Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/13/2008
Publication Date: 10/30/2008
Citation: Unruh, T.R., Willett, L.S. 2008. Survey for Resistance to Four Inecticides in Myzus persicae Clones from Peach and Weeds in South-central Washington. Journal of Economic Entomology 101:1919-1929. Interpretive Summary: Insecticide resistance is an increasing problem that causes billions of dollars to world agriculture annually. Recent changes of pesticide use patterns in the potato industry put it at risk of insecticide resistance development in the green peach aphid. We used traditional laboratory bioassay procedures to assess resistance to four insecticide classes in green peach aphid collected from the peach and potato production areas of central Washington. Low levels of resistance were shown with the cyclodiene insecticide endosulfan. No resistance was seen in for methamidophos, the commonly used rescue insecticide, or to imidacloprid, the insecticide class receiving the greatest use pressure. Fairly high variation in tolerance was seen with the pyrethroid esfenvalerate but not enough to classify this as resistance. The study suggests there are no significant resistance problems in green peach aphid that may disrupt Washington potato production at this time.
Technical Abstract: The insecticides esfenvalerate, endosulfan, imidacloprid, and methamidophos were screened against 74 clonal populations of the green peach aphid, Myzus persicae (Sulzer) collected as fundatrices from peach and as apterous virginoparae from peach, and various weeds near potato fields in the Yakima Valley and Columbia Basin regions of Washington State. Response to discriminating concentration of four insecticide products demonstrated a bi-modal pattern of survival to endosulfan (Phaser) suggesting two phenotype classes responding to this insecticide. This pattern was not observed with the other products. Statistically significant correlations in mortality to discriminating concentrations were observed in comparisons of endsosulfan to methamidophos and imidoclprid to methamidophos, but not for any of the remaining four possible comparisons. Concentration-response bioassays were conducted on 16 clones with the four insecticides and the highest LC50 ratios observed of 7-fold observed with for endosulfan. LC50 ratios of only four-fold was observed for esfenvalerate and less than 4-fold for both imidacloprid and methamidiphos. Only the endosulfan response is of biological significance and reflects the same cyclodiene resistance discovered in this region over a decade ago.