|Prabhaker, Nilima - UC RIVERSIDE, CA|
|Toscano, Nick - UC RIEVRSIDE, CA|
Submitted to: Entomological Research Bulletin of
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 21, 2005
Publication Date: December 1, 2005
Citation: Prabhaker, N., Castle, S.J., Henneberry, T.J., Toscano, N.C. 2005. Assessment of cross-resistance potential to neonicotinoid insecticides in Bemisia tabaci (Hemiptera: Aleyrodidae). Bulletin of Entomological Research 95: 535-543. Interpretive Summary: The neonicotinoids are a recently developed class of insecticides that have been pivotal in protecting crops from some of the world's most serious pests. The first commercial use of imidacloprid in California in 1993 soon became the foundation of a chemical management program that has strengthened over time with the registration of additional neonicotinoid compounds and insect growth regulators. Concerns over potential resistance development to neonicotinoid compounds have been expressed in light of the heavy reliance that has been placed on certain members of this class, in particular imidacloprid. To test for the possibility of cross-resistance among neonicotinoids, evaluations were conducted on three different imidacloprid-resistant strains of Bemisia tabaci and various field populations. Levels of resistance to imidacloprid and cross-resistance varied to three other neonicotinoids-acetamiprid, dinotefuran and thiamethoxam. Differences in responses to the various neonicotinoids may be due to differences in binding at the target site or in detoxification mediated by metabolic pathways influenced potentially by ecological and operational factors.
Technical Abstract: Laboratory bioassays were carried out with four neonicotinoids on multiple strains of Bemisia tabaci to evaluate resistance and cross-resistance patterns. Three imidacloprid-resistant strains and field populations from three different locations in the Southwest of USA were compared in systemic uptake bioassays with acetamiprid, dinotefuran, imidacloprid and thiamethoxam. An imidacloprid-resistant strain (IM-R) with 120-fold resistance originally collected from Imperial Valley, CA, did not show cross-resistance to acetamiprid, dinotefuran or thiamethoxam. The Guatemala-resistant strain (GT-R) was also highly resistant to imidacloprid (RR=109-fold) showed low levels of cross-resistance when bioassayed with acetamiprid and thiamethoxam. However, dinotefuran was more toxic than either imidacloprid or thiamethoxam to both IM-R and GU-R strains as indicated by low LC50s. By contrast, a Q-biotype Spanish-resistant strain (SQ-R) of B. tabaci highly resistant to imidacloprid demonstrated high cross-resistance to the two related neonicotinoids. Field populations from Imperial Valley, Maricopa and Yuma showed variable susceptibility to imidacloprid (LC50's ranging from 3.39-115 ug/ml) but did not exhibit cross-resistance to the three neonicotinoids suggesting that all three compounds would be effective in managing whiteflies. Yuma populations were the most susceptible to imidacloprid followed by Imperial Valley whitefly populations. Dinotefuran was the most toxic of the four neonicotinoids against field populations of whiteflies. Although differences in binding at the target site, nicotinic acetylcholine receptors (nAChR) of the neonicotinoids and preexisting metabolic pathways may influence the variability in cross-resistance patterns among whitefly populations, comparison of whitefly responses from various geographic regions to the four neonicotinoids indicates the importance of ecological and operational factors on development of cross-resistance to the neonicotinoids.