The ejected material, castings, are used to line the burrow or are deposited at the entrance. Earthworm activity depends directly on soil moisture and temperature. They become active when soil thaws in the spring and move deeper in late summer as the soil dries. Pesticides and Earthworms Pesticides applied to control turf diseases or insect pests may severely affect earthworms. This can be avoided by accurately identifying and assessing problems and, if a treatment is necessary, selecting products that have the least detrimental effect.
Products commonly used on turf areas vary greatly in their toxicity to earthworms.
Most of the common earthworm species in Kentucky grow slowly, live for several years, and have low reproductive rates. Consequently, repopulation of poisoned soil is slow. Preservation of earthworms is important where thatch is a problem. Generally, the only time an insecticide application is necessary for most turf situations is to control white grubs. An application, if needed, should be made in about mid-August.