With their distinctive black and yellow stripes and tendency to hang out in groups, wasps receive attention no matter the time of year. As we move into fall, wasps attract more attention and more questions about what to do about them. Wasps, such as yellowjackets and paper wasps, have annual nests, so most of the individuals that are active now will not survive the winter. Only the newly produced queens will find a sheltered location to overwinter and begin a new colony next spring.
Surprisingly, many annual wasp nests escape detection for most of the season. These nests start out small and are often hidden. Since the colonies are at or close to their maximum size by late summer, the nesting areas become more apparent. Soffits, eaves, shutters, and other voids on the exterior of a home or garage are all potential places for wasps to build their nests (Figure 1).
Figure 1. European paper wasps on a shutter. Their nest is between the siding and the shutter. Courtesy: Amanda Bachmann
With the rapidly cooling temperatures, attempting to control annual wasps at this time of year is considered unnecessary unless they are located in a high traffic area. After the first one or two hard frosts, the colony will die. Managing wasps is best done in the spring when their activity is first noticed. Never seal up a void or opening that contains live wasps or an active nest, as they may chew their way out and end up inside the affected structure. Wasp control should be attempted only with great care and preparation. If applying an insecticide to an active nest, choose a time with cooler temperatures as the wasps will be more sluggish. Wasps have difficulty seeing in the dark, so spraying the nest at night may further reduce their aggressive behavior.
Not every wasp nest has to be controlled. Wasps are actually considered beneficial insects because they contribute to pollination and hunt or scavenge for other insects to feed to their young (Figure 2). If they are nesting in an out of the way location, consider allowing them to stay as they can provide benefits around the garden.
Figure 2. Wasps scavenging insect remains in a car grille. Courtesy: Amanda Bachmann