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Archive for Sunday, July 29, 2012

Garden Calendar: Cicada killers’ buzz worse than their sting

July 29, 2012

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A cicada killer wasp rests on milkweed vine. Cicada killers are easily distinguished from yellowjackets and other wasps by their large size — they are about one and a half inches long. Yellowjackets and other wasps are typically 3/4-inch long.

A cicada killer wasp rests on milkweed vine. Cicada killers are easily distinguished from yellowjackets and other wasps by their large size — they are about one and a half inches long. Yellowjackets and other wasps are typically 3/4-inch long.

Upcoming gardening classes

• Saturday, Aug. 18, 10 a.m.: “Waterfalls, Bogs, and Frogs: Planning and Creating a Pond Garden Habitat” by Master Gardener Jim Harmon. Dreher Family 4-H Building, 2110 Harper St. Free, no reservations required.

• Saturday, Aug. 25, 9 a.m.-noon: “Gardening 102: Basics of Gardening around the Home” by multiple Master Gardeners. Covers climate, soil, lawns, trees and shrubs, houseplants and plant pests. Dreher Family 4-H Building. Pre-registration is required by calling 843-7058. $10 covers course materials.

• Tuesdays, Aug. 21-Nov. 13, 9 a.m.-4 p.m. weekly: Basic Extension Master Gardener Training. Applications and more information available at K-State Research and Extension—Douglas County, 2110 Harper St., or at douglascountymastergardeners.org.

Cicada killers look almost as intimidating as their name sounds and are abundant in our area in the heat of summer, but are little cause for concern to people.

They rarely sting, and like other wasps, only females have the ability to do so. Also, a cicada killer’s sting is about as potent as that of a sweat bee.

With just a little buzzing around and a short landing on someone’s shoulder, cicada killers and other wasps sure know how to stir up a crowd, though.

I witnessed it firsthand a few weeks ago, waiting in a mass of people for a race. A cicada killer, which had probably just emerged as an adult and was still finding its way around, flitted into crowd. Suddenly the crowd is moving — adult men and women flailing their arms and shrieking like children on the playground.

Someone shouts: “Just stay calm and it will go away!” but no one listens, and the stirring spreads across the crowd. Then, just as I wonder how many people will be trampled, the wasp catches her bearings and heads toward a group of trees in the distance.

Cicada killers, which can grow to an inch and a half long, are about twice the size of their more aggressive counterparts known as baldfaced hornets, yellow jackets, and Polistes (paper nest) wasps. Their bodies are black with yellow marks that could be confused by an unknowing eye with another wasp species, but their size gives them away. Cicada killers also fly slowly in comparison with other wasps.

Unless you are raising cicadas, the best thing to do with a cicada killer is simply ignore it. Cicada killer females are most interested in hunting down cicadas to feed to their young. Cicada killer males (who cannot sting) mostly hang out on plants near the females’ in-ground nests, waiting for the ladies to come home. Both male and female cicada killers feed on nectar and sap in their adult lives.

When female cicada killers find a cicada, they sting it to paralyze it before dragging it back to the burrow where they will lay eggs. The eggs hatch after just a few days, and larvae then feed for four to 10 days on the paralyzed cicadas. Once the cicadas are gone, larvae spin a silken case to pupate in and will remain in the ground until they emerge as an adult the following summer. Adults live only a few months, and there is only one generation per year.

If control is absolutely necessary, cicada killers can easily be captured in an insect net or knocked out with a tennis racket. In extreme cases, nests can be treated (at night to ensure the female is inside) with an insecticide labeled for bees and wasps. Carbaryl and permethrin are two examples of active ingredients that may be effective. Always read and follow label directions when using any type of insecticide.

Other wasp types

Mud dauber wasps, potter wasps and a number of other species are solitary, unaggressive and often considered beneficial. They are often pollinators and predators of plant pests. Unless their nesting locations are problematic, they can generally be ignored.

More defensive wasp species in Kansas include baldfaced hornets, yellowjackets, and Polistes wasps.

Baldfaced hornets are black with white, yellow, gray or brown markings, and they nest in tree branches. They can be controlled by treating the nest with a labeled insecticide, used according to directions. Treat the nest at night for best results.

Baldfaced hornets are somewhat unusual in our area, although they do occur.

Yellowjackets are black with distinctive yellow bands and nest in underground burrows or around the base of stumps. They are sometimes discovered the hard way by unsuspecting homeowners working in the yard.

They are beneficial — yellowjackets feed on caterpillars and other insects ­— but if in a nuisance location can also be controlled with a labeled insecticide. The nest should be located and entrance hole treated for best results.

Polistes wasps also feed on caterpillars and are considered beneficial, but they often build their nests under eaves or other nuisance locations. They can be controlled by removing and destroying nests in fall, winter or early summer or using a labeled insecticide.

And, if you happen to be in a crowd and a wasp swoops down, you hopefully now know to be more concerned for the ensuing hysteria than an actual sting. Yelling “don’t worry, it’s just a cicada killer” may not help the situation.

— Jennifer Smith is the Horticulture Extension Agent for K-State Research and Extension in Douglas County. Contact her or an Extension Master Gardener with your gardening questions at 843-7058 or dgemg@sunflower.com.

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