Paper Wasps, Hornets, and Yellowjackets

Paper wasps, hornets, and yellowjackets are social insects that build nests of chewed plant fibers and salivary secretions.  The nests include cells in which wasp larvae are reared on a diet consisting of caterpillars and other insects captured as the adults forage over plants (Figure 1).  So far, so good, because this results in some natural pest control. However, an accidental encounter with a nest can lead to painful stings and potentially serious allergic responses.

Paper Wasps

Paper wasps typically build open-faced umbrella-shaped nests (Figure 2) suspended in protected locations, such as under eaves, gutters, and ledges.  These species are not overly aggressive, but they will attack anyone who gets too near. They are the most exposed of the different species of wasp nests and easiest to treat, if necessary.

Figure 1. A red wasp with a macerated caterpillar, food for developing larvae. (Photo: Lee Townsend, UK)

Figure 2.  A European paper wasp nest under deck joists. Note the yellow faces of the guard wasps that are watching an intruder.  (Photo: Lee Townsend, UK)

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Baldfaced Hornet

Baldfaced hornet nests usually are attached to branches, in shrubbery, or the side of buildings. Often, the nests are concealed among branches, especially in densely canopied trees.  Hornet nests generally have a single opening, usually toward the bottom, where the wasps enter and leave. Nests tend to be well above ground so access can be difficult. However, residents of higher nests are less likely to be disturbed by people and pets.

European Hornet

European hornets nest in protected voids, such as hollow trees or attics (Figure 4).  The nests often are located out of reach and elimination is best accomplished by a professional pest control firm.

Figure 3. A Baldfaced hornet nest. Late in the season, a nest will contain several hundred hornets.  Notice the guard peering from the nest entrance. (Photo: Unknown)

Figure 4.  European hornet nests are usually located in hollow tree trunks but most any void will do. A nest this size will contain several hundred insects. (Photo: Unknown)

Yellowjacket

Yellowjackets build nests similar to the European hornet and baldfaced hornet but they are underground, often in abandoned mammal burrows.

Treatment Considerations

Do nothing

Do nothing unless it is absolutely necessary. Treating wasp and hornet nests is dangerous.  Colonies are at peak numbers by midsummer so there are many individuals on guard and available to respond to perceived threats.  By late summer, food is getting scarce and the colonies seem to be more irritable and apt to respond. Consequently, it is best to do nothing unless there is a significant threat to people or animals.

Colonies of these wasps and hornets do not survive winter. Allow the colony to die naturally, if possible.

Use a professional

If treatment is necessary, use a professional pest control operator who has the proper equipment, products, and experience to handle the job.

Do-it-yourself tips

Here are tips to follow for do-it-yourself attempts:

  • Use an aerosol-type wasp and hornet spray. These can be sprayed as far as 20 feet away from the nest.
  • Treat hornet nests at night when most insects are within the nest and less active.
  • Although it is best to treat wasp nests at night, paper wasps can be eliminated during the day provided you do not stand directly below the nest during treatment. Most wasp aerosol sprays cause insects to drop instantly. Standing directly under a nest increases the risk of being stung
  • Do not break the outer covering of hornet nests during treatment. Disrupting the nest cover will allow the irritated wasps to scatter in all directions, causing even greater problems.
  • Wait at least 3 days after treatment to remove the nest. If hornets continue to be seen, the application may need to be repeated.

 

Lee Townsend and Mike Potter, Extension Entomologists

 

 

Posted in Human Pests