Wednesday, March 30, 2011

Botrytis & berry breakdown - UPDATE 30/3/2011

Some vineyards are starting to have berry skin breakdown and shrivel. This seems to be due to wet conditions that the vines have experienced. For these vineyards the end of the season has come and we expect them to only further worsen and have more skin breakdown.

Above - Berry skin breakdown with some botrytis.

One of the challenges this berry breakdown causes is the effect of managing the fungus Botrytis cinerea. When the Botrytis fungus infects red grapes it produces the laccase enzyme.

Why is Laccase a problem?

It is a problem when the grapes are made into red wine. The Laccase enzyme degrades the lignin and oxidizes the red pigments. In wine, this enzyme causes a reaction that turns the wine brown and detrimentally affects it smell and taste. Browning of the red pigments is caused by an oxidation reaction, which laccase ‘catalyses’ or speeds up.

Laccase is a difficult problem for wine makers to manage as the enzyme can survive the fermentation process, has low sensitivity to sulphur dioxide (this is added to many wines as a preservative) and thrives in the natural pH of wine. This means the laccase enzyme will be present in the wine end product. Consumers would not like this as the flavour and colour is not what they expect, like or paid for (no one wants a brown wine!). And because oxygen is required for the laccase reaction, the consumer doesn’t know the wine is bad until the bottle is opened.

The laccase enzyme targets ‘phenolics’. Phenolics are the coloured compounds or pigments in grapes. These are found in the skins (the most common pigments are anthocyanins). When laccase and the phenolics come into contact, an oxidiation reaction occurs.

Red wine turns brown!

Wednesday, March 23, 2011

Do you sell to a winery that only sells wine domestically?

Note that AWRI witholding periods are for exported wine. In emergency situations you should consult your winery and see if you can use products inside there export withholding periods.

McLaren Vale - Botrytis increasing but some hope of a good harvest if fruit handled with care - UPDATE 23/3/2011

We have spent the last two days in and out of vineyards in McLaren Vale. We are worried, but consider ourselves quite fortunate. Considering what is being reported from vineyards in Langhorne Creek, Currency Creek, Adelaide Hills we are grateful in McLaren Vale for our luck with the weather.

Where Chardonnay, Sauv Blanc etc have already been harvested, they have come off in good condition. What white varieties that remain unpicked are now developing high levels of botrytis bunch rot and are unlikely to be suitable for making table wine if they are not picked immediately.

Cabernet Sauvignon is still in good condition and could hold together the 7-14 days needed to develop full ripeness.

Viognier, Sangiovese, Tempranillo, Grenache have varying amounts of bunch rot. Some sites are in quite good condition at the moment, especially where canopies are open and/or good flowering and prebunch botrytis treatments were applied, other sites have 10-20% infections and are likely to be downgraded or not suitable for winemaking.

McLaren Vale's A & B grade Shiraz will be mostly harvested by middle of next week and is still in good condition with less than 1% bunch bot. A & B grade fruit would account for around 20-30% of the district.
The better C grade Shiraz vineayrds are also holding with only 1-5 single berries of bunch infection per panel, ie less than 1%. These vineyards are sitting around 12.5 – 13.5 baume and many will be harvested by the end of next week.

All up this would see around 70-80% of the Shiraz crop harvested in good condition.

Areas of heavier canopy and where canopy manipulation, irrigation management has been poor we do have some Shiraz crops in trouble, with continued rain today, we may lose 5-10% of the Shiraz crop.

We are hopeful that a good harvest can still occur if the weather clears. The majority of the botrytis we are seeing has come from single berries with latent infection.

If we get dry weather we would expect these berries/bunches to shrivel and fall off.

We are on the edge at present - and hope for dry conditions.

Derek Cameron & James Hook

Proprietors/Senior Horticultural Consultants

Monday, March 21, 2011

Botrytis & berry breakdown - UPDATE 21/3/2011

Heavy rain on the evening of Sunday the 20th of March has been ideal for Botrytis Bunch rot. Very high humidity in vineyards has seen an increase in Botrytis - with fresh sporulation seen. In some cases Botrytis has appeared in vineyards that were clean at the end of last week.

Above and Below - Heavy bunched Shiraz and Chardonnay has suffered from a large increase in the about of Botrytis in the last 24 hours.

In many situations vineyards will need to be picked as soon as possible, or the fruit will not be sound for harvest. If fruit is close to harvest ripeness then it should get 'over the line', the main concern is for vigourous Shiraz vineyards and Grenache in McLaren Vale, The Barossa and Langhorne Creek, plus any white grapes that haven't been harvested yet.

Thursday, March 17, 2011

Downy Mildew - UPDATE 17/3/2011

Very serious infections of Downy Mildew are now obvious in vineyards that were not adequately protected this growing season. This is showing up as severe leaf burning (below).

Grapevine leaves with a high level of oilspots.
The main concern is that these heavily infected vineyards are defoliating, by infected leaves falling off and may not be able to ripen their crops.

Vine defoliation.
CropWatch 1011_vol8_31

Wednesday, March 16, 2011

WineGrape Council SA- ‘Wine grape growers facing another decade of oversupply?’

Media release from the WineGrape Council SA.

What do you think? Will grape businesses break under the strain of the high Australian dollar.MediaRelease_WGCSA_16March11

Wednesday, March 9, 2011

Botrytis & berry breakdown - UPDATE 9/3/2011

Above - Berry skin breakdown in Shiraz after 24 hours of wet conditions.
Below - Botrytis has increased in both Red and White varieties after widespread wet conditions. In many cases grapes will be harvest ripe within the next 7-10 days and using late season sprays is not practical.

Tuesday, March 8, 2011

Downy Mildew - UPDATE 8/3/2011

Above - Severe oilspot infection on this abandoned vineyard near Willunga has caused leaves to fall out of the canopy.

Below - The vineyard neighboring the abandoned vineyard shown above has struggled to keep their leaves clean. While they have done a good job of keeping up a protective cover before rain events oilspots can clearly be seen.

Monday, March 7, 2011

Botrytis in Chardonnay - UPDATE 7/3/2011

Berry skins in Chardonnay are breaking down. The level of Botrytis has increased in the last 7 days and most vineyards have some signs of bunch infection. Single berry infections of Botrytis that were seen last week have spread to now take up 5-10% of berries in bunches.