Growing Green

By Robin Trott, Extension Educator

One of the most common questions I receive during the fall is how to get rid of a bees’ nest. Before you go about destroying a nest, you need to determine whether it is a nest of bees, wasps or hornets. Why does this matter? It is important to know that bees are different insects than hornets or wasps. While all of these species have their own important role and place within the ecosystem, native bees are especially important for pollination services that provide much of our food, food for wildlife, and beauty in the landscape.

Is it a bee, wasp or hornet?

Why are bees, hornets and wasps so often confused? Maybe it is the fact they all buzz and many of us associate that sound with bees. They also all defend their territory by stinging. Whatever the reason, it is important to properly identify what buzzing critter has built a nest to assess what steps to take in the best interest of both humans and the insect. To make an identification, visit www.extension.umn.edu/garden/diagnose/insect/, bring a sample into your local extension office, or send a photo to your local extension educator.

Ground nesting bees

You may notice some individual holes in the ground. They may be located in a more undisturbed area, in your vegetable garden or even within your lawn. These will most likely be from solitary native bee species, so they do not have a queen and rarely want to sting. These bees have a hairy body and will want to fly away rather than stay and defend their territory like a wasp or hornet. 

Ground nesting wasps

Ground nesters could also be the eastern yellow jacket. Different from ground nesting bees, they have formed a colony beneath the surface and will aggressively protect it. This species is often attracted to our food during family picnics. If you have this wasp nesting in an area that is frequented by you or others, you will want to get rid of this nest for human safety. 

Nests in trees

Wasps and hornets often create their nests in areas that interfere with our daily human travel, such as building a paper nest under a house eave. If they feel threatened, hornets and wasps will defend their territory by repeatedly stinging. Interestingly, hornets and wasps are also predatory insects, preying upon other insects, bees included, and eating them.

Killing off a wasp 

nest is tricky business.

The occupants of these nests tend to resist any effort to kill them by stinging those attempting to do so. The wasps most problematic this time of year are yellow jackets, bald-faced hornets and paper wasps, which are social insects that live in large colonies. They construct their nests in the ground, in trees, under eves and inside wall voids and attics. Nest construction starts in late spring and continues throughout the summer. The last brood raised includes males and next year’s queens. Due to the importance of these reproducers, the worker wasps become very protective and aggressive toward those who get too close to the nest this time of year. In the fall, after the new queens leave, the nests are abandoned, and all the workers eventually die due to starvation and cold weather. Old nests are never reused, but a favorable nesting site may be selected year after year.

Nests located in out-of-the-way sites that are not likely to be disturbed can be ignored since they are going to die out later in the year. Small, exposed paper wasp nests are easily controlled by aerosol wasp sprays that produce a concentrated stream of insecticide that has a range of 15 to 20 feet. Paper wasps do not cover their nests in a papier-mache exterior like those of yellow jackets and bald-faced hornets, so their brood cells and workers are exposed and vulnerable. Simply point the nozzle at the nest, shoot and watch them die.

The larger nests of yellow jackets and bald-faced hornets that are protected by a paper mache coating are more challenging and best left to pest control professionals. No attempt should be made to kill a nest that is located high in the upper branches of a tree, especially if using ladder is required to reach the nest. If the nest is located close to the ground in a tree, shrub or on a building, then you may have a fighting chance to survive the experience unscathed. The best time of day to spray is early morning, when most of the wasps will be inside the nest and activity is at a minimum.

Spray the main opening at the bottom of the nest first, and keep spraying this opening for at least 10 seconds, then spray other openings that may be present on the sides of the nest. Spray the openings for as long as possible and then quickly leave the immediate area via a predetermined escape route. Watch the nest throughout the day. If activity persists, hit it again the next morning following the procedures outlined above. Once activity has tapered off and most of the wasps are killed, knock the nest down with a rake or other long-handle tool, break it apart and saturate the pieces with spray.

Removing yellow jacket ground nests

Ground-nesting yellow jackets are often discovered, sometimes painfully, while mowing the lawn or weeding gardens and flower beds. Ground nests are easily controlled with a single application of an insecticidal dust directed at the nest opening. Insecticidal dusts work well in these cases because the wasps pick the dust up as they enter the nest and carry it to the core of the nest. This contaminates the entire nest and soon all the wasps will die off, normally within one or two days. Early morning is the preferred treatment time. Pour the recommended amount of insecticidal garden dust (like Sevin 5) in a disposable paper cup and approach the nest cautiously. Pour the cup directly into the opening and quickly move away from the nest. If this is done correctly, white, dust-covered wasps will quickly emerge from the opening and fly off. Don’t cover the opening with soil or a rock; leave it open so the wasps can enter and leave as they please. 

If you discover yellow jackets nesting inside your home, you can choose to ignore it or call a pest control company to destroy it. Never plug the outside opening of these nests because this will force the wasps to chew their way into the interior of the house and this is never a good thing.

Be sure to read and follow all instructions and safety precautions found on the label before using any pesticide.

Until next time, happy gardening!

 * * * * * * * * * * * * * * 

“It’s easy to cry ‘bug’ when the truth is that you’ve got a complex system and sometimes it takes a while to get all the components to co-exist peacefully.” – Doug Vargas