Wednesday, February 19, 2014

Botrytis - UPDATE 19/2/2014

Early Botrytis begins in tight bunches.As bunches become tighter, sugar levels increase and the risk of berries detaching from the bunch stems increases which can lead to the release of juice within the bunch.
Heavy rain, 40 mm from Midnight Wednesday the 12th of February, has radically changed the local climate. Our region received 50-60 mm by Saturday morning (15th) when the rain cleared.
Botrytis is sensitive to rainfall and humidity. Checking vineyards this week the first signs of Botrytis were seen triggered by Light Brown Apple Moth damage in tight bunches of Sangiovese. This is expected to increase and berry splitting in other thin skinned vines is likely.

DOWNLOAD BERRY SPLITTING PICTURE (1.4MB) & VIDEO (65MB) – 14/2/2014. 


Check your vineyards now for bunch disease. General levels are low but significant mould has been seen where vines have big canopies and bunches have stayed wet for several days. Berry splitting is common in Grenache and Shiraz especially in the small immature fruit.
Grape growers do have the option of using late season fungicides and bio-control products and/or products that dry out berry damage.

Late Season Fungicides.

PMS - (Potassium metabisulphite) dries out the bunch and can help heal berry splitting. PMS rates higher than 3kg per 1000 litres are needed and the pH of the spray solution should be adjusted to between 2.9 and 3.0 using 1.5 kg 100% tartaric acid per 1000L.

Dicarboximides - Rovral, Chief, Corvette etc should be applied as an acidic spray tank mix (water pH less than 7) to be stable. 1kg/1000lts of tartaric acid, citric acid or similar, or a commercial buffer- tradenames include AGRI-BUFFER will acidify the water and lower pH.

Ecoprotector - 14 day withholding period.

Check with winery requirements before spraying, particularly in vineyards that are within 14 days of harvest.

2 comments:

jenni said...

Dear James,

Will the rain have put ripening back significantly? We have a small Chard vineyard in the Hills and our Baume is about 10-10.5 currently, we normally pick at about 12.5. Is there any rule of thumb for ripening if the weather stays stable? I was trying to pencil in a picking date.

Thanks

Jenni

James Hook said...

Hi Jenni,

The rain has put back baume (sugar) level by causing dilution by 1-2o.I would think 1-0.75 baume a week will be a suitable rule of thumb. I think you would be ready to pick in 2-3 weeks. Watch for dews though as we have been having cold nights.

Regards,

James