Lawn grubs are usually one of three types -- annual white (from June beetles), true, and aetenius. The annual white types typically cause the most problems.
Annual white grubs emerge as adults in late June, depending on weather conditions. Eggs are laid in moist soil, near sidewalks or driveways or under night lights around the fourth of July. Eggs hatch during the first week or so in August. Grubs feed on grass roots.
Large, dead patches in late summer may be an indication of grubs. Only inspection under the dead turf can indicate grub presence. Control may be necessary if twelve to fourteen grubs per square foot are found in an actively growing lawn. If the lawn is dormant or less than active or dormant, fewer grubs may be needed to cause noticeable injury to the turf.
Dead grass killed by grubs comes up "like carpet" if pulled.
Chemical controls must be watered in to place the chemical in the area that grubs are located. Usually one-half (1/2) inch of water is sufficient. Check the current University of Illinois Urban Pest Management Handbook for recommendations. Make sure to physically locate grubs in the turf before applying chemicals.
Grubs frequent the best looking lawns, which tend to be more suitable for egg laying.
See: Sod Webworms
Articles in this collection were copyrighted 1995 by the Board of Trustees of the University of Illinois. For full copyright information about the articles in this encyclopedia, click here.