Don’t get lazy with lesions

Early treatment for late blight in potatoes

The potato growing season is well underway, and as temperatures cool and moisture increases, late blight becomes more of a threat.


If growers don’t act proactively, damage from the disease can be severe. A few lesions can lead to complete defoliation in just a few days. Once vines are destroyed, photosynthesis halts and yield is dramatically impacted since tubers can become infected.


Knowing that a proactive approach is the best defense against late blight, growers should start to scout for signs of the disease as soon as the crop starts to emerge and continue scouting throughout the growing season.


Lesions will start to appear in the cool, moist weather and will quickly enlarge into dark brown or black lesions. Growers should check in low spots, compacted areas, rows close to tree lines, field edges along creeks or ponds, pivot center points, pivot wheel tracks and weedy areas of their fields.


In addition to scouting for the disease, growers can use a proactive application of a fungicide, such as Forum® fungicide, to control this disease.


“Forum fungicide is ideal for prevention and control of late blight because it greatly reduces sporulation of the disease,” said Curtis Rainbolt, Technical Service Representative at BASF. “Forum fungicide disrupts fungal cell wall formation by interfering with cellulose synthase.” In other words, it devastates fungal cell walls and prevents them from repair.


When disease-favoring conditions are present, multiple fungicide applications up to more than once a week might be necessary. With this in mind, growers should be aware of resistance management best practices. Rainbolt recommends growers rotate chemistries and avoid pairing them from the same Fungicide Resistance Action Committee (FRAC) group.


Management of late blight shouldn’t stop with scouting and fungicide applications. To prevent late blight from spreading to other parts of a field and a neighbor’s field, it’s vital for growers to work with their local university extension program since they track late blight very closely. If late blight is confirmed in a grower’s field, the university will issue an alert to the area.


Pairing communication with proper management practices and the right chemistries can go a long way in preventing the devastation late blight can cause to potato farms.


For more information, visit or contact your local BASF representative.


Always read and follow label directions.


Forum fungicide is a registered trademark of BASF. © 2018 BASF Corporation. All rights reserved.


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