Verticillium wilt of tomato.
3 (1 = rare 5 = annual)
5 (1 = very little damage 5 = plants killed)
Pepper, tomato, potato and eggplant are the four vegetable crops most commonly affected by this disease. Both of these Verticillium species attack a wide range of plants besides vegetables.
The plant symptoms that result when this fungus attacks may be confused with natural death of the plant as well asother plant problems such as fusarium wilt, bacterial wilt, root rots as well as drought and damage due to excessive soil moisture.
Plants may be infected for awhile before symtoms become visible. Initial symptoms include wilting - either the entire plant may wilt or only parts of the plant may wilt. Partially wilting plants are only partially infected. Partialling wilted plants may recover at night till the fungus spreads through more of the plant. On wilting tissue, the leaves soon begin to yellow then turn brown and die. Internal discoloration or streaking of the sapwood occurs in most plants.
Verticilium albo-atrum is adapted for the cooler soils in the world so is not usually found in tropical soils. Verticillium dahlia is more commonly found in most soils around the world. Even though V. albo-atrum is not as common as V. dahlia, it is more likely to be fatal to most plants.
These two Verticillium species are root invaders. They do not live in the soil as saprophytic fungi but can survive in the soil for several years as specialized "structures". Infected dead root systems improve the survival of these fungi in the soil. These fungi are often moved with infected soil or plants. They invade stressed roots. Plants that are blooming or fruiting tend to be more susceptible.
Try to avoid stressing plants, especially the roots. Maintain/provide proper moisture and soil drainage. Avoid high nitrogen fertilizers - use balanced fertilizers or fertilizers with slightly higher phosphorus levels. Avoid deep cultivation around plants while they are growing. Avoid using herbicides if possible. If herbicides are used - spot treat (treat individual weeds very carefully). Rotate crops yearly - do not rotate with a related crop such as tomato and pepper. Remove infected plants and as much of the infected root system as soon as posible. Destroy the infected plants by burning or aerobic composting. Buy resistant plants whenever possible.
Commercial growers often grow a cover crop during the winter and plow/disk it in before cover crop goes to seed in the spring. This tends to help reduce infection the following growing season. This may or may not be practical for the home garden.
Filed under problems: Fungal Disease