White Stuff On Roots Of Vegetable

Q: Can you please help me identify what’s killing my vegetable plants? They were started indoors, given excellent growing conditions in raised beds with compost, and irrigated with drip irrigation. The condition starts with the plant wilting overnight, and when I pull it up, I find white stuff on the roots and on the base of the stem. 

A: Your plants have Southern blight. It is almost impossible to control in a home garden. The disease is also called southern wilt, southern stem rot and southern root rot. It results from infection by a soilborne fungus: Sclerotium rolfsii. The fungus survives in the soil as tiny, tan to brown, round balls of sclerotia. The fungus produces lots of stringy white hyphae or mycelia around infected parts and in and on the soil. Commercial growers fumigate the soil to control the disease. Home gardeners have few options other than providing perfect growing conditions. One strategy is to invert the soil in your beds each year. This buries infected plant debris and sclerotia. Modify planting dates to avoid conditions that favor disease development; wait until May to plant in a shaded bed. Maintain adequate soil pH for optimum plant growth. Lower soil pH encourages disease.