This is the time of year that Extension agents receive numerous calls about yellow jackets, hornets and how to control them.
Many folks don’t know the difference between the various types of hornets and yellow jackets we have in Georgia. The confusion is understandable, considering yellow jackets, wasps and hornets are all in the Vespidae family, and they all make their home in the state.
Even within the same species individual wasps, hornets and yellow jackets have varying color patterns, depending on whether they are a male, a worker or a queen. To add to the confusion, many people use the terms hornet and yellow jacket interchangeably. For example, the bald-faced hornet is actually a type of yellow jacket.
In general, the term hornet is used for species that nest above ground, and the term yellow jacket is used for those that make nests in the ground.
Colonies start each spring when a single queen, who mated the previous fall and then overwintered in the soil or leaf litter — starts a nest. The nest is made of horizontal combs completely surrounded by a paper envelope made of tiny bits of wood fiber that are chewed into a paper-like pulp. Wasps and hornets use a new nest every year.
During the summer months, colonies rapidly increases in size and may reach several hundred workers by September. In late fall, new queens emerge from the colony, mate, and seek shelter for the winter. The old founder queen dies, and as winter arrives, the remaining colony also dies. Wasps and hornets don’t reuse the same nest the following year.
Hornets will build their nests from the bark of thin-barked trees, like crepe myrtles or fig bushes, for nest building. This is generally not harmful to trees and shrubs, but may girdle small branches and cause some dieback.
Homeowners often call their Extension office after finding a hornets’ nest that is the size of a basketball. A nest this size wasn’t built overnight, and you’ve likely been living next to this colony all summer. I can sympathize with not wanting your closest neighbors to be a colony of hornets. However, I would also argue that if they haven’t bothered you by late summer, why worry about them now?
The best course of action is to warn your family and neighbors about the nest and avoid contact. Mark the nested tree with caution tape to remind everyone to be extra cautious. Hornets are often attracted to porch lights. If they are becoming a nuisance, turn off your porch light and only use it when necessary.
It is possible to treat and kill a wasp or hornet nest with pesticides. However, the odds of getting stung during the process are fairly high.
If you leave the nest alone, your chances of getting stung are much less likely than if you try to tackle the problem yourself. The colony will die as winter approaches so leaving the colony alone late in the season is a practical solution the problem. They're going to die soon anyway.
Remember, hornets and wasps perform a valuable service in controlling many other insects that attack cultivated and ornamental plants.
When dealing with ground-nesting yellow jackets, sometimes you have to take action — especially when you encounter them when mowing the lawn. Any attempt to destroy nests should be done in the late evening, when nest activity is at a minimum.
Even at night, any disturbance will result in instant activity by the colony. Work cautiously, but quickly, and wear protective clothing. Yellow jackets are attracted to light, so do not hold a flashlight while applying an insecticide to a nest.
A quick knockdown, jet-aerosol spray insecticide is preferred because yellow jackets may fly out to defend the colony. Direct the insecticide dispenser nozzle toward the nest entrance for best control. These spray compounds, which contain highly volatile solvents mixed with resmethrin, pyrethrins, carbamates or some of the newer pyrethroids, produce almost instant knockdown for wasps hit. Check the colony entrance the next day for activity, and reapply again if necessary.
Sometimes, the location of the ground nest will make it hard to direct insecticide into the nest's entrance. In this case, gently apply a dust type insecticide containing the active ingredient carbaryl to the nest opening. Yellow jackets will track the dust inside the colony over the course of several days and eventually the entire colony will die. As with all pesticides, read and follow all labeled application rates and safety precautions.
For more information about hornets and yellow jackets, search for Bulletin 1412: Management of Pest Insects In and Around the Home at pubs.caes.uga.edu.