JULl^iSSOCooperative ExtensionDivision of Agriculture and Natural ResourcesUniversity of California(Z^ntura County

Mck SakoTichFarm Advisor

800 South Victoria Avenue * Ventura, California 93009-0042 * Phone (805) 654-2924

Column ReleaseLOOK OUT FOR YELLOWJACKET WASPS

Look out for yellowjacket wasps. The pests are more numerous and began

earlier this year than in the recent past. The wasps will become especially

aggressive from midsummer to fall. The relatively dry winter allowed very

successful survival of these pests from colonies made last year.

Usually only the fertilized queens overwinter. In the spring each begins

making a colony in a hole in the ground - - any abandoned gopher burrow or

large crack will suffice.

The colony builds up slowly and reaches maximum number of up to several

thousand wasps in mid to late summer. Foraging wasps seek out the protein and

sweets from refuse containers, a barbecue, and ripening fruit. The

yellowjackets are not all bad, though. They feed heavily on caterpillars

found in oaks and other plants.

When yellowjackets nest in backyards or in other areas frequented by

people, problems often arise. After reproduction stops, about midsummer, the

pests are particularly agressive.

Nests discovered early in the year are much easier to destroy than those

found late, for wasp numbers are lower and the insects are not nearly so

likely to sting.

Nicholas J. Sakovich, Farm Advisor

Information and programs availabia to all without dlscrimln^dlon. The University of California, in compliance with the Civil Rights Act of 1964, Title IX of the Education Amendments of 1972, and theRehabilitation Act of 1973, does not discriminate on the basis of race, creed, religion, color, national origin, sex, or mental or physical handicap in any of its programs or activities or with respect toj.ny of its empioyment policies, practices, or procedures. The University of California does not discriminate on the basis of age, ancestry, sexual orientation, marital status, citizenship, medicalcondition (as defined in Section 12926 of the California Government CcxJe), nor because individuals are disabled or Vietnam era veterans. Inquiries regarding this policy may be directed to thePersonnel Studies and Affirmative Action Manager, Division of Agriculture and Natural Resources, 300 Lakeside Drive, 6th Floor, Oakland, CA 94612-3560, (415)987-0097

U.S. Department of Agriculture, University of California Cooperating.

If you decide to control the wasps by destroying their nests, wear

clothing which covers the body thoroughly (slick surfaces materials such as

nylon provide better protection than cottons or wools), Wear rubberized

gloves, a hat, and secure your pant legs and jacket cuffs tightly over shoe

tops and gloves. Where possible, treat the nest after dark when most of the

wasps are inside the nest.

Effective materials for destroying ground nests include acephate

(Orthene), carbaryl (Sevin), and chlorpyrifos (Dursban). However, few such

product labels specifically mention control of yellowjackets or other ground-

infesting wasps. Find one of the above liquid products (some are lawn insect

control materials) whose label describes control of imported fire ants by the

mound-drenching method. In a bucket, mix the insecticide with one gallon of

water according to dosage directions.

Approach the nest quietly because yellowjackets are alerted by vibrations

of heavy footsteps. Quickly pour the solution into the nest entrance. Leave

the nest site immediately.

Although some household aerosol sprays list wasps among the insects they

will kill, they are satisfactory only for killing individual wasps, since they

do not deliver insecticide quickly enough to safely destroy yellowjacket

nests.

U.C. Cooperative Extension programs and information are open and

available to all without discrimination.

Prepared by Carl Koehler.

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