Never Mind the Weather!

I now feel like a proper farmer as I'm always complaining about the weather!

This year it has been pretty awful for growing grapes. The wind and rain at the end of June/early July resulted in poor fruit set, and we have had little sun since then to ripen the grapes. In July we had 12% less sunshine compared to the average of 1971-2000 and in August 20% less. Temperatures were also much lower and the average rainfall from June to the end of August has been more than 10% higher.

Comparison with 1971-2000 (Av)	June	July	August
Sunshine	11%	-12%	-20%
Temperature (C)	0.2	-1	-0.5
Rainfall	119%	106%	107%

Hopefully we will get some sun to ripen the grapes during the few weeks before we have to harvest. We monitor the grapes daily for disease, the main potential problems being powdery mildew and botrytis. Whilst some botrytis can be tolerated for still wine it is a big problem for bubbly.

If we can't get the pinot ripe enough it will be difficult to make a good still rose. This would set our marketing activities back a year as I'm adamant that the first wine we release will be something we are proud of. C'est la vie!

Canopy Management

Richard Smart at Denbies

Dr Richard Smart is an Australian viticulturist and a leading expert in canopy management. He is often referred to as "the flying vine doctor". See www.smartvit.com.au

Recently Richard visited our vineyard and also gave a Masterclass seminar at Denbies Wine Estate in Dorking. The subject of his talk was "Practical Applications of Canopy Management" and covered optimum vigor, vine balance, summer pruning, shoot positioning, shoot and cluster thinning, leaf removal and vine training.

The produce the best fruit the ideal canopy should have the following characteristics:

• Balanced growth
• Intercepts as much sunlight as possible
• Shoots that are spaced about 2.5 inches apart and 15 nodes long
• 40% canopy gaps and 60% fruit exposure

To achieve this involves a lot of work during the growing season, much of which has to be done manually!

Powdery Mildew Lifecycle

Powdery Mildew on Pinot Noir

Unfortunately we now have Powdery Mildew on the some of the Pinot Noir and a few of the Chardonnay grapes. It's quite isolated at the moment and interestingly is mainly in the rows where the FrostGuard machine was sited which prevented proper spraying earlier in the year.

Powdery Mildew is caused by the fungus Erisiphe necator. It only infects green parts of the vine and the grapes but survives over the winter in dormant buds and in the bark crevices or leaf debris on the ground.

Powdery Mildew Lifecycle

Alex is spraying the whole of Block A this morning with sulphur and potassium bicarbonate which is the standard organic treatment. It is not curative but will hopefully prevent it from spreading.

Bunch Thinning

The 3rd bunch gets the chop!

Vines will often produce more fruit than the trunk and root system can support, which can stress the vine and also result in the bunches not ripening properly. This isn't a big problem for us this year, as many of the berries didn't pollinate properly which has resulted in small and incomplete bunches (see earlier post - Coulour and Millerandage).

Non the less Alex has convinced me that we should cut off any 3rd and 4th bunches on any one cane, so that the grapes have the best possible chance of ripening in this dreadful weather. Whilst good quality sparkling wine can be made from fairly acidic grapes, we need fruit with a reasonably high sugar content to make a good quality still rosé.

All in all it's been a pretty dreadful year so far weather wise. We are still hopeful of releasing our first rosé wine next year but will only do so if the quality is good enough. Hopefully an Indian summer!

Veraison

Veraison - Pinot Noir

The Pinot Noir grapes are starting to change colour from green to red. This is the start of the ripening process and in viticulture is called veraison.

Grape berries have two distinct growth phases. The initial phase is when the cells divide and expand and the grapes begin to swell and fill out the bunch. After veraison the acidity decreases due to degradation of Malic acid, making Tartaric acid the predominant acid. At the same time sugars (glucose and fractose) are accumulated and the volume of water entering the grapes decreases resulting in an increase in sugar concentration. The level of sugar accumulation in the berries is dependant on leaf photosynthesis which is why we could do with some more sun!

As the fruit ripens it becomes more attractive to the birds. As well as the KiteHawk and Helium Ballon we will be netting the outer rows of the vines early next week.

Leaf Pulling/Plucking

A Pinot Noir vine before leaf removal  

After leaf pulling

Leaf pulling is the removal of leaves around the grape bunches, which allows the vines to dry off much quicker after rain or heavy dew which in turn makes the vines less susceptible to the spread of fungal diseases like mildew and botrytis. It also improves the coverage of spray applications, and improves sunlight penetration which helps to ripen the fruit and improve aroma.

In Germany they remove leaves early (soon after fruit set) as they believe that this helps to thicken the berry skin making the berries more resistant to botrytis.  Leave are removed again just before veraison.

We've just started the process of leaf pulling. Hopefully it will be worth it as it's very labour intensive; each row takes about an hour which equates to more than 20 man days for the whole vineyard. Next year we will investigate buying or renting a machine to do the work!

Postscript

It seems that I have been too aggressive with my leaf pulling; it's important not to take off too many leaves as they are needed for photosynthesis. Also, not surprisingly, Alex is much faster and only takes 30 minutes/row!

Powdery Mildew, Sulphur and Compost Teas

Powdery Mildew

Sadly Powdery Mildew has arrived at the vineyard, at the moment primarily infecting some of the Pinot Noir on Block A.

Powdery Mildew survives the winter either within infected buds, which subsequently germinate to form mildewed “flag shoots”, or as tiny fruiting bodies that lodge in the bark on the vine which release new spores to infect young tissues in the spring. Leaves are highly susceptible to infection while they are expanding but become resistant soon after they’re fully expanded. Berries are highly susceptible from flowering until shortly after fruit set, but become much more resistant afterwards. Interestingly, research has shown that significant berry infection at harvest can almost always be traced back infection soon after flowering.

So far our strategy to deter fungal infections has been to use compost teas, the theory being that by populating the foliage with the good guys there will be no room for the mildews to infect the plant. Unfortunately recent weather conditions have been ideal for powdery mildew which thrives in temperatures between 15C and 25C with a high relative humidity and as a result the compost tea hasn't been fully effective.

The standard organic treatment for Powdery Mildew is Sulphur and Potassium Bicarbonate (baking powder), both of which are sprayed onto the foliage of the plant. Garlic sprays are also be used as garlic naturally contains high levels of sulphur. Rain and free moisture on the surface are also unfavourable for colonisation, sporulation and dispersal, so the sulphur and baking powder are often sprayed with high quantities of water in the morning so that the foliage takes most of the day to dry.

The problem with sulphur is that it also prevents the good bacteria and fungal content from the compost tea from doing their job; so unfortunately it's one or the other. We have decided that for the time being we cannot risk the further spread of the disease so we will be spraying the plants on Block A with sulphur and baking powder.

We will have to review our spray programme for next year; as sulphur is a preventative measure and not curative, we should really be using it from the beginning of the year if it is to be fully effective.