The role of Diaporthe perjuncta in delayed budburst and death of grapevine buds

Abstract

Diaporthe perjuncta has been associated with Phomopsis cane and leaf spot disease of grapevine in Australia. Both D. perjuncta and Phomopsis viticola cause bleaching of cane and, for this reason, diagnosis of the two fungi is often confused in the vineyard. P. viticola causes leaf spots and shoot lesions in the growing season, whereas more recent studies have indicated that D. perjuncta might not be a pathogen. Field studies were conducted to assess the role of D. perjuncta in delayed budburst and death of grapevine buds. Over three seasons (1999–2001), vines were assessed at four vineyards in South Australia for percentage of budburst and incidence of D. perjuncta. A D. perjuncta-specific probe, pT1P180, was used to detect D. perjuncta in unburst buds, cane and shoots on spurs having buds that failed to burst. D. perjuncta was detected in both bleached and non-bleached cane. Although there was a significant association between the incidence of D. perjuncta and buds that failed to burst in 1999 only, overall bud burst was normal in all vineyards and bud loss was not a concern. Bunch number and shoot growth was not affected. Mites were considered as a possible factor in damage to unburst buds, but it was more likely that failure of buds to burst was related to physiological or environmental effects. D. perjuncta did not adversely affect grapevine productivity and cannot be regarded as a pathogen of grapevine.