Management of bunch rot diseases of grapes in sub-tropical vineyards in Australia
Ripe rot (Colletotrichum spp.) and bitter rot (Greeneria uvicola) are two non-Botrytis bunch rot diseases that are frequently encountered in grape growing regions prone to high summer rainfall during the berry ripening period. Surveys of vineyards in the Hastings and Hunter Valleys of NSW, Australia revealed that these two fungi are responsible for the majority of bunch rot diseases of grapes in these two regions. Management practices for ripe rot and bitter rot remain limited. In previous work, isolates of C. acutatum and G. uvicola were screened for sensitivity to a range of fungicides by assessing their growth on fungicide amended media. Based on the results of this initial screening the field efficacy of fungicides was tested at a number of vineyards in the Hastings and Hunter Valleys. Shirlan (a.i. fluazinam), applied as a dormant spray, reduced the severity of bitter rot at harvest in a trial conducted in the Hunter Valley but not in the Hastings Valley, a region prone to higher disease pressures. Strobilurin fungicide sprays applied at flowering and post-veraison close to harvest led to decreases in bitter rot and ripe rot occurrence. However there are restrictions on fungicide application for wine grapes in Australia if the wine is destined for the export market and this limits the use of fungicides in commercial production. Alternative approaches to bunch rot management include canopy management practices that limited extreme temperatures associated with sunburn damage that may predispose fruit to ripe rot susceptibility. This contrasts with current standard management practices for Botrytis cinerea (grey mould) control where canopies are opened up to increase fruit exposure. Avoidance of planting late maturing varieties which ripen during periods of late summer rains is also a recommended management practice for ripe rot and bitter rot control.
Steel, C.C., Savocchia, S. and Greer, L.A. (2016). Management of bunch rot diseases of grapes in sub-tropical vineyards in Australia. Acta Hortic. 1115, 265-272
bitter rot, ripe rot, Greeneria uvicola, Colletotrichum acutatum, strobilurin, fluazinam, canopy management