Effect of methyl bromide, metham sodium and the biofumigants Indian mustard and canola on the incidence of soilborne fungal pathogens and growth of grapevine nursery stock

Abstract

The potential of the biofumigant crops Indian mustard and canola (cv. Dunkeld) to replace methyl bromide (MeBr) and metham sodium for the control of root pathogens on Shiraz on Ramsey rootstocks was evaluated in a commercial grapevine nursery in the Riverland district of South Australia. The application of MeBr and metham sodium resulted in a significant 78% and 40% increase, respectively, in the percentage of first grade vines at harvest. In contrast, Indian mustard and canola incorporated into the soil at equivalent rates of 12.2 and 9.8 t dry matter per ha, respectively, had no significant effect upon the percentage of first grade vines. There was a significant reduction in vine establishment in the plots treated with Indian mustard (87.5%), compared to the control (93.5%). This reduction was related to a significant increase in the number of Pythium propagules in soil in the plots treated with Indian mustard and canola. Pythium spp. were isolated from >86% of stunted vines in the brassica amended plots. MeBr and metham sodium caused significant reductions in the number of Pythium propagules in the soil and caused significant reductions in the incidence of Cylindrocarpon spp. and Rhizoctonia spp, in the first grade vine roots at harvest. These results demonstrate that, at the rates of incorporation, Indian mustard and canola were unable to replace the beneficial effects and economic returns of MeBr or metham sodium on nursery grapevine growth.