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Title: EVALUATION OF INSECTICIDE ROTATIONS AND MIXTURES AS RESISTANCE MANAGEMENT STRATEGIES FOR BEMISIA ARGENTIFOLII (HOMOPTERA: ALEYRODIDAE)

Author
item PRABHAKER, NILIMA - UNIV OF CA, RIVERSIDE, CA
item TOSCANO, NICK - UNIV OF CA RIVERSIDE CA
item HENNEBERRY, THOMAS

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: Development of insecticide-resistance is a major problem in crop protection entomology. The authors have previously, in a series of publications, demonstrated that the silverleaf whiteflies readily develop resistance to a wide range of insecticide chemistries. One of the proposed strategies for delaying or preventing resistance development is a rotation of different chemistries to limit exposure to any single chemistry type. We investigate this hypothesis by selecting for silverleaf whitefly resistance in a field population by: (1) continuous applications of bifenthrin, endosulfan, chlorpyrifos; (2) bifenthrin-endosulfan-chlorpyrifos; and (3) a 1:2 bifenthrin+endosulfan mixture. Resistance developed at variable rates. Early resistance development occurred with bifenthrin that steadily increased to 752-fold after 27 generations of continuous selection. With chlorpyrifos and endosulfan selection treatments, low levels of resistance (8-fold) developed of 7 for chlorpyrifos and 15 generations for endosulfan Resistance for the insecticide rotation and insecticide mixture treatments was delayed for an additional 10 generations. Resistance to the bifenthrin+ endosulfan mixture was 17-fold after 23 generations. Compared with single continuous insecticide selections in the greenhouse, the rate of resistance development was significantly reduced by rotations and mixtures of insecticides compared with continuous insecticide selection with a single chemical.

Technical Abstract: A field population of Bemisia argentifolii Bellows & Perring was subjected to selective pressure with five insecticide regimens: continuous applications of bifenthrin, endo-sulfan, chlorpyrifos; bifenthrin- endosulfan-chlorpyrifos rotation and a 1:2 bifenthrin+endosulfan mixture. Insecticide resistance developed at variable rates in all whitefly populations under selection during the study period. Selection with bifenthrin resulted in early resistance development that steadily increased under continuous selection to 752-fold by generation F27. With chlorpyrifos and endosulfan selection treatments, low levels of resistance developed in generations F7 and F15, respectively (Resistance ratios [RR] of 8-fold). Resistance development in the rotation and mixture regimens was delayed for an additional 10 generations. The magnitude of resistance ranged from a high of 752-fold for the single continuous use of bifenthrin to a low of 16-fold resistance for the bifenthrin-endosulfan-chlorpyrifos rotation. The level of resistance was also low under selection by the bifenthrin+end- osulfan mixture after 23 generations (RR= 17-fold). Compared with single continuous insecticide selections in the greenhouse, the rate of resistance development was significantly reduced by rotations and mixtures of insecticides. For all insecticide-selection regimens, slopes of regression lines increased over many generations. The whitefly population treated with the bifenthrin+endosulfan mixture generated the steepest lines.