Pit Fruits:Diagnostics

PIT FRUIT PESTS AND NUTRITIONAL DISORDERS

ALTERNARIA ROT AND RED SPOT FRUIT BLEMISH (ALTERNARIA ALTERNATA)

‘‘‘Alternaria Rot and Red Spot Fruit Blemish (Alternaria alternata) ‘‘‘ Alternaria rot is characterized by circular, dry, firm, shallow lesions covered with dark, olive green to black surface mycelial growth. The infected tissue is brown and the firm decayed portion can be removed easily from the healthy part of the fruit. Alternaria rot commonly develops near insect feeding injuries or in split pits of fruit. After harvest, established infections can continue to progress in fruit held under cold storage. The best form of control is to hand sort infected fruit before packing, rinse contaminated fruit in chlorinated water, and applying a postharvest application of iprodione to the tree. (Disease Caused by Fungi -- Fruit Disease)

ANTHRACNOSE (COLLETOTRICHUM GLOEOSPORIOIDES AND ACUTATUM)

‘‘‘Anthracnose (Colletotrichum gloeosporioides and acutatum) ‘‘‘ Anthracnose on peach, plum, and sour cherry fruit is characterized by circular, tan to brown dry lesions with concentric rings. Orange spore masses often occur in the center. Lesions enlarge rapidly and generally occur in ripe or nearly ripe fruit. The best form of control is to apply captan, a registered fungicide and to keep the orchard floor clean of any infected material. (Disease Caused by Fungi -- Fruit Disease)

APPLE CHLOROTIC LEAF SPOT (ACLV)

‘‘‘Apple Chlorotic Leaf Spot Virus (ACLV) ‘‘‘ This disease is characterized by fruit symptoms resembling apricot ring pox in apricot and plum and fruit distortion may occur in cherries. Leaf symptoms of dark green, sunken spots can develop but usually there are no foliage symptoms. The best form of control is touse virus-free understocks and budwood. (Diseases Caused by Viruses and Viruslike Agents -- Spread by Grafting)

APRICOT GUMBOIL

‘‘‘Apricot Gumboil: ‘‘‘ Severely affected trees are usually at least 10 years old, smaller, exhibit shoot dieback and less overall vegetative growth than healthy trees. The trunk and scaffold branches appear rough with bark cracks. Pockets of dry tissues and accumulations of dark-colored gum (named gumboil) are present in inner bark tissues and gum pockets extend into the xylem tissues of branches more than three years old. (Genetic and Physiological Disorders)

APRICOT RING POX

‘‘‘Apricot Ring Pox and Cherry Twisted Leaf: ‘‘‘ In apricot, the first leaves develop without symptoms. Veinbanding, yellow spots, streaks, and rings develop on later-emerging leaves and increase in severity during the growing season. In midsummer, many of the spots and rings become dry and drop off, giving a shot-hole appearance. Another diagnostic symptom consists of dark purple discoloration of short sections approximately 1-3 mm of at least a few petioles in affected trees and similar dark red spots can appear on current season twigs. The most typical diagnostic feature of ring pox are the black pox or concentric rings, which can extend deep into the flesh, reaching as far as the seed but not affecting the seed coat. Immediate removal of infected orchard trees and use of virus-free nursery stock are recommended. (Diseases Caused by Viruses and Viruslike Agents -- Spread by Grafting)

ARMILLARIA AND CLITOCYBE CROWN ROTS (ARMILLARIA MELLEA AND TABESCENS)

‘‘‘Armillaria and Clitocybe Root and Crown Rots (Armillaria mellea and tabescens) ‘‘‘ Trees infected that are at least five years old often exhibit poor terminal growth and small leaves. Another symptom is sudden collapse of trees in midsummer, rather than a gradual yellowing of leaves followed by defoliation. A fan-shaped, white fungal mat often is present between the bark and the wood on the crown of affected trees. Dark brown to black threadlike rhizomorphs may be observed on the surface of the bark. Rhizomorphs are about the size of a shoestring and are found on the surface of live roots before the tissues dry out, on dead roots, and in the soil around the roots of infected trees. Fumigation has been only moderately effective in controlling the disease, because the fungus can survive deep in the soil and in roots that are not easily permeated by chemical vapors. (Disease Caused by Fungi -- Cankers, Blights, and Wood Rots)

BACTERIAL CANKER (PSEUDOMONAS SYRINGAE PV SYRINGAE AND SYRINGAE PV MORSPRUNORUM)

‘‘‘Bacterial Canker (Pseudomonas syringae pv syringae and syringae pv morsprunorum) ‘‘‘ Cankers, the most characteristic symptom, may not appear on some hosts. Cankers develop on twigs at the base of flower and leaf buds, in pruning wounds including those made during removal of suckers, and at the base of infected spurs. Cankers generally spread upward, and the infected, sunken areas are usually formed in late winter or early spring. Gum often exudes from cankers, especially early in the growing season. Terminal shoots or twigs of cankered trees may die back and if girdled by a canker, the diseased lateral branch or trunk dies within weeks. Infected buds often are killed. Leaves from these buds wilt, and fruit tends to dry out. Major outbreaks of bacterial canker in young orchards often are attributed to poor cultural practices, which account for the best control of the disease. (Disease Caused by Bacteria)

BACTERIAL DECLINE (PSEUDOMONAS SYRINGAE PV PERSICAE)

‘‘‘Bacterial Decline (Pseudomonas syringae pv persicae) ‘‘‘ Dieback of shoots occur in autumn, on the current season's growth, and in spring, following the development of girdling lesions from nodal infections. Small, elliptical lesions may develop at internodes. In spring and early summer, wilting of flowers and leaves on branches or on entire trees indicates the development of extensive drying in the main leaders or trunk. No completely satisfactory control program has been developed. (Disease Caused by Bacteria)

BACTERIAL SPOT (XANTHOMONAS CAMPESTRIS PV PRUNI)

‘‘‘Bacterial Spot (Xanthomonas campestris pv pruni) ‘‘‘ Bacterial spot occurs on leaves, twigs, and fruit. Leaf symptoms are first visible as angular, grayish, water-soaked lesions, often located along the midrib, leaf tip, or both, or along the leaf margin. As the lesions age and enlarge to several millimeters in diameter, lesion centers become purple and dry. Visible about the time of leaf emergence, spring cankers appear as slightly raised, blisterlike areas that can extend several centimeters along the twig. The terminal bud usually fails to open, and a dark cankered area, completely surrounding the twig, can extend several downward from the top. Fruit symptoms first are visible about 3 to 5 weeks after petal fall as small, water-soaked, brownish lesions. Successful chemical control may depend highly on timing of applications. Chemical sprays applied at bloom and for several weeks after bloom have reduced the amount of diseased fruit at harvest. (Disease Caused by Bacteria)

BLACK KNOT (APIOSPORINA MORBOSA)

‘‘‘Black Knot (Apiosporina morbosa) ‘‘‘ The disease affects only woody parts of trees, primarily twigs, and is characterized by elongated swellings 1.5-30 cm long and 2.5-7.5 cm in circumference. The knots seldom surround the entire limb, but numerous infections on twigs or small branches may cause general decline in growth and lead to loss of branches and tree death after a few years. When first formed, knots are olive green and firm but rather corky. Later, they turn black and become hard and brittle. The best forms of control include using resistant cultivars, applying fungicides, and removing infected trees from orchard sites. (Disease Caused by Fungi -- Cankers, Blights, and Wood Rots)

BLOSSOM END ROT OF PEACHES

‘‘‘Blossom-End Rot</b></S></CF> Blossom end rot causes deterioration of the distal ends of canning peaches. In severe cases, the rotting can cover the entire surface.

