Control of tuber-borne black scurf [Rhizoctonia solani] and common scab [Streptomyces scabies] of potatoes with a combination of sodium hypochlorite and thiophanate-methyl preplanting seed tuber treatment
2001
Errampalli, D. | Johnston, H.W.
In a 2-year field experiment, preplanting seed tuber treatments with sodium hypochlorite solution (as NaOCl 500 ppm for 8 min), thiophanate-methyl (TPM; as Easout, 50 g active ingredients/100 kg seed tubers), or a combination treatment with NaOCl followed by TPM were evaluated for control of black scurf, caused by Rhizoctonia solani Kuhn, and common scab, caused by Streptomyces scabies (Thaxter) Lambert & Loria, on potato, Solanum tuberosum L., cv. Russet Burbank. The combination treatment with NaOCl and TPM reduced Rhizoctonia on progeny tubers at harvest and after storage. The low incidence of scab on progeny tubers, in untreated checks, hindered the evaluation of the efficacy of the combination treatment and also showed that conditions were not favourable for scab development during this period and at this location. A comparison between NaOCl and the combination treatment indicates that preplanting NaOCl treatment may have killed the majority of the black scurf sclerotia on the tuber surface and that the combination TPM fungicide treatment following NaOCl disinfection suppressed the growth of the R. solani. A higher (1995) or similar (1996) marketable yield in the combination treatment compared to that in the untreated check showed that there was no phytotoxicity in the treated tubers. Disease incidence of black scurf and common scab varied from year to year. The results confirm that tuber-borne inoculum of R. solani reduces progeny tuber quality and marketable yields.
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