U Of I Says Conditions Favorable For Blight
University of Idaho extension potato specialists predict that based on conditions, there could be outbreaks of the late blight this year.
William Bohl, extension educator-potatotes based in Blackfoot, ID, Jeff Miller, assistant research professor located in Aberdeen, ID, and Phillip Nolte, extension seed potato specialist, Idaho Falls, ID, say that because the organism can overwinter, volunteer potatoes could carry the pathogen.
The trio also say that if Idaho is hit by a lot of thunderstorms, sporangia could be moved through an infected field and into neighboring fields. A disease forecast model indicates the probability of seeing late blight to be "very high."
Applications of a fungicide should be made just before plants close rows with a second application coming 10 days later. Growing conditions will determine the need for additional applications.
The trio also said that sprinkler irrigation systems also supply the necessary moisture for disease development. Irrigators are advised to let foliage dry in the evening before dew sets in. This will decrease the time the plants are wet and lessen the chances of infection.
In addition, growers are advised to let plants dry before applying water in the morning after a heavy dew. They said for infection to occur, plants need to be wet for 10-12 hours.