Symptoms: Commonly found throughout the United States, Fusarium wilt is a fungal disease that attacks potato, tomato, eggplant and pepper. Disease fungi (Fusarium oxysporum) enter through the roots and interfere with the water conducting vessels of the plant. As the infection spreads up into the stems and leaves it restricts water flow, causing the foliage to wilt and turn yellow. Symptoms often appear later in the growing season and are first noticed on the lower (older) leaves. As the disease progresses, the younger leaves will also be affected and the plant eventually dies. In many cases, only one branch or side of the plant show symptoms.
Fusarium wilt can survive for years in the soil and is spread by water, insects and garden equipment. It develops during hot weather and is most destructive when soil temperatures approach 80 degrees F. Dry weather and low soil moisture encourage this plant disease.
Control: Choose resistant varieties when available. Remove stricken growth and sterilize clippers (one part bleach to 4 parts water) between cuts. Control garden insects, such as cucumber beetles, which are known to spread the disease. Remove all weeds from the garden (many weed species host the disease). The biological fungicide Mycostop will control wilt caused by Fusarium. If the disease persists, it is best to remove the entire plant and solarize the soil* before planting again.
* To solarize the soil, you must leave a clear plastic tarp on the soil surface for 4-6 weeks during the hottest part of the year. Soil solarization will reduce or eliminate many soil inhabiting pests, including nematodes, fungi, insects, weeds and weed seeds.
Photo Credit: Tamil Nadu Agricultural University, India