragile, the growth in inhibited and have weak root tips which interferes with the roots spreading normally. The roots may discolor during active growth of the plant, but fortunately there is little loss in the efficiency of the root. This disease is difficult to control because of the wide range of hosts that carry the disease, but participating in a crop management system and minimizing the stress on the plant from other factors are the best forms of controlling the disease. (Disease Caused By Nematodes)


SULFUR

‘‘‘Sulfur: ‘‘‘ Plants suffering from sulfur deficiency initially have light green younger leaves and as the deficiency progresses the older leaves also turn light green. (Nutritional disorder)


SUNSCALD

‘‘‘Sunscald: ‘‘‘ Sunscald affects mature green and breaker tomatoes and develops white dry tissue on the fruit surrounded by a yellow halo. The damage is generally on the side or top half of the tomato and occurs when the fruit that has been covered by leaves is suddenly exposed to sunlight. The best form of control is to prune and harvest carefully and use a good foliar-disease control program. (Physiological Disorders)


SYRINGAE LEAF SPOT (PSEUDOMONAS SYRINGAE PV SYRINGAE)

‘‘‘Syringae Leaf Spot (Pseudomonas syringae pv syringae) ‘‘‘ This disease is characterized by either small brown lesions that do not develop halos or dark black lesions that have a bright yellow halo. This disease is favored by high humidity and wounding. The best form of control is weekly applications of bactericides. (Disease Caused By Bacteria)


TARGET SPOT (CORYNESPORA CASSIICOLA)

‘‘‘Target Spot (Corynespora cassiicola) ‘‘‘ This disease is characterized by small, pinpoint, water-soaked lesions that first appear on the upper surface of the leaves, petioles and stems. The fruit also develops lesions that first appear as dark, sunken, pinpoint, brown spots. The best form of control is to use protective fungicides. (Disease Caused by Fungi)


THIOCARBAMATES

‘‘‘Thiocarbamates: ‘‘‘ Plants exposed to thoicarbamates may be mildly or severely stunted and the leaves may be twisted, and cupped inward and upward depending on the amount of exposure. The foliage may also develop a crinkled appearance with dry margins. (Herbicide Damage)


THRIPS

‘‘‘Thrips: ‘‘‘ Plants that are infected with thrips have damaged tissue that initially appears silvery but may turn dry or black and flower parts, particularly the pistils, become damaged and may cause bloom abscission. It must be noted that bloom abscission is associated with a number of nutritional, environmental and physiological disorders and that it is not singly associated with thrips.


TOBACCO ETCH (TEV)

‘‘‘Tobacco Etch (TEV) ‘‘‘ This disease is characterized by intense spotting, puckering, and rugosity of the leaves and plants that are severely stunted at an early age. Infected fruit is spotted, never achieves marketable size, and must be discarded as culls. The best form of control is to avoid planting where peppers have been grown and apply mineral oils weekly which can greatly reduce the rate of virus spread. (Disease Caused By Viruses)


TOMATO BIG BUD

‘‘‘Tomato Big Bud: ‘‘‘ This disease is characterized by thick, apical stems that are stiff and grow directly upward. The leaves are small, distorted and yellowish green. Internodes are shortened, and flower buds are greatly enlarged and imperfectly developed. Fruit that is immature when it becomes infected is deformed. The best form of control is to apply insecticides to control leafhoppers and destroy weed hosts on the borders of the tomato crop. (Disease Caused by Mycoplasmalike Organisms)



TOMATO BUSHY STUNT (TBSV)

‘‘‘Tomato Bushy Stunt (TBSV) ‘‘‘ When tomato seedlings are inoculated, the first symptoms appear as dry, circular local lesions 5 days after infection. These leaves become yellow and frequently drop off. Systemic symptoms consist of twisting of the youngest leaves and top drying, which causes proliferation of lateral shoots and leads to a bushy appearance. Lower leaves on such plants show general yellowing and purple discoloration. Fruit symptoms consist of yellow blotching and ring and line patterns on ripened fruit. No control measures have been developed. (Disease Caused By Viruses)


TOMATO DECLINE

‘‘‘Tomato Decline ‘‘‘ Tomato decline causes stunting, droopy petiole and leaves to curl on young foliage. Older leaves may have brown edges and yellow between the veins. These leaves will roll up, become brittle, and die. Root systems are also affected. The best form of control is not to plant tomatoes more than two seasons on the same ground.


