Tuesday, November 23, 2010

Pest and Disease - UPDATE 23/11/10

Flowering is underway in all varieties in McLaren Vale. Adelaide Hills vineyards are about 2-3 weeks away.

Conditions have been ideal for a successful flowering and berry set. Capfall has occurred rapidly in all varieties in all locations. Later blocks and varieties will complete flowering over the coming days. Shiraz Blocks should finish flowering next week. Chardonnay will begin setting berries next week.

The season is about 3 weeks later than last year and about a week later than the 2004, 2005 and 2006 vintages, which we not significantly affected by droughts, or heat waves.

Powdery Mildew


Powdery Mildew is a creeping disease. It ‘hides’ deep in the canopy. Under humid overcast conditions Powdery multiples more quickly. Powdery doesn’t need rain to spread, but it does do well in the humid conditions before and after rain showers.

Many hours during recent days and nights have had temperatures between 20 and 28oC - this means that the temperature for Powdery has been ideal favouring maximum production of spores.

We have seen some very significant Powdery Mildew in poorly covered vineyards (below).

Powdery Mildew in the upper surface of a vine leaf.

We believe Powdery Mildew pressure is very high this season – and growers should take care to keep up a good coverage over flowering.


The good news is good coverage = good disease control. Good effective sprays now before the canopy gets too big to spray are worthwhile.

Downy Mildew


Downy Mildew is a wet disease and needs rain to start its lifecycle. Some Downy Mildew has been seen in any Adelaide Hills vineyards. This confirms that regions CropWatch’s recommendations that a Downy Mildew infection occurred when 10:10:24 Primary Event conditions were recorded at the end of October.

Berries that are bigger than peasize (EL 31) are resistant though the bunch stalks and the leaves remain susceptible.

Growers in the Adelaide Hills must protect their vineyards as close as possible to any Downy Mildew secondary events (warm, wet nights).  


These warm, wet nights spread Downy Mildew onto unprotected leaves and bunches.

Vineyards in Currency Creek have a low level of Downy Mildew and should take a similar approach to growers in the Adelaide Hills.

McLaren Vale only have one confirmed vineyard with Downy Mildew at McLaren Flat. Caution is needed in the district, and if more rain events occur keeping up protection with registered Downy Mildew products is a low risk strategy.

Light Brown Apple Moth


Light Brown Apple Moth residue in a flowering vine inflorescence.
Check your flowers for signs of caterpillar damage. Apple moth damage is usually found in ‘hotspots’. If you find one damaged flower like this (above) check other bunches and in nearby leaves for more apple moth activity.

We have seen a big increase in the number of newly hatched Apple Moth in all subregions of McLaren Vale. We are also beginning to see Apple Moth in the Adelaide Hills.

Vine Moth caterpillar.
Vine Moth have also hatched in vineyards over the last 14 days. These hatchings are also found in hotspots or clusters (left).

Botrytis


Botryis Bunch Rot needs rain or moisture to spread. Any Botrytis present in your vineyard now is ‘dormant’ inside your berries or present in small amounts on any flower caps or dead plant material trapped inside bunches as they close. No rain before harvest = no botrytis.

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