Management of Botryosphaeria species infection in grapevine propagation materials

Abstract

In New Zealand grapevine propagation nurseries, Botryosphaeria spp. were isolated from 23% of grapevine plant materials. The pathogens were widespread in mother vine blocks and infections were often present in the bark, not wood, of cuttings. Studies into control methods began with attempts to wash the Botryosphaeria conidia from cuttings, however they were unsuccessful as conidia adhered rapidly (within 5 min) to canes. Hot water treatment (HWT) of rootstock 5C cuttings, previously infected with Neofusicoccum parvum and N. luteum, at 50°C for 30 min resulted in internal infection incidences of 50% and 100%, respectively. HWT at 53°C for both 30 and 60 min reduced infection incidence for N. luteum and N. parvum to 0 and 8.5%, respectively, but killed the buds. In naturally infected cuttings, 50°C for 30 min reduced infection incidence from 35% in controls, to 0–15% over all Botryosphaeria spp. Shorter periods of HWT, at 55°C for 5 min, designed to kill bark infections, were ineffective. To determine fungicide efficacy for eliminating bark infection, Sauvignon blanc cuttings superficially infected with N. luteum were soaked for 30 min in carbendazim, tebuconazole, thiophanate methyl or flusilazole, with and without an organosilicone adjuvant. Results showed that carbendazim with no adjuvant and tebuconazole with 0.5 mL L-1 adjuvant eliminated 100% of bark infections. A further experiment that soaked 2,000 cuttings (Sauvignon blanc and Pinot noir) in a carbendazim solution prior to rooting found that all cuttings were free of Botryosphaeria spp. infection, compared to 13% natural incidence.