Toxicity of spinosyns to the honey bee in two exposure modes

Abstract

The efficiency of bees makes them the primary pollinator of cultivated plants, giving them significant economic and ecological value. However, the excessive use of pesticides contributes to the disappearance of bees in agricultural areas, as poisoning can be lethal or cause adverse effects on the physiology and behavior of these insects. Therefore, this study evaluated the toxicity of the insecticides Spinetoram and Spinosad, both belonging to the spinosyn chemical group, on the survival and flight capacity of the Africanized honey bee Apis mellifera. The bioassays were conducted under laboratory conditions (at 25 ± 2 ºC, 60 ± 10% RH and 12 h photophase), using adult worker bees. The experiments tested five commercial doses of Spinetoram (0.02; 0.03; 0.04; 0.05; 0.1 g a.i./L) and Spinosad (0.024; 0.048; 0.096; 0.12; 0.144 g a.i./L) registered for pest control in several crops. Two exposure methods were evaluated: direct spraying of insecticides on bees and provision of contaminated diet. Spinetoram and Spinosad were extremely toxic to A. mellifera both via direct spraying, causing 100% mortality and LT₅₀ values ranging from 8.2 to 24.1 hours, and via contaminated diet, with mortality of 90.02% for Spinetoram and 90.14% for Spinosad, with LT₅₀ values ranging from 38.2 and 43.5 hours for Spinetoram and 27.3 and 43.5 hours for Spinosad. Both insecticides impaired the flight capacity of A. mellifera, regardless of exposure modes and evaluated doses. Spinetoram and Spinosad are toxic to A. mellifera through direct spraying and ingestion of contaminated diet.