Affected parts of the field have been disked under and Curzate and a contact fungicide have been applied to the rest of the field and surrounding fields. The genotype has not yet been identified. Late blight has not been found in North Dakota or Minnesota.
The conditions for the development of late blight continue to be generally unfavorable over the weekend at nearly all locations excluding Mandan and Linton. All sites except Williston have reached the threshold late blight severity values of 15, and only late blight favorability will be reported in future Blightline editions.
Growers are encouraged to scout their fields for late blight, concentrating on those areas most conducive for disease development and where fungicide application may have been challenging.
Under irrigation, growers should pay attention to the center of the pivots where foliage stays wetter for a longer period of time. At this point in time, irrigated potato fields should be sprayed on a 7 day schedule with standard protectants. Non-irrigated potato fields should be sprayed on a 10 day schedule with protectant fungicides.
Early blight continues to build under irrigated production systems. If early blight lesions can be found in the upper one third of the canopy growers may want to consider an application of a fungicide with enhanced activity against early blight such as a triphenyl tin hydroxide, Revus Top, or Quash.
