Make sure vines have plenty of moisture down in the root-zone before this weekend’s blast of hot weather. Limited water availability during the critical spring growing period can severely impact on the vines’ ability to grow canopies to protect and ripen fruit. The hot and dry conditions, coupled with the relatively early season growth present a unique opportunity to really gain some effective powdery control for this year and also next. Powdery is hampered by hot and dry conditions, and effective control options at this time will create a ‘double whammy effect and really hit the disease hard. BUT, be mindful of the risk of the potential for ‘burn’ with Sulphur applications prior to the hot weather.
Continue with protective spray programs, paying particular attention to Powdery Mildew. Thorough coverage and correct timing early in the season is critical in preventing disease outbreaks later.
Newly emerging buds are most susceptible to infection up to 24 days, after which the physiological changes to the outer bud scales, appear to prevent entry of the pathogen. To avoid infected flag shoots for the following season, effective control of Powdery before the bud scales ‘close’ is critical.
When vines are spur pruned, the buds left after pruning were the very first to emerge in the previous growing season, and hence the first to reach the 24 day mark. This is why early season disease control is so important … it helps for both this year, and also for next!
Fungicide treatments to prevent bud infection should be applied at regular intervals to prevent infection of the surface of young buds on shoots as they develop. The interval between treatments will depend on shoot growth rate, which in turn, is related to temperature and other factors such as vine water availability and nutrition.