The Purdue Plant and Pest Diagnostic Laboratory

What's Hot at the P&PDL
March 2, 2012

Pest Predictions Without Winter

Timothy J. Gibb, Extension Entomologist and
Douglas Richmond, Turfgrass Entomologist

With the very mild winter that most of Indiana experienced so far, we are being asked about its effect on insect populations for this year. The consensus among entomologists is that although insect populations were probably not especially hurt by low temperatures this winter, they probably have not benefitted that much either.  Insect pests have developed behavioral and physiological strategies to get through even very cold winters, so the lack of cold this winter probably will not affect the kinds of pests we have this year.  However, because the emergence of insects is tied directly with temperature accumulations, we do expect to see insects emerge much earlier during years with mild winter compared to more normal years.  In fact, we are already seeing the late winter emergence of many arthropods such as lady beetles, clover mites, and crane flies that usually begin later in March.  Take, for example, clover mites.  We are already receiving calls about these very tiny mites (smaller than a pin head) that may occur in high numbers, first around windows, but later over entire walls of buildings.

Clover mites most often originate in turfgrass stands that are relatively young (2 – 5 yrs old), well maintained and fertilized.  During the late winter and again in the fall time, these mites seem to migrate in large numbers and often end up inside structures, including homes.   Clover mites are small enough to squeeze through the tiniest of cracks and openings in buildings, making it nearly impossible to seal them out.  Turfgass grown right up to and in direct contact with building foundations can also facilitate their entry into structures. Although they are harmless to humans and pets, the presence of large numbers of these mites inside structures can be unsettling and attempts to wipe or sweep them from light colored surfaces such as walls often smashes them, resulting in brown/red steaks that can be difficult to clean.

The temporary application of double-sided tape around window sills can help stop migrating mites from gaining further access into affected structures, but once inside, these mites often become dehydrated rather quickly making vacuum cleaning of their tiny dead bodies one of the best options.   


Click image to enlarge

Clover mites

Size of clover mites

Purdue Plant & Pest Diagnostic Lab Purdue Cooperative Extension Service