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Problem
(factsheet)
Plant NameTypeDescription 
Bacterial cankerPeachDiseaseBacterial canker is favored by cool, wet weather and is common in western Washington. The bacteria overwinter in cankers, buds and other host tissues. Dark cankered areas on trunks and branches may develop and expand in early spring. The infected tissues may produce gum, although gumming can also be caused by other factors. The cankers often girdle twigs and branches, causing dieback above the lesion. Leaves on girdled twigs often yellow and fall by late summer. Infected buds may be killed or leaf infections may occur as the new growth emerges, resulting in collapse of leaves. Infection can be spread by wind, rain, insects, pruning tools, or by planting or grafting with infected stock. The disease may spread throughout the entire tree with or without visible symptoms (systemic infection).
Brown rotPeachDiseaseBrown rot is a blossom-infecting fungal disease. Infected flowers wilt and die. The brown blossoms remain attached to the twigs, becoming covered with a grayish-brown fungal growth during wet weather. Blossom or fruit infections may spread to twigs. Infected twigs develop sunken, elongate cankers with gumming at the margins. Leaves on girdled shoots turn brown and remain attached. Infected fruit initially show a small brown spot which rapidly enlarges. The fruit remains fairly firm and often becomes covered with gray-brown fungus. Fruit may dry and harden into mummies, which serve as a source of infection the following spring.
Crown gallPeachDiseaseCrown gall is caused by a soilborne bacterium. The bacteria infect through wounds on the crown and roots. Young galls are fleshy, white, enlarged masses on the roots or stems. Older galls are hardened and turn dark brown and woody or corky in appearance. They range in size from less than an inch to several inches across. The bacteria can be spread from contaminated to clean soil by water movement. Damage varies with location and size of galls. Small galls are essentially harmless. Large galls on the crown may weaken or girdle trees. The growths can also be an aesthetic concern.
Cytospora cankerPeachDiseaseThe fungi which cause Cytospora canker attack through wounds on twigs and branches. Initial cankers are small, but enlarge quickly and may streak up and down the stems without girdling. The cankers may also girdle twigs, resulting in dieback above the infection site and causing "flags" of dead material to appear in the canopy. The leaves on the dead twigs turn color and droop, but often remain attached. The canker itself appears as a dark, sunken area of dead bark and wood. Later callus forms at the margin of the canker. Amber gumming is often present. Pinhead-sized black fruiting structures of the fungi often erupt through the bark and produce reddish tendrils or droplets of spores in wet weather. Spores are easily spread by wind, rain, and insects. The cankers enlarge for several seasons.
Leaf curlPeachDiseasePeach leaf curl is a fungal disease affecting primarily the leaves and shoots. Fruit is occasionally attacked. Young leaves develop yellow to reddish discoloration and become thickened, crisp, and crinkled. Affected leaves are curled and deformed. A white powdery coating of the fungus later develops on infected leaves. Infected leaves either turn yellow and drop or remain on the tree, turning dark brown as the season progresses. Infected green shoots become thickened and distorted. Fruits may show swollen, reddish areas on the surface. These areas lack the normal peach fuzz. The fungus overwinters on twigs and buds. This disease is a major problem of peaches in western Washington. Severe leaf drop affects fruit production, reduces vigor of trees, and increases susceptibility to winter injury.
Powdery mildewPeachDiseasePowdery mildew of peach attacks leaves, young shoots, and fruit. This fungal disease produces a characteristic white, powdery coating on the surface of affected leaves. Older leaves may show patchy areas of fungal growth, while shoots may become covered with the fungus. Diseased tissues are often deformed and stunted. Fruits first develop white circular spots, which may enlarge and coalesce to cover the entire fruit. Young fruit may be somewhat deformed, while older fruit may show scabby or dead areas. At this stage, the white fungal growth may not be visible. The fungus can overwinter on twigs and in infected buds. Powdery mildew is favored by high humidity, warm days, and cool nights.
