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Selected Vegetable Diseases

ID

426-363

Authors as Published

Allen Straw, Extension Specialist, Southwest Virginia Agricultural Research and Extension Center.

 

Disease or Other CauseVegetablesSymptomsHow to Control
Fungi
AnthracnoseBeans
Cucumbers
Cantaloups
Watermelons
Peppers
Tomatoes
Check for reddish-brown or black sunken spots or blotches on leaves, stems, pods, and/or fruits.Practice two-year or longer rotation. Avoid overcrowding and keep weeds removed. Destroy plant wastes after harvest. Spray or dust with approved fungicides. Use certified seed.
Early Blight or Target SpotTomatoes
Potatoes
Brown to black spots on leaves and stems. Spots are angular to round with concentric rings (targets). Spots may merge to kill portions of leaves and defoliate the plants, starting at the base. Tomato fruit may sunscald and show sunken leathery spots near the stem.Practice crop rotation and destroy plant wastes after harvest. Use well-drained soil and keep weeds down. Space plants to allow good air circulation. Use resistant varieties. Spray or dust with approved chemical controls.
Late BlightPotatoes
Tomatoes
Develops during wet, humid season. Irregular, greenish-black, watersoaked spots develop on leaves, petioles, and stems. May resemble sunscald or frost damage in advanced stage. A sparse whitish mold appears on underleaf surface. Fruits and tubers also affected.Same as for Early Blight. See above.
Septorial Leaf BlightTomatoForms circular spots randomly scattered across leaflets. The centers are often gray and under favorable conditions, will have small black fruiting bodies. Lower leaves affected first. Spotted leaves become chlorotic and dry out quickly.Treat seed with hot water. Control weeds, especially of solanaceous family. Pick off affected leaves and destroy.
Downy MildewBeans
Cucumbers
Cantaloupes
Yellow to dark areas that may be vague or sharply defined, occurring on upper surface of older leaves. White to dark cottony mold on underside of leaves and on bean pods. Vines may be scorched and killed.For cultural controls, same as Powdery Mildew. Consult Extension agent for approved chemical controls.
Powdery MildewSquash
Pumpkins
Watermelons
Cantaloupes
Cucumbers
White or brown mealy growth on leaves and young stems, especially on upper surface and occasionally on the fruit. Plants may yellow and wither, while fruit sun-scalds or ripens prematurely.Use resistant varieties. Practice rotation and good weed control. Space plants well. Destroy crop residues. Spray or dust with approved chemical controls.
Fusarium and/or Verticillium WiltTomatoes
Watermelons
Cantaloupes
Seedlings wilt and die. Older plants are stunted while leaves wilt, turn yellow, wither, and drop. Dark streaks appear in lower stem and roots. If only wilting symptom occurs, may be black walnut wilt if a tree is near garden.Plant in well-drained, wilt-free soil and follow a 3- to 4-year crop rotation. Use resistant varieties where possible.
Yeast SpotLima beansDark brown, often wrinkled lesions occur on the lima bean. Pod must be opened to see this condition.Caused by a yeast that is transmitted by a stink bug. Control of sting bugs will prevent this disease.
Bean RustBeans (many species)Reddish-brown or “rusty” pustules form most abundantly on underside of leaves. Lesions will also form on the top of leaves and sometimes on stems and pods. Defoliation may occur.Rotation of crops is useful for large plantings but is of little use for home gardens. Use resistant varieties. Do not work in beans when leaves are wet. Use fungicide if necessary. Remove plant wastes when harvest is over.
Scab or PoxCucumbers
Muskmelon
Honeydew
Pumpkin
Squash
All aboveground tissues are susceptible. Leaf spots watersoaked at first, angular in outline, soon becoming dry. Dead tissue often falls out, leaving leaf tattered. Canker may form on vines. Fruit spots sunken, may exude sticky sap. Green velvety growth of spores and mycelium will form in the cavity.Plant in well-drained soil; treat seed with hot water. Plant resistant varieties if possible.
Root RotMany vegetablesPlants may become pale, yellow, and/or stunted. May wilt, die back or collapse. They do not respond to fertilizer or water. Decayed roots may be mushy or firm and covered with mold.Practice rotation. Avoid wet, poorly drained soils. Remove and destroy affected plants. Control nematodes and avoid root injury.
Damping-offMany vegetablesSeeds rot and fail to emerge. Seedlings appear but wilt and turn brown or fall over.Select a well-drained garden site. Plant seed treated with fungicide. Indoors, use sterile seed-starting mixture. Do not keep soil too wet.
Bacteria
Bacterial Wilt (Pswudomonas)Tomato
Potato
Other species of Solanaceae
Wilting of foliage. Youngest leaves often wilt first and oldest may become chlorotic. Browning of internal stem tissues or rotting of pith.Select well-drained site. Practice weed control. Avoid planting susceptible crops in infested soil.
Bacterial Wilt (Erwinia)CucurbitsLeaves wilt from the leaves toward plant. Whole vine eventually wilts. Resistant plants may be dwarfed rather than wilt.Spread by cucumber beetle. Control disease by keeping beetle populations under control. Small seedlings can be protected from beetles with cheesecloth cages.
Common Scab or Potato ScabIrish potatoes
Other plants with fleshy roots
Scab-like lesions may be either sunken or raised. Potatoes usually have sunken lesions.Keep soil pH below 5.3. Avoid alkaline fertilizers. Use certified seed potatoes. Rotate crops.
Other Organisms
VirusesMany vegetablesSymptoms vary considerably. May consist of yellowing, mosaic pattern, streaking, stunting, spotting, mottling, etc.Use resistant varieties where possible. Control weeds, insects, and nematodes, which may transmit disease.
NematodesCucumbers
Cantaloupes
Tomatoes
Carrots
Many others
Plants may be stunted, yellow, and have galls or swellings on roots. Or roots may be stunted, bushy, and discolored. Plants may suddenly wilt in dry weather.Move garden to a different area or treat soil with approved chemical controls. Crop rotation with certain plants may be effective.
Cultural
Blossom End RotTomatoes
Peppers
Watermelons
Squash
Blossom end of fruit becomes dry, sunken, leathery and brownblack; or light colored and papery in pepper. Half of fruit may be affected.Maintain even soil moisture by watering during dry periods. Mulch or cultivate shallowly during drought. Fertilize according to soil test, being certain calcium is sufficient.
2,4-D and Dicamba InjuryTomatoes
Beans (most susceptible)
All vegetables may be affected
Leaves and stems curl, become distorted and twisted. Leaf margins are wavy or frilled. Tomato fruit may be cracked and distorted.Do not use 2,4-D in or near the vegetable garden.

 

Original author: Diane Relf, Extension Horticulturist (retired), Virgina Tech.

Rights


Virginia Cooperative Extension materials are available for public use, re-print, or citation without further permission, provided the use includes credit to the author and to Virginia Cooperative Extension, Virginia Tech, and Virginia State University.

Publisher

Issued in furtherance of Cooperative Extension work, Virginia Polytechnic Institute and State University, Virginia State University, and the U.S. Department of Agriculture cooperating. Edwin J. Jones, Director, Virginia Cooperative Extension, Virginia Tech, Blacksburg; Jewel E. Hairston, Administrator, 1890 Extension Program, Virginia State, Petersburg.

Date

May 1, 2009