Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/5/2007
Publication Date: 8/1/2007
Citation: Prabhaker, N., Toscano, N.C., Morse, J., Naranjo, S.E., Henneberry, T.J., Castle, S.J. 2007. Toxicity of seven foliar insecticides to four insect parasitoids attacking citrus and cotton pests. Journal of Economic Entomology. 100(4):1053-1061.
Interpretive Summary: Insecticides remain one of the primary tactics for controlling pest insect populations in many crops; however, many insecticides developed over the past 10-15 years have more limited spectra of activity and may be more compatible with biological control tactics in an integrated pest management system. Seven insecticides, including conventional, broad-spectrum materials as well as several putatively selective materials were tested in laboratory bioassays on four common species of insect parasitoids attacking pests in citrus and cotton in order to establish baseline toxicity to these compounds. The broad-spectrum material chlorpyrifos was consistently the most toxic to all four species of parasitoids. Among the broad-spectrum pyrethroids, fenpropathrin was the only insecticide that demonstrated lower toxicity to some of the parasitoids compared to bifenthrin or cyfluthrin. The reduced-spectrum neonicotinoid acetamiprid was less toxic than bifenthrin but similar in activity to cyfluthrin with Gonatocerus ashmeadi and Eretmocerus eremicus while being more toxic to Aphytis melinus. In general, A. melinus was the most susceptible parasitoid. The narrow-spectra insect growth regulators buprofezin and pyriproxyfen were least toxic overall. Results will provide pest managers with specific information on the compatibility of select insecticides with various natural enemies.
Technical Abstract: Laboratory studies were carried out to compare the relative toxicity of seven foliar insecticides against four species of beneficial insects representing two families of HYmenoptera: Aphelinidae (Aphytis melinus Debach, Eretmocerus eremicus Rose & Zolnerowich, and Encarsia formosa Gahan) and MYmaridae (Gonatocerus ashmeadi Girault). Insecticides from four pesticide groups were evaluated by a Petri dish bioassay technique across a range of concentrations to develop dosage-mortality regressions. Insecticides tested included acetamiprid (neonicotinoid), chlorpyrifos organophosphate), bifenthrin, cyfluthrin, and fenpropathrin (pyrethroids); and buprofezin and pyriproxyfen (insect growth regulators). Chlorpyrifos was consistently the most toxic to all four species of beneficial insects tested within 24 h after treatment. Among the pyrethroids, fenpropathrin was the only insecticide that demonstrated lower toxicity to parasitoids compared to bifenthrin or cyfluthrin. Acetamiprid was less toxic than bifenthrin but similar in activity to cyfluthrin with G. ashmeadi and E. eremicus while being more toxic to A. melinus. A. melinus was the most susceptible parasitoid among the four test species. Buprofezin and pyriproxyfen were less toxic to the parasitoids compared to conventional insecticides. The data presented here will provide pest managers with specific information on the compatibility of select insecticides with various natural enemies.