Mancozeb resistance patterns among Kampimodromus aberrans and Typhlodromus pyri (Acari: Phytoseiidae) strains from French vineyards

Abstract

AbstractLaboratory bioassays were carried out on two species of phytoseiid mites to investigate their resistance to the fungicide mancozeb. Susceptible and suspected resistant strains of Kampimodromus aberrans (Oudemans) and Typhlodromus pyri Scheuten were tested. Mancozeb resistance factors were low to moderate: they reached 6.3 and 11.7 for K. aberrans and T. pyri, respectively. Intrinsic toxicity of mancozeb was approximately 5–10-fold more pronounced in females of K. aberrans than in females of T. pyri. The female susceptibility pattern of the most resistant strain of K. aberrans was quite close to that of the most susceptible strain of T. pyri. The LC50 values for the most resistant strains of K. aberrans and T. pyri were 4.6 and 43 times higher, respectively, than the maximum field application rate of mancozeb recommended for control of downy mildew in vineyards. Using a diagnostic concentration, a limited survey in vine plots indicated that most of the K. aberrans strains we tested were susceptible to mancozeb, but a few consisted of both resistant and susceptible individuals. All strains of T. pyri collected in Burgundy were susceptible. Half of the T. pyri strains from Bordeaux were susceptible and the other half were mixed populations of resistant and susceptible individuals.