From Clemson Plant Pathologist Tony Keinath in The South Carolina Grower . As part of a U.S. Department of Agriculture Organic Transitions Program grant, we tested 10 biopesticides on organic kale ‘Oldenbor’ to determine if any product controlled Alternaria leaf spot, a.k.a. black spot on kale. None look promising. No biopesticides reduced black spot on kale compared to the non-treated …