EFFECTS OF DELAYED ACARICIDE TREATMENT IN HONEY-BEE COLONIES PARASITIZED BY VARROA-JACOBSONI AND A LATE-SEASON TREATMENT THRESHOLD FOR THE SOUTHEASTERN USA

We set up 72 colonies of honey bees (Apis mellifera) in the piedmont r egion of Georgia and South Carolina, USA (2 states x 6 apiaries per st ate x 6 colonies per apiary) in April 1995. Colonies were individually housed in single-chamber Langstroth hive bodies and one honey super, started with standard mail-order 0.9 kg (2 lb) packages of bees contai ning small incipient populations of the parasitic mite Varroa jacobson i, and managed optimally as for honey production. Within each state, e ach apiary was assigned one of the following treatments: (1) treatment with Apistan acaricide in June, (2) treatment in August, (3) treatmen t in October, or (4) no treatment. By December, colony bee populations were optimum in August-treated apiaries. Month of treatment did not a ffect bee body weight. There were treatment by state interactions for number of sealed brood cells, colony mite populations, and percentage of brood cells with disease-like symptoms. Our data suggest that late- season acaricide treatments in first-year colonies in the south-easter n USA piedmont are justified at colony mite populations of 3172 +/- 32 4, 300-bee ether roll mite levels of 15 +/- 1.4, and overnight adhesiv e bottom board insert mite levels of 117 +/- 15 in colonies with 24 80 8 +/- 2245 bees and 1825 +/- 327 cm(2) sealed brood; these conditions occurred in mid-August. Acaricide treatments in or before August may e liminate mite-associated brood pathology in the south-eastern USA. Bot tom board inserts were more reliable predictors of colony mite populat ions compared to the ether roll method.