Shothole (Coryneum blight)PeachDiseaseShothole is a fungal disease typically attacking buds, twigs, and fruit. Infected buds are killed and covered with a shiny, gummy material. Twigs develop small, raised purplish areas which later become elongate brown or black cankers. Twig lesions often begin at infected buds and may girdle twigs. Lesions on leaves and fruit are initially small purplish areas which expand into brown spots with light centers. The lesions are typically up to 1/4" in diameter. Infected areas on leaves often die and drop out in warm weather, giving leaves the characteristic "shothole" appearance of the disease. The fungus overwinters in cankers. Spores are easily spread by water. Shothole occurs on many species of stone fruits.
X-diseasePeachDiseaseX-disease of peaches is caused by a mycoplasma-like organism (MLO). The MLO is transmitted by leafhoppers. Symptoms of infection typically appear in the summer. Leaves exhibit irregular yellow spotting. Leaves roll and the spots die and drop out, giving leaves a tattered appearance (holes caused by Coryneum blight are more regularly circular). Infected trees are subject to early leaf drop, and produce less fruit and fruit of inferior quality, while the whole tree declines gradually. X-disease spreads throughout the tree over the course of a few years and may kill the tree. Cherry is also a host of X-disease.
AphidsPeachInsectThe green peach aphid is a soft-bodied, green aphid up to 1/8" in length. It is typically found on peach leaves in the spring, where it feeds on sap sucked from the plant tissues. Heavy infestations can result in curled leaves and death of forming flowers and fruit. Nectarine fruits in particular may be severely damaged by aphid feeding. Aphids produce honeydew, a sweet, sticky material which may attract ants or become covered with a growth of dark sooty mold. The green peach aphid moves to and feeds on vegetable crops and weeds during the summer. It is an important vector (carrier) of several virus diseases, including the Leafroll Virus of potato.
Brown marmorated stink bugPeachInsectThe brown marmorated stink bug (BMSB) is an introduced pest species from Asia that is spreading quickly across the United States. Nymphs and adults feed on a wide variety of plant hosts. BMSB prefers to feed on fruit, seeds, and seed pods, but will also feed on stems and leaves of some hosts. Both adults and nymphs have piercing-sucking mouthparts and inject digestive enzymes into plant tissues to aid in feeding. Sunken areas and deformities (catfacing) on the surface of the fruit are typical symptoms. Damaged areas are discolored beneath the fruit’s skin and become hard and pithy or corky in texture. Stone fruits such as cherry, peach, plum, and apricot may show gumming at the injury site and from the corky areas beneath the surface. Other known tree fruit/nut hosts of BMSB include apple, pear, filbert, and stone fruits including apricot, cherry, and plum. One or two generations of BMSB per year are expected in the Pacific Northwest. Adults overwinter in sheltered locations (including houses, where they can become a significant nuisance pest). In the spring, light green to white eggs are laid in groups of about 20 to 30 on the underside of leaves. Young stink bugs, or nymphs, are black with a red-and-black striped abdomen. Nymphs often feed in groups when young. Older nymphs are dark with white bands on body, legs, and antennae. They may feed in groups or singly. Adults are a little over 1/2 inch long, with a shield-shaped body. Body color on adults is mottled gray and brown, while the legs and antennae have alternating dark and light bands. The abdomen also has dark and light bands which are visible at the edge of the wings. NOTE: BMSB adults closely resemble other stink bugs found in WA and OR. For more information on BMSB identification, see FS079E, Pest Watch: Brown Marmorated Stink Bug, available at https://pubs.wsu.edu/.
EarwigsPeachInsectEarwigs are reddish-brown insects about 3/4" or less in length. Both males and females have pincers at the rear end. Earwigs are largely beneficial, feeding on many pests such as aphids, mites, and nematodes, as well as on algae, fungi, and decaying plant material. However, earwigs can also damage plants. They sometimes feed on flowers, shoot tips, leaves, or fruit. Damaged shoot tips may fail to develop properly, sometimes stunting growth. Damaged leaves exhibit small to large holes. Fruit damage consists of shallow, irregular areas chewed into the surface.
