Disease: Curly top
Pathogen: Curly top virus
Host crops: Numerous plant species including many vegetables such as bean, beet, carrot, eggplant,
coriander, pepper, potato, tomato, and various cucurbits such as squash, cucumber, pumpkin, and
watermelon, etc.

curly top on winter squash — Squash, winter.
**Photo Source:** E. J. Sorensen

curly top symptoms on acorn squash leaves-4 — Symptoms of curly top in an acorn squash crop.
**Photo Source:** Phil Ham, OSU plant pathologist

symptoms of curly top on squash leaves — Symptoms of curly top in an acorn squash crop.
**Photo Source:** Phil Ham, OSU plant pathologist

On-Line Resources:

Pacific Northwest Plant Disease Management Handbook: Squash (Cucurbita spp.) – Curly Top.
Cucumber, Pumpkin, Squash: Curly top (Beet curly top virus), Washington State University Hortsense.

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Powdery mildew

Common name: Powdery mildew
Latin binomial: Golovinomyces cichoracearum (formerly Erysiphe cichoracearum) and Podosphaera fuliginea (formerly Sphaerotheca fuliginea)
Host crops: All cucurbit vegetables (e.g. cucumber, cantaloupe, melon, pumpkin, and squash). There are different races of the pathogens.

powdery mildew on squash leaves — **Photo Source:** Lyndon Porter, USDA-ARS

powdery mildew on squash leaves-2 — **Photo Source:** Lyndon Porter, USDA-ARS

powdery mildew on squash leaf-3 — **Photo Source:** Lyndon Porter, USDA-ARS

powdery mildew on squash leaf-4 — **Photo Source:** Lyndon Porter, USDA-ARS

On-Line Resources:

How to Manage Pests: Pests in Gardens and Landscapes: Powdery Mildew on Vegetables. UC IPM Online, University of California.
Pacific Northwest Plant Disease Management Handbook: Squash (Cucurbita spp.) – Powdery Mildew.
Cucumber, Pumpkin, Squash: Powdery mildew, Washington State University Hortsense.

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Mosaic

Disease: Mosaic
Pathogen: Suspected watermelon mosaic virus

On-Line Resources:

Pacific Northwest Plant Disease Management Handbook: Squash (Cucurbita spp.) – Virus Diseases.

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White mold

Common name: White mold
Latin binomial: Sclerotinia sclerotiorum
Host crops: Cucurbit vegetables (e.g. cucumber, pumpkin, and squash), pepper, snap bean, carrot, cabbage, cauliflower, lentil, field pea, potato, radish, and many weed species.

white mold on squash vines-6 — Pathogen bleaches the vines white. Black sclerotia (dormant survival structures) of the pathogen are often produced inside infected vines.
**Photo Source:** Lyndon Porter, USDA-ARS

white mold on squash-2 — White mold infecting of a gourd of a squash plant.
**Photo Source:** Lyndon Porter, USDA-ARS

close up of white mold on squash vines — Pathogen bleaches the vines white. Black sclerotia (dormant survival structures) of the pathogen are often produced inside infected vines.
**Photo Source:** Lyndon Porter, USDA-ARS

white mold on squash-3 — White mold infecting of a gourd of a squash plant.
**Photo Source:** Lyndon Porter, USDA-ARS

white mold on squash vines-5 — White mold on squash vines.
**Photo Source:** Lyndon Porter, USDA-ARS

On-Line Resources:

Pacific Northwest Plant Disease Management Handbook: Cucumber (Cucumis sativus) – Sclerotinia Stem Rot {White Mold}.
Fruit Rots of Squash and Pumpkins: Sclerotinia White Mold, Vegetable MD Online, Cornell University.
White Mold of Vegetables, Pest Management Fact Sheet #5084, The University of Maine.

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Insect/Mite Pests

Aphids

Common name: Bean aphid, green peach aphid, melon aphid, and potato aphid
Latin binomial: Aphis fabae , Myzus persicae, Aphis gossypii, and Macrosiphum euphorbiae respectively
Host crops: In addition to tomato, eggplant and pepper, bean, melon, sweet corn, corn seed, carrot, cucumber, and eggplant the bean aphid can feed on spinach, Swiss chard, squash, pumpkin, and beet. The green peach aphid can feed on potato, tomato, eggplant, pepper, broccoli, cabbage, spinach, Swiss chard, squash, pumpkin, beet and many weed species including Brassicaceae (cruciferous) weeds. The melon aphid can feed on cucumber, melon, pumpkin, squash, spinach and spinach seed. The potato aphid can feed on cucumber, potato, melon, tomato, pumpkins, squash, and corn seed.

