Title : Techniques for Identification and managing bacterial and fungal diseases of tomatoes
Abstract:
Illinois is an important state in producing fresh-market tomatoes in the United States. In this state, tomatoes are produced in open-fields and indoors (greenhouses and high tunnels). Weather conditions in Illinois are conducive for developing biotic and abiotic diseases. Several bacterial and fungal diseases occur in both open-fields and indoor tomato production in Illinois. Bacterial diseases, which develop only in open-field productions, are bacterial canker (Clavibacter michiganensis subsp. michiganensis), bacterial speck (Pseudomonas syringae pv. tomato), and bacterial spot (Xanthomonas spp.). In the past nine years, bacterial spot disease occurred in all Illinois commercial tomato fields. A study was conducted to assess the occurrence of bacterial spot disease in commercial tomato fields, identify the causal species, and develop effective management of the disease. Field surveys were conducted for three years, and severity of foliage and fruit infection was recorded. Severity of symptomatic foliage ranged from 0% to 91% (mean 36.7%) and incidence of symptomatic fruit ranged from 0% to 30% (mean 10.8%). During the surveys, 266 Xanthomonas isolates were collected and identified as Xanthomonas gardneri and X. perforans, using Xanthomonas-specific hrp primers. Eighty-six percent of the isolates from northern Illinois were identified as X. gardneri, whereas 73% of the isolates from southern Illinois were X. perforans. Isolates from central Illinois were identified as X. perforans and X. gardneri, 53% and 47%, respectively. At present, foliage blight caused by Xanthomonas spp. is widespread, and fruit infection occurs mainly in northern Illinois. Major fungal diseases in commercial open-field productions are early-blight (Alternaria solani), Septoria leaf spot (Septoria lycopersici), anthracnose (Colletotrichum coccodes), and southern blight (Sclerotium rolfsii). In indoor production, major fungal diseases are leaf mold (Fulvia fulva), Verticillium wilt (Verticillium spp.), and Sclerotinia blight (Sclerotinia sclerotiorum). Multi-year open-field testing on ‘Red Duce’ and ‘Mt. Fresh’ tomatoes have shown that the lowest disease severity was in the plots with weekly spray-applications of copper hydroxide (Kocide-3000 46.1DF) plus mancozeb (Manzate Pro-Stick), Kocide-3000 46.1DF plus chlerothalonil (Bravo Weather Stik 6F), and Regalia. Applications of these compounds not only prevent or significantly reduce occurrence of bacterial spot disease (Xanthomonas spp.), but also are effective in managing other bacterial and fungal diseases in open-field production.
