September 15, 2004

Yellow jacket and bee populations peak in fall

WEST LAFAYETTE, Ind. - There's a pesky critter ready to attend your next picnic, and it's not an ant.

Tim Gibb, a Purdue Extension entomologist, said this is the time of year that yellow jackets and bees are out in force looking for food.

"Yellow jackets and honey bees forage pretty widely at this particular time of year, so they will frequent picnics, outdoor weddings and gatherings, fairs and football games," he said. "They're looking for proteins and sugars, and that's primarily what we use as refreshments, so they will swarm around your soda pop or your hamburger."

This isn't the only time that yellow jackets and other stinging insects are foraging for food, but it is the time that people are most likely to encounter them.

"It's the time of year that wasp and bee colonies are at their peak," Gibb said. "They've been working all summer long. The queen has been reproducing, and the colonies have been growing. Some yellow jacket colonies have several thousand individuals at this point in time."

Yellow jackets and bees can sting, but when they visit outdoor events they're more interested in finding food than protecting their nest. Because of this, Gibb said, it's easier to avoid being stung.

"Those individuals can be controlled primarily by removing whatever it is they're attracted to. Things like covering garbage cans and moving them away from places where people are going to gather are a good idea," he said.

He also suggested opening food only when necessary.

"Bees and wasps are social insects, and they recruit each other," he said. "Once they find a food source, they will go back and tell their nest mates where it is. So the longer you have a food source open, whether that's a garbage can or your ham sandwich, the more chance bees and wasps are going to try to feed on it."

Dealing with an entire colony is another matter all together.

"Often people will either see a nest in their eaves or happen to be out mowing near a tree and all of a sudden a whole bunch of yellow jackets come swarming out of the ground. Every year people die because they are hyperallergic to the venom from either yellow jackets or honey bees, so it's a very serious situation," Gibb said. "On the other hand, we know that bees and wasps both are very beneficial in the environment."

For this reason the choice to control a nest or hive depends largely on location.

"If the nest is in an area we know is frequented by kids and there's a high probability that someone is going to agitate it, yes we need to take those out," he said. "But if they're higher in the tree, say 12 to 20 feet, we can warn people that there is a nest there, don't get close to it. And, if it's in the backwoods where nobody is going to get to it, by all means we need to leave those, because they are beneficial."

Sometimes bees and wasps take up residence in homes. In this case, it's important to determine what kind of insect is present, Gibb said.

"Honey bee nests in the home really have to be taken out by a professional. If you go in with pesticides and kill the bees, you've still got all of that honey stored in the wall void," he said.

Without the bees there's no temperature regulation, and on a hot day the wax and honey will melt and seep through walls. "It's going to ferment and attract other insects, pests and all that vermin that you really don't want to see inside your home," Gibb said.

Yellow jacket are wasps, and so their nests are less messy. "Wasps will not reuse the nest the following year," he said. "So if you can wait until the first or second good solid freeze, the wasps will disappear on their own."

A lot of people mistake yellow jackets for honey bees. There are a couple of ways homeowners can tell them apart.

"Wasps generally do not have a hairy abdomen, bees generally do. And yellow jackets often have a little more distinct separation between the blacks and the yellows - the stripes are more defined," he said. "If you're not sure, collecting one and taking it to a county Extension educator or sending it to Purdue or a professional pest controller is your best option."

Control recommendations for bee hives and wasp nests are available from Purdue Extension through a local Extension educator, or by calling Purdue Extension's toll-free helpline at (888) EXT-INFO.

Information about controlling wasps and bees also is available on the Department of Entomology web page and Household and Public Health page.

Writer: Kay Hagen, (765) 494-6682, kjh@purdue.edu

Source: Tim Gibb, (765) 494-4570, gibb@purdue.edu

Ag Communications: (765) 494-2722; Beth Forbes, forbes@purdue.edu
Agriculture News Page

Related Web site:
Purdue entomology publications

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