Pacific Northwest Vegetable Extension Group

of Washington State University, Oregon State University, and University of Idaho

Photo Gallery of Vegetable Problems

Watermelon

(Click on photo to enlarge)

Diseases

Disease: Curly top
Pathogen: Various strains of Beet curly top virus (BCTV), which are vectored by the beet leafhopper (Circulifer tenellus)
Host crops: Numerous plant species including many vegetables such as bean, beet, carrot, eggplant, coriander, pepper, potato, tomato, various cucurbits such as squash, cucumber, pumpkin, watermelon, etc.

Photo showing symptoms of curly top on pumpkin leaves Phot of curly top symptoms on acorn squash leaves Photo of symptoms of curly top on squash leaves
Symptoms of curly top on pumpkin leaves. Note yellowing of the foliage. Squash, acorn Squash
Photo Source: Ken Eastwell, Washington State University virologist Photo Source: Phil Ham, OSU plant pathologist

On-Line Resources:

Pacific Northwest Plant Disease Management Handbook: Squash (Cucurbita spp.) – Curly Top
 

Disease: Damping-off/Seedling blight
Pathogen: Pythium
Host crops: Most vegetables are susceptible to damping-off/seedling blight.

Photo of phthium root rot of watermelon
Photo Source: Lindsey du Toit

On-Line Resources:

Pacific Northwest Plant Disease Management Handbook: Watermelon (Citrullus lanatus) – Damping-off

See Diseases, pests, and other problems common to many vegetables: Damping-off/seedling blight.

Disease: Verticillium wilt
Pathogen: Verticillium species
Host crops: Numerous vegetables including many brassica vegetables (but not broccoli), cucumber, eggplant, pepper, potato, pumpkin, radish, spinach, tomato, watermelon, etc.

Photo of symptom of chlorosis of watermelon leaves Photo of symptoms of verticillium wilt on watermelon leaves Photo of symptoms of verticillium wilt on watermelon leaves
Foliar chlorosis and early stages of necrosis associated with Verticillium wilt of watermelon. Partial foliar wilt associated with early stages of Verticillium wilt of watermelon. Complete foliar wilt associated with later stages of Verticillium wilt of watermelon.
Photo Source: Sacha Johnson

On-Line Resources:

Pacific Northwest Plant Disease Management Handbook: Watermelon (Citrullus sp.) – Verticillium Wilt

See Diseases, pests, and other problems common to many vegetables: Verticillium Wilt.

Insect/Mite Pests


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

Photo of adult Western flower thrips Photo of immature Western flower thips
Adult Western flower thrips are minute (less than 1/8 inch long) narrow-bodied insects that range from straw to dark yellowish-brown in color. Their four wings are very narrow and characterized by long fringed hairs. 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,

Cucurbits: Thrips, UC IPM Online, University of California

See Diseases, pests, and other problems common to many vegetables: Western flower thrips.
 

Abiotic Problems

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.
 

Severe wart-like growths on a pumpkin caused by edema Close-up view of severe edema symptoms on a pumpkin Small but extensive symptoms of edema on a winter squash Close-up view of edema symptoms on the surface of a winter squash
Severe wart-like growths on a pumpkin caused by edema. Close-up view of severe edema symptoms on a pumpkin. Small but extensive symptoms of edema on a winter squash.Close-up view of edema symptoms on the surface of a winter squash.
Photo Source: Lindsey du Toit, Washington State University. Photo Source:
Phil Hamm, Oregon State University.
Photo Source: Lindsey du Toit, Washington State University.

On-Line Resources:

http://www.omafra.gov.on.ca/english/crops/facts/00-031.htm#oedema

http://www.ces.ncsu.edu/depts/pp/notes/oldnotes/gp3.htm

Our pages provide links to external sites for the convenience of users. WSU Extension does not manage these external sites, nor does Extension review, control, or take responsibility for the content of these sites. These external sites do not implicitly or explicitly represent official positions and policies of WSU Extension.

WSU Mount Vernon NWREC, 16650 State Route 536, Mount Vernon, WA 98273-4768, 360-848-6120
Contact Us: Lindsey du Toit and Carol Miles