green peach aphid nymph on leaf — Green peach aphid may be found along the midrib on the underside of leaves of a host plant. Mature aphids are about 2 mm long (ca. 1/16 inch), egg-shaped, and the color of the wingless nymphs and adults ranges from pinkish yellow to yellowish green. There are usually multiple individuals in a single colony.
**Photo Source:** Michael Bush, WSU Extension, Yakima, WA

green peach aphid developed wings — The green peach aphid tends to overwinter in stone fruit trees. By late May to early June, individual aphids in a colony develop wings and fly to vegetable crops and a wide range of weeds. As the aphids disperse (June to August), they can transmit important viruses including potato leaf roll virus and potato virus Y.
**Photo Source:** Michael Bush, WSU Extension, Yakima, WA

aphid damage on leaf — The easiest way to scout for aphid colonies is to search perimeter vegetable plants for copious amounts of sticky, glistening honeydew coating the upper surfaces of lower leaves of plants. Honeydew may contain numerous cast (shed) skins (white to gray) and a black sooty mold (fungus) that colonizes aphid honeydew.
**Photo Source:** Michael Bush, WSU Extension, Yakima, WA

On-Line Resources:

Pacific Northwest Insect Management Handbook: Vegetable crop pests-Aphid.
Pacific Northwest Insect Management Handbook: Pumpkin and squash – Aphid.
Common Insect & Mite: Aphids, Washington State University. Hortsense.
See Diseases, pests, and other problems common to many vegetables: Aphids.
For aphids on other crops see: potato, and pumpkin.

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Squash bug

Common name: Squash bug
Latin binomial: Anasa tristis
Host crops: Cucurbit vegetables (e.g. pumpkin and squash).

adult adult squash bug — The adult squash bug has a flattened, elongate body, dark to grayish brown with a speckled pattern on the dorsum, and measure about 1/2 to 5/8 inch long. They may appear to have yellow to orange-striped borders on the abdomen. They release a foul odor when crushed.
**Photo Source:** Michael Bush, WSU Extension, Yakima, WA

squash bug showing long beak — Squash bugs have a long “beak” that they insert into the vine or foliage, and feed by sucking sap from the plant. Yellow specking that later turns brown may appear on leaves where they feed. Severe feeding on young vines, or older vines during the heat of summer, can lead to plant wilingt distal to the point of feeding.
**Photo Source:** Michael Bush, WSU Extension, Yakima, WA

On-Line Resources:

Pacific Northwest Insect Management Handbook. Chapter: Vegetables, Section: Pumpkin and Squash, pt.2.
Vegetables: Cucumber, Pumpkin, Squash: Squash bug. Washington State University Hortsense.
See See Diseases, pests, and other problems common to many vegetables: Squash bug.

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Western flower thrips

Common name: Western flower thrips
Latin binomial: Frankliniella occidentalis.
Hostcrops: Basil, Broccoli, Cabbage , Cauliflower, Cucumber, Onion , Potato , Pumpkin, Squash , Tomato, and Watermelon.

immature Western flower thips — Immature Western flower thrips resemble the adults but are smaller, wingless and translucent yellow in color. There are multiple generations per year and thrips may invade vegetable fields when alternate flowering plants dry up in the summer or when an adjacent host crop is harvested.
**Photo Source:** Michael Bush, WSU Extension, Yakima, WA

On-Line Resources:

Western Flower Thrips Thysanoptera: Thripidae Frankiniella occidentalis (pdf).
Cucurbits: Thrips, UC IPM Online, University of California.
See Diseases, pests, and other problems common to many vegetables: Western flower thrips.

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Abiotic Problems Common to Cucurbits

Edema

Problem: Edema
A physiological problem: prominent when air is cooler than the soil, soil moisture is high, and relative humidity is high. The low plant transpiration rates combined with an increase in water absorption by roots from the soil leads to increased cell turgor pressure, resulting in eruption of epidermal cells as the inner cells enlarge. Protrusion of the inner cells causes epidermal cells to die and discolor, resulting in a ’warty’ appearance that can be misidentified as a disease. In addition to foliar symptoms on some hosts, many cucurbit crops develop wart-like protruberances on the fruit.

edema symptoms on pumpkin-2 — Close-up view of severe edema symptoms on a pumpkin.
**Photo Source:** Phil Hamm, Oregon State University.

edema symptoms on squash-1 — Small but extensive symptoms of edema on a winter squash.
**Photo Source:** Lindsey du Toit, Washington State University

edema symptoms on squash-2 — Close-up view of edema symptoms on the surface of a winter squash.
**Photo Source:** Lindsey du Toit, Washington State University

On-Line Resources:

OEDEMA – Ontario CropIPM, diseases-and-disorders.
Edema – Plant Disease and Insect Clinic, North Carolina State University.

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please contact: Lindsey du Toit at dutoit@wsu.edu or at 360-848-6140.

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