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A Technical Guide for Wine Producers
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RECENT ARTICLES | WYNBOER HOME
ANALYSIS OF VINEYARD DISEASES AT NIETVOORBIJ: AN INDISPENSABLE SERVICE TO PRODUCERS The Plant Protection Division at ARC-Nietvoorbij is involved not only in extensive studies on vine diseases and pests, but also provides producers, extension officers and technical field staff with a comprehensive analytical service of vine diseases. During 1997 more than 500 samples were analysed for soil pathogens and complete reports sent to clients. Sampling In order to make a correct diagnosis of a vine disease, samping is very important. Where distinct spots or scars occur on leaves only, a representative leaf sample of five leaves is sufficient. If scars occur on shoots, such shoots must be cut off at the base together with the leaves attached to it. Five shoots collected representatively suffice for disease identification. Three to five bunches are sufficient if bunch problems occur. If overall weak growth of a vine or several vines occurs in a vineyard, at least two of these vines, together with as many roots as possible, should be taken out for analysis. A good criterion of sufficient roots is when the roots are cut off approximately 30 cm from the stem all around the vine. When analyses are required to determine soil pathogens such as Phytophthora and Pythium in new plantings, samples should be taken in the following manner: Take a soil sample to a depth of 20 cm (spade depth) by first digging a hole and then peeling off a thin layer of soil with the spade from the wall of the hole and throwing it into a bag. Holes must be made every 20 m criss-cross over the area to be sampled. Mix the soil properly and take a 4 kg sample to be submitted for analysis. Packaging and transport To transport leaf, bunch and shoot samples, they should be wrapped in a few pages of newspaper and placed in a plastic bag. The newspaper serves as isolation material, which prevents the sample from drying out quickly or burning when transported on a hot day. Alternatively leaf and shoot samples may also be placed in a plastic bag, into which a little water (2 teaspoons) has been poured. The bag must then be inflated and tied. Exposure of the samples to the sun must be avoided at all times. To transport a vine with roots, the vine may be sawn off above the grafting union and placed in a clean fertiliser or similar plastic bag into which half a cup of water has been poured. It is not necessary to put soil in the bag. The bag must be tied around the stem of the vine, above the roots, in order to prevent dessiccation of the root section. Information on the particular sample The following information must accompany each sample:
The information should not be written in ink and placed inside the bag with the sample. Attach a sticker with the information to the outside of the bag. A complete report with the findings and recommendations will be sent to the producer as soon as possible after the result of the analysis is known. Timely analyses of affected vines will inform the producer of the disease status of his vineyard(s) so that control measures may be implemented in good time. In the case of some diseases, it is possible to determine the success of the control measures implemented in the past. The analytical service has the added advantage of informing the researcher of diseases which present an intrinstic danger to the industry, so that certain aspects thereof may be researched in good time to implement efficient control measures. Cost The cost involved in the identification of a disease currently amounts to R70,00 (incl. VAT) per sample. If a producer requires a consultation subsequent to the findings, an additional consultation fee will be charged. For further information, contact Dr Strauss Ferreira at Nietvoorbij (021) 809 3040 or e-mail him at strauss@nietvoor.agric.za. |
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