Late blight: Specialist warns US growers to be on lookout for genotype US-8

According to Amanda J. Gevens, Associate Professor & Extension Vegetable Plant Pathologist, UW-Madison, http://usablight.org is again up and running for 2018 in an effort to support the detection and characterization of late blight on tomato and potato crops from the U.S. Already this year, late blight has been confirmed on potato and tomato in Florida, she says. In all cases reported to the usablight website, the pathogen genotype was US-23. This has been the predominant genotype in Wisconsin, and across the U.S., in recent years. US-23 can still generally be managed well with use of phenylamide fungicides such as mefenoxam and metalaxyl (ie: Ridomil). However, a potato sample from northeastern FL was sent to Gevens’ lab recently and the genotype was US-8. This information does pose some additional concern for management as US-8 cannot be managed with phenylamide fungicides as isolates are resistant to the fungicide. Gevens says. More