BOTRYOSPHAERIA FRUIT ROT ON PEACHES (BOTRYOSPHAERIA SPP)

‘‘‘Botryosphaeria Fruit Rot (Botryosphaeria spp) </b></S></CF> Peaches infected with this disease develop brown to black, sunken lesions which causes the surface to be firm and leathery. Young peaches that are attacked may appear bruised and diseased tissue may become thickened and darker in color.

BROWN ROT (MONILINIA SPP)

‘‘‘Brown Rot (Monilinia spp.) ‘‘‘ Typical disease symptoms include blossom and twig blight. On peach, the first symptom of blossom blight is drying of the anthers. As infected flowers wilt and turn brown, they often become affixed to the twig in a gummy mass. Apricot is most susceptible to blossom blight, followed in order by prune, sweet cherry, peach, sour cherry, and plum. Symptoms appear first on sepals, then on petals, anthers, and stigmata as the blossoms open. Brown rot on ripening or mature fruit typically develops as a rapidly spreading, firm, brown decay. Protective fungicidal treatments provide the best control for both blossom and fruit rot. (Disease Caused by Fungi -- Fruit Disease)

CERATOCYSTIS CANKER (CERATOCYSTIS FIMBRIATA)

‘‘‘Ceratocystis Canker (Ceratocystis fimbriata) ‘‘‘ Diseased bark becomes water-soaked, darkened, sunken and amber colored gum commonly is released from the canker margin. Removal of the loosened bark of a recently infected wound often reveals the whitish mycelium of the pathogen on the exposed cambium. Since most injuries that lead to infection result from mechanical harvesting, shakers that cause minimal damage should be used. Irrigation should be avoided during the three weeks preceding harvest and severely cankered or dead limbs should be removed. (Disease Caused by Fungi -- Cankers, Blights, and Wood Rots)

CEROSPORA LEAF SPOT (CERCOSPORA CIRCUMSCISSA)

‘‘‘Cercospora Leaf Spot (Cercospora circumscissa) ‘‘‘ Lesions of Cercospora leaf spot disease appear as round dry spots that are reddish brown at first and later the central portion becomes light brown with brownish red edges. Lesions may group together to form large dry areas and can develop on both leaf surfaces. The disease causes early defoliation, and severely affected trees may be completely defoliated by the beginning of summer. The best form of control is to apply fungicides and to remove infected material in the orchard. (Disease Caused by Fungi -- Foliar Disease)

CHERRY ALBINO

‘‘‘Cherry Albino</b></S></CF> This disease is similar to the X-disease in peach trees, however, it only attacks cherries. It is spread through MLOs but has not been found on crops of recent years.

CHERRY BLACK CANKER

‘‘‘Cherry Black Canker</b></S></CF> This disease is of minor importance because of its limited occurrence. Rough black cankers develop on the scaffold limbs and branches creating a swelling that splits open to form thickened wounds. Trees infected with the virus will die. No fruit or leaf symptoms of the disease have been identified.

CHERRY BLOSSOM ANOMALY

‘‘‘Cherry Blossom Anomaly: ‘‘‘ Symptoms first appear at bloom time as varying amounts of green along the veins and midribs in the normally white petals. The amount of green coloration varies from narrow streaks to broad bands covering entire petals. In some instances, the entire flower bud assumes a leaf-like appearance except for the yellow anthers in the center. In some flowers, a few of the anthers differentiate into wide, white, petal-like structures with green centers. In others, the entire stamen resembles a narrow petal. (Disease Caused by Mycoplasmalike Organisms)

CHERRY CRINKLE LEAF

‘‘‘Sweet, Cherry Crinkle Leaf and Deep Suture Disorders: ‘‘‘ Leaves of trees affected by crinkle leaf are misshapen, with irregularly indented, coarsely serrated margins. In addition, the leaves develop yellow or light green patches along the leaf margins. Affected trees produce defective blossoms, and the fruit are small, misshapen, and pointed, with a raised suture. The best form of control is to use clean propagative materials. (Genetic and Physiological Disorders)

CHERRY LEAF SPOT (BLUMERIELLA JAAPII)

‘‘‘Cherry Leaf Spot (Blumeriella jaapii) ‘‘‘ On leaves, lesions first appear as small reddish to purple spots on the upper surface that are 3 mm or less in diameter. Although affected leaves turn yellow or brown, the area around the lesions may remain green, particularly on sour cherry, giving the leaves a spotted appearance. Fruit on severely defoliated trees fail to mature normally and are light colored, low in soluble solids, soft, and watery. They may be smaller or larger than normal, depending on time and severity of defoliation. Cherry leaf spot is controlled by fungicides. Applications should begin at petal fall, after the first leaves have unfolded, and at 7 to 10 day intervals to harvest, plus a postharvest application two to three weeks after harvest. (Disease Caused by Fungi -- Foliar Disease)

CHERRY MOTTLE LEAF (CMLV)

‘‘‘Cherry Mottle Leaf Virus (CMLV) ‘‘‘ Characteristic symptoms on most cherry cultivars consist of light green or whitish, diffuse discoloration between the secondary leaf veins. The transition from yellow to healthy green tissue tends to be gradual and affected leaves often develop an irregular shape. During the early part of the growing season, the outline of leaves can be severely affected, to the extent that the margin may appear shredded. The best form of control is to use of virus-free certified understock and budwood. (Diseases Caused by Viruses and Viruslike Agents -- Spread by Insects, Mites, and Nematodes)

CHERRY NECROTIC RUSTY

‘‘‘Cherry Necrotic Rusty-Mottle, Lambert Mottle, and Frogmore Virus Canker: ‘‘‘ In affected cherry trees, brown, angular dry spots appear on the leaves three to six weeks after full bloom. The dry areas either dehisce or continue to expand until most of the leaf is affected. At this point, the leaves tend to turn yellow along the veins and leaf abscission can occur. The best form of control is to use virus-free budwood and understocks and remove any infected material in orchards. (Diseases Caused by Viruses and Viruslike Agents -- Spread by Grafting)

CHERRY RASP LEAF (CRLV)

‘‘‘Cherry Rasp Leaf Virus (CRLV) ‘‘‘ In cherry, leaf-like projections (enations) develop along the midrib on the underside of affected leaves and in severe cases, the whole leaf can be affected. Disease symptoms are initially restricted to the lower branches and limbs of mature trees because the virus is introduced into the roots. The use of fumigants for nematode vector control and elimination of known weed hosts is the most effective method of control. (Diseases Caused by Viruses and Viruslike Agents -- Spread by Insects, Mites, and Nematodes)

CHERRY RUSTY MOTTLE

‘‘‘Cherry Rusty Mottle: ‘‘‘ Leaf symptoms first appear as yellow spots or rings on basal leaves four to five weeks after full bloom. Subsequently, yellow rings develop on expanded leaves of rapidly growing shoots located within the canopy of the tree. Just before harvest, many older leaves on main branches become bright yellow and then develop a spotting of brown, orange, green, and yellow shades. Many of the spotted leaves abscise. Tree removal is the only eradicative control. (Diseases Caused by Viruses and Viruslike Agents -- Spread by Grafting)

CHERRY SHORT STEM

‘‘‘Cherry Short Stem</b></S></CF> This disease causes necrosis and constriction of the midribs of spur leaves and fruit take on an irregular shape with a rough surface. The most characteristic symptom is that normally developed fruit with shortened stems, appear in the second year of infection and thereafter. All diseased trees should be removed, and only certified trees should be replanted.

