Early planted/emerged potatoes in the Hancock and Plover areas are at/near Blitecast threshold of 18. This threshold indicates that we’ve had temperature and humidity which has been favorable for late blight disease development if inoculum is present. (Hancock 17 DSVs on 6/1/16; Plover 18 DSVs on 6/1/16). UWEX Vegetable Crop Updates Newsletter #10 (link below) provides further information on how the Blitecast tool works.
This threshold indicates the need for preventive application of fungicide to limit late blight for early planted potatoes in the Plover and Hancock areas. This is quite early – however – the tool has been very reliable for growers here in WI during the previous 7 years. This fungicide recommendation is urgent especially if you’ve planted seed grown in locations in which late blight may have been present (even if not detected within the seed lot) during 2015. Early prevention can significantly reduce this early risk of potential inoculum – and limit more extensive spread.
Also, additional late blight has been confirmed in additional parts of southern CA as well as in Walla Walla Co. Washington on potato just today.
Amanda Gevens
Associate Professor & Extension Specialist
Potato & Vegetable Pathology
Plant Pathology Department
University of Wisconsin-Madison
Madison, WI 53706
