Honeybees exposed to pesticides direct or indirect ways through their food
research trips. Herein, this study examined the toxicity effects on laboratory of
seven tested pesticides insecticides from different pesticide groups. emamectin
benzoate, imidacloprid, chlorpyrifos, indoxacarb, lambada cyhalothrine,
glyphosate and thiophanate-methyl on honeybee workers, Apis mellifera L.
through different exposure periods of time at 24, 48, and 72 hours. The selected
pesticides were ranked based on their toxicity from the most to least one as
following: emamectin benzoate, imidacloprid, chlorpyrifos, indoxacarb, and
lambda cyhalothrine. Further, thiophanate-methyl and glyphosate were the lowest
toxicity among selected pesticides. The highest toxic pesticide during the exposure
period 24, 48 and 72 hrs was emamectin benzoate with LC50 values (0.247, 0.047
and 0.020 ppm) and with LC90 values (5.752, 0.302 and 0.072 ppm) respectively,
and the least one was glyphosate with LC50 values of (6861.151, 3366.968 and
2477.267 ppm) and LC90 values of (28243.795, 9033.695 and 6203.485 ppm) after
24, 48 and 72hr of exposure respectively. However, chlorpyrifos ranked the third
toxic pesticide at 24 and 48 hrs of treatment with LC50 values of 10.226 and 2.731
ppm and with LC90 values of (101.224 and 7.496 ppm for 24 and 48 hrs,
respectively). Whereas, after 72 hrs chlorpyrifos recorded the fourth toxic pesticide
with LC502.086 ppm and LC90 5.179ppm. Based on the toxicity index, results
showed that, the most to least toxic pesticides were arranged as followed:
emamectin benzoate>imidacloprid >chlorpyrifos >indoxacarb >lambada
cyhalothrine> thiophanate -methyl > glyphosate. These results demonstrated that
pesticides are very toxic to honeybee workers and must avoid applying them
during the times when bees are most active such as during flowering periods.