Thursday, December 27, 2007

Vineyard Insect Pests

We don’t see a lot of insect pests in the vineyard. During the season there is some evidence of caterpillars but usually not enough to warrant spraying. A quick squeeze between the fingers during other vineyard operations eg. shoot positioning, is all that is needed.
From our experience there are three potential problems.
One of these is the caterpillar of the vine hawk moth (Hippotion celerio). They are a grey green colour with a spine on the upper rear end of the body and grow to about 6cm. They can cause rapid defoliation.
Because of their colour they are hard to spot but during routine inspections of the vines a trained eye can see activity on the leaves.
The grapevine moth caterpillar (Phalaenoides glycine) grows to about 5cm and is black with transverse white markings and several red spots. It is easier to notice. These can also quickly defoliate vines if not controlled.

By not spraying for insect pests on a regular basis we have allowed a population of natural predators to build up in the vineyard. These include shield bugs, lacewings, ladybirds, wasps and spiders.
If we needed to spray we would always select the biological control Bacillus thuringiensis (BT) eg. Dipel, as it selectively kills caterpillars and does not harm their predators.
Chemical sprays such as carbamates and organophosphates would soon wipe out any populations of natural enemies.
Another potential pest is the blister mite (Colomerus vitis). They are about 0.2mm long and cannot be seen with the naked eye. They live on the underside of the leaves and produce blister like galls which bulge from the upper surface.

Luckily the application of wettable sulphur for powdery mildew also controls the mite.
Even if it didn’t, there are predatory mites which build up in an insecticide free vineyard who take care of the problem eg. Typhlodromus doreenae.
Leaf galling can have a detrimental affect on the growth of young vines but is little consequence on mature vines.
The sight of leaf galls could frighten the inexperienced grape grower who might think this is a sign of grape phylloxera (Daktulosphaira vitifolii) which is regarded as the world’s worst grape pest.
This aphid like insect is a native of North America that lives in and feeds on the roots of native American grapes of which there are about 20 species. These eg. Vitis riparia, V.rupestris, V.labrusca, V.berlandiera have become resistant to the insect over thousands of years.
Unfortunately the European grape (Vitis vinifera) is not resistant and the importation of the pest into Europe in the mid 1800’s all but wiped out the wine industry in the Old World at that time.
It came to Australia too but has been confined to certain areas of the country eg. Rutherglen, King Valley, Goulburn Valley, Corowa and the Sydney basin.
We are just south of Sydney and our wine growing region has been inspected many times by the Department of Agriculture over the last few years and we have basically been given the all clear and are designated a phylloxera free zone.

Phylloxera can reduce productivity and eventually kill a vineyard in a very short time. Nymphs feed on the roots which form fleshy yellow galls. These cut off the nutrient flow to the vine. Unlike its native host, leaf galls seldom form on the European grape so root inspection to a depth of 0.5m is required in suspect areas mainly from November to March.
There is no known economic cure.
Vineyards in infested areas survive by grafting Vitis vinifera scions onto American grape rootstock.
There is a concerted effort Australia wide to prevent the pest from spreading, so far, successful. Although it will only spread naturally to around 2km, man’s activity is the main danger with it being spread by the illegal transfer of plant material, on fruit, on machinery, on harvest equipment and even tourists’ shoes and cars.
Quarantine and disinfection rules apply to infested areas and there is a constant vigil by growers outside these areas to put in place procedures that minimise the threat.
In this area many vineyards have set up exclusion zones with signs up asking people not to walk among the vines and the reason why. There seems to be almost 100% acceptance of this “rule”.

Thursday, December 06, 2007

Some Grapevine Diseases

With all the rain we have been having lately, our thoughts turn to disease prevention.
There are a large number of fungal, bacterial and viral diseases which can attack grapevines.
We have to deal with three of the most common fungal diseases here.
Downy Mildew (Plasmopara viticola) is the most prevalent and is spread by rainfall.
It attacks leaves, shoots and berries and will quickly defoliate a vine leading to entire crop losses.
Primary infection takes place after 10:10:24 conditions occur ie. at least 10mm of rain at a temperature 10C or more, over 24 hours.
The fungus survives as spores for 3 to 5 years in old infected leaf material in the soil and, with rain, are splashed onto the foliage. If the spores remain wet long enough the disease begins to develope.
This shows up as "oil spots" on leaves (see top picture)