CHERRY STEM PITTING

‘‘‘Cherry Stem Pitting: ‘‘‘ The initial spring symptom is delayed budbreak. Leaves are small and more erect than those on healthy limbs or trees. The lower portions of affected trees are often bare and occasionally only a single scaffold branch may be involved. The use of resistant cultivars is the best control if available. (Diseases Caused by Viruses and Viruslike Agents -- Spread by Grafting)

CONSTRICTION CANKER (PHOMOPSIS AMYGDALI)

‘‘‘Constriction Canker (Phomopsis amygdali) ‘‘‘ On leaves, the pathogen induces large, brown, zonate spots that are circular or irregular in outline. Centers of lesions become sparsely dotted with black pycnidia. On twigs, reddish brown to brown elongate lesions are centered on an infected bud or node of one year old shoots. Lesions first become visible early in the spring, and as they enlarge, they cause girdling and a blighted appearance of shoots. The best form of control is to apply fungicides and to prune diseased twigs. It is important to destroy the diseased prunings to avoid further inoculation. (Disease Caused by Fungi -- Cankers, Blights, and Wood Rots)

CROWN GALL (AGROBACTERIUM TUMEFACIENS)

‘‘‘Crown Gall (Agrobacterium tumefaciens) ‘‘‘ This disease is characterized by the development of galls on roots, crowns, and occasionally aerial parts of stone fruit trees. They appear first as rapidly growing, white, fleshy swellings that usually become tan to brownish during the dormant season. Galls develop at wound sites and can be confused with normal callus tissue when they are small. The best form of control is good cultural and sanitation practices. (Disease Caused by Bacteria)

DAGGER NEMATODES (XIPHINEMA SPP)

‘‘‘Dagger Nematodes (Xiphinema spp.): ‘‘‘ High populations of dagger nematodes injure stone fruit trees by causing extensive root drying and swollen tips of fine root hairs. Fumigant and nonfumigant nematicides are effective against dagger nematodes, but they are often difficult to apply in soils where these nematodes thrive. (Diseases Caused by Plant-Parasitic Nematodes)

DEAD BUTTON

‘‘‘Dead Button: ‘‘‘ Drying begins at the stylar end of immature tart cherries and progresses as the fruit matures. The dry area varies in size but extends internally to the pit of the fruit. As fruits ripen, the dry tissue separates from healthy tissue, leaving a hole in the stylar end. (Genetic and Physiological Disorders)

DIEBACK (PHIALOPHORA PARASITICA)

‘‘‘Dieback (Phialophora parasitica) ‘‘‘ Twigs may fail to form leaves in the spring and on some branches the leaves suddenly wilt and abscise. Except for drying of the tissues, no other visible symptoms appear on affected twigs, but the disease continues to spread downward on the branch to the trunk. Little is known of the disease cycle or of control practices. (Disease Caused by Fungi -- Cankers, Blights, and Wood Rots)

EUROPEAN STONE FRUIT YELLOWS (ESFY)

‘‘‘European Stone Fruit Yellows (ESFY) ‘‘‘ Apricot--In spring, leaves emerge on infected trees before flowers. Later in the season, leaves show interveinal yellowing, are conically rolled along the longitudinal axis, and may be brittle and smaller than normal, with a rough, stiff texture. In late summer and fall, early budbreak produces a proliferation of weak shoots with short internodes, numerous rudimentary buds, and small, discolored, rolled leaves. Japanese plum--The first symptoms, in summer, are smaller, slightly yellow, and cylindrically (rather than conically) rolled leaves that become thick and brittle and often brownish red. Defoliation is earlier than normal, and often new growth starts between October and December. Fewer flowers and fruit develop on diseased trees, and the fruit are smaller and ripen later than on healthy trees. The use of pathogen-tested scion budwood and rootstocks and removing infected trees in the best form of control. (Disease Caused by Mycoplasmalike Organisms)

EUTYPA DIEBACK (EUTYPA LATA)

‘‘‘Eutypa Dieback (Eutypa lata) ‘‘‘ The first visible symptom is a branch canker, most commonly centered on a pruning wound made several years previously. Extending upward and downward from the canker, a zone of discolored sapwood may be found, usually terminating in a light brown and somewhat diffuse margin. Leaves on the portion of the branch beyond an established canker may wilt suddenly, signaling death of that part of the branch. Leaf wilting occurs typically in mid to late summer, often when the tree is bearing a heavy load of fruit, which stimulates moisture stress. Pruning is the best control known. (Disease Caused by Fungi -- Cankers, Blights, and Wood Rots)

FALSE SHOT HOLE

‘‘‘False Shot-Hole Disease</b></S></CF> Trees infected with false shot hole develop black necrotic spots on the leaves, which may enlarge and abscise. Mostly sweet cherry and plum trees are infected.

FASCIATION

‘‘‘Fasciation</b></S></CF> This abnormal growth habit of shoots is ascribed to a mutation of the terminal meristem induced by natural radiation. Several terminal shoots on different parts of the same tree may exhibit typical symptoms, which include curved, flat, thickened stems with shortened internodes. Hence, the potential to produce abnormal growth is believed to reside in the vegetative and reproductive cells and may be transmitted sexually or by grafting.

FLYSPECK (ZYGOPHIALA JAMAICENSIS)

‘‘‘Flyspeck (Zygophiala jamaicensis) ‘‘‘ Symptoms occur on the surface of mature fruits and shoots as numerous shiny, black, superficial, sclerotium-like structures in small patches. Fungicide sprays using ethylenebisdithiocarbamates and benzimidazoles, removing reservoir hosts, and pruning of trees or thinning of fruit to alter the microclimate may help to mitigate disease development. (Disease Caused by Fungi -- Fruit Disease)

FROSTY MILDEW OF PEACH (MYCOSPHAERELLA PRUNI-PERSICAE)

‘‘‘Frosty Mildew of Peach (Mycosphaerella pruni-persicae) </b></S></CF> This disease is characterized by white, powdery patches on lower leaf surfaces that may be small or cover the leaf surface. Yellowish areas may or may not appear on the upper surfaces, which become reddish in the autumn. This disease generally only occurs in neglected orchards.

FUNGAL GUMMOSIS (BOTRYOSPHAERIA DOTHIDEA)

‘‘‘Fungal Gummosis (Botryosphaeria dothidea) ‘‘‘ The earliest symptoms appear on young bark of vigorous trees as blisters that are 1-6 mm in diameter and usually each have a lenticel at its center. Blisters may be observed late in the season when infection occurs or the following spring. Dead wood should be removed during winter pruning, and prunings should be taken from the orchard or destroyed mechanically to reduce inoculum from these sources. Summer pruning should be avoided, because available inoculum can germinate and colonize wounds rapidly at this time. Also, alleviating water and nutrient stress can reduce disease incidence and severity. (Disease Caused by Fungi -- Cankers, Blights, and Wood Rots)

GNOMONIOSIS (APIOGNOMONIA ERYTHROSTOMA)

‘‘‘Gnomoniosis (Apiognomonia erythrostoma) ‘‘‘ The red spots on cherry leaves are typically surrounded by a large yellow halo. Infected leaves turn brown and remain attached to the stem until the following spring. Leaf scorch symptoms sometimes develop superficially on apricot fruit. Triazole fungicides applied when leaves appear in the spring may be used to control gnomoniosis. Zineb, mancozeb, dodine, or dithianon can also be effective with three to five applications. (Disease Caused by Fungi -- Foliar Disease)

GREEN FRUIT ROT (BOTRYTIS CINEREA, MONILINIA SPP AND SCLEROTINIA SCLEROTIORUM)

‘‘‘Green Fruit Rot (Botrytis cinerea, Monilinia spp, and Sclerotinia sclerotiorum) ‘‘‘ This disease attacks all floral parts, and entire clusters of blossoms may be blighted. Infection may spread into the peduncle, and in rare cases it may proceed into the twig, causing a canker. In wet or humid conditions, it can be identified on senescing blossoms by typical gray masses of conidia and by the small sclerotia that are sometimes formed. Protective fungicides should be applied during full bloom for best control. (Disease Caused by Fungi -- Fruit Disease)

GUMMING OF PEACH

‘‘‘Gumming</b></S></CF> Gums are found in the vascular bundles, but then they are stressed, they may rupture causing exudate to leak through weak places in the fruit tissue. These infected fruits usually abscise early in the season. Gumming may also be caused by insects, bird pecks, and hail damage.

