Comparative Risks of Several Insecticides towards Honeybee Workers

Abstract

The risk level of several insecticides of various chemical classes was estimated for honeybee workers, Apis mellifera L. (Hymenoptera: Apidae). Lethal time calculation was used to risk assessment for honeybees. Bioassay tests were conducted with six insecticides [dinotefuran (neonicotinoid), methomyl (carbamate), profenofos (organophosphate), azadirachtin (botanicalbioinsecticide), spinosad (bioinsecticide-an extract of the fermentation broth of soil actinomycete) and chlorfluazuron (IGR)] on honeybee workers by the insecticide / food mixture technique, at seven concentrations as ratios of recommended field rate [F (ug a. i. mL-1)], for 15 days. Results revealed that dinotefuran was significantly the most toxic to bees, which gave the shortest median lethal times (LT 50s), 4.4, 4.9, 5.8, 6.4 and 10.3 days at concentrations of 1F×10-2 , 5F×10-3 , 1F×10-3 , 5F×10-4 and 1F×10-4 , respectively. Moreover, it gave 100% bee mortality after one day exposure time, at two higher concentrations, (1F×10-1) and (5F×10-2). The toxicity order of the tested insecticides for honey bees (Based on LT 95s) varied by the reducing in their concentrations, whereas it was: dinotefuran > methomyl > profenofos > azadirachtin > chlorfluazuron > spinosad, at the higher concentrations and this became azadirachtin > dinotefuran > profenofos > chlorfluazuron > methomyl > spinosad at the lowest concentrations. It was concluded that the

The influence of recent Brazilian policy and legislation on increasing bee mortality

“…The later one is a neonicotinoid insecticide never approved to be marketed in the European Union and currently under reevaluation in the USA, because of the high risk offered to bees and other pollinators. Azab and Morsy (2017) demonstrated that in higher concentrations (1Fx10 -1 and 5Fx10 -2 , F = recommended field rate in ug active ingredient mL -1 ), dinotefuran caused 100% of bee mortality after one day of exposure. Corroborating these data, Yasuda et al (2017) shown that among the neonicotinoid's insecticides acetamiprid, imidacloprid, clothianidin, thiamethoxam, and dinotefuran, the latter was the most toxic for bees (LD50, 1.4 ng/bee).…”