European red mitePeachInsectSeveral species of spider mites may be found on peaches, including the European red mite, the twospotted spider mite, and the McDaniel spider mite. They may be various colors including yellow, greenish, brown, or red. All species feed on the leaves (typically on the underside), causing a whitish, yellow, or brown stippling. More severe damage results in leaves taking on a bronzed appearance. Heavy infestations may cause leaf drop. Spider mite feeding is usually accompanied by webbing on leaves and between leaves and twigs. The European red mite typically produces smaller amounts of webbing than other species. Spider mite infestations are worse in hot, dry, dusty conditions.
LeafrollersPeachInsectPandemis and fruittree leafrollers may feed on peach. The larvae may feed on leaves or buds, or cause surface damage on young fruit. Fruittree leafrollers are pale to dark green with a shiny black head, and measure about 3/4" long at maturity. The pandemis leafroller larva is similar in appearance, but has a light-colored head. Typical symptoms of leafroller feeding include leaves that are rolled and tied in place with webbing and fruit with shallow surface damage. The caterpillars are active when disturbed, wiggling vigorously or dropping to the ground on a thread. The adult moths are 1/2" to 3/4" long. The adult fruittree leafroller moth is mottled tan and brown. The pandemis adult is light tan with darker bands on the wings.
Peach twig borerPeachInsectThe peach twig borer is an important pest of peaches, particularly in eastern Washington. In the spring, overwintering larvae bore down the center of shoots, causing the tip to wilt or "flag". Each caterpillar can damage several shoots. Later generations of larvae feed on both shoots and fruit. They often burrow into the stem end of young fruit. Pits of infested fruit are often split. They may also feed on the fruit surface. The caterpillars are reddish-brown with black heads and yellowish rings on the body. Mature caterpillars are up to 1/2" long. The adult moth is dark gray and about 1/3" long. Apricot, nectarine, plum, and prune may also be attacked.
Peachtree borerPeachInsectThe peachtree borer adult is a dark, bluish, clear-winged moth which somewhat resembles a wasp or hornet. The female, which has dark forewings and a red-orange band on the abdomen, lays eggs on the tree. Emerging larvae move to ground level or just below ground, where they burrow beneath the bark on the trunk and feed in the crown region. Signs of larval feeding include the presence near ground level of jelly-like gum mixed with dirt and pellets of excrement. Heavy infestations can weaken older trees, and foliage may be yellowed as if nitrogen-deficient. Young trees may be girdled and killed.
Spotted wing Drosophila (SWD)PeachInsectSpotted wing Drosophila (SWD) resembles other Drosophila species (fruit flies or vinegar flies) in appearance, but unlike other members of the family which attack only overripe, damaged or decaying fruit, SWD attacks healthy fruit as it ripens on the plant. Adult SWD flies are about 1/8 inch long, with red eyes and a yellow-brown body. Darker bands may be visible on the abdomen. Male flies have a distinctive dark spot on the leading edge of the wing near the tip. SWD is the only fruit fly species in our area with this spotted wing, making identification of males relatively simple. Females lack the spotted wing, but have a large, sawlike egg-laying organ called an ovipositor at the tip of their abdomen. It is used to deposit eggs in fruit (oviposition). The eggs are laid beneath the surface of ripening fruit as it begins to soften and show color, continuing through to harvest. Scars left by oviposition may appear as indented, soft spots on the fruit surface. Small white- or cream-colored larvae hatch within a few days and feed in the fruit, causing the fruit to soften and collapse around the feeding site. Further damage may be caused by secondary pathogens (fungi and bacteria) which attack the damaged fruit. At maturity, the larvae may be up to 1/8 inch long. They may pupate inside or outside the fruit. The length of the life cycle depends on temperature, with adults most active at cool temperatures (around 68 degrees F). Most soft-skinned fruits are vulnerable to attack by SWD, including peach, plum, cherry, grapes (table and wine), strawberry, blueberry, and cane fruits. It has also been found in Asian pear, fig, and hardy kiwi. See SWD under Common Insects for an additional image of the larval stage.