Cause Verticillium dahliae, a soilborne fungus that infects a wide range of crops, vegetables, fruits, and ornamentals. It survives in soil for many years through the production of microsclerotia in infested plant tissue. It infects via roots, invading water-conducting tissue. Cool, moist soil favors the disease. Some varieties have a greater degree of resistance. Young plants can be infected but symptoms won't develop until after fruit-set.
Symptoms Under stress from heat and/or fruit set, wilting and yellow, V-shaped areas develop at the leaf edge. Leaves turn completely yellow and dry up. Wilting may be one-sided and progresses up the plant until the plant dies. A cross-section of a node near the plant base may reveal discolored vascular tissue.
- Delay planting until temperatures are warm.
- Avoid planting in fields known to have a Verticillium wilt problem.
- Avoid former potato, tomato, or mint fields.
- Remove diseased plants and postharvest debris to reduce fungal buildup.
Chemical control Fumigating soil has been effective in the Hermiston, OR area.
- Metam sodium (Vapam HL) at various rates. See label for details. Restricted-use pesticide.
- Double Nickel LC at 0.5 to 4.5 pints/A for soil application on 14- to 28-day intervals. Can be applied the day of harvest. 4-hr reentry. O