Earthworms are clearly beneficial in soil for aeration, water penetration, thatch control, addition of bacteria, organic matter and other benefits. Most soils are probably lacking in worm populations and much has been written about the benefits of worms and using them for soil improvement. However, on rare occasions and in rare situations, earthworms may become undesirable. Earthworms are also a major food source for some species of moles and are the main host for certain cluster flies.

Several of the worm species found in soils are introduced species from other countries or continents. Some of our native species of earthworms may be being displaced by the introduced species Extremely high populations may disrupt roots or create so much upturned castings on the surface as to smother low growing blades and create a bumpy surface. Heavy rains may cause worms to be stranded on sidewalks and driveways. These worms will die quickly due to ultraviolet light exposure and drying.
It is possible that the reduced number of lawn insecticides available (and toxic to worms) for insect control has allowed worm populations to rebound. Current pesticides may kill the parasites and predators that reduce worm populations without killing the worms. Worms do not like highly acid soils and reportedly do not inhabit soils below 4.5 pH. Some soil acidification with ammonium sulfate might be helpful, but treat only based on recommendations following soil tests and consider the pH requirements of the turf.

Each earthworm is both male and female so any two adult earthworms can mate. Mating tends to take place on or just below the soil surface and at night. During the Winter, earthworms will migrate deeper in the soil. Night crawlers will mature in about one year and may live up to six years. We have well tested control methods.