Evaluation of the susceptibility of different strains of Panonychus ulmi to three M.E.T.I. acaricides (fenazaquin - fenpyroximate - tebufenpyrad) and to propargite [Malus pumila Mill. - Trentino -mitochondrial electron transport inhibitor]
2000
Ioriatti, C. | Sofia | M. | Menapace, L. (Istituto Agrario Provinciale, San Michele all'Adige, Trento (Italy))
Samples of European spider mite Panonychus ulmi, collected in various apple commercial orchards, were tested for susceptibility to commercial formulations of fenazaquin, fenpyroximate, tebufenpyrad and propargite. The efficacy, evaluated in laboratory leaf disk bioassays, was compared either with the response of a susceptible strain collected in an organic orchard or with that one collected in an unsprayed home-garden. When the number of mites was enough, the dose-response lines were calculated. Resistant ratios and security index have been used to evaluate the level of resistance; where the dose-response lines were not available, resistance was detected with discriminating doses. Resistance to fenpiroxymate and propargite results widespread in all the apple orchards investigated, even though the last one has not been used in the region long since. Not significant loss of efficacy has been found for fenazaquin and tebufenpyrad. Contrary to all expectation, no evidence of cross resistance between fenpiroxymate and the other two M.E.T.I. (Mitocondrial Electron Transport Inhibitor) has been found in this study
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