Carbofuran: Effect of Long-Term Feeding of Low Doses in Sucrose Syrup on Honey Bees1 in Standard-Size Field Colonies2

Standard-size (10-frame Langstroth) field colonies of honey bees, Apis mellifera L., located in an area that forced the bees to accept offered food because of lack of natural bee forage, were fed long-term, controlled low doses of carbofuran in sucrose syrup throughout the summers of 1976 and 1977. The effect of poisoning on queens by feeding carbofuran at any level that killed colonies was indirect, because queen mortality was related to insufficient care through lack of attendants to feed, groom, and regulate temperatures vital to queen survival. Queens were fed mostly glandular secretions by attendants, rather than honey or pollen, and evidently the glandular food contained no poison. Feeding honey bee colonies sucrose syrup contaming 0.1- or 0.01-ppm carbofuran did little to impede survival of sealed brood or adult bees to maintain the population of colonies at functional levels. However, 1.0-ppm carbofuran was the threshold of serious damage; colonies fed this level of the insecticide sustained continual reduction of sealed brood and adult bees that led to eventual death of these colonies in the winter.