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Problem
(factsheet)
Plant NameTypeDescription 
Botrytis bunch rot (Gray mold)GrapeDiseaseThis fruit rot is caused by a fungus which also causes disease in strawberries, raspberries, and many other plants. In grapes, the disease is typically limited to fruit. Infection may occur throughout the season and in storage. Early-season infections often occur through the flower. A characteristic, fuzzy, gray-brown coating of fungal growth develops on the young fruit, which may later dry into infected mummies. Later infections may develop as a result of rain during harvest, causing a condition known as "slip-skin". Brownish patches develop on the fruit and the skin separates from the flesh. After harvest, storage rot may cause a brown, soft rot of the fruit. The fungus overwinters on old cluster stems, canes, or mummified, diseased fruit. Disease development is favored by tight fruit clusters, dense foliage, and cool, moist conditions.
Powdery mildewGrapeDiseasePowdery mildew is a fungal disease which affects all aboveground portions of grapes. Leaves develop characteristic white to grayish patches of fungus on the underside. Both surfaces of shaded leaves may be affected. Young leaves are deformed and stunted, while older leaves may show some yellow spotting. Stems are infected while green and develop brown to black patches which later show as a reddish discoloration. Infected flowers fail to set fruit. Infected fruit develops grayish spots on the skin. These spots later appear russetted and the affected fruit may crack and drop. Disease development is favored by warm, dry weather. The spores are spread by wind, and the fungus overwinters on the bark or in infected buds. European cultivars (Vitis vinifera) are more susceptible than juice grapes. 'Thompson Seedless' is also affected.
Brown marmorated stink bugGrapeInsectThe 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. BMSB feeding on the surface of the grape berry initially causes a small brown necrotic spot at the puncture site. Over time, the spot enlarges and the fruit shrivels or deforms or aborts. Secondary damage may occur from rot at the feeding site. BMSB feeding on the stems which support fruit clusters may cause entire bunches of grapes to be ruined or drop from the plant. BMSB can also be a contaminant of harvested fruit and may taint freshly crushed juice. Other known fruit/nut hosts of BMSB include caneberries, blueberry, apple, pear, filbert, and stone fruits including apricot, cherry, and peach. 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/.
Cutworms and armywormsGrapeInsectCutworms are the larvae of noctuid moths. These common moths are medium-sized with fairly dull coloration. The greenish, grayish, or tan caterpillars are hairless, nocturnal, and generally spotted, striped, or otherwise marked. They may be 1/4" to 1" in length and tend to curl up when disturbed. At night, cutworms climb into the plant and feed on buds and shoots. They typically spend the day just beneath the soil surface or under debris near the host. Weeds are the primary food source for cutworms.
Grape erineum miteGrapeInsectThe grape erineum mite, Collomerus vitus, is actually a type of eriophyid mite. They are very tiny, whitish, worm-like, and spindle-shaped. Their bodies have definite annulations or rings, and only two pairs of legs directly behind the mouthparts. They overwinter under outer bud scales and feed on leaves during summer. The upper leaf surface becomes blistered, and blisters on the lower leaf surface turn white, yellow, or brown. Colonies of mites live inside the blisters (erinea) formed by their feeding on the lower surfaces. The blisters contain masses of enlarged leaf hairs. Large infestations can cause major stress on young vines. From mid-August to leaf drop, the mites migrate back to the overwintering sites beneath bud scales.
Spider mitesGrapeInsectSpider mites are tiny, eight-legged mites which may range in color from yellowish to green or red. Several species may occur on grape. They typically feed on the underside of leaves, causing a yellowish stippling or speckling of the leaf. Severe infestations can cause entire leaves to turn yellow and drop, sometimes resulting in considerable leaf loss and reduced yield. Spider mite feeding is usually accompanied by webbing on the underside of leaves and between leaves and stems. Mites are worse in hot, dry, dusty conditions.
Spotted wing Drosophila (SWD)GrapeInsectSpotted 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.