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 & Fleurieu Visitors Centre vineyard has moved to Berries Peasize (E-L 31) and have early Bunch Closure (E-L 32), pictured.
There has been an increase in the amount of Powdery Mildew. Most symptoms have been seen as single leaf infections. Pictured.
Ensure you are getting good coverage between now at the end of December. Make sure what you are applying is penetrating into the canopy as shaded leaves are where the disease will establish and multiply.
Check 100 bunches and the leaves around them for signs of grey growth as pictured. Bunch infections will need good spray coverage to hold at low levels.
The AWRI Online Chemical Search lists these products for use up to E-L 31 Berries Peasize: Powdery Mildew Products available to E-L 31 as of 8/12/2017
Current symptoms appear as Oilspots. Look for these. Levels are currently low, but will increase after the Downy Mildew Primary Event we experienced last week.
Check wild vines near your property for both Downy Mildew and Powdery Mildew. Wild vines are acting as hosts for disease and spreading it into commercial vineyards. Pictured.
A low risk approach it is recommended to keep up Downy Mildew protection during December and January, using a Downy Mildew pre-infection fungicide. Include these with your scheduled fungicide sprays.
The AWRI Online Chemical Search lists these products for use up to E-L 31 Berries Peasize: Downy Mildew Products as of 8/12/2017
Wet weather favours Botrytis.
We have been fortunate to only have had limited falls compared to other wine growing regions.
Bunch closure is occurring in many varieties. If trash is trapped in your bunches in increases the risk of bunch rot at harvest. Any steps that you can undertake to reduce the size of your bunches, the tightness or the trash trapped inside help.
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:
Check for Grapevine Scale as a new generation of scale has been seen. Pictured.
Vine Weevil, and the closely related Curculio Weevil, are active near Aldinga and Maslins Beach. They chew leaves and bunch racchi during the night. Damage is usually patchy and limited to a few vines. Take extra care in checking young vines, or grafted vines. Damage is pictured.
There are some localised patches of severe insect damage, caused by a combination of Common Garden Snails, Earwigs and Weevils (Pictured) on the Ngaltinga Geology (check the McLaren Vale Geology Map). Pictures taken on Plains Rd, Aldinga and Flour Mill Rd, Whites Valley.
Please see images included below.
While monitoring vineyards this week the ‘sickly’ shoot symptoms of Eutypa dieback, aka dead arm, are still obvious, pictured below. As the canopy begins to grow over 100cm shoots, they will droop down and cover over any stunted Eutypa shoots.
Survey your vines now. Establish a percentage of your cordon that is affected. Make your future decisions based on the amount that you are find now.
Both Light Brown Apple Moth (LBAM) caterpillars are present at all the CropWatch weather station sites. Levels were less than one caterpillar per vine on average. In all cases predatory insects were also present.
A tip for finding LBAM caterpillars is to look for trash in the bunch as pictured in the Botrytis photo.
The most common predatory insects seen during spring and early summer are Ladybugs, Green Lacewings (as eggs), spiders, shield bugs and airborne wasps. Check for these now.
Note that using high rates of wettable sulphur may interfere with predatory insect populations, particularly their ability to breed and multiply. High rates of sulphur in the McLaren Vale region we would class as applying would be applying concentrated rates above 3-4 kg/ha total (300 to 400g/100Lt applied at 1000Lt Dilute Spray Volume).
We are looking at establishing trial work into the relationship between our use of sulphur and predatory insects.