Utah Pests News Summer 2009

click here for pdf version

Natural Control of Invasive Wasp 

  A viral or protozoan pathogen that causes wing deformation and sick larvae may help to bring the burgeoning European paper wasp population under control.

The European paper wasp, Polistes dominulus, was introduced into eastern North America almost 30 years ago and has been making its way westward, arriving in northern Utah less than 10 years ago. Since its arrival, it has overwhelmed and displaced a number of native species of paper wasps. This is a common phenomenon with newly invasive insects. They arrive with few or no natural enemies (predators, parasites, and pathogens) to keep their populations in balance, and quickly elevate to pest status.

There is some good news on P. dominulus populations in northern Utah – wasp individuals infected with an entomopathogen, most likely a virus or protozoan, have been spotted. In 2006, I first observed European paper wasp adults with deformed wings on the ground below several nests hanging from a porch ceiling. Adults typically fly to and from their nests to find food. But these adults were spending significant time on the ground below their nests which indicated they may not be orientating or navigating properly. Then I noticed flaccid wasp larvae on the ground underneath their nests. Adults will clean their nests of sick or dead larvae, but the number of sick larvae was unusually high. These symptoms fit with those of an insect infected by a pathogen. These first observations were made in eastern Logan. Since then I have observed similarly “diseased” wasps in Richmond and other locations in Cache Valley.

If you have observed “diseased” European paper wasps in any areas outside of Cache County, please send me an e-mail message informing me of the location and approximate date of observation (diane.alston@usu.edu). It will be interesting to follow the spread of this pathogen that may help reduce P. dominulus to being just another paper wasp, rather than the dominant nuisance and stinging wasp in northern Utah.

-Diane Alston, Extension Entomologist