Living With Wasps

by Marlys Bell

Recently we created some wine barrel water gardens for a large paved area needing something green. We filled the lined barrels with colorful cannas, elegant reeds and many other water loving plants to get an instant, virtually maintenance free garden that is especially rewarding in this hot weather. The hummingbirds and I love them. Unfortunately, so do the wasps that are attracted to the water. They were always on the property but now too many of them are too close to human activity, especially me, when I fine-tune the water gardens. The question is, what to do?

So far the wasps and I have had a “live and let live” attitude because most of them are not inclined to be aggressive, but learning more about them insures their survival and mine. Obviously my big fear is being stung or having them terrorize the area making it unpleasant for normal outdoor activity such as swimming, grilling and eating outside. But I also recognize they have a role in the ecosystem as predator or prey and am reluctant to intervene unnecessarily.

To help manage the situation, my questions are: what kind are they, what do they eat, how aggressive are they under what circumstances, where is their nest, what is their role in the environment and what options are there for control or risk management? The “good news” is that usually the problem goes away with cold weather when most die. Nature takes care of an issue that seems overwhelming in the hottest weather when they are most apparent.

The wasp family is huge and most of them are beneficial to the environment. The ones commonly encountered by homeowners are paper wasps and several kinds of yellowjackets. Paper wasps are usually brown and yellow with long slender bodies, a tiny waist and drooping legs. They are not usually aggressive except when trapped or the nest is threatened. Nests often hang down like an upside down open umbrella with an obvious cell structure. They live in colonies smaller than 200, so nests do not usually get bigger than 7-10 inches. They are often found in fruit orchards. Unfortunately, they also build nests near other human activity such as over doors, under eaves and in accessible outdoor structures. They usually eat insects but will switch to protein when stressed.

The mere mention of “yellowjackets” prompts a fear response because most of us have experienced their interest in our food, but not all yellowjackets are food aggressive. There are many varieties that eat only insects (Dolichovespula wasps and Vespula rufa). They will not be interested in what you are having for dinner because they are eating flies, ants, grasshoppers, caterpillars and other disease or crop damaging insects. The “meat bee” that terrorize the picnic table scavenging meat and sodas are yellowjackets from the Vespula vulgaris group. Referred to as the western yellowjacket (Vespula vulgaris pennsylvanica), and the German yellowjacket (Vespula vulgaris germanica), they eat meat, decaying fruit and some insects. Starting with a single fertile queen each spring, their colonies get large-ranging from 1500 to 15,000 insects. The nests can be in rodent burrows, tree trunks, houses, shrubs, groundcovers and rotted tree stumps. Nests usually have several cell layers covered with a paper substance, a single entrance hole, and can get to be quite large. These wasps are extremely protective of the nest and have repeat stinging capacity to cause extreme pain and, for those who are allergic, serious health risk. Yellowjackets are usually black and yellow, with stocky bodies and little hair (unlike bees). If close observation is possible, look for two longitudinal bands on the thorax and yellow bands circling the eyes.

Before undertaking elimination tactics, observe behavior and find the nest. Confirm that they are indeed aggressive yellowjacket pests and not a “look alike” such as the beneficial mud dauber, which is the predator for the black widow spider. Mud daubers are solitary insects that create a mud nest usually found on walls or ceilings. They are not aggressive and do not usually defend their nest. When in close proximity to social wasps living in colonies, locate the nest by observing flight patterns.

If the nest´s location becomes a major problem, consider spraying one of the commercially available eco-friendly products labeled for hornets and wasps or call a pest management company. Any spraying should be done after dark when wasps are in the nest. It is also important to thoroughly wash surrounding areas with soapy water to remove the pheromones; otherwise, wasps will return to the site to rebuild their next nest.

Early spring is the best time to intervene with commercially available traps to catch the fertile queens. Bait traps can also be used to redirect traffic away from eating and other sensitive areas. Usually paper wasps will not be attracted to traps baited for yellowjackets. A year round prevention effort is needed in mild winters.

When working outdoors avoid colorful or patterned clothing, shiny jewelry, perfume and scented soaps. When around significant wasp activity, wear a hat, long sleeves tucked into gloves and pants tucked into socks. Always wear shoes since some nests may be on the ground. When spraying, take extreme precautions to cover from head to toe, protect eyes from spray and flying insects, and keep your distance from the nest. Spraying insect repellent on your clothes will help discourage them.

If a wasp lands on you stay still and it will leave on its own. Do not swat it, run or make wild hand/arm motions. If stung, a cold compress and antihistamines can help reduce the pain and swelling. If the reaction is severe, around the face or neck, or from multiple stings, seek medical attention. Individuals known to have severe allergic reactions need to plan for stings and have appropriate medical supplies on hand. The article “About Bee and Wasp Stings” provides more detailed advice. For additional information about wasps, see Publication 7450, “Yellowjackets and Other Social Wasps” of the Pest Notes Series on Integrated Pest Management. It can also be found at http://www.ipm.ucdavis.edu.

With this information, I am hopeful that the wasps and I will survive the summer without incident. I now am much more aware that, before putting my hand into the water, I need to make sure none are trapped in the water. I also am going to put goldfish into all of the barrels to eat both the mosquito larvae and the wasps because I noticed they do not congregate in the one where I already have the goldfish. In the meantime, I am thinking of creating a special water garden for them that is in a far corner of the yard where they can drink to their hearts content. Instead of branding all wasps as pests, I am going to give them a chance to play a beneficial role in my garden until they prove they have other malicious intent. For the moment, we have reached an understanding of how to cautiously live together, at least for the summer.

Marlys Bell is trying to live green on her property and is looking for solutions that recognize the role of insects as predator and prey within the ecosystem.