Verticillium wilt is a soil-borne fungus that strikes tomato, pepper, berries, snapdragon, eggplant, potato, olives, and over 300 other garden varieties. Non-host species include beans, broccoli, corn and cereal grains.
Fungal spores can be carried into the garden on infected plants, shoes, seeds and tools. Infected plants can also contaminate the surrounding soil and irrigation water. The biggest problem with wilt diseases is that the fungi (Verticillium dahliae) can stay in the soil for several years. All it takes is an insignificant wound to nearby roots to create an entryway for the disease. Older specimens may be able to survive, losing branches on only one side, but smaller plants and seedlings nearly always die. Infected plants contain millions of fungal spores and should be removed completely from the garden and thrown in the trash.
Symptoms of Verticillium wilt
Verticillium wilt looks an awful lot like Fusarium wilt. The most obvious sign is, you guessed it, wilting! Wilting occurs when the xylem is blocked by fungal spores, halting the flow of food and water within the plant. Tissue death, yellowing of leaves (chlorosis), and leaf loss are also symptoms. If you cut the stem of an infected plant, you may see discoloration of the vascular tissue. Just be sure to clean your cutting tool with a solution of 1 part bleach and 9 parts water afterward, to avoid spreading the contamination.
The biggest difference between Fusarium and Verticillium wilts is that the damage is often restricted to the lower or outer parts of the plant when it is the Verticillium fungi causing the problem.
How to prevent Verticillium wilt
Since there are no effective controls of wilt disease, prevention is the only way to go. Use these tips to keep your garden (relatively) free of this fungal disease:
If Verticillium wilt is present, removal of the infected plant(s) should be the first response. If the infection becomes widespread, soil solarization may be the only effective treatment. Fungicides are not effective on small scale gardens.
I hope this information inspires you to grow more of your own food. You can ask your garden questions on my Home page.