INTERNAL BROWNING

‘‘‘Internal Browning of Stone Fruits</b></S></CF> Peaches, nectarines, and plums often turn dark brown around the pit after a long period in ordinary cold storage.

INTERNAL PRUNE BROWNING

‘‘‘Internal Browning of Prunes</b></S></CF> The mesocarp tissue of prunes normally turns from light green to amber and then to brown or even black as fruit ripen. The rate of darkening is hastened by high temperatures and is accentuated if the crop is handled roughly at harvest, because compression of the flesh causes the cells to rapture and the cell contents to become oxidized.

IRON

‘‘‘Iron: ‘‘‘ Symptoms are leaf yellowing in interveinal areas, which can lead to ivory or even white leaves with yellow spots. Fruit skins become pale and do not blush, and fruit size is also small. Control can include good soil aeration, lowering soil pH, and iron chelates as soil treatments. (Nutritional Disorder)

LEAF CURL (TAPHRINA DEFORMANS)

‘‘‘Leaf Curl (Taphrina deformans) ‘‘‘ Yellow to reddish areas appear on young developing leaves in the spring. These areas progressively thicken and pucker, causing the leaf to curl. Puckered areas are crisp and may develop a white coating of spores. Infected leaves abscise prematurely or sometimes remain attached, gradually turning dark brown on severely infected trees. Peach leaf curl is controlled primarily by fungicides and resistant cultivars. (Disease Caused by Fungi -- Foliar Disease)

LEAF SCORCH

‘‘‘Leaf Scorch</b></S></CF> Leaves exposed to the direct rays of the sun on very hot days become scorched, often beginning at the margins. The direct cause, however, is considered to be increased water stress. High temperatures trigger higher transpiration rates, thereby decreasing leaf water potential.

LEUCOSTOMA CANKER (LEUCOSTOMA CINCTA AND PERSOONII)

‘‘‘Leucostoma Canker (Leucostoma cincta and persoonii) ‘‘‘ Infections of small twigs appear as sunken, discolored areas, often with lines that alternate in zones, usually around winter-killed buds or leaf scars from the previous year's foliage. Cankers often form and are typically elliptical and are accompanied by a large quantity of amber colored gum. As the cankers age, the gum becomes dark brown, and the infected bark dries and cracks open, exposing blackened tissue beneath. Branch or twig infections may produce leaf symptoms during the growing season. Leaves on an infected branch often turn yellow, droop, and may wilt and die. The best form of control is an integrated cop management system that includes preventive measures that minimize winter injury, sunburn, and insect damage, promote optimum plant health, and facilitate rapid wound healing. (Disease Caused by Fungi -- Cankers, Blights, and Wood Rots)

LEUCOTELIUM WHITE RUST (LEUCOTELIUM PRUNI-PERSICAE)

‘‘‘Leucotelium White Rust (Leucotelium pruni-persicae) ‘‘‘ Lesions on peach leaves are polygonal or irregularly shaped, pale green to yellow, and approximately 1 mm in diameter. Cinnamon-colored uredia are produced on the underside of leaf lesions. Little is known about control of white rust but elimination of the alternate host is recommended for control of the disease. Applications of zineb in early summer may provide effective control. (Disease Caused by Fungi -- Foliar Disease)

LITTLE CHERRY

‘‘‘Little Cherry: ‘‘‘ Fruits of sweet cherry are more severely affected than any other part of the tree. In the first year after infection, fruit is about half normal size and triangularly shaped when viewed from the bottom. The fruit skin on two of the three sides tends to shrivel slightly, causing a leathery appearance. Fruit color develops normally until approximately 10 days before harvest, when normally dark-colored cultivars do not develop beyond the bright red stage. Flavor is bland but not bitter, which is one way to distinguish between little cherry and the mycoplasma-induced X-disease of cherry. The best form of control is to apply insecticides and eliminate infected trees from the area. (Diseases Caused by Viruses and Viruslike Agents -- Spread by Insects, Mites, and Nematodes)

LOW TEMPERATURE INJURIES

‘‘‘Low-Temperature Injuries: ‘‘‘ The first sign of frost damage is flower abscission or browning of the seed coat. Damage from spring frosts can be alleviated by using orchard heaters, using wind machines to mix colder air on the orchard floor with warmer air above the trees, disking under the cover crop and tamping the soil to allow the soil to absorb heat, and irrigating with sprinklers, furrows or basins. (Environmental Disorder)

MISTLETOE

‘‘‘Mistletoe: ‘‘‘ Host tissue swells to form a gall at the point of infection by the mistletoe. Proliferation of mistletoe shoots form dense evergreen clusters or clumps in the canopy of the host. These clusters of aerial mistletoe shoots resemble witches'-brooms but are actually shoots of the mistletoe plant. Pruning infected branches that contain aerial and internal portions of the parasitic plant, as well as removing heavily infected trees, can control the disease and prevent new infections of healthy branches and trees in the orchard. (Parasitic Plants)

MOLIERES DISEASE

‘‘‘Molieres Disease: ‘‘‘ The first symptoms in both cherry and plum are slightly yellow leaves in the summer. The following year, the trees bloom abundantly, but flowers are often malformed and fruit set is poor. The few fruit that do develop have short pedicels or peduncles, remain small, and drop prematurely. Small, deformed leaves, rosetting, and poor lignification of young shoots as well as phloem and bark drying are also associated with the disease. Young shoots die back, and as the disease progresses, all of the scaffolds die. In new orchards, diseased trees are not usually observed until three to seven years after planting. (Disease Caused by Mycoplasmalike Organisms)

MONILLA LEAF BLIGHT AND GREEN FRUIT ROT (MONILIA KUSANOI)

‘‘‘Monilia Leaf Blight and Green Fruit Rot (Monilia kusanoi) ‘‘‘ In early spring, infected young leaves develop small, brown spots that rapidly expand along the veins and midribs. White powdery masses of conidia form on the midribs and veins. Within one or two weeks after blooming, young fruits develop a small brown fleck on the stylar end as infection enters the fruit from the stigma. Later, the entire fruit rots, turns brown, and gradually mummifies. The best form of control is to apply chemicals and use good cultural practices that include removing and burning or burying diseased fruits. (Disease Caused by Fungi -- Foliar Disease)

NECTARINE POX

‘‘‘Nectarine Pox: ‘‘‘ Symptoms initially are observed about 40 days after anthesis, sometimes as a pale white or light-colored circular spot about 0.5-1.0 mm in diameter. More often, the area is a slightly raised protuberance of about 0.5 mm, rounded or slightly pointed and 1.0-2.0 mm in diameter at the base. The protuberances, or "warts," are occasionally clustered together, forming a larger irregular, rough, singular outgrowth of the epidermis and subepidermal tissue. Root pruning significantly reduces the incidence of nectarine pox. Thinning and irrigation programs that stimulate excessive tree growth and reduce crop production should be avoided. (Genetic and Physiological Disorders)

NITROGEN

‘‘‘Nitrogen: ‘‘‘ Deficiency results in pale green leaves and reduced shoot growth. Fruit will be highly colored in deficient trees and reddish spots may occur on peaches. Nitrogen deficiency can be corrected by application of nitrogen fertilizers. (Nutritional Disorder)

PEACH MOSAIC (PMV)

