Toxicity of pyriproxifen and fenoxycarb to bumble bee brood using a new method for testing insect growth regulators
L De Wael; M De Greef; O Van Laere
These insect growth regulators were administered in 1:1 sucrose solution to young bumble bee (Bombus terrestris) colonies kept in the dark in a controlled climate chamber and fed with 50% sucrose solution and bee-collected pollen. Three colonies received Admiral (pyriproxifen at either 20 ppm a.i., or 2 ppm a.i., or 0.2 ppm a.i.) and one received Insegar (fenoxycarb 100 ppm a.i.). One colony was fed with Nomolt (teflubenzuron 150 ppm a.i.), which was known to be toxic to bumble bee brood. A sixth colony, fed with pure sucrose solution, acted as a negative control. After the 24-h feeding period the amounts of ingested sucrose solutions were determined and the colonies, which had been photographed daily for one week before treatment, were photographed daily for the next five weeks. There was no significant difference between colonies in the amount of food consumed on the day of treatment. The only colony to show larval mortality and arrested egg development was the one fed on teflubenzuron-sucrose solution. After five weeks there was no developing brood in this colony. Colonies treated with pyriproxifen and fenoxycarb developed normally.