The wasps of August 2006

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

Since mid-July we have received many calls from people that have discovered our largest wasp, the cicada killer, Sphecius speciosus(Hymenoptera: Sphecidae).  These freakishly large solitary wasps dig nesting burrows in bare areas in our yards, then pack them with paralyzed cicadas and lay an egg.  The developing larva feeds on the cicadas provided by the adult.

They overwinter as larvae in the soil and pupate in the spring.   Adults begin to emerge in early July.   Females feed nectar, mate and dig burrows for several weeks before preying on cicadas.  Excess soil thrown out of the burrow forms a regular, U-shaped mound at the entrance.  Only one generation occurs each year.  Despite their large size and very prominent stinger, cicada killers tend to ignore people for the most part and seldom sting us.

For those of us who find near bird-sized wasps a bit intimidating, cultural practices that promote a thick growth of turf can usually eliminate a cicada killer infestation in one or two seasons.  In case of a severe infestation or complete intolerance to the wasp, chemical controls may be employed to rid an area of these impressive wasps.

As we approach mid-August, other wasps will take the center stage in our yards and minds.  This is the time when yellow jackets and European paper wasps reach their peak numbers and begin to raise next year’s queens.   More importantly to us, this is the time when their intolerance to those who venture to close to their nests also increases.   Those that don’t take notice of them are more likely to be lit up by their stings than in the earlier part of the summer.

People often discover ground-nesting yellow jackets while gardening or mowing their lawns, often with painful results.  Since European paper wasp will build a nest almost anywhere, people often discover their nests while moving lawn furniture, filling bird feeders or opening their mailboxes.  They also like outdoor light fixtures and covered electrical outlet boxes. They will nest inside enclosed soffits and behind vinyl siding if there is enough space. Most of these nests are small with 10 to 20 adult wasps in attendance.

Control of ground-nesting yellow jackets and paper wasps with insecticides is easy and straightforward.  A few tablespoons of an insecticidal dust (like Sevin) dumped down the hole of a yellow jacket nest will provide control in three or four days.  Long distance wasp sprays are just the ticket for eliminating exposed paper wasp nests.   Be smart, be careful and be quick.

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