It’s that time of year when yellowjackets (Vespula germanica), those black and yellow wasps that seem to increase in numbers in the early fall months of September and October besiege our homes and gardens. The reason for the increase in numbers is because the colony begins to produce males for mating purposes. The males of this species are produced to mate with females and then the males die. Females overwinter as fertilized females. After overwintering and when the weather turns warm, they start their life cycle and make colonies for the upcoming spring. Many of you will experience them this fall when you attend outdoor sporting events such as soccer and other fall sports. The good news is that while irritating, they are welcome visitors in the garden.
Yellowjackets: Fall pests in Gardens and Homes!
Yellow jackets wasps feed their young liquefied insects, with caterpillars, flies and spiders comprising the largest food groups in the yellow jacket diet during most of the summer. In late summer, yellow jackets start looking for flower nectar and other sources of sugar, which are necessary nutrients for the next season’s queens. At this point yellow jackets become an obnoxious presence outdoors, whether they are trying to steal your sandwich or swarming over apple cores in your compost. Preferred food for yellow jackets are, honeydew, and other sweet substances. If your garden (or your plants and shrubbery around your home) has a lot of aphids, leafhoppers, treehoppers, scale insects and other plant juice feeders that product honeydew; yellowjackets and other wasps will be close by to dine on this sweet substance. The queen of a vigorous yellowjacket colony may lay 25,000–30,000 eggs during her lifetime.
The same cell may be used two or three times for rearing larvae. Development time to complete the larval and pupal stage is about30days. For species that have large colonies, the queen maintains control of the colony with a queen pheromone. Yellowjackets do not store honey as do bees and some other vespids. They feed their larvae malaxated portions of arthropods, especially insects, and also nectar and honeydew. Adults feed on nectar, liquid from the larval food, and larval secretions. The first workers to emerge in the colony assume all duties of maintenance and food gathering; the queen confines her activity to laying eggs and remains with the nest. There are three castes in each colony: the queen; males, which are produced from unfertilized eggs; and workers, which are infertile females. Late in the season, workers build large reproductive cells in which males and queens are produced.
During this period workers are more aggressive and likely to sting, even when away from the nest. When new queens and males emerge they leave the nest and mate. Males die after mating, and fertilized queens enter a period of reproductive diapause, and in cold climates they overwinter. They hibernate in protected locations, such as under loose bark of trees, under boards and debris around buildings, and in other peridomestic locations. Nest construction materials include plant fibers from decayed or weathered wood, the cortex of dead plants, and domestic debris, such as newspaper, cardboard, and paper bags. Nest building is continuous until the colony declines.
They do little damage to agricultural crops, except for the cases where their presence disrupts or prevents harvesting. Yellowjacket stings result in intense pain to most people, and can result in death from anaphylaxis in sensitive individuals. Ground nests of Dolichovespula and Paravespula create problems when they occur in peridomestic habitats or recreational areas. Below-ground nests are usually unnoticed until people and pets come near or into direct contact with them. Simply allowing selected nests to remain in place is all you must do to receive free pest control service from yellow jackets. Coexisting peacefully with yellow jackets is another issue, especially if you grow tree fruits. Yellow jackets eagerly feed on fallen apples, pears and other fruits, so wear a light glove when cleaning up the orchard. Bury fruit waste beneath 2 inches of soil, or establish a fruit waste compost pile far from your house, where the yellow jackets can eat their fill.