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European hornets, bald-faced hornets, and yellow jackets are intimidating creatures, and spend the summer searching plants for insects to capture and carry back to the nest as food for developing larvae.
How-ever, most are not outwardly aggressive, and tend to stay within a few hundred feet of their nests. Aggressiveness can change quickly. Movements toward the nest may provoke an aggressive defense.
Hornets and yellowjackets can sting repeatedly and often attack as a group if disturbed. Their sharp stingers produce a painful sensation that may intensify after their venom is injected. Severe reactions can occur in sensitive people or those who are stung many times.
European hornets (or giant hornets) are 1½-inch-long yellow and brown insects with dark wings. They build enclosed paper nests in hollow trees, barns, attics and wall voids.
These large hornets usually only sting when threatened, but will defend their nests vigorously. They fly at night and are attracted to lights, so they may crash into windows after dark.
European hornet workers and males die in the fall, leaving an empty nest. Fertilized females survive the winter under the protective covering of loose bark or other sheltered places, and create new colonies in the spring.
European hornets capture large insects (grasshoppers, flies, bees, etc.) to chew and feed to their larvae. Some will girdle twigs and branches of lilac, birch, ash, and other species. Sap collected from the wounds provides them with energy and water.
The bald-faced hornet is ½ to ¾ inch long with distinct black and white markings with dark wings.
Also called the aerial yellowjacket, this species builds paper-covered football-shaped nests that often hang from tree limbs. Often the nests are high enough to minimize encounters with people.
Bald-faced hornets are not aggressive while searching for insects to feed their young, but they will defend their nest.
Workers search for flies, caterpillars, and spiders to feed to their developing larvae. All individuals except fertilized queens die in fall. Surviving queens develop a new nest in spring.
Yellowjackets build paper nests below ground, often in abandoned chipmunk burrows or other tunnels made by small mammals.
Like the other species, fertilized queens survive winter in sheltered places and establish colonies in spring. Yellowjackets capture insects to feed their developing larvae but also will collect meat from carcasses or scraps.
Key management techniques for hornets and yellowjackets include the following:
• Do not seal openings to active nests.
• Unless a nest poses a serious threat, leave it alone and avoid the area until late fall.
• If nest removal is required, hire a professional with the equipment and experience to do the job safely. Serious injuries can occur while treating an active nest.
• Know which wasp or hornet is causing the problem. Differences in nesting site, colony size, and food preferences may call for different strategies.
Yellowjackets are attracted to soft drinks, some meats, candy, fruit, and ice cream. Keep these items covered, especially soft drink cans and cups.
Outdoor trashcans are very attractive to yellowjackets. Use plastic can liners, tight fitting lids, and remove trash frequently. Yellowjackets return repeatedly to a good food source from nests more than 1,000 feet away.
For more information on hornets and yellowjackets, please contact the Carroll County Cooperative Extension Service at (502) 732-7030.
Christin Herbst is the Carroll County Extension agent for agriculture and natural resources. Call her at (502) 732-7030 or send e-mail to Christin.Herbst@uky.edu.