US: Fungicide-resistant late blight found in Wisconsin spud field

Late blight was confirmed in a potato field in Portage County, Wisconsin, July 18, but it’s not the same strain as has been found elsewhere this year. Until now, all of the genotypes of Phytophthora infestans have been US-23, according to a University of Wisconsin grower e-newsletter. The genotype found in Wisconsin was US-8, a type that dominated the 1990s and that can infect both tomatoes and potatoes. US-8 also was found in Portage County in 2013. The US-8 genotype is resistant to mefenoxam/metalaxyl fungicides, which has been associated with the A2 mating type. (Source: The Grower)