‘‘‘Peach Mosaic (PMV) ‘‘‘ Budbreak is retarded on infected trees. Leaves show yellow spots that vary from tiny flecks to streaks to vein feathering or bold blotches. These symptoms are best viewed with the aid of backlight illumination of fully expanded leaves. The foliage of infected trees turns a darker green by midsummer, and the leaves may be small, narrow, and asymmetric, with deformed, crinkled margins. The yellow areas become dry and drop out, producing a shot-hole and tattered appearance. Peach mosaic is best controlled through planting virus-certified nursery stock and by prompt detection and removal of diseased trees. (Diseases Caused by Viruses and Viruslike Agents -- Spread by Insects, Mites, and Nematodes)

PEACH MOTTLE

‘‘‘Peach Mottle: ‘‘‘ Affected leaves are slightly smaller than healthy ones and exhibit a yellow spotting. Leaf margins are also turned upward and puckered. The tree canopy is lighter in color and ragged in appearance, but these symptoms fade by the middle of the growing season. Infection of young trees results in death. (Diseases Caused by Viruses and Viruslike Agents -- Spread by Grafting)

PEACH RED SUTURE

‘‘‘Peach Red Suture: ‘‘‘ Diseased fruit show a roughened, bumpy, swollen, or bulged suture with intense internal color along the swelling. The surface of suture swellings is blotched or splashed with intense color that ranges from dark red to purple on red cultivars or a deeper yellow on yellow cultivars. Affected fruit often have an insipid flavor. Symptoms on trees infected with red suture occur annually, whereas those caused by herbicides are temporary. Red suture is controlled by removal of diseased trees. (Disease Caused by Mycoplasmalike Organisms)

PEACH ROSETTE

‘‘‘Peach Rosette: ‘‘‘ Peach--Leaves on diseased limbs are of nearly normal size and become somewhat yellow during the growing season. Shoot internodes are very short causing the leaves to be borne in very tight clusters or brooms. Plum--Leaves on infected trees develop a yellow and often a reddish blush, but the trees do not produce the dense brooms observed in diseased peach trees. Diseased trees should be removed. (Disease Caused by Mycoplasmalike Organisms)

PEACH ROSETTE MOSAIC (PRMV)

‘‘‘Peach Rosette Mosaic Virus (PRMV) ‘‘‘ Leaf emergence of infected peach trees is delayed and then the leaves develop yellow spotting. Leaf distortion may follow a yellow lesion that forms on one side of the leaf lamina. Leaves formed later in the season are narrower than healthy leaves. A shortening of internodes is a prominent symptom in late spring and summer. Roguing of diseased trees and preplant fumigation are recommended. (Diseases Caused by Viruses and Viruslike Agents -- Spread by Insects, Mites, and Nematodes)

PEACH SKIN DISCOLORATION

‘‘‘Peach Skin Discoloration: ‘‘‘ Discoloration can occur in two forms. The typical form first appears as water-soaked areas on the red or blushed surface of the fruit, which eventually turn purplish black. The yellow portion of the fruit surface shows a discoloration described as a "grease spot". The fruit appear to have gone over too many grading rollers and been extensively bruised. Preventive measures for avoiding peach skin discoloration are primarily based on minimizing physical damage to the fruit surface of susceptible cultivars. (Genetic and Physiological Disorders)

PEACH TREE SHORT LIFE

‘‘‘Peach Tree Short Life: ‘‘‘ Wilt symptoms appear suddenly in the spring, and true death often follows within a few weeks. During warm spring weather, bark on the trunk, crotch, and scaffold limbs develops a reddish, wet appearance, often accompanied by droplets of yellow or orange exudate. A "sour-sap" odor is often associated with tissues with this appearance. Fumigate the soil and prune as late as possible to avoid having problems with the disease. Also, remove prunings promptly from the orchard and destroy all dead and dying trees. (Disease Complexes)

PEACH WART

‘‘‘Peach Wart</b></S></CF> Peach wart causes wartlike outgrowths to develop on the fruit surfaces of sensitive peach cultivars. These outgrowths usually grow around the stylar end of young fruit and the fruit will probably be small and sparse. The tissues beneath the affected area are coarse-textured and contain gum pockets. Diseased trees should be removed promptly and only disease-free rootstocks should be used.

PEACH YELLOWS

‘‘‘Peach Yellows: ‘‘‘ Leaf buds on diseased peach trees break dormancy two to four weeks earlier than those on healthy trees. Leaves that develop from these buds are narrower and smaller than healthy leaves, and as the season progresses, they become yellow and often develop red spots. The numerous small leaves borne on these shoots are often severely yellow. Fruits produced on diseased limbs develop prematurely, usually two to three weeks ahead of healthy fruit. Although the fruits are of normal or larger than normal size, they taste bland or even bitter. Removal of the diseased trees is the best form of control. (Disease Caused by Mycoplasmalike Organisms)

PHONY PEACH (XYELLA FASTIDIOSA)

‘‘‘Phony Peach (Xyella fastidiosa) ‘‘‘ The canopy of peach trees is flattened, compact, and umbrella-like as a consequence of shortened stem internodes, and the foliage is unusually dense and dark green. Other symptoms include early bloom and fruit set and reduced fruit size. A rigorous program of early detection, tree removal, and eradication of the wild plum from the vicinity of peach orchards reduces the possibly of disease. (Disease Caused by Bacteria)

PHYMATOTRICHUM ROOT ROT (PHYMATOTRICHOPSIS OMNIVORA)

‘‘‘Phymatotrichum Root Rot (Phymatotrichopsis omnivora) ‘‘‘ Leaves develop a slight yellowing or bronzing, followed by loss of turgidity. Susceptible trees die quickly and leaves may abscise but usually remain attached to the branches for some time, depending on the rate of plant death. Cortical tissue is killed, sloughs off easily, and is often covered by a network of visible strands of the fungus. Before an orchard is established, the land should be planted with a herbaceous host to identify infested regions. (Disease Caused by Fungi -- Cankers, Blights, and Wood Rots)

PHYTOPHTHORA ROOT AND CROWN ROTS (PHYTOPHTHORA SPP)

‘‘‘Phytophthora Root and Crown Rots (Phytophthora spp) ‘‘‘ Leaves on affected trees usually become sparse, small, and yellow. Fruits may be undersized, highly colored, and sunburned. As the disease progresses, shoot and scaffold dieback may occur, often accompanied by sunburning of the exposed bark and secondary invasion by bark-boring insects. Trees often die within weeks or months of the first symptoms, but in other cases tree decline is gradual, extending over several growing seasons. Trees affected often have few feeder roots, and those roots remaining are often decayed, with dark brown to black discoloration in the cortex and stele. The best forms of control include careful soil water management, genetically resistant rootstocks, and fungicides. (Disease Caused by Fungi -- Cankers, Blights, and Wood Rots)

PIT BURNING & BLACKENING

‘‘‘Pit-Burning of Apricot and Pit-Blackening of Peach</b></S></CF> Air temperatures that approach 40°C for a few days when apricots are ripening turn the inner mesocarp tissue brown and gelatinous. Similarly, with many clingstone peach cultivars, the inner mesocarp becomes grayish, especially near the endocarp. The high temperature tends to accelerate the respiration rate of the ripening fruit to a point that leads to insufficient oxygen in inner tissues.

