Early spring spawns more wasps, hornets

Amy Olson

With spring arriving earlier than usual, so will less happily anticipated signs of summer: wasps and hornets.
University of Minnesota Extension Service entomologist Jeffrey Hahn said not only will the wasps and hornets arrive earlier, but they will swarm in larger numbers.
While unable to speculate on the number of wasps expected to hatch this year, Hahn said the warm, early spring will allow the yellow jacket and hornet queens to produce more offspring throughout summer.
“The queens survive over the winter and start (the nests) from scratch in spring,” Hahn said. Since they started building the nests earlier, he said, the queens will be able to reproduce more workers.
Queen wasps reproduce until the end of the summer. Hahn said early eradication of wasp nests will help control reproduction levels.
Facilities Management supervisor Jim Blake said his crews are on the lookout for bees and wasps.
“I haven’t noticed any yet, but it’s been cloudy and cool lately,” Blake said, noting that bees and wasps are more active during warmer weather. Facilities Management crews exterminate the insects in nests by spraying them with insecticides.
Blake said crab trees, lilacs and other blooming bushes have produced more flowers, an indication of larger bee populations in previous years.
Once the weather warms up, bees and other insects will likely swarm the fragrant plants.
Facilities Management installed bee sting kits in its vehicles to treat allergic reactions should the bees sting any workers. Blake noted that landscape crews are at greater risk of getting stung by wasps in underground nests.
Blake said he knew of no reports of wasp nests this season.
Although wasps build nests in open areas such as trees, shrubs or parts of buildings, wasps can build nests underground.
Nests built in the open can be eradicated by spraying an aerosol insecticide labeled for wasps and hornets into the opening of the nest.
Ground nests can be exterminated by dumping soapy water into the entrance of the nests. If soapy water fails to kill the wasps, they can be eliminated with dust or powder insecticides such as diazinon or chlorpyrifos. Insecticides will not destroy the nests, however.
Nests that are not visible, where wasps and hornets are only seen flying around an opening, are the most difficult to remove.
Hahn said professional pest control companies are best equipped to exterminate wasps that build nests in these locations, especially inside houses.
Hahn said the best time to spray or dust insecticide into wasp or hornet nests is at night because they are less active than during the day.
But the key is to exterminate wasp nests early, he said.
“You don’t want to wait until then (later this summer) to deal with troublesome wasp nests,” Hahn said.
The larger-than-average number of wasps this year will have no direct impact on the number of wasps that hatch next summer. Since only queen wasps survive over the winter, Hahn says only a similar early and warm spring will produce a larger wasp population.