How to Manage Pests

White mold
(Sclerotinia lettuce drop)—Sclerotinia spp.

White mold is a distinctive disease that most often affects stems and foliage at the base of cole crops and lettuce plants. Affected tissue develops a soft, watery rot and white, cottony mycelium forms on the surface. Plants may wilt if stems are girdled by the decay. As affected tissue dries up, it turns yellow to white, and hard black sclerotia form on the surface or inside the dead stems.

Life cycle

The white mold fungus, Sclerotinia spp., survives from one crop to the next as sclerotia in or on dead plant tissue. Because prolonged wetness is required for infection, disease usually occurs at the base of plants or beneath heavy plant canopies. Infection and development is favored by cool, moist conditions.

Solutions

White mold is favored by a wet soil surface. Use of raised beds and careful furrow irrigation that does not overflow onto bed surfaces can help limit damage. Space plants well enough to allow good air circulation. Remove and destroy entire infected plants and crop residues as soon as you see the mold. Sclerotia can be destroyed by burying them 10 inches or more below the soil surface. Solarization may also give control.