PLUM & PEACH DAPPLE

‘‘‘Plum and Peach Dapple Fruit Viroid: ‘‘‘ Symptoms have been observed on several cultivars of plums and peaches. Clear reddish and yellow blotches appear on diseased fruit as it begins to color. The blotches become prominent on mature fruit of plums such as Santa Rosa and several peach cultivars. (Diseases Caused by Viruses and Viruslike Agents -- Spread by Grafting)

PLUM CHLOROTIC FLECK

‘‘‘Plum Chlorotic Fleck and Peach Yellow Spot: ‘‘‘ Circular, yellow spots and flecks are formed along the midrib and lateral veins. If flecks are abundant, the leaves become distorted and twisted. Severely affected seedlings are stunted. Oval, reddish flecks in the young bark are associated with this disorder. The mite is easily controlled by timely use of various acaricides registered for use on stone fruits. (Genetic and Physiological Disorders)

PLUM LEAF SCALD (XYLELLA FASTIDIOSA)

‘‘‘Plum Leaf Scald (Xylella fastidiosa) ‘‘‘ Plum leaves first exhibit a slight, irregular yellowing or browning along the margin or tip in early to midsummer, which intensifies as the season progresses. As the dry area spreads from the leaf margin, the brown, dry margin becomes separated from the unaffected area by a diffuse yellow band. The best form of control is to remove infected trees and wild plums adjacent to the orchard and control the ground cover in and near the orchard to destroy possible vector hosts. (Disease Caused by Bacteria)

PLUM LINE ILARVIRUSES

‘‘‘Plum Line Pattern Ilarviruses: ‘‘‘ Leaves develop yellow lines, bands, or oak-leaf patterns. Virus certification programs provide a source of trees free of plum line pattern diseases. (Diseases Caused by Viruses and Viruslike Agents -- Spread on Pollen)

PLUM POCKETS (TAPHRINA SPP)

‘‘‘Plum Pockets (Taphrina spp) ‘‘‘ Symptoms of fruit infection are both more obvious and more prevalent than those on leaves or shoots. Fruit become distorted and enlarged as much as 10 times the normal size, with spongy or hollow centers with or without pits. Early symptoms are small whitish spots or blisters that enlarge rapidly and eventually become reddish and display a velvety gray appearance. The best form of control is to use resistant cultivars or applying a single fungicide spray in late autumn or before budbreak in the spring. (Disease Caused by Fungi -- Fruit Disease)

PLUM POX VIRUS

‘‘‘Plum Pox Virus: ‘‘‘ Foliar symptoms in plum consists of pale green yellowing spots, rings, and lines that are visible from early summer onward. These markings can become dry and symptoms frequently are restricted to only a few leaves per shoot. Infected trees usually are not stunted and are difficult to identify. Fruit symptoms in red and dark-colored plums consist of rings and blotches in fully expanded unripe fruit. Rigorous spraying for aphids may delay the spread of virus but the best form of control is to use resistant cultivars where they are available. (Diseases Caused by Viruses and Viruslike Agents -- Spread by Insects, Mites, and Nematodes)

PLUM RUSTY BLOTCH

‘‘‘Plum Rusty Blotch: ‘‘‘ Yellowing appears along the margins of leaves on affected trees. Within a few weeks, the yellow areas may turn reddish brown, and many small spots appear in the discolored areas. These spots may grow larger, but usually they become dry and drop out, giving the leaf a shot-hole appearance. Affected leaves are much smaller than normal. (Genetic and Physiological Disorders)

POTASSIUM

‘‘‘Potassium: ‘‘‘ Deficiency resembles nitrogen deficiency in that leaves are slightly pale, and leaves may show curling and rolling of edges. Potassium deficiency also leads to smaller fruit and is generally corrected by potassium fertilizers applied in bands on the surface or drilled into the soil or applied through drip irrigation. (Nutritional Disorder)

POWDERY MILDEW

‘‘‘Powdery Mildew: ‘‘‘ Early symptoms on foliage include a fine, netlike growth. As infections progress, large numbers of conidia produced on the surface result in a white, mealy appearance. Yellowing of severely infected leaves may be followed by severe drying. Young fruits may also be affected in early spring by dry fruit lesions that cause surface cracking. Infected areas turn brown or remain green. Control of mildew on stone fruit depends on the use of fungicides and removal of hosts or the use of resistant cultivars. Removal of susceptible rose bushes near apricot, nectarine, peach, and plum orchards is recommended. (Disease Caused by Fungi -- Fruit Disease)

PRUNE CRINKLE LEAF

‘‘‘Prune Crinkle Leaf: ‘‘‘ Affected trees produce leaves that are deformed and have uneven margins. Leaves are small and light green with scattered yellow areas and they appear marbled in texture. Crinkle leaf trees are dwarfed and fail to produce mature fruit. (Genetic and Physiological Disorders)

PRUNE DWARF (PDV)

‘‘‘Prune Dwarf Virus (PDV) ‘‘‘ Symptoms of sour cherry yellows consist of yellow rings or spotting on young expanding leaves of newly infected sour cherry trees. When tissues in some yellow areas dry out, they may fall out, causing a shot-hole appearance. One or more years after acute symptoms appear, leaves on infected trees develop a distinctly yellow and green spot and begin to drop. The best form of control is to use resistant cultivars. (Diseases Caused by Viruses and Viruslike Agents -- Spread in Pollen)

PRUNE LEAF CASTING MOTTLE

‘‘‘Prune Leaf Casting Mottle: ‘‘‘ In the East, yellow spots appear on leaves in midsummer and the spots turn brownish and become translucent, with indistinct margins. Later, the leaf lamina becomes yellow, and the spots are encircled by a green halo. The spots then dry out and severely affected leaves abscise. In the West, a yellow mosaic pattern is formed and gray or purple-brown dry centers develop in the yellow areas. Affected leaves usually abscise, but those that persist turn gray and develop yellow leaf margins. On symptomatic trees, fruit set is reduced, and fruit drop prematurely. (Genetic and Physiological Disorders)

PRUNUS NECROTIC RINGSPOT (PNRSV)

‘‘‘Prunus Necrotic Ringspot Virus (PNRSV) ‘‘‘ Symptoms occur on young leaves during the first year of systemic infection but few, if any, symptoms appear on leaves or fruit in later years. Still other isolates produce dry reactions in the first year, followed by chronic dry, yellow leaf spot, leaf enation, deformity, delayed fruit maturity, and fruit-marking symptoms. A few isolates cause yellow line patterns and mosaics on leaves of several plum cultivars. The best form of control is to use virus-free wood, obtain cultivars from a certification program, and remove and destroy any diseased plants in the orchard. (Diseases Caused by Viruses and Viruslike Agents -- Spread in Pollen)

RED LEAF SPOT (POLYSTIGMA RUBRUM)

‘‘‘Red Leaf Spot (Polystigma rubrum)</b></S></CF> This disease is characterized by irregularly shaped red lesions that become black and are slightly sunken on the upper side of the leaves and raised on the lower sides. Partial or complete defoliation may occur and other tissues are significantly reduces, i.e. flower buds, fruit set, yield. Only leaves are affected.

REPLANT DISORDERS

‘‘‘Replant Disorders: ‘‘‘ The trees produce fewer and smaller leaves and shoots, which often have a lighter color than does normal growth. Root systems of such trees have few fine feeder roots, often with darkened or discolored dry lesions. (Disease Complexes)

RHIZOPUS ROT (RHIZOPUS SPP)

‘‘‘Rhizopus Rot (Rhizopus spp) ‘‘‘ Rhizopus rot on packaged fruit is characterized by a mass of white mycelium, with long mycelial stolons extending to and infecting adjacent fruit. Black sporangia usually occur in abundance near the edge of the container. Decaying fruit on the orchard floor are covered with black sporangia, but in areas with dry summers the sporangiophores and mycelia are inconspicuous because of low relative humidity. Control consists of storing fruit at temperatures below 4.4 °C (40 °F) or providing a pre- or postharvest chemical treatment. Also avoid mechanical injury during harvest. (Disease Caused by Fungi -- Fruit Disease)

RHODOSTICTA CANKER (RHODOSTICTA QUERCINA)

