CropWatch Update

Recent rainfalls were quite variable across the Riverland with areas around Kingston on Murray registering falls of more than 40mm. Renmark registered approximately 4mm, Waikerie received around 7mm and Barmera, Pyap, Loxton had falls of 20mm or more. 

Downy Mildew
The weather station at Loxton recorded conditions suitable for primary infection following the recent rains.  Adequate duration of rain fell at optimum temperatures.  There was a lesser risk at New Residence and a slight risk at Yamba.
Little risk is associated with an infection at this time of the year. At least two follow up secondary infections would be required to have an impact on canopy health.

Secondary infections require oilspots to be present and at least 4 hours of darkness at high relative humidity (≥ 98%) with temperatures above 13°C. If these conditions, occur leaves then need to be wet in the morning.  If these conditions prevail, continue to monitor your vines looking for oilspots that would appear, if at all, next 5-7 days from today.  If considering a spray, communicate with your winery about their withholding periods which effectively rule out any chemical control at this time of year.

Berri Split and Bunch Rots

CropWatch Monitors have received enquiries about split berries. Shiraz, in particular, appears to have been affected.
The best remedy for berry split is good canopy structure and dry weather. The winds that followed the rains and the forecast warm dry weather is good.
In varieties such as Colombard that are renowned for carrying larger crops and subsequently fruit clumping, moisture may present more of a problem. Monitor your vineyards for secondary bunch rots. If a problem exists, chemical control options such as iprodione (Rovral Liquid®) or hydrogen peroxide + peroxyacetic acid (Peractec®) could be considered (WHP 7days).

If an application of Rovral Liquid etc. is considered remember a buffering agent may need to be added to the tank mix if the solution prior to addition, is greater than pH 7. Always read labels before chemical use.

Potassium Metabisulphite is a preservative that is regularly used in the winemaking process. It has often been used on vines were split berries exist. There is much conjecture about the impacts of such a remedy and some wineries may forbid its use for preventing the establishment of bunch rots. The thought is that PMS assists with drying the wound. If you wish to consider using this, please consult your winery for details.

Should spraying be required, high volumes and slow ground speeds will be required to adequately cover and wash through the clusters.

Given the current weather conditions, CropWatch would consider the risk of bunch rot infection low but good monitoring of your vineyard will provide the best ‘peace of mind’.