Suppression of clubroot by dazomet fumigant.

Hwang, S.F., Ahmed, H.U., Strelkov, S.E., Zhou, Q., Gossen, B.D., McDonald, M.R., and Turnbull, G.D. 2017. Suppression of clubroot by dazomet fumigant. Can. J. Plant Sci. 98: 172–182. dx.doi.org/10.1139/cjps-2017-0099.

Abstract

Experiments were conducted to examine the effectiveness of the prill formulation of the soil fumigant dazomet (tetrahydro-3,5-dimethyl-2H-1,3,5-thiadiazine-2-thione, trade name Basamid), on infection by Plasmodiophora brassicae, clubroot severity, and growth and yield of canola (Brassica napus). Greenhouse studies showed that seedling emergence and plant height increased, and infection (both primary and secondary) and clubroot severity decreased with increasing rates of a dazomet pre-treatment. Under field conditions, clubroot severity was reduced and seed yield increased with increasing dosage of dazomet. However, seedling emergence, root mass and seed yield were reduced, especially at high rates (e.g., 0.4 0.8 T a.i. ha-1). A study conducted under controlled conditions indicated that an inadequate interval between the dazomet treatment and seeding was the underlying cause of the phytotoxic effect on canola in the field study. Further field studies showed that covering with construction-grade plastic after application increased the efficacy of dazomet, reducing gall weight and clubroot severity, and increasing seed yield. Dazomet also increased emergence, plant survival and plant biomass in clubroot-infested soils that were inoculated with the soil-borne fungal pathogens Fusarium avenaceum, Pythium ultimum and Rhizoctonia solani. These results indicate that dazomet is effective against both clubroot and seedling blight of canola.

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