In vitro evaluation of fungicides for the management of Botryosphaeria canker

The ascomycete genus Botryosphaeria comprises numerous species that occur on a wide range of hosts, including both mono- and dicotyledons, and gymnosperms, but is most commonly associated with cankers, dieback and decline in mature grapevines. In the latter, infection of pruning wounds results in a characteristic wedge shaped discoloration in the trunks and canes of declining vines, resulting in a distinctive 'dead-arm' appearance, now commonly referred to as 'Bot canker'. To date, there are no effective chemical recommendations available for the management of this disease in Australian vineyards. In this study, fifteen fungicides registered for use on grapevines were tested in vitro for their effect on radial growth of four species of Botryosphaeria, previously isolated from declining grapevines in the Hunter Valley and Mudgee regions of northern New South Wales. Fludioxonil, fluazinam and flusilazole were the most effective fungicides with EC50 values < 0.1 mg/L. Tebuconazole, penconazole and iprodione were intermediately effective, while the anilino-pyrimidine, morpholine and phenoxy-quinoline fungicides were largely ineffective. Selected products showing potential for disease control will be further tested under field conditions for protection of pruning wounds.