How to Kill Soil-Borne Fungus

Wash empty containers and tools in very hot, soapy water before adding new soil to a pot. Remove all particles of dirt or plant material, as these can harbor spores that will continue the spread of harmful fungi if not destroyed. Add bleach at a rate of one part bleach to five parts soapy water for an extra boost in biologically safe and low-cost fungi killing treatments.

Solarize soil-borne fungus in containers, flats or open fields by heating the soil under a layer of plastic. Wrap containers or flats in plastic and leave them out in the sun for about 30 minutes. Soil will reach a temperature of about 158 degrees Fahrenheit, killing many fungi and bacteria. In large areas or open fields, a larger sheet of plastic is needed to cover the ground. The soil will not reach a temperature as high as it will in pots or flats, and the plastic will need to remain in place for four to six weeks, according to the University of California.

Apply soil fumigants that contain methyl bromide and chloropicrin only as a last resort as these chemicals can be harmful to the ozone. Soil that is to be fumigated with methyl bromide should be covered with a gas-proof covering such as polyethylene sheeting to keep this gaseous compound in the soil. Chloropicrin is effective but can be as irritating to the mucous membranes as tear gas is. You need a permit from your county agricultural commissioner to purchase this product.

Apply a fungicide such as SoilGard to control Pythium and Rhizoctonia fungi. Fungicides such as SoilGard contain helpful fungi that destroy bad fungi and are generally sprayed on the soil or directly onto the foliage of a plant. Several varieties of fungicides are available that kill a few select fungi or a combination of destructive fungi. It is best to have your soil tested to determine which product would be most effective.