Acute and Chronic Toxicity of Selected Pesticides Used in Strawberry Greenhouse to Honeybee (Apis mellifera) Larvae

Abstract

Honey bee colonies have often collapsed when introduced in strawberry greenhouses for pollination. Toxicological risk assessments conducted to determine the likelihood how a given pesticide would impact honey bees primarily consider the survival of adult bees exposed to the pesticide. However, larvae are also exposed to pesticides as their diets can contain contaminated nectar and pollen collected by foragers. To understand the effect of pesticides in greenhouses on honey bee larvae, we investigated the effects of some insecticides used in strawberry greenhouse on A. mellifera larvae, by acute and chronic toxicity bioassay. Commercial formulations were serially diluted from the recommended concentration to 10SUP-6/SUP times. For acute toxicity, 30 μL of desired concentration of pesticides in diet C were fed to the three-day-old larvae. Mortality of larvae was monitored until the 6th day. For chronic exposure of larvae toxicity, residue level concentrations of pesticides were exposed from 2SUPnd/SUP to the 5SUPth/SUP days. Our results show toxicity order of emamectin benzoate, lufenuron, fluxametamide, acequinocyl, and Acetamiprid with LDSUB50/SUB values 0.000, 0.4, 8.1, 10 and 982.3 ㎍/larvae respectively. Among the two pesticides tested chronically, honey bee larvae were highly sensitive to emamectin benzoate that killed more than 50% in the 6SUPth/SUP day at 35, and 73 ppb. These results show that exposure of larvae to emamectin benzoate results in negative effects on the survival of bees, possibly compromising the dynamics of the colony, contributing to the decline of bee populations.