M A Y / J U N E 2 0 1 7 24 POTATO GROWER • Scout fields regularly, especially in low wet areas, along tree lines, at the center of the pivot and other areas that remain wet for longer periods where late blight may first occur. • Use foliar fungicides on a regular and continuing schedule. Once late blight is present, only foliar fungicide applications can man- age late blight in the field. (A cur- rent list of fungicides can be found in the NDSU Fungicide Guide PP-622). • Keep up to date on late blight forecasts. In our region, the NDSU Potato Blightline operates during the growing season and provides weekly late blight updates and forecasting. https://ndawn.ndsu .nodak.zedu/potato-late-blight. html. • Quickly destroy hot spots of late blight. • Kill vines completely two to three weeks before harvest. • Application of phosphorous acid to potatoes after harvest and before piling can prevent infec- tion and spread of late blight in storage. • Monitor home garden and mar- ket tomatoes near you for late blight. Late blight can move from these local sources to potato fields. Figure 8. Late blight infection of tubers is characterized by irregularly shaped, slightly depressed areas of that can vary considerably in color from brown to purplish color of variable size on the skin. (Photo credit: Eugenia Banks, Ontario Ministry of Agriculture and Food) Figure 9. Late blight causes a tan to reddish-brown, dry, gran- ular rot is found under the skin in the discolored areas, extending into the tuber. (Photo credit: Andy Robinson, NDSU/UMN) Figure 10. The margin of the diseased tissue is not always dis- tinct but can be, particularly in seed potatoes that have been stored at cold storage temperatures. (Photo credit: Francisco Bittara Molina, NDSU)