Bacterial spot of tomato incited by Xanthomonas spp. in Illinois: occurrence and management

This study was conducted to assess incidence of bacterial spot, incited by Xanthomonas spp., in Illinois and evaluate effectiveness of selected chemicals and biocontrol agents for management of the disease. In 2017 and 2018, 146 symptomatic leaf and fruit samples were collected from 21 commercial tomato fields in Illinois. Xanthomonas gardneri, X. perforans, and X. euvesicatoria were isolated from the samples. During 2016 and 2017, field trials were conducted to evaluate the effectiveness of selected chemicals and biocontrol agents for managing bacterial spot. Each trial was performed in a randomized complete block design with four replications, each with 10 plants. Spray-applications of the compounds, at 7-day intervals, began at fruit set and ended two weeks prior to the final fruit pick. Severity of bacterial spot on foliage and incidence of fruits with bacterial spot were visually assessed 6 days after each application of the compounds. The most effective compounds in reducing disease severity were mancozeb ( Manzate PRO Stick) plus copper hydroxide (Kocide-3000 46.1DF), mancozeb (Dithane M-45) plus Kocide-3000, quinoxyfen (Quintec 2.08SC) plus Kocide-3000, Regalia (a plant extract) plus Kocide-3000, and copper sulfate (Phyton Spectrum XP).