‘‘‘Rhodosticta Canker (Rhodosticta quercina) ‘‘‘ Symptoms are most apparent during the growing season, when branches and limbs of plum trees are girdled by cankers. Leaves turn brown and flag the presence of cankers. Cankers seldom if ever originate at pruning wounds. Avoidance of sunburn on branches and limbs, either through careful pruning or by use of whitewash, has been the most effective approach for controlling this disease. (Disease Caused by Fungi -- Cankers, Blights, and Wood Rots)

RING NEMATODES (CRICONEMELLA SPP)

‘‘‘Ring Nematodes (Criconema and Criconemella spp.): ‘‘‘ Microscopic symptoms of ring nematode-infected trees are similar to those caused by other nematodes with the most prominent symptom being the destruction and death of feeder roots. Fine roots that remain have gray drying of the cortex and sometimes dense clusters of free roots. Feeding by large numbers of nematodes stunts roots and shoots. Control of ring nematodes has been accomplished largely through soil treatment with chemical nematicides. No resistance has been discovered yet. (Diseases Caused by Plant-Parasitic Nematodes)

ROOT KNOT NEMATODES (MELOIDOGYNE SPP)

‘‘‘Root-Knot Nematodes (Meloidogyne spp.): ‘‘‘ Root-knot nematode infection is characterized by gall formation, which disrupts normal root growth and nutrient and water uptake. The combined effect of these changes is reduced root and shoot growth, small shoot and mot biomass, leaf yellowing, low fruit yield, poor fruit quality, and sometimes tree death. The best form of control is to use resistant cultivars and apply fumigant and nonfumigant nematicides. (Diseases Caused by Plant-Parasitic Nematodes)

ROOT LESION NEMATODES (PRATYLENCHUS SPP)

‘‘‘Root-Lesion Nematodes (Pratylenchus spp.): ‘‘‘ Nematode invasion of young roots induces reddish brown, elongated lesions. Root lesions darken with age, become dry and spreads to the entire root, growth ceases, and the root dies. The best form of control is to use nematode-free nursery stock and apply fumigant nematicides on a very regular basis to avoid further reinfestations. (Diseases Caused by Plant-Parasitic Nematodes)

ROSELLINIA ROOT ROT (ROSELLINIA NECATRIX)

‘‘‘Rosellinia (Dematophora) Root Rot (Rosellinia necatrix) ‘‘‘ Aerial symptoms include premature yellowing of foliage and poor growth of one or all limbs and new shoots in spring. Fruit cease to grow and may shrivel or drop. Leaves are small and almost white, and some premature defoliation may occur. The characteristic belowground symptom is the rotting of fibrous roots by a whitish, layer of mycelium which then invades larger roots. No entirely satisfactory control methods have been developed. (Disease Caused by Fungi -- Cankers, Blights, and Wood Rots)

RUSSET SCAB

‘‘‘Russet Scab: ‘‘‘ Symptoms are first apparent on green fruit during or shortly after shuck fall. Wax on the affected surface of the fruit is lacking, and the area, first shiny, later develops a brown russet with a netted pattern a condition originally called "lacy scab". Fungicides applied at full bloom control the disease. (Genetic and Physiological Disorders)

RUST (TRANZSCHELIA DISCOLOR AND TRANZSCHELIA PRUNI-SPINOSAE)

‘‘‘Rust (Tranzschelia discolor and Tranzschelia pruni-spinosae) ‘‘‘ Symptoms begin to develop as pale yellowish green spots on both leaf surfaces. The spots are somewhat angular in shape and become bright yellow. Those on the lower leaf surface develop typical orange-brown sori bearing urediniospores. Black teliospores may develop in late season to varied extents among the orange-brown urediniospores. Rust can be controlled with preventive fungicide sprays. Treatments one, two, and three months before harvest are applied when early-season disease outbreaks are common. In areas with less frequent or late-season disease problems, fungicides after harvest may be beneficial. (Disease Caused by Fungi -- Foliar Disease)

RUSTY SPOT (PODOSPHAERA LEUCOTRICHA)

‘‘‘Rusty Spot (Podosphaera leucotricha) ‘‘‘ The initial symptoms on peach fruit are small, spherical, orange-tan lesions, which gradually enlarge and become indeterminate. Enlargement of lesions parallels fruit enlargement. Fungal mycelium can occasionally be observed in the lesions. Leaves and stems are not affected. Rusty spot has been controlled when wettable sulfur was applied to peach at shuck split and continued on an eight to ten day schedule. Controlling mildew in adjacent apple orchards reduces rusty spot in peach orchards. (Disease Caused by Fungi -- Fruit Disease)

SCAB (CLADOSPORIUM CARPOPHILUM

‘‘‘Scab (Cladosporium carpophilum) ‘‘‘ Twigs, leaves, and fruit are infected, but the symptoms are most noticeable on fruit. Symptoms appear when the fruit are about half grown. Small, greenish to olive color, circular spots appear on exposed fruit surfaces, most frequently near the stem end. These enlarge, become olive to black, and sometimes have a green to yellow halo on the blush surface. Young or mature leaves are infected on the lower surface. Initially, lesions are imperfectly defined, angular to circular, and of a color similar to that of healthy tissue. Scab is controlled entirely by fungicidal sprays and pruning. (Disease Caused by Fungi -- Fruit Disease)

SCLEROTIUM STEM ROT (SCLEROTIUM ROLFSII)

‘‘‘Sclerotium Stem Rot (Sclerotium rolfsii) </b></S></CF> This disease occurs in areas of high temperatures, wet soils, and high levels of organic matter. The fungus invades stems near the soil line, develops a prominent white mycelium on the tissue surface, and later invades roots. Some fungicides have been successful in controlling the disease.

SEPTORIA LEAF SPOT

‘‘‘Septoria Leaf Spot</b></S></CF> This disease develop lesions on leaves that are small, circular and often fall out leaving a hole in the leaf. Severely infected leaves die and fall off. Lesions also develop on the fruit that have a blue-gray edge and are 3-7 mm in diameter. This disease seldom causes losses of economic importance, and specific control measures have not been described.

SHOT HOLE (WILSONOMYCES CARPOPHILUS)

‘‘‘Shot Hole (Wilsonomyces carpophilus) ‘‘‘ Symptoms on peach, nectarine, and apricot are similar. During wet winter months, the fungus infects and kills dormant buds. Dead buds sometimes are covered with a gummy exudate that gives them a varnished appearance. On fruit, lesions develop mostly on the upper side and eventually become corky and rough. Leaf lesions abscise in a warm, dry environment giving it the name "shot hole." Control requires protection of dormant buds, shoots, and fruit, with chemicals. (Disease Caused by Fungi -- Fruit Disease)

SILVER LEAF DISEASE (CHONDROSTEREUM PURPUREUM)

‘‘‘Silver Leaf Disease (Chondrostereum purpureum) ‘‘‘ Leaf silvering is the characteristic symptom on most fruit species and occurs soon after the fungus gains entry into the trees. Severely affected leaves are silver-gray, curl upward slightly at the edges, and may dry out. The silver-gray color contrasts dramatically with the dark green of adjacent healthy foliage. The best form of control is to destroy all infected material from prunings, shelter belt trimmings, stumps, or logs. (Disease Caused by Fungi -- Cankers, Blights, and Wood Rots)

SOOTY BLOTCH (GLOEODES POMIGENA)

‘‘‘Sooty Blotch (Gloeodes pomigena)</b></S></CF> Sooty blotch occurs in damp areas of high relative humidity and discrete olive green patches of fungus appears on the fruit. The disease is of minor importance.

