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Notes for next season

deformed leaf
Blisters on a grape leaf caused by a blister mite. Photo source: DAFWA.

By Dave Antrobus, Solutions Development Lead

Harvest can be an anxious and busy period, so before you really get into the thick of things, taking time to capture some important information now can really help you prepare for next season.

Mapping blocks leading into harvest, block-by-block, for yield and quality is important, as is tracking disease and pest levels. Focus your time now on mites, mildews and Eutypa dieback as these all require very early attention.

If you find mites, first you need to identify which species you have, because not all mites are pests.  The broader management principles for the control of troublesome mites like rust, bud and blister mite are similar, however recommended control strategies differ for each. With beneficial species, the most efficient natural predators of mite pests are Euseius victoriensis and Typhlodromus doreenae. These predatory mites are particularly important in several Australian viticultural regions for maintaining low pest mite populations. Predatory mites are susceptible to several insecticides and fungicides, so if you identify predatory mites plan to use products that are predator mite-friendly to ensure high numbers survive in your vineyard.

If you have the unwanted species, early mite management is vital. The best time to control bud mites is just after budburst when mites are exposed on bud scales and leaf axils. If you are looking to control blister mite, initiate measures at the woolly bud stage. Rust mite is most effectively treated by spraying high volumes of wettable sulphur and oil to runoff at the time of chardonnay woolly bud stage and when temperatures reach at least 15°C. For control of all mite pests, use a registered crop protection product according to label instructions.

Identify high-pressure powdery mildew sites now, as they can be a major source of primary infections at the start of next season. There are number of things you can do to help the vine recover, such as opening the canopy to sun and air circulation to improve ventilation and reduce mildew and rot pressure. This also enables spray applications to penetrate the canopy effectively and contact the fruit, instead of dripping off the first few leaf layers. It will also help with the management of other diseases and pests. The trick is finding how open your canopy can be and how much sun the clusters can take without burning or raisining.

Eutypa dieback is the other disease I suggest you look to identify around this time. This airborne disease fungus is spread via spores released from infected dead wood during rainfall events, infecting exposed pruning wounds. Eutypa dieback progressively kills spurs, cordons and trunks. Wounds are most susceptible to infection in the first two weeks after pruning. Disease control requires preventative wound treatments and curative remedial surgery. The best preventive method is wound protection and then control the disease with remedial surgery. Decide which limbs to prune, prune hard and manage with fungicide treatment.