Impact of Neonicotinoid Insecticides on the Foraging Preference of Indian Honey Bee, Apis cerana indica (Fab.) (Hymenoptera, Apidae) Visiting Sunflower Helianthus annus L. Crop

Aim: Forage preference of Indian honey bee on neonicotinoid insecticides treated sunflower

Study Design: Randomized Block Design (RBD)

Place and Duration of Study: Insectary, Department of Agricultural Entomology, Tamil Nadu Agricultural University, Coimbatore between August 2021 to December 2021 during the Adipattam season

Methodology: Bee activity was recorded by in situ counting method. Seven treatments with three replications (5flowers/replication) in Randomized Block Design were followed. Different treatments viz., Imidacloprid 17.8 SL @ 280µl/l, Clothianidin 50 WDG @ 80µg/l, Thiamethoxam 25 WG @ 250µg/l, Thiacloprid 21.7 SC @ 1100/µl, Dimethoate 30 EC @ 1400µl/l (chemical check), Water control (Water spray) and Absolute control (no spray) were given at 50% flowering period using Knapsack sprayer. The number of bees visiting 5 flowers per 5 minutes was observed during morning (09.00-11.00), afternoon (13.00-15.00) and evening (16.00-18.00) hours of the day for seven days after spray (DAS). DAS. Statistical Analysis Software (SAS) academics was used to statistically analyse the data.

Results: The mean population of Apis cerana indica Fab. was more in absolute control (5.97) followed by water control (4.77), imidacloprid (4.10), clothianidin (3.40), thiacloprid (3.21), thiamethoxam (3.14) and dimethoate (1.90) during morning hours (09.00-11.00) of the day. The mean bee visitation rate was high in control (3.40), followed by water control (2.65), imidacloprid (1.77), clothianidin (1.52), thiacloprid (1.55), thiamethoxam (1.40) and dimethoate (1.17) during afternoon hours (13.00-15.00) of the day. In the evening hours (16.00-18.00), mean bee activity was high in control (4.95) followed by water control (4.27), imidacloprid (3.40), clothianidin (3.13), thiamethoxam (2.75), thiacloprid (2.53) and dimethoate (1.88). Among these different hours, morning forage activity of the bees are high in morning hours of the day followed by evening and very less in afternoon hours.

Conclusion: The present study revealed that Indian honey bees preferred to forage both on neonicotinoid treated, however at a reduced rate, and untreated flowers. Since, neonicotinoids are odourless, tasteless compounds that increase the risk of pesticide exposure for the bee colony owing to less capability for segregation of insecticide treated surfaces.