SOUR CHERRY GREEN RING MOTTLE (SCGRV)

‘‘‘Sour Cherry Green Ring Mottle Virus (SCGRMV) ‘‘‘ Leaves of infected sour cherry trees show yellow spotting with green islands or ringlike bands and constricting yellowing along the veins and midrib. Affected fruit are misshapen and bitter and may exhibit dry pits or dimples on the surface. Longitudinal cracks and fissures may occur in the bark. Diseased trees should be removed and replaced with virus-tested stock. (Diseases Caused by Viruses and Viruslike Agents -- Spread by Grafting)

SOUR CHERRY PINK FRUIT

‘‘‘Sour Cherry Pink Fruit: ‘‘‘ The first visible symptom is delayed bloom. Affected leaves roll slightly toward the midrib and mimic symptoms associated with drought stress. Tree growth is suppressed. Fruit symptoms begin to appear about two weeks before harvest. Fruits are slightly smaller than healthy fruit and are pinkish to pinkish brown, in contrast to the bright red color of healthy fruit. Dry areas develop in the fruit flesh. Only disease-free propagation material should be used when new orchards are established. (Diseases Caused by Viruses and Viruslike Agents -- Spread by Grafting)

SOUR PIT (TORULOPSIS INCONSPICUOUS)

‘‘‘Sour Pit (Torulopsis inconspicus) </b></S></CF> Sour pit creates abnormal softening of the stem-end cavity of peach fruit. When fruits are cut open, the flesh near the pit is brown to light brown, with slimy appearance and watersoaking of tissues accompanied by a sour or yeasty odor. The disease can also infect pears, apples, and watermelons. Fruit flies transmit the disease.

SOUR ROT (GEOTRICHUM CANDIDUM AND MONILIA IMPLICATA)

‘‘‘Sour Rot (Geotrichum candidum and Monilia implicata) ‘‘‘ Sour rot is primarily a postharvest disorder of peaches that is characterized by a dark brown, wet discoloration of the fruit surface that quickly develops into a wet, mushy decay of the entire fruit. Lesions then become covered with white mycelium. A sour, vinegar-like odor accompanies the decay. (Disease Caused by Fungi -- Fruit Disease)

SPUR CHERRY

‘‘‘Spur Cherry: ‘‘‘ Certain sweet cherry cultivars exhibit severe rosetting, leaf growth, and bark drying in new growth. Among other cultivars that were experimentally infected, some grew in a spiral fashion, some were dwarfed, and some had no symptoms. No fruit symptom has been observed. Propagation of trees with virus-free budwood controls this disease. (Diseases Caused by Viruses and Viruslike Agents -- Spread by Grafting)

SUNBURN

‘‘‘Sunburning of Trunks, Scaffold Limbs, and Fruits: ‘‘‘ Sunburn occurs mostly on trees exposed to afternoon sun.. Control includes leaving primary and secondary scaffolding branches in an upright position, pinching back leafy branches on trunks of young trees during summer, retaining short shoots on the upper side of scaffold limbs during dormant pruning to provide shade, painting the trunks and upper sides of branches with white latex paint or whitewash, and sprinkling trees with overhead sprinkling to provide evaporative cooling. (Environmental Disorder)

SWEET CHERRY CRACKING

‘‘‘Cracking of Sweet Cherry: ‘‘‘ Water droplet on cherries for extended periods of time allow the fruit to absorb the water though the skin, causing the epidermis to stretch and eventually crack. Spraying with soluble organic or inorganic calcium salts tends to reduce cracking. (Environmental Disorder)

TARGET LEAF SPOT OF PEACH (PHYLLOSTICTA PERSICAE)

‘‘‘Target Leaf Spot (Phyllosticta persicae) </b></S></CF> Although the small circular lesions may be numerous and widespread in some parts of Italy and India, the disease has not been of serious concern. The pathogen occurs on Prunus in the United States but is not of economic importance on food crops.

TOMATO BUSHY STUNT (TBSV)

‘‘‘Tomato Bushy Stunt Virus (TBSV) ‘‘‘ The most obvious symptom is severely and irregularly distorted fruits. Necrotic fruit symptoms are accompanied by sporadic dry lesions or spots on or near the midrib of leaves. Affected leaves and fruit pedicels often display a sharp bend at the point of drying, while petals become dry and misshapen. No specific control measures have been tested. (Diseases Caused by Viruses and Viruslike Agents -- Spread by Grafting)

TOMATO RINGSPOT (TmRSV)

‘‘‘Tomato Ringspot Virus (TmRSV) ‘‘‘ Affected areas show various phloem disorders near the ground line that result in thickened bark and pitting of the young xylem under the bark. Dry phloem tissue develops at the graft union in trees on virus susceptible rootstocks. Growers should obtain and plant trees derived from a virus certification program. Thorough land preparation also is important because weeds can serve as a virus reservoir. The best form of control is the use of resistant cultivars. (Diseases Caused by Viruses and Viruslike Agents -- Spread by Insects, Mites, and Nematodes)

VERTICILLIUM WILT (VERTICILLIUM DAHLIAE)

‘‘‘Verticillium Wilt (Verticillium dahliae) ‘‘‘ Initial symptoms appear as a sudden wilting of leaves on one or more branches in early summer. Leaves become dull and rapidly tan and wither. Often the leaves remain attached, resulting in a one-sided, flagged appearance. At times, symptoms develop on leaves at the base of branches and progress upward until the entire branch is affected. The result of repeated wilting is generally stunted terminal growth and low productivity or death. (Disease Caused by Fungi -- Cankers, Blights, and Wood Rots)

VIOLET ROOT ROT (HELICOBASIDIUM MOMPA)

‘‘‘Violet Root Rot Helicobasicium mompa ‘‘‘ Symptoms include reduced shoot growth, small, light green leaves, dieback of twigs and shoots, and gradual decline of the whole tree. The affected root surface of an infected tree is covered with a purplish or dark brown network of mycelium. New plantings should be established in noninfested soils. Rootstocks resistant to this fungus are not available. (Disease Caused by Fungi -- Cankers, Blights, and Wood Rots)

WOOD DECAY

‘‘‘Wood Decay: ‘‘‘ White rots, which are the most common, are generally moist, soft or spongy, and lighter in color than sound wood. All major structural components of the cell wall are degraded. Control of wood rot disorders involves cultural practices that promote tree growth and vigor, while minimizing injuries that expose wood. Orchard management begins with proper site and cultivar selection, followed by appropriate programs for irrigation and fertilization. Sanitation may also help reduce infection. Ideally, pruning should be done when inoculum is sparse or absent. (Disease Complexes)

X DISEASE

‘‘‘X-Disease: ‘‘‘ Symptoms on trees include normal sized leaves that exhibit a reddish blush on the leaf undersides and an upward rolling of the leaf margins prior to tree collapse. The fruit on affected trees is usually of normal appearance but may be sweeter than fruit on healthy trees because extra sugars are diverted to fruits following girdling at the graft union. Leaves on infected limbs are smaller than normal and develop a red tinge on the upper lamina at mid-growing season. The most important strategy of management is to identify and remove infected plant sources. (Disease Caused by Mycoplasmalike Organisms)

ZINC

‘‘‘Zinc: ‘‘‘ Deficiency is characterized by delayed opening of buds in the spring, small yellow leaves, shortened internodes and tufts of small leaves along the shoots. Fruits are small, poorly colored and sometimes misshapen. Deficiency is best corrected by foliar and dormant sprays. (Nutritional Disorder)

ZONATE LEAF SPOT (CRISTULARIELLA PRUNI)

‘‘‘Zonate Leaf Spot of Stone Fruits (Cristulariella pruni) ‘‘‘ Minute, dark green spots that develop on leaves gradually turn gray and enlarge up to 2-30 mm in diameter with concentric rings. The dead or diseased tissues on the spots often fall out, leaving perforations or "shot holes". On leaves, water-soaked lesions rapidly develop and group together to form large, irregular gray spots on defoliated leaves on the orchard floor. Removal and destruction of diseased leaves are advisable along with the use of chemical sprays. (Disease Caused by Fungi -- Foliar Disease)