Submitted to: Bulletin of Entomological Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/19/2008
Publication Date: 10/24/2008
Citation: Castle, S.J., Prabhaker, N., Henneberry, T.J., Toscano, N.C. 2008. Host plant influences on susceptibility of bemisia tabaci (Hemiptera: Aleyrodidae) to insecticides. Bulletin of Entomological Research. 99:263-273.
Interpretive Summary: Insecticide resistance monitoring is an essential element of resistance management. A resistance monitoring program for Bemisia tabaci was carried out in the Imperial Valley, CA during the mid-1990s. The monitoring data was characterized more by subtle trends in LC50s than major shifts in resistance levels. Significant differences in mean LC50s were measured for whiteflies collected from three different crops. This result led to an experiment that measured LC50s of whiteflies on broccoli or cantaloupe in the field and then in the greenhouse after establishing colonies. Significantly higher LC50s were again recorded for whiteflies cultured on broccoli compared to cantaloupes. Colonies established on the opposite host from their field host showed changes in LC50s that corroborated previous observations. The resistance monitoring data together with the experimental results demonstrate that particular host plants can significantly influence susceptibility of B. tabaci to insecticides.
Technical Abstract: : A resistance monitoring program conducted for the polyphagous whitefly Bemisia tabaci (Gennadius) in Imperial Valley, CA, USA generated a large set of LC50s for adults collected from broccoli, cantaloupe and cotton crops over a four-year period. A vial bioassay and subsequently a yellow-sticky card bioassay produced similar temporal profiles in relative susceptibilities to the pyrethroid insecticide bifenthrin. Both bioassays revealed that whiteflies collected from broccoli were significantly less susceptible to bifenthrin compared to the other two crops. A similar finding was observed for endosulfan and the mixture of bifenthrin+endosulfan in the yellow-sticky card bioassay. The possibility that seasonal differences contributed to the observed differences in susceptibility served as the impetus to conduct a reciprocal transfer experiment using broccoli (or kale) and cantaloupe grown simultaneously in the field and greenhouse. Whitefly adults collected from an organic farm over three consecutive weeks had significantly higher LC50s on kale than those collected the same day on cantaloupe. After culturing in the greenhouse on broccoli or cantaloupe and testing again, LC50s remained significantly higher on broccoli after one week and again at the F1 generation. In contrast, whiteflies originating on kale in the field and transferred to cantaloupes in the greenhouse had significantly reduced LC50s at the F1 generation. When tested against the bifenthrin+endosulfan mixture, significantly higher LC50s were generated for whiteflies reared on broccoli in the greenhouse at one week and the F1 compared to the field source from cantaloupes. The consistently higher LC50s for whiteflies on broccoli and other cole crops compared to cantaloupes or cotton point to statistically significant host-plant influences that are expressed in both field-collected and greenhouse reared populations of whiteflies.