2009 Grapevine utilisation survey.

McLarenV09

Powdery Mildew Late Season

Look out for these signs deep in the canopy. Powdery Mildew in bunches (above).

Some Powdery Mildew is beginning to show in vineyards not sprayed effectively earlier this season.

Powdery Mildew is called a dry weather disease because it does not need rain to spread. In fact, large rainfalls can wash the disease from leaves and berries. Organic growers use this principle by using mild anti-fungal agents applied with high water rates.

Powdery does however like warm (21-28OC), humid (RH<70%) conditions like those from weather that comes from the tropical north.

Monitor now for the disease. Pay close attention to areas like low-hanging shoots or freshly growing laterals. Take time to check inside your canopy to assess your program.

Any sprays now may help reduce the amount of disease on outer leaves but at this late stage, they will not help in reducing levels of powdery on the bunches.

Avoid spraying sulphur at high temperatures (>350C) when the humidity is >70% within 24 hours of spraying.

Before spraying crops designated for sparkling wine, check your winery’s withholding periods. White varieties for table wine are likely to begin harvest in mid February.

Early Verasion

Early colour change in McLaren Vale Shiraz has been seen. Vineyards that normally begin to change colour (begin veraison) around the 2nd - 5th of January have started colour change on the 25th of December.

Chardonnay and Verdelho are also softening and beginning to produce sugar.

Based on this he season is likely to be an early harvest this vintage.

Following fruit set, the grape berries are green and hard to the touch. They have very little sugar and are high in organic acids. They begin to grow to about half their final size when they enter the stage of veraison. This stage signals the beginning of the ripening process and normally takes places around 40-50 days after fruit set.

During this stage the colours of the grape take from - red/black or yellow/green depending on the grape varieties. This color changing is due to the chlorophyll in the berry skin being replaced by anthocyanins (red wine grapes) and carotenoids (white wine grapes). In a process known as engustment, the berries start to soften as they build up sugars.

Within six days of the start of veraison, grape berries begin to grow dramatically as they accumulate glucose and fructose and acids begin to fall.

Blister Mite

Blister mite (above) is one of the most obvious pest problems seen in the vineyard. Luckily it causes no real economic damage. Leaves covered with blister mite still produce energy to ripen your fruit.

Downy Mildew Oilspots - Secondary Spread in the Adelaide Hills

There is some Downy Mildew in the Adams Rd, Schuller Rd area of Blewitt Springs in the McLaren Vale GI. Some higher levels have been found in the Adelaide Hills, including vineyards on Range Rd and in Kuitpo.

Where growers have taken action Downy Mildew levels have largely remained steady with little secondary spread. Generally the warnings have been heard and acted upon in an adequate period.

The main disease issues have been seen in vineyards that have not been adequately protected, or have been mothballed. Abandoned Vineyards are looking like becoming a real headache for neighbours over the coming month!

Unfortunately in vineyards that are on minimum spray programmes or have not been protected against Downy Mildew, disease levels are increasing.

Berries Peasize EL31.

LBAM insecticides Avatar®, Entrust®, Proclaim® & Success® all have a with-holding period of peasize (EL 31). In most vineyards berries have grown past Peasize 7mm (EL 31). For Chardonnay, Shiraz, Merlot and Sangiovese in the warmer parts of McLaren Vale, only the biological insecticide BT’s can be used now.

Vineyards in the Adelaide Hills are 2 weeks away from the Berries Peasize cut off.

Above: A good guy- predatory shield bugs feed on caterpillars. Click here for more beneficial insect pictures. Beneficial insects can be your most effective tool in controlling LBAM in the lead up to harvest. A ‘hungry’ predator population will eat apple moth and keep them from eating berries.

Powdery Mildew - last chance for good control.

Powdery mildew has been spreading this week. Flag-shoots have been found. Cleistothecia infections have developed further with heavy, shaded, humid canopies aiding the development and spread of the disease.

Weeds have also enjoyed the weather recently, with levels increasing rapidly Wireweed and Fathen have been the main types seen.

Downy Mildew Secondary Photos

Matthew Wilson has found Downy Mildew has spread in the Adelaide Hills.

He says, "The Secondary Downy Mildew Event recorded on the morning of the 8th of December 2009, has caused spread of primary Oilspots within unprotected, infected blocks.

Interestingly, the majority of this secondary spread is located below the cordon or on fresh growth either up high on VSP systems or out on tips with sprawled canopies. This new growth is difficult to protect, but growers should be reminded to adjust
spray coverage as the canopies develop. This season’s growth rates (relative to previous seasons), require some level of adjustment."

Matthew will be keeping a close eye on the weather in the Adelaide Hills as part of the CropWatch Programme.

Downy Mildew Secondary Event in the Adelaide Hills.

Above: Downy Mildew Oilspots as found in Woodside, yesterday the 7th of December.

CropWatch Adelaide Hills reports a Downy Mildew Secondary Event (warm, wet night) on the 8th of December. Balhannah received 8mm of rain last night in the four hours before dawn. This will cause Downy Mildew to spore and spread in unprotected vineyards.

What does this mean for Adelaide Hills vineyards?

Your fruit is immune to Downy infection once berries are appx. 2-5mm in size but leaves (and berry stems) remain at risk until harvest.

There is a low risk of Adelaide Hills grape growers losing bunches to Downy Mildew. CropWatch is more concerned about of further warm wet nights through December and January causing a build up of Downy Mildew Oilspots on vine leaves causing defoliation.

Berry splitting from rain and sunburn

Above - Developing berries that have been split by heavy rain last week.

Above - Sunburn / sulphur burnt fruit.

Light Brown Apple Moth

This season has seen high levels of Light Brown Apple Moth caterpillars. Look for any flower parts that are stuck together - above.

How many Apple moth grubs are a problem? Apple Moth caterpillars, cause damage to bunches which makes them much more susceptible to botrytis infection and spread. Also in high numbers, apple moth reduce the yield of your block – which for high value fruit may become an issue.

Glyphosate Herbicide Drift

Physical drift is a risk with Glyposate based herbicides as this photo shows -above. This vineyard was sprayed 6 weeks ago and unfortunately a small amount of drift has affected some shoots.

Latest Powdery Mildew Pictures

Above - Powdery Mildew has been seen on bunches for the first time this week. Defuse Powdery mildew is almost impossible to see it looks like a faint web pattern on berry skin. It is caused by an infection just before the berries become naturally immune approximately 4 weeks after the end of flowering.

We have also been finding leaf spots of fine white growth like the one shown below.