TOMATO MOSAIC & TOBACCO MOSAIC (TOMV AND TMV)

‘‘‘Tomato Mosaic and Tobacco Mosaic (TOMV and TMV) ‘‘‘ The most characteristic symptoms of the disease caused by common strains are mottled areas of light and dark green of the leaves. Leaves may also be curled, reduced in size, and malformed. Fruit may show uneven ripening and be reduced in size and number. Fruit may develop a symptom referred to as internal browning or brownwall. Seedlings should not be transplanted into fields where root debris is present. Resistant cultivars, should be used, when applicable. (Disease Caused By Viruses)


TOMATO NECROTIC DWARF

‘‘‘Tomato Necrotic Dwarf ‘‘‘ This virus is transmitted by whiteflies and causes plants to become compact, rounded, and appear brownish green. If flowers develop, they quickly die and drop off the plant and no fruit is formed. Remove any plants containing the virus and plant resistant cultivars.


TOMATO PITH NECROSIS (PSEUDOMONAS CORRUGATA)

‘‘‘Tomato Pith Necrosis (Pseudomonas corrugata) ‘‘‘ This disease is characterized by yellowing of the young leaves and gray to brown lesions on the surface of infected stems. These are the initial symptoms and since the disease does not progress, these symptoms may go unnoticed until considerable damage has been done to the plant. The best forms of control include avoiding excessive nitrogen and high humidity where feasible. (Disease Caused By Bacteria)


TOMATO POX

‘‘‘Tomato Pox ‘‘‘ Tomato pox is a genetic disorder causing dark green spots to develop on small green fruit. As the fruit ripens, the spots become gold and split open, exposing the fruit to other decay causing organisms.


TOMATO RUSSET MITE (ACULOPS LYCOPERSICI)

‘‘‘Tomato Russet Mite (Aculops lycopersici) ‘‘‘ Plants that have been exposed to mites have infected undersides of the lower leaves causing them to become silvery and yellow and then dry. As the infestation spreads, the stems and leaf petioles appear bronzed and the lower foliage dries up. If the population if unchecked, symptoms progress toward the tops of plants until all the foliage turns brown and dries up.


TOMATO SPOTTED WILT (TSWV)

‘‘‘Tomato Spotted Wilt (TSWV) ‘‘‘ Symptoms of spotted wilt vary, but young leaves usually turn bronze and later develop numerous small, dark spots. Affected plants may have a one-sided growth habit or may be entirely stunted and have drooping leaves, suggesting a wilt. Plants infected early in the season may produce not fruit, and those infected after fruit-set produce fruit with yellow ring spots. Because of the wide host range of this virus and its presence in perennial ornamentals and weeds, it is extremely difficult to eliminate the disease. The use of reflective mulches under tomatoes may reduce but not eliminate losses. Use resistant cultivars when available. (Disease Caused By Viruses)


TOMATO YELLOW LEAF CURL (TYLCV)

‘‘‘Tomato Yellow Leaf Curl (TYLCV) ‘‘‘ Tomato plants infected at an early age are severely stunted. Leaves that develop soon after infection are cupped downward, whereas leaves developing later are prominently yellow and deformed, with leaf margins curling upward. This disease certainly affects the plants ability to produce marketable fruit. Applications of insecticides with mineral oil sprays may reduce the incidence of this disease. Use healthy transplants. Use resistant cultivars when available. (Disease Caused By Viruses)


TOMATO YELLOW TOP (TYTV)

