Published on Wednesday, 30 November -0001 00:00
I have been receiving numerous calls regarding "bees" around hummingbird and oriole feeders. These "bees" are usually yellowjackets or bald-faced hornets, although honeybees may occasionally visit sugar water sources. Yellowjackets are coming out of nests which are hidden in cracks in the foundation, behind loose bricks, holes in the ground and from nests hanging on shrubbery or buildings. Changes in their dietary habits this time of year bring yellowjackets near human food, making them the most common and, unfortunately, the chances of being stung increases. Wasps are predators, feeding insects including caterpillars, flies, crickets, and many other pests to their young that develop in their nest. During late summer and fall, the queens stop laying eggs and their nests decline. At this time the wasps change their food to sweets and other carbohydrates and they may become aggressive scavengers around human food making them common around outdoor activities where food or drinks are served. Yellowjackets are particularly attracted to sweets and may become very numerous when food is served outdoors. They are also attracted to ripening or decaying fruit such as apples and raspberries, which also brings them into contact with humans. Yellowjackets and bald-faced hornets both construct paper mâché type nests made from chewed up wood. Nests are small at the beginning, but can become as large as a basketball or larger as the colony grows. These nests can be found in various sites including exposed areas like hanging under eaves or on the limbs of trees and shrubs. Yellowjacket nests are also common in underground sites like old rodent burrows and they will also take advantage of cavities in buildings such as wall voids, spaces behind brick facing and spaces in blocks. You will see workers fly back and forth from cracks or spaces that lead to the nest. It is important to note that the nest may actually be located some distance from the opening that they are using. When dealing with nesting colonies around homes, ignore nests that are up high in buildings or trees, or otherwise located where the wasps do not come in contact with humans. These nests found hanging in trees or attached to buildings have been there since spring and have gone undetected until the activity of the wasps drew attention to them. However, if these nests are close to human traffic, there is an increased risk of stings and they should be controlled. Unlike bees, yellowjackets can sting multiple times. The best way to destroy wasps in these nests is to use a pressurized aerosol insecticide, often called "wasp and hornet killers." Wait until evening, when the yellowjackets or other wasps are less active, and spray the aerosol insecticide directly into the opening where the wasps have been flying back and forth. Check the nest for activity and if there are still live wasps, repeat the treatment in a few days. Nests located underground are more challenging to control. Waituntil night when the wasps are less active and then use an insecticide that is labeled for insects in the grass or soil such as Ortho Bug-B-Gon MAX Insect Killer (bifenthrin) or Sevin (carbaryl). Dusts work better than liquids. After you are sure the yellowjackets are dead, fill in the burrow with soil. The most challenging type of wasp nests are those hidden behind steps, in wall voids or in other inaccessible areas. The wasps are often seen flying back and forth through a crack or small hole, but the nest is not observed. It is important not to seal the opening because the wasps will then seek an alternative exit which may be into the living quarters of the home. Aerosol insecticides are not effective in these situations because the nest may be located in a site far removed from the entrance opening. The best way to control a hidden nest is to apply an insecticide dust like bifenthrin or one of the insecticides listed for nests found in the ground. When the entrance is obvious, the dust may be applied directly into the opening by putting the insecticidal dust in a plastic dispensing bottle and squeezing it into the entrance. As the wasps move in and out, the dust adheres to their bodies and they carry it to the nest. If there is a nest in the wall, but no entrance is found, it is probably best to contact an experienced pest control service to eradicate the hidden nest. Remember the following important tips when applying insecticides to a wasp nest. Wait until evening when it is cooler and the insects are not actively flying in and out of the nest. As wasps are attracted to light, avoid using a bright flashlight as much as possible. Wear protective clothing to help prevent being stung by the insects. Always read all the directions and precautions on the label of the product you are using and follow them carefully.