Effectiveness of chemical compounds and biocontrol agents for management of bacterial spot of Pumpkin caused by Xanthomonas cucurbitae

Bacterial spot, caused by Xanthomonas cucurbitae, has become one of the most important diseases of pumpkin. Seventeen chemical compounds and five biocontrol agents were evaluated for their efficacy for management of the disease. The EC₅₀ for reduction in cell multiplication of the pathogen ranged from 0.17 ppm for mancozeb (Dithane 75 DF) to 64.53 ppm for cuprous oxide (Nordox 75 WG) in nutrient broth, and from 0.23 ppm for Dithane 75 DF to 38.87 ppm Nordox 75 WG in casitone yeast extract broth. The inhibition zones produced by biocontrol agents on Luria Bertani culture medium ranged from 3.1 mm for Bacillus pumilus (Sonata ASO) to 10.6 mm for Streptomyces lydicus (Actinovate AG). In the field trials, copper oxychloride + copper hydroxide (Badge X2 DF), copper sulfate (Cuprofix Ultra 40 DF), oxytetracycline (Mycoshield 40 WSP), copper sulfate pentahydrate (Phyton-016B), copper hydroxide (Kocide-3000 46.1 DF) plus acibenzolar-s-methyl (ActiGard 50 WG), Kocide-3000 46.1 DF plus famoxadone + cymoxanil (Tanos 50D WG), an extract from Reynoutria sachalinensis (Regalia), and B. subtilis (Serenade ASO) were more effective in reducing incidence and severity of bacterial spot on both leaves and fruit compared to controls. These chemical compounds or biocontrol agents may be used in combination with other methods to manage X. cucurbitae in pumpkin.