Clemson Plant Pathologist Tony Keinath provided updated fungicide recommendations to manage Alternaria leaf spot (black spot) in brassicas. The update was made in the South Carolina Grower.
Keinath emphasized Alternaria black spot is active on overwintered brassicas. Growers should be looking for symptoms like tan to gray to black spots, about one-quarter to one inch in diameter on leaves. Longer, narrower spots are also found on the top or bottom of the main rib of collard and kale leaves. The number of spots per leaf varies.
Multiple Fungicide Options
Producers have multiple fungicide options at their disposal. Three fungicides provide good control of Alternaria black spot on leafy brassica greens, based on research work on ‘Oldenbor’ kale at Clemson Coastal Research and Education Center from September to October 2025.
“Priaxor, Quadris Top and Miravis Prime clearly reduced leaf spotting symptoms and increased the weight of healthy leaves without spots compared to control plants sprayed with water,” Keinath said.
Producers should also be aware that Priaxor, Quadris Top and Miravis Prime remain active in the plant longer than Inspire Super does.
“At least, that’s my interpretation of the difference between the performance of Inspire Super based on disease symptoms and on based on yield,” Keinath added.
All three recommended fungicides is that they have limits on the number of applications and how many times they can be sprayed in a row. Miravis Prime and Quadris Top must be rotated 1:1 with another fungicide, while Priaxor can be sprayed twice before rotating.
“In this trial, I used Badge X2 copper as the rotation partner. In commercial fields, potassium phosphite could be rotated to provide protection against downy mildew,” Keinath said. “Note that Quadris and Quadris Top will control both black spot and downy mildew. Zampro controls downy mildew, but it has no effect on black spot.”
The organic-approved fungicides Oso and Badge X2 were ineffective in this trial. Organic growers should consider other management options.