Verticillium wilt is caused by six different species of fungus, all of the genus Verticillium. These six fungi can attack most of the plants and trees that gardeners like to grow, including vegetables, fruits, and ornamental plants.
Verticillium fungi spend the winter in plant debris lying on the ground. Cool, wet weather triggers it to spread rapidly, creeping into wounded tissue or entering the soil where it can be taken up in plant roots. Once verticillium has established a presence inside a plant, it colonizes the xylem, or vascular tissue, of its host. When hot weather hits, the fungus interferes with the plant’s ability to transport water to its branches and leaves, causing the demise of the host.
- Generalized wilting over time.
- Stunted growth.
- Yellow leaves with scorched edges.
- Gradual leaf drop.
- Brown to black streaks on runners.
- Wilting and death of branches.
- Stem discoloration, starting at the base and gradually moving upward.
- Pinkish potato tubers.
- Small fruits.
- Excessive seed production.
- Premature death.
Unfortunately, there is no fungicide, natural or otherwise, that is entirely effective for treating verticillium wilt. Annual plants should be carefully bagged up and burned as soon as symptoms appear. Because verticillium fungi can survive in the soil for over 10 years without a host, a new garden site should be chosen. If this is not possible, cover the ground with clear plastic and allow the sun to thoroughly cook the soil before further use.
If you want to make an effort to save a valuable perennial plant, note that your options are limited and that you will have to be careful to avoid spreading the fungus to other plants. Prune out all obviously affected tissue, sterilizing pruning tools in bleach solution between every cut. Rake up and destroy all fallen leaves and fruits. Pay close attention to maintaining plant health with adequate water. If verticillium wilt symptoms worsen or continue into the next growing season, you are probably better off to destroy the plant.
Choosing verticillium-resistant plant varieties is a great starting point. Otherwise, avoiding this fungal disease is a matter of garden sanitation:
- Buy seeds from reputable sources.
- Practice crop rotation in the garden.
- Keep weeds in check.
- Don’t overdo the fertilizer, which causes rapid growth of soft, disease-prone tissue.
- Clean up dead plant matter on a regular basis.