What is Verticillium?

Verticillium is a large fungal genus with representatives found all over the world. These fungi are often pathogenic, causing health problems for plants and animals they infect, and they can be a serious problem for the agricultural industry. A Verticillium infestation can ruin a crop or cause severe damage, which lead to significant financial losses for a farmer. Once present in an environment, the fungus can also be extremely difficult to get rid of, which makes an infection even more costly.

These fungi manifest in the form of woolly colonies of mold which can be yellowish to green in color. Most species grow into the substrate, covering the organism they infest with a thin layer of mold which is difficult to remove because it is entangled in the vascular system of the organism. As a result, the fungus often kills its hosts by cutting off the supply of fluids and nutrients. Verticillium infection can kill insects in less than a week, while infected trees and plants may struggle for several weeks before eventually succumbing.

Certain Verticillium species which prey on insects are used in natural pest control. Farmers can spray the fungus over a crop so that when insects land on the crop, they ingest the sticky fungal spores. The fungi start to grow inside the bodies of the insects, eventually breaking through the body and causing death. Infected insects can spread the fungus in the days before their deaths, and the fungus also produces spores after the death of the insect which can spread across a wide area. Nematodes can also be managed with Verticillium applications.

In plants, one of the most problematic Verticillium species is V. dahliae, which lives in the soil in a dormant state. When the fungus detects plants which could be a useful source of nutrients, the spores attach to the plants and begin growing, causing a condition known as Verticillium wilt. The wilt classically starts at the margins of the plants and works its way in, slowly killing the plant.

If Verticillium wilt does begin to appear, infected plants should be removed immediately and burned. In the case of trees, sometimes trimming the infected branches back and fertilizing the tree is enough to prevent the spread of the fungus. Because the spores can live for up to 15 years in the soil, gardeners need to be vigilant about managing the first signs of Verticillium wilt in their plants, and they may want to consider planting things which are resistant to the fungus. If there is a high concentration of spores, soil fumigation to kill the fungus is also an option, although this can be a costly endeavor, and it may damage beneficial fungi which are naturally present in the soil.