CropWatch is an ad-hoc viticultural advisory publication distributed to financial grower members of McLaren Vale Grape Wine & Tourism Association.
The data - including weather station information, Bureau of Meteorology forecasts and vineyard observations - is collected and reported by one of the region's agronomists.
CropWatch endeavors to provide our region's growers with technical information on key viticultural issues such as pest and disease identification, risk and management.
The McLaren Vale Visitors Centre Shiraz block is now at Berries Ripening EL-36, pictured below (1).
Early variety harvesting is now in full swing, with early Shiraz being harvested this week, also. Our grapevine development (ripening) is running close to long term average. Recent hot weather has meant rapid development and sugar accumulation. Milder conditions this week have been perfect in allowing ripening to progress at a more steady rate.
Forecasts for the coming week are for maximums in the high 20’s to low 30’s. Night time temperatures (important for maturation) are likely to increase into the low 20’s toward the middle of next week.
Berry condition is mostly ideal. Early berry shrivel is increasing in the district this week on red varieties. Bunch stem necrosis is observable also this week as vines stressed during the recent heat terminate bunches, pictured below (2).
Current weather patterns, rate of ripening and canopy conditions are not conducive to the spread of powdery mildew. Observations around the district are showing low levels of dead or semi active powdery. The photo below shows dead powdery mildew scars on canes. This will have no impact on winemaking.
The level of Downy Mildew continues to reduce in the Kangarilla area it is now unlikely to affect harvest in any way.
Current conditions are predominantly unfavourable for the development of botrytis in bunches. No botrytis infections have been observed in monitored vineyards this week. Fruit will only be susceptible at this point to infection, if weather conditions dramatically change.
You are likely to have seen communications from the AWRI and Vine Health Australia during the last week regarding testing for Grapevine Pinot Gris (GVPG) virus.
This virus is misleadingly named as it can occur on a wide range of host grapevine cultivars.
It is not currently known in the McLaren Vale Wine Region, however testing has only just begun and no results have been published.
If you are seeing a vineyard symptoms that you have previously assumed were mite damage, testing these to eliminate the possibility of GVPG virus.
Testing for GPGV
There are two laboratories for testing:
Sunburn and heat stress signs are common.
Irrigation advice is remains to keep up soil moisture as best as is practical.
Replacing soil moisture allows the vine to rehydrate after heat stress. While we have been having cooler weather this week, at all sites, monitor for water stress and balance your vines water requirements.
If vines stress too much they can "panic ripen", in lay terms, and sugar levels can spike before grapes are fully flavoured.
As vine canopies have grown over and rolled, they have drooped down and covered over any stunted Eutypa shoots. Assessing your level of Eytupa (aka. Dead Arm, Dieback) during summer is difficult.
Make your future decisions based on the amount of Eutypa you saw during Spring 2017: Pictured.
Summer weeds including Caltrop, Three Corner Jack and Innocent Weed are now actively growing – pictured below. They will be setting seed through the harvest period. This is a reminder of the importance of controlling the entry of machinery onto your property.
Before you enter vineyard property you should ensure;
When moving around your vineyard;
Keep your vineyard on headland tracks and, if possible, limit the areas that you drive over and where you park. The more area you drive over the greater the risks of spreading weed seeds and other soil borne problems like disease.
Check for Grapevine Scale, pictured below. Look for a summer generation of scale. Grapevine and other closely related scale can trigger sooty mould infections because they secrete honeydew.
We have found honeydew on leaves and bunches, pictured below.
We have also seen a small amount of Sooty Mould triggered by the honeydew, pictured below.
Continue to look for these symptoms as vines ripen. If you are finding a significant level, seek specific advice.