GTD - Control of grapevine wood fungi in commercial nurseries

Previous surveys conducted in commercial nurseries found that different wood fungi, namely Cylindrocarpon spp., Botryosphaeriaceae, Phomopsis viticola and Phaeomoniella chlamydospora infect grapevine cuttings. Two field trials were carried out to evaluate the effectiveness of cyprodinil + fludioxonil, pyraclostrobin + metiram, fludioxonil and cyprodinil to prevent or reduce natural infections caused by such fungi. Rootstock and scion cuttings were soaked in fungicidal suspensions for 50 min prior to grafting. After callusing, the grafted cuttings were planted in two commercial field nurseries with and without a previous history of grapevine cultivation. After nine months in the nursery, the plants were uprooted and analysed for the incidence and severity of the wood fungi. Plants uprooted from the field without a previous history of grapevine cultivation were generally less strongly infected by wood fungi. Under this condition, only the mixture cyprodinil + fludioxonil simultaneously reduced the incidence of Cylindrocarpon and Botryosphaeriaceae fungi, as well as the severity of Cylindrocarpon infections. Treatments did not produce significant differences in the incidence and severity of P. viticola, and Pa. chlamydospora. For plants grown in the field with a grapevine history, all fungicides except cyprodinil significantly reduced the incidence and severity of Cylindrocarpon fungi. Also, the incidence and severity of Botryosphaeriaceae pathogens were significantly decreased both by cyprodinil + fludioxonil and by cyprodinil. No significant differences were noticed for P. viticola incidence and severity, and Pa. chlamydospora was not, detected again. These results suggest that the practice of soaking grapevine cuttings in selected fungicides prior to grafting significantly reduces Cylindrocarpon spp. and Botryosphaeriaceae infections, thus improving the quality of planting material.