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Management of common scab of potato in the field using biopesticides, fungicides, soil additives, or soil fumigants

Al-Mughrabi, Khalil I., Vikram, Appanna, Poirier, Rene, Jayasuriya, Kithsiri, Moreau, Gilles
Biocontrol science and technology 2016 v.26 no.1 pp. 125-135
Bacillus subtilis, Enterobacter cloacae, Streptomyces scabiei, additives, biological control, biopesticides, chloropicrin, disease incidence, field experimentation, fludioxonil, fresh market, fumigants, industry, mancozeb, manganese sulfate, mustard meal, on-farm research, potatoes, seed treatment, soil, soil fumigation, tubers, New Brunswick
Common scab, caused by Streptomyces scabiei is an economically important potato disease worldwide. The potato industry in New Brunswick, Canada experience $1.2 million loss every year due to this disease. Superficial, raised, or deep-pitted brownish lesions on infected tubers reduce the quality and marketability of both fresh-market and processing potatoes, and hence, common scab is considered a priority disease for which adequate control measures are lacking. The objective of this research was to compare various potential treatments in suppressing the disease. Two field experiments were conducted at McCain's Research Farm, Florenceville-Bristol, New Brunswick, Canada, in 2008 and 2009 to assess the efficacy of Bacillus subtilis, Enterobacter cloacae , Chloropicrin, Pic-Plus, manganese sulphate and mustard meal in comparison with the chemical controls fludioxonil and mancozeb against common scab of potato. The disease incidence was significantly reduced by 36% due to the addition of mustard meal to the soil; 35.4% due to fludioxonil seed treatment; 30.0% due to soil fumigation with Pic-Plus; or by 27.2% due to soil fumigation with Chloropicrin. Potato tubers with scab severity ≥5% which are considered unmarketable in Canada were significantly reduced by 56.1% due to seed treatments with B. subtilis ; by 57.8% due to fludioxonil; or by 63.1% due to the soil addition of mustard meal. The same treatments significantly increased marketable yield by 32.5%, 24.6%, and 24.6%, respectively. Soil fumigation with Chloropicrin or Pic-Plus increased marketable yield by 9.5% or 7.1%, respectively. These findings indicate that, in addition to the fludioxonil seed treatment, the seed treatment with the biopesticide containing B. subtilis and the soil addition of mustard meal treatments are potential alternatives for managing common scab of potatoes.