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Hot Weather and Wasps

There is a lot of chatter coming from Europe and Great Britain saying the abnormally hot weather has resulted in an increase in their wasp population. Is that so on this side of the Atlantic? Authorities say, not! First, let’s look at what we are calling a wasp. In the Mid-Atlantic states, we have several native species of tinywaisted, often black-and-yellow stinging insects. A familiar ground nesting wasp is the Eastern yellowjacket (Vespula maculifrons). Its relative, the bald-faced hornet (Dolichovespula maculata), is the one that creates the football-or-larger sized paper nests in trees or shrubs. Our native paper wasp (Polistes sp.) makes the small, honey-combed, openstyle nest in the eaves of our houses. All three of these common species are annual wasps with only an inseminated queen surviving the winter. Their nests will disintegrate naturally in the winter and not be used again. In the spring, the queen emerges from hibernation and forms a small paper nest. She will start the hive with about 30–40 eggs; fewer in the case of paper wasps. The larvae hatch and within 18–20 days become the infertile female workers. The workers take over building the nest and tending of the larvae. The queen stays in the hive and lays more eggs. Bald-faced hornets can reach popula-

By Carol Allen

tions of several hundred before dying with the frost. Yellowjacket nests can have thousands of individuals by the end of the season. Paper wasps’ numbers peak at about 100. In each case, only the inseminated queens live through the winter by hibernating in a sheltered spot. They start the cycle over again in the spring If the nests of these beneficial insects are out of the way, leave them be. The larvae are fed chewedup insects by the workers and those insects are usually the ones we consider pests. These wasps are great friends of gardeners and an important part of the ecosystem. Toward the end of the season, workers start to feed on sugarbased substances and can become pests themselves. They will feed on ripening fruit and an open can of soda, so beware! The workers of all three of these wasps can sting multiple times if agitated. Yellowjackets and bald-faced hornets are known for their aggression. Let professional exterminators remove a nest if it is too near where people walk or play. The venom will pack a wallop. If someone is stung and exhibits signs of difficulty with breathing, extreme swelling, or muscle pain, get them to the emergency room as they may be experiencing a severe allergic reaction. But back to our original thought: Will wasp populations increase with

Eastern Yellowjacket (Vespula maculifrons) with a juicy earthworm. Rock Creek Park, Washington, DC. Photo by Katja Schulz. Flickr.com.

the climate becoming warmer? Insect populations normally fluctuate over time. Some years, the combination of warm early spring weather and abundant food may result in a population boom. Conversely, cold springs and a decrease in the insects that wasps feed on may result in smaller numbers. As favorable habitats diminish, wasps too will be less plentiful. If our winter weather becomes warmer, will our common wasp hives not die in the fall? Or will sub-tropical wasps move north and find our region to their liking? One such wasp is more common in the south than here. That is Vespula squamosa, the Southern yellowjacket. Their nests do not always die in the winter and the wasp populations can rise into the several thousands. Yes, they have been found in this area. It is the stuff of nightmares! o

Carol Allen describes herself as a committable plant-a-holic. She has more than 25 years’ experience in the horticulture industry, with a special interest in plant pests and diseases; is a Licensed Pesticide Applicator in the state of Maryland; and is an ISACertified Arborist. She can be contacted at carolallen@erols.com.