SEASONAL CHANGES OF SENSITIVITIES TO STEROL DEMETHYLATION INHIBITORS IN VENTURIA INAEQUALIS POPULATIONS

摘要

During three seasons and at three different orchard sites, the sensitivities of V. inaequalis populations to sterol demethylation inhibitors were reduced over the course of the summer and in the absence of exposure to these fungicides. A seasonal fluctuation was not observed for dodine with a mode of action unrelated to inhibition of sterol demethylation. Seasonal fluctuations of population sensitivities to sterol demethylation inhibitors are of theoretical and practical importance. They not only reflect a rarely reported population response to changing environmental conditions over a growing season, but also have implications regarding the development of anti-resistance strategies for the control of apple scab with sterol demethylation inhibitors. As the frequency of the least sensitive population segment increases in late summer, the performance of these fungicides is most likely decreased. The resulting effect on disease incidence and selection of a resistant subpopulation can be expected to accelerate the speed of resistance development.