How Spotted Wing Drosophila Foes Are Affected by Insecticides
Scientists at the Federal University of Pelotas in Brazil investigated how two parasitoid wasps ( Trichopria anastrephae and Pachycrepoideus vindemmiae)are affected by eight commercial insecticides used to control spotted wing drosophila. The results of their study were published in the Journal of Economic Entomology.
Daniele Cristine Hoffmann Schlesener, Ph.D., Flávio Roberto Mello Garcia, Ph.D., examined the extent that two parasitoids were affected by the insecticides abamectin, acetamiprid, deltamethrin, malathion, phosmet, spinetoram, spinosad, and thiamethoxam.
For the parasitoid T. anastrephae, abamectin, spinetoram, and spinosad caused no significant increase in mortality; acetamiprid caused moderate mortality; deltamethrin caused 90% mortality; and thiamethoxam, phosmet, and malathion caused 100% mortality. For the parasitoid P. vindemmiae, all insecticides caused significant increases in mortality. In all the treatments, the amount of time to reach 10% mortality, and the amount of time to reach 50% mortality, was longer in T. anastrephae than in P. vindemmiae.
Adults of the two parasitoids species were exposed also to insecticides residues for four hours to test for effects of insecticides on parasitism. After four hours, the parasitoids were moved to glass vials, and pupae of D. suzukii were offered for parasitism for 24 hours. The research team then measured the degree of parasitism of the spotted-wing drosophila pupae and the emergence rates of the parasitoids.
In this experiment, T. anastrephae showed no significantly decreased parasitism when treated with abamectin, spinetoram, or spinosad, but showed no parasitism at all when exposed toacetamiprid, malathion, phosmet, or deltamethrin. P. vindemmiae showed decreased parasitism after exposure to every one of the insecticides.