IDENTIFICATION — If the leaves of your annual flowers and vegetable plants seem to be yellowing and curling, your garden may be infected with verticillium wilt. Older, lower leaves fall off first, as younger, higher leaves become discolored and distorted. Only a few healthy leaves will remain at the top of the plant until it eventually dies.
To make sure wilt is the culprit, cut open an infected plant stem horizontally, near the soil line. Look for a narrow tan ring between the center and stem wall, or dark streaks shooting up the middle of the stalk.
CONTROL — Plants infected with verticillium wilt should be destroyed promptly because there is no control. The disease-causing fungus can live in the soil many years after the plant has died, so rotate your crop every four to six years. And make sure to keep it far away from your compost pile.
Protect your garden from wilt by buying resistant plants. Look for kinds that are labeled “VFN resistant.” These plants are less susceptible to verticillium wilt (V), fusarium wilt (F) and nematodes (N), which are all common pests.
Verticillium wilt also attacks some trees and shrubs. In large woody plants, the fungus causes leaves to yellow and curl and branches to die suddenly. If you suspect verticillium wilt has infected a tree or shrub, cut a twig from the infected area. Look for the ring in the cross section; there may also be streaking along the length of the twig if you peel back the bark. Before removing a valuable tree, consult with a plant pathologist to be sure of your diagnosis.