Dynamics of Resistance to the Neonicotino ids Acetamiprid and Thiamethoxam in Bemis ia Tabaci.pdf

I NSECTICIDE RESISTANCE AND R ESISTANCE M ANAGEMENT Dynamics of Resistance to the Neonicotinoids Acetamiprid and Thiamethoxam in Bemisia tabaci (Homoptera: Aleyrodidae) A. RAMI HOROWITZ, 1SVETLANA KONTSEDALOV, 2 AND ISAAC ISHAAYA 2 J. Econ. Entomol. 97(6): 2051D2056 (2004) ABSTRACT The dynamics of resistance in the sweetpotato white?y, Bemisia tabaci (Gennadius), to the neonicotinoids acetamiprid and thiamethoxam was studied extensively in cotton Telds in Israel during the cotton-growing seasons 1999D2003. White?ystrains werecollected in early and late seasons mainly in three locations in northern, central, and southern Israel. The white?ies were assayed under laboratory conditions for susceptibility to neonicotinoids, as part of the Israeli cotton insecticide resistance management strategy. Selections to both acetamiprid and thiamethoxam and cross-resis- tance between them also were conducted in the laboratory. Although no appreciable resistance to acetamiprid was observed up to 2001, a slight increase of approximately Tve-fold resistance was detected during 2002 and 2003. However, from 2001 to 2003 thiamethoxam resistance increased ?100-fold in the Ayalon Valley and Carmel Coast cotton Telds. In cross-resistance assays with both neonicotinoids, the strain that had been selected with thiamethoxam for 12 generations demonstrated almost no cross-resistance to acetamiprid, wherea