Evaluation of Fungicides for Controlling Alternaria Leaf Spot of Cabbage in Arizona, 2025

Alternaria leaf spot, caused by Alternaria brassicicola, is a common foliar disease of brassica crops, including cabbage, cauliflower, broccoli, kale, and brussels sprouts. Symptoms include small black spots with a yellow halo that grow into large lesions with characteristic concentric rings on leaves and stems. This report evaluates the efficacy and crop safety of fungicides in controlling Alternaria leaf spot. The field trial was conducted in 2025 on Brassica oleracea var. capitata ‘Primo Vantage’. The results from this trial will help cabbage growers in the Southwestern region make informed decisions when developing spray programs.