IDAHO FALLS, Idaho — Continued wet August weather has caused late blight infections to proliferate throughout Eastern Idaho, according to University of Idaho Extension potato pathologist Phil Nolte.
As of Aug. 26, Nolte said eight fields in Fremont, Madison, Bingham, Bonneville and Power counties had confirmed cases of late blight, which thrives in high humidity. Based on reports from crop consultants and field men who have been out scouting fields for the disease, however, Nolte is certain infections are far more rampant.
Nolte believes growers have simply become more aware of the fungal disease and are no longer seeking his assistance with testing.
Nolte said most Eastern Idaho growers have been aggressively stepping up fungicidal spraying and have caught it in time to limit patches of infection to just a few feet. He’s optimistic that a change to more conventional weather patterns will stop late blight before area growers take a significant financial hit, aside from increased input costs associated with spraying.
He suggested growers in the region may limit the need for extra spraying by inducing vine kill early and mixing in a fungicide.
Though Magic Valley has been wetter than Eastern Idaho, Jeff Miller, with Rupert-based Miller Research, said no samples have been submitted for testing from his area and no cases have been confirmed, likely due to the absence of late blight spores. Miller’s best guess is that infected tomatoes were delivered to Eastern Idaho.
In Eastern Idaho, Miller said “growers need to be spraying all the way up until harvest, and even after they vine kill.”
Miller suggests using products that contain mancozeb, a protectant fungicide that can block spores from penetrating through soil to tubers. Especially in fields in which late blight has been detected, he recommends post-harvest treatments with phosphorous acid, proven to be extremely effective at limiting the disease from spreading in his storage trials. Without the treatment, Miller said late blight can “cause the whole storage to just melt down.”
James Hoff, who farms in Bonneville County south of Idaho Falls, typically doesn’t use fungicide beyond an in-furrow treatment at planting. About a week ago, he said started a 10-day spraying schedule upon hearing that the disease “went widespread” in his area. Hoff said he’s been aggressively scouting fields and has seen no problems.
American Falls grower Kamren Koompin sent two samples in for late blight testing, but the infection proved to be early blight. After the first case in Power County was reported earlier this month within close proximity to one of his fields, Koompin started using a fungicide effective at killing late blight spores on a seven- to 10-day interval, rather than every two to three weeks.