Survey and Genetic Analysis of Demethylation Inhibitor Fungicide Resistance in From Michigan Orchards.

Resistance to sterol demethylation inhibitor (DMI) fungicides in , causal agent of brown rot of stone fruit, has been reported in the southeastern and eastern United States and in Brazil. DMI resistance of some isolates, in particular those recovered from the southeastern United States, is associated with a sequence element termed "Mona" that causes overexpression of the cytochrome demethylase target gene . In this study, we conducted statewide surveys of Michigan stone fruit orchards from 2009 to 2011 and in 2019, and we determined the sensitivity to propiconazole of a total of 813 isolates of .

Occurrence of QoI Resistance and Detection of the G143A Mutation in Michigan Populations of Venturia inaequalis.

Control strategies for Venturia inaequalis rely heavily on chemical fungicides. Single-site fungicides such as the quinone-outside inhibitors (QoI) have been used in Michigan apple orchards for more than 11 years. In 2008, we sampled eight commercial orchards in the Fruit Ridge growing region of Michigan in which apple scab control failures were observed on 'McIntosh' apple following applications of kresoxim-methyl or trifloxystrobin.