Impacts of Sub-Lethal concentrations of Two Macrocyclic Lactone Insecticides on Nurse Bees (Apis Mellifera L.) Hypopharyngeal Glands Development

Abstract

Recent studies have shown negative sublethal effects of the microbial bioinsecticides, spinosad (Spd) and spinetoram (Spm) on honeybees concern behavioral effects; only a few concern physiological effects. Therefore, under laboratory conditions we investigated sublethal effects of Spd and Spm on food consumption, the hypopharyngeal glands (HPG) development and activity in nursing honeybee workers. We introduced newly emerged worker honeybees into cages and provided sugar solution and pollen dough ad libitum. Insecticides (Spd and Spm) were administered in sugar solution. The present results showed that continuous exposure to Spd during the first 10 days of adult life in honeybees negatively affects the rate of pollen consumption, HPG development and activity. On the other hand, Spm treatment displayed only negative effect on HPG activity. Therefore, special attention needs to be paid to sublethal effects of some microbial bioinsecticides on honeybee. Overall, data indicate that the microbial bioinsecticides (Spd and Spm) should not be exempted from risk assessment analysis due to their lethal and sublethal components.