Verticillium Wilt

Verticillium wilt is a soil-borne fungus that strikes tomatoes, peppers, berries, snapdragon, eggplant,  olives, potatoes, and over 300 other garden varieties. Non-host species include beans, broccoli, corn, and cereal grains.

Healthy strawberry plant (left) and plant infected with Verticillium wilt (right). (Brian Prechtel) Public Domain

Fungal spores can come 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. Smaller plants and seedlings nearly always die. Infected plants contain millions of fungal spores and should be removed from the garden and thrown in the trash.

Symptoms of verticillium wilt

Verticillium wilt looks a 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 sanitize your cutting tool afterward with a household cleaner to avoid spreading the contamination.

The primary 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 controls for wilt disease, prevention is the only option. Use these tips to keep your garden (relatively) free of this fungal disease:

• Install resistant varieties.
• Rotate crops every 2-3 years, using non-host species.
• Compost broccoli residue in areas susceptible to this disease (it gives off chemicals that harm the fungi).

If Verticillium wilt is present, remove the infected plant(s). If the infection becomes widespread, soil solarization may be the only effective treatment. Fungicides are not effective in small-scale gardens.