Monday, October 01, 2012

Vintage 2013 Continues

Warm weather and some sporadic rain have encouraged pretty rapid shoot growth of the Pinot Noir.
In viticulture talk it had reached growth stage E-L 12 ie. five to six leaves unfolded with inflorescence clearly visible.
The E-L system designates the phenological stages of grapevine development described by Eichhorn and Lorenz and there are 47 of them.
A simpler system is the modified Baggiolini one which is limited to 15 stages ie. A to O.
In that case the Pinot Noir was at F
It was time for the first spraying.
In my opinion it is essential in the early stages of growth to protect the vines from both downy and powdery mildew, especially in a warm maritime climate like ours.
Then again there is another school of thought that believes only curative sprays should be applied ie. spray only after a weather event that would be conducive to the development of those diseases. However while there are suitable curative sprays for downy mildew, there are none that are really effective for powdery mildew.
After last year's disaster with a modified version of a curative spray program, it was a no brainer to apply protective sprays this season.

Against downy mildew (Plasmopara viticola), I use the copper based spray copper oxychloride. The dried copper spray droplets sit on the leaf surface and slowly release a supply of cupric ions.
These are picked up by the fungus spores and travel through their cell walls to eventually disrupt cellular enzyme activity. Copper sprays are not systemic ie. they don't get into the plant's sap system and get translocated around the plant. They are surface sprays. Droplets remain static so as the vine grows, additional sprays must be applied to protect new growth as well as replenishing the already sprayed areas. Under normal circumstances this is done approximately every two weeks. Rain events shorten the spray intervals.
Against powdery mildew (Uncinula necator), I use a micronised wettable sulphur powder.
Despite sulphur usage dating back some 180 years the mode of action still remains unclear.
Actual contact of the sulfur particle with the fungus is necessary before fungicidal action can occur. There is some debate as to whether vapour inhibits spore germination. The jury is still out on that one.

                      A sulphur spray forms a protective barrier on the plant surfaces. This barrier kills fungi by interfering with cellular respiration preventing it from accumulating the materials and energy it needs to survive.
Sulphur also keeps the vines clear of blister mites (Colomerus vitis). Although I have never seen them here, they are in the area.
Blister mites feed on the under-surface of leaves and cause very obvious blisters on the upper surface of leaves and white or brown hairy growths within the raised blisters on the lower surface of leaves.
Damage by the mite is more unsightly than economically consequential.
As with copper, sulphur sprays need to be reapplied on a regular basis.
Both copper and sulphur can be mixed and applied at the same time.
A little care has to be taken with sulphur sprays. Application at temperatures above 30C and high humidity can lead to phytotoxicity problems on young growth.
As far as shoot development is concerned, the Semillon is a little behind the Pinot Noir and the Tempranillo slightly behind the Semillon.
We are just now getting Cabernet Sauvignon bud burst.

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