Yellowjackets can be a nuisance this time of year


Wasps and bees can be a serious nuisance problem throughout Colorado, particularly late in the summer when certain yellowjacket wasps forage at garbage and outdoor food areas.

Several wasps are social insects that produce a colony. Colonies begin anew each spring, initiated by a single fertilized female (queen) that has survived winter. The social wasps construct their nest of paper, which they produce by chewing on wood, scraps of paper and cardboard.

Social wasp colonies are very small early in the season, but expand rapidly through the summer as more wasps are raised that assist in colony development. By the end of summer, a colony may include dozens, or even several hundred, individuals. Some wasps reared at the end of the season are fertile females (potential queens) and a few males. In fall, colonies are abandoned, never to be reused, and the fertilized females scatter to find protection during the winter. The remaining members of the colony perish with cold weather. Since temperatures are dropping each morning and cold weather is not far away, doing nothing as a management technique is appropriate as the colony will soon disappear.

Most social wasps rear their young on a diet of live insects. Several types of social wasps are important in controlling insect pests such as caterpillars. An exception to this is the western yellowjacket, which primarily scavenges dead insects, earthworms and other carrion, including garbage. This scavenging habit is usually why yellowjackets become serious nuisance problems. Male wasps occasionally visit flowers to feed on nectar; however, social wasps are generally not important plant pollinators.

All social wasps are capable of producing a painful sting, but none leave the stinger embedded, as do honeybee workers. Most stings occur when the colony is accidentally disturbed. Yellowjackets are banded yellow or orange and black and are commonly mistaken for honeybees, but they lack the hairy body and are more intensely colored. Yellowjackets typically nest underground using existing hollows. Occasionally nests can be found in dark, enclosed areas of a building, such as crawl spaces or wall voids.

Nests are enclosed in a paper envelope, but they are not exposed nor observed unless excavated. The nest entrance is small and inconspicuous. Colonies are readily defended and yellowjackets will sting when the nest area is disturbed.

The western yellowjacket is, by far, the most important stinging insect in Colorado. Late in the season, when colonies may include up to 200 individuals, they become serious nuisance pests around outdoor sources of food or garbage. The western yellowjacket is estimated to cause at least 90 percent of the “bee stings” in the state.

Many concerns with social wasps occur late in the season when colonies grow large and the above-ground nests of hornets and paper wasps become apparent. If the wasps are not causing a problem, the best solution is to wait until the nest is abandoned in the fall. The nest can be safely removed in the winter or, if left alone, will break up during late fall and winter.

Yellowjackets will regularly return to sites where food and water sources are available. Therefore, it is important to deter yellowjackets from visiting an area by eliminating all food sources (e.g. open garbage cans, pet foods). Water sources around the yard may also attract yellowjackets during hot, drought-stricken periods.

There has been some success using baits and traps for control of yellowjackets. The western yellowjacket is attracted to the chemical heptyl butyrate, which is included as a lure in many wasp traps. Such traps can be helpful when used early in the season, June and early July, when the number of yellowjackets is small and the colonies are struggling to become established. However, these traps will not attract European paper wasp and are worthless for control of this species.

The above information was taken from the Colorado State University Fact Sheet No. 5.525, “Nuisance Wasps and Bees,” written by W.S. Cranshaw, and can be found in its entirety on the Extension website at

Community Shred-It Event Sept. 28

Throwing out financial, medical and other private papers or throwing them in the recycle bin can leave you open to identity theft.

On Sept. 28 from 4 to 6 p.m. in the downtown Citizens Bank parking lot, you can watch your papers being safely shredded on-site.

For only $5 per box, you can shred up to three boxes of papers and feel confident that your important information does not fall into the wrong hands.

All proceeds support the Archuleta County 4-H program and 4-H youth will be on hand to help you unload your boxes. No registration is necessary, but for more information, call the CSU Extension office at 264-5931.