Spores form under the oil spot and show up as a "white down" (lower picture). If conditions are right, secondary infection occurs from these spores and the spread of the disease becomes quite rapid.
Downy mildew can be controlled by the spray application of various chemicals either pre infection or post infection. In a damp maritime climate like ours, we prefer the pre infection strategy. This involves spraying at least every two weeks from when the shoots are 10cm long or at shorter intervals if rain conditions prevail.
There are two groups of spray chemicals, those with single site activity which act on only one site within the fungus organism or those with multi site activity which act on more than one site within the fungus. Overuse of the former group can lead to small mutational changes in the fungus which in turn can lead to the fungus being resistant to that particular chemical.
We use the relatively safe and multi site copper oxychloride as our main preventative for downy.
In the unlikely event that infection does occur we use phosphorous acid, which is also multi site, as a curative.
Powdery mildew (Uncinula necator) is also common and attacks leaves, shoots and bunches. It is evidenced by an ash grey to white powdery growth on both the upper and lower surfaces of the leaves which eventually distort and shrivel.

The disease also attacks the bunches with the same ash grey/white powder showing up on the berries and stalks.
Crop losses can occur but more importantly, bunches with as little as 5% disease may be rejected by wineries as the disease causes off flavours in wine.

Powdery mildew spores hide in the buds of dormant vines. Mild cloudy weather and low light in the canopy encourage development of this disease. It does not need a lot of rain to spread.
There are no approved post infection sprays so a two weekly application of a protective spray from budburst is necessary. Again there is a multiple choice of chemicals from the two groups. We use the relatively safe and multi site active wettable sulphur.
Botrytis or grey mould (Botrytis cinerea) is a common bunch rot in regions with warm, wet conditions but it can also attack shoots and leaves.
Large crop losses can occur and infected grapes will cause off flavours in wine.
It should be mentioned here that not all botrytis infection is bad. Under some conditions, the fungus takes hold and dehydrates the bunches increasing the sugar content without causing rot. This enables very sweet dessert wines with their traditional marmalade favour caused by fungus enzymes to be made eg. Sauterne in France or in Australia, Noble One et al. The disease is then known as noble rot. Conditions on the south coast hardly ever allow for this and it is too much of a risk to hold off spraying just in case they might.

The disease hides in decaying plant debris such as dead canes and mummified fruit. Spores are spread by wind and find a place in the developing bunch flowers. Once the bunch has "closed" and wet weather and high humidity occurs the disease spreads rapidly. There are virtually no curative sprays and it is essential that a protective spray be applied at very definite times of bunch development ie. 80% capfall (towards the end of flowering) and again just before bunch closure (just before the berries have stopped growing and become 'squished' together in the bunch). We use chlorothalonil for this purpose, again, multi site active but a bit "nasty".
This chemical is also a protectant against downy mildew so we can replace the copper with it at these two spray times.
All the chemicals we use are compatible so it is possible to mix them in the one spray application.
Lucklily we dont see other diseases like Phomopsis or Black Spot in the area.
But the three we have are quite enough.

Tuesday, December 04, 2007

A Busy Month

The vines have been jumping out of the ground due to the amount of rain we have been getting. This has meant lots of spraying, green pruning, shoot positioning and interrow mowing. At the same time I have been videoing all the activities for my upcoming classic. I had never before realised how time consuming all the viticultural activities are. And videoing yourself doing them can be a logistical nightmare. With most the vitcultural activites "in the can" and the winemaking ones to go early next year I think the video will be a two bags of popcorn and potty break epic. It's already 18 minutes. There has been a suggestion I make two versions, one for those with passing interest and one for those with more. I think all DVD players have fast forward buttons so it will be a warts and all production although I agree there is room for some tighter editing.
So all you out there be ready for "From Vine to Wine" due for release mid 2008 but maybe earlier if I decide to exclude pruning.

The election is over. Australia has a new government. The conservatives were given a huge whopping with the prime minister of 11 years (and a political career of 30) losing his seat. Hopefully now we can return to being a society as well as an economy.
The publicity campaign for the wine show has been going well. So well in fact that I have been asked to do a similar job for the Shoalhaven Coast Wine Festival which takes place on the Queen's Birthday long weekend in June 2008. Eleven wineries offer tastings, culinary events, music and other entertainment over the 3 days. This year's festival was a success despite atrocious weather so they are hoping for a huge turnout next year. It will be my job to be in touch with the print and electronic media to make sure it is. You can follow progress on
Meanwhile the traveller has returned from 3 weeks in the USA and preparations for Christmas have begun. It will be a quiet one for us. My daughter and her partner are heading for the UK so there will be just we two indulging in an early morning swim at the beach on Christmas morning followed by oysters, prawns, Balmain bugs and maybe a lobster for lunch. And of course plum pudding for the traditionalist. And there might be a bottle or two of Sancerre plus Noble One hidden away somewhere to help wash it all down.
So for all you who have been complaining about the lack of activity on this blog, there is your update!