Cherry powdery mildew is developing resistance to common fungicides in some Pacific Northwest orchards, according to preliminary data from Oregon State University. Powdery mildew isolates from ten Washington and Oregon sweet cherry orchards were collected during 2005 and from five orchards in the two states in 2006. The data showed reduced sensitivity to dimethylation-inhibitor fungicides, known as DMIs, said Jill Calabro, OSU graduate student who conducted the studies. Calabro tested resistance to the same five DMI fungicides in both years. Cross resistance “Once resistance develops, growers need to be concerned with cross resistance from within the same category,” she said […]