Effect of sub-lethal doses of thiamethoxam on hypopharyngeal glands of Apis mellifera Linnaeus

Honey bees provide key ecosystem services i.e., pollination but are functioning under various biotic and abiotic stresses. Among various stresses, thiamethoxam has been criticized worldwide. Since no scientific study on its sub-lethal effects on honey bees has been conducted in India, the present work was carried out at the Department of Entomology, Punjab Agricultural University, Ludhiana for two seasons during 2017-19. The median lethal dietary dose (LDD50) of thiamethoxam upon chronically feeding the sub-lethal doses for 10 days for a group of adult Apis mellifera bees (age 10 days) was 0.421 ng bee(-1 )day(-1). At this level, the reduction in the area of an acinus of the hypopharyngeal gland was significant i.e., 36.62 and 37.92 percent over control during spring and winter seasons, respectively. The adverse impact of thiamethoxam on hypopharyngeal glands will be limiting the development and productivity of the honey bee colonies.