Focusing on pruning

When pruning vines, parameters such as bud number, cane quality and sacrifice canes are all important. One major concern, however, is grapevine trunk disease (GTDs). Research shows wound protection can protect against GTDs like dead-arm Eutypa or Botryosphaeria.

Any wound is a portal for infection, but protecting them all is not practical. Experience suggests larger wounds (more than 15 mm diameter) on the main trunk are most at risk, so avoid making them and if unavoidable, protect them.

Options

υ Prune late – as temperature rises, vines callus more quickly and rising sap displaces spores on the cuts by simple physical action.

υ Prune in dry conditions – practiced as much as possible as damp or wet conditions favours spore release and dispersal.

υ Apply a physical barrier – preventing spores from entering. A multi-year study by the PPO BV in the Netherlands showed spraying pruning wounds with a wound-protecting agent reduces infections. Application must be carried out immediately, by brush, coarse spray or Felco secateurs adaptation. BlocCade™ forms a sealed physical barrier over the wound, fighting against infections and aiding wound healing by creating a closed barrier over the cut. But infections have been known to become trapped between sealant and vine cut.

υ Apply a garlic barrier. Physical barrier treatments containing garlic are in use in Australia (mostly by organic growers). Garlic is rich in organosulphur compounds (thiols) which help the plant combat infection. Hutchinsons and Solufeed formulated and trialled a garlic product (Garlic Wonder wound paint) in 2017 with promising results.

υ Disposing of prunings – many growers go to the trouble of removing or burning. Burning prunings can provide a natural heat source in the winter if a mobile burning bin (photo) is used. This will lower inoculum levels but some spores will remain on the trunk and canes. Pulverising is easier and if the wood is pulverised small enough and the soil is healthy, it will quickly be broken down and unlikely to add much to the infection bridge to next season.

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