Fall is when all wasps, including paper wasps, yellowjackets and baldfaced hornets, reach their peak numbers for the year. It is also the time when their behavior changes and people are more likely to notice colonies, or are more likely to be stung by wasps from a colony they hadn't yet found. Fall is the time to keep an eye out for wasp activity and for wasp nests.
Previously we described the recent spread of a new species of paper wasp into the state that is now common in Iowa. See an earlier article about the European paper wasp in the July 6, 2016 Horticulture & Home Pest News.
The European paper wasp, Polistes dominula, was first reported in Massachusetts in 1981 and has since spread through the U.S. The European paper wasp is somewhat smaller than the northern paper wasp (Polistes fuscatus) and is black with bright yellow stripes and spots. European paper wasps tend to locate their nests where humans are more likely to come into contact with them, making them a slightly larger threat.
European paper wasps have more individuals in a colony than native paper wasps and this is the time of the year when colonies will have many individuals and be very noticeable. European paper wasps also prefer to nest in concealed locations which can result in nests in places where they may encounter humans.
Nests that are in locations where encounters with humans or pets are likely can be managed with an insecticide spray. Nests should be sprayed at night or very early in the morning when colder temperatures reduce wasp activity. Do not attempt this if you know or suspect you may be allergic to wasp stings. Take precautions such as tucking pant legs into socks and making sure sleeves are not loose. Wasps can sting multiple times and once under clothing against the skin a single wasp can sting many times and you cannot run away from them.
For more information on wasps and bees in Iowa please see Social Wasps and Bees in the Upper Midwest from the University of Minnesota.
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