‘‘‘Tomato Yellow Top (TYTV) ‘‘‘ This disease is characterized by interveinal and marginal yellowing and downward leaf rolling on the young terminal shoots. Established plants that become infected have yellow, mature, rugged leaves that are leathery in texture and may begin to roll. Purplish discoloration appear on the stems and branches and the fruit is deformed, with ribbiness on the shoulders and a puffy appearance. The best form of control is to use resistant cultivars is available, use mineral oil sprays to reduce the spread of the virus, use insecticides to eliminate aphid populations, and destroy weed reservoirs located near the crops. (Disease Caused By Viruses)


TRIAZINES

‘‘‘Triazines: ‘‘‘ Plants that have been exposed to triazine herbicides develop yellowing in the leaf veins which spreads to the interveinal areas and the whole plant becomes dry and brittle. (Herbicide Damage)


TRUE BUGS

‘‘‘True Bugs: ‘‘‘ Plants that are infected with true bugs have infected fruit that is usually attacked when it is small and the damage appears as small pinpricks surrounded by white, corky tissue below the epidermis. This tissue remains firm and turns yellow as the fruit ripens.


URACILS

‘‘‘Uracils: ‘‘‘ Plants that have been exposed to uracils have leaves which develop yellow veins which may spread to the interveinal tissues and dry out. (Herbicide Damage)


VERTICILLIUM WILT (VERTICILLIUM ALBO ATRUM AND DAHLIAE)

‘‘‘Verticillium Wilt (Verticillium albo-atrum and dahliae) ‘‘‘ This disease is characterize by plants that show mild to moderate wilting during the warmest part of the day but recover at night. The best form of control is to use resistant cultivars and steam sterilization and fumigation of the soils. (Disease Caused by Fungi)


WATER WILT

‘‘‘Water Wilt: ‘‘‘ This disease is characterized by wilting of the plant which may develop yellow and dry areas and the stems collapse due to the waterlogged conditions. Although these symptoms appear similar to those of bacterial wilt, there is no discoloration of the vascular system. The best form of control is to make sure that the fields are well drained and cultivated as soon as possible after a heavy rain to break water tension in the soil. (Physiological Disorders)


WHITE MOLD (SCLEROTINIA SCLEROTIORUM)

‘‘‘White Mold (Sclerotinia sclerotiorum) ‘‘‘ This disease is characterized by a white cottony mycelium on the stems in cool, moist weather. The infection usually begins in leaf axils or in stem joints where flower petals have fallen and lodged and the fungus may also enter plants at the soil line. Fruit that has been infected is gray and rapidly breaks down in a watery rot. The best form of control includes applying fungicides and fumigants. Full-bed plastic mulch is commonly used in the culture of fresh-market tomatoes. (Disease Caused by Fungi)


WHITEFLIES (TRIALEURODES VAPORARIORUM AND BEMISIA TABACI)

‘‘‘Whiteflies (Trialeurodes vaporariorum and Bemisia tabaci) ‘‘‘ Plants that are infected with whiteflies develop yellow spots, yellowing of the leaves, spots on the fruit and stunting and wilting of plants. The aphids consume more plant juices than they need and excrete the excess as a sugary substance called honeydew resulting in reduced photosynthesis and fruit quality. The damage is inflicted by whiteflies that consume more plant juices than they need and excrete the excess as a sugary substance called honeydew resulting in reduced photosynthesis and fruit quality.


YELLOW TOP, PERSISTENT GREEN SHOULDER (YELLOW SHOULDER)

‘‘‘(Yellow Top, Persistent Green Shoulder) (Yellow Shoulder) ‘‘‘ This disease is characterized by fruit that has green or yellow shoulders but they never turn red. The best form of control is to use resistant cultivars and have good cultural practices. (Physiological Disorders)


ZINC

‘‘‘Zinc: ‘‘‘ Plants suffering from zinc deficiency have thick leaves that curl downward and faint interveinal yellowing. (Nutritional disorder)


ZIPPERING

‘‘‘Zippering: ‘‘‘ This disease is characterized by thin, brown, dry scars, which start at the stem scar and extend part or all of the way to the blossom end. The best form of control is to use tolerant cultivars and maintain proper temperatures when growing under greenhouse conditions. (Physiological Disorders)