The Latest on Bee Mite Resistance to Pesticides

Farmers have long known about insect resistance to chemicals. In recent years, U.S. beekeepers have discovered the same problem when it comes to controlling bee mites.

Over the last decade, the honeybee-attacking varroa mite has developed resistance to the pyrethroid pesticide fluvalinate. That has spurred interest in alternative chemical controls for the mite, the number one pest of U.S. honeybees.

But finding alternatives can be costly. Agricultural Research Service (ARS) studies on toxicities of anti-mite compounds could help prevent future wasteful outlays of research dollars on development of pesticides most likely to soon become ineffective.

For example, recent research points to futility in considering the formerly registered acaricide amitraz as an alternative for varroa mite control. Scientists at the Kika De La Garza Subtropical Agricultural Research Center, Weslaco, Texas, have found that resistance to fluvalinate commonly goes hand-in-hand with resistance to amitraz. Chemically, fluvalinate and amitraz aren’t related, but mite detoxifying enzymes may render both ineffective.

On a positive note, ARS research at Weslaco does show that fluvalinate-resistant varroa mites become significantly less resistant after a two-year hiatus from treatments.

The Weslaco scientists are seeking alternatives to extensive use of less environmentally friendly pesticides such as coumaphos, an organophosphate. For example, the scientists are researching the biology of fluvalinate-resistant varroa mites, hoping to find ways to survey mite populations for lack of resistance so coumaphos treatments can often be avoided.

By late last year, the U.S. Environmental Protection Agency (EPA) had approved exemption labels in 45 states to allow strictly controlled use of plastic strips impregnated with coumaphos to control varroa mite and another pest, the small hive beetle Aethina tumida.

Honey bees provide a $14.6 billion annual benefit to U.S. agriculture.

ARS is the U.S. Department of Agriculture's chief scientific research agency.

Scientific contact: Patti J. Elzen, ARS Beneficial Insects Research Unit, Weslaco, Texas; phone (956) 969-5012, fax (956) 969-5033, pelzen@weslaco.ars.usda.gov.