The acute toxicity and risk assessment of 25 pesticides used in nectar plant to Apis mellifera L.

Twenty-five pesticides,which were commonly used in the period of flowering of 4 main nectar plants in Zhejiang province,were chosen to determine the acute toxicity to bees(Apis mellifera L.) combining with the field maximum dose.The results showed that: the 48 h LC50 values of 1.8% EC abamectin to Apis mellifera L.was 0.0528(0.0462-0.0603) mg·L-1,belongs to very high toxic grade;the 48 h LC50 values range of 1% EC emamectin benzoate,40% EC methidathion,10% AS nitenpyram,40% EC phoxim,2.5% EC lambda-cyhalothrin,4.5% EC beta-cypermethrin,480 g·L-1 EC chlorpyrifos,45% EC malathion,10% WP imidacloprid and 90% TC trichlorfon to Apis mellifera L.were 1.02(0.869-1.14) mg·L-1 to 13.9(12.4-15.5) mg·L-1,belongs to high toxic grade;the 48 h LC50 values range of 15% EC pyridaben,20% SP acetamiprid and 15% WP ethylicin to Apis mellifera L.were 43.3(37.5-50.0) mg·L-1 to 163(127-210) mg·L-1,belongs to moderate toxic grade;the LC50 values of 5% SC fenpyroximate,250 g·L-1 EC prochloraz,25% WP diflubenzuron,40% EC propargite,50% WP cyromazine,50% WG dimethomorph,75% WG carbendazim,25% WP buprofezin,35% SC procymidone,50% WP iprodione and 75% WP chlorothalonil to Apis mellifera L.were higher than 200 mg·L-1,belongs to low toxic grade.The results showed that 1.8% EC abamectin,1% EC emamectin benzoate,40% EC methidathion,10% AS nitenpyram,40% EC phoxim,2.5% EC lambda-cyhalothrin,4.5% EC beta-cypermethrin,480 g·L-1 EC chlorpyrifos,45% EC malathion and 90% TC trichlorfon had very high risk to Apis mellifera L.10% WP imidacloprid,15% EC pyridaben and 5% SC fenpyroximate had high risk to Apis mellifera L.20% SP acetamiprid,15% WP ethylicin,250 g·L-1 EC prochloraz,40% EC propargite,50% WP cyromazine and 50% WG dimethomorph were moderately risk to Apis mellifera L.,while other pesticides were low-risk to Apis mellifera L.