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09/03/99

YELLOW JACKETS, HORNETS, AND WASPS

Jeffrey P. McMorran, Area Extension Agent & Agronomist

We all know yellowjackets as the unwanted pests at picnics who are particularly attracted to fresh meat, but do they do anything "good" for us?

Yellowjackets and Hornets are closely related to the familiar honey bee, but have decidedly different lifestyles. Jack DeAngelis (OSU Extension Entomologist) tells us that, where as bees gather pollen and flower nectar helping pollinate many of our fruits and vegetables, yellowjackets are mostly meat eaters, who favor some rotting fruit for dessert. Yellowjackets are more likely than honey bees to sting without provocation, perhaps because yellowjackets don't leave their stinger in your skin, and can thus inflict several painful venomous stings.

Yellowjackets live in gray papery nests found below ground, suspended in trees, or within walls. Like honey bees, each nest is controlled by a single queen who lays eggs that hatch into hundreds, or even thousands, of workers by the end of summer. Thus, an extended warm fall, like we have had this year, results in a large buildup of yellowjackets. Populations rapidly decrease with the first cold weather.

Yellowjackets aren't all bad. In fact Rodale, in the Encyclopedia of Organic Gardening, asks us not to automatically destroy yellowjackets, or their gray paper nests, because these insects are excellent pest predators. "They dive into forage and carry off flies, caterpillars, and other larvae to feed to their brood". I suspect they must also foray in lawns for various pests. Next time you are about to swat one, think about all the good it does eating insects in your yard! However, if the nests are in a place frequented by people, or if a family member is highly allergic to stings, control is necessary.

CONTROL
Avoid attracting yellowjackets to your yard in the first place by controlling their access to garbage. Use tight fitting lids on your cans, and routinely treat containers with dichlorvos sprays, or by placing an insecticide-impregnated strip inside.

Simple traps using a fish bait over a pan containing water and dishwashing soap can be quite effective in lowering populations of yellow jackets in a small area.

When nests must be destroyed, treat them in the cool of the night when workers are inside and relatively calm. Above ground nests can be treated by use of a quick knockdown type aerosol insecticide labeled for wasps and yellowjacket control. The aerosol should be capable of propelling a stream of insecticide up to 20 feet so you can stand a safe distance away. Subterranean colonies can be treated by pouring insecticides such as carbaryl or propoxur down the entrance of the tunnel, plugging the tunnel with cotton or steel wool, and then treating the surrounding area to kill any foragers returning the next day. Nests in wall voids can be controlled by the use of synthetic pyrethoid generators or application of carbaryl dust to the plugged entrance hole. To locate a "hidden" nest, place a bowl of 50% honey or tuna fish out, and watch as the Yellow Jackets leave after feeding. They will be returning directly to their nests.

If all else fails, a teaspoon of an encapsulated forms of diazinon called "Knox Out 2 FM" can be mixed with tuna. The wasps or yellow jackets will feed on the tuna and return to the nest to spread the encapsulated diazinon around. Only encapsulated diazinon will work, because yellow jackets will avoid other formulations (they smell the pesticide). Also BE SURE THE POISON BAIT IS PLACED IN SUCH A MANNER THAT OTHER ANIMALS WILL NOT EAT IT! One method is to place the bait in a can hung above the ground which has nails holes in it only large enough for a yellow jacket to crawl in. Contacting a professional exterminator is also a good alternative.

Keep in mind that yellowjacket activity will naturally drop off as soon as the weather gets cool in the fall, eliminating your need to control them. As winter sets in, newly fertilized queens find some protected place to over winter leaving the rest of the yellow jackets to die with the first killing frost. Generally, the new queens won't return to the same nest next year.

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