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GRAPE GRO WING are probably beneficial. Plant pathogenic nematodes are problematic because they impair roots from water and nutrient up- take. Mostly they feed on the smaller feed- er roots that grow in spring and fall and are not very suberized (woody). Feeding injuries may also allow secondary patho- gens into the root system such as Fusarium oxysporum, which aren't necessarily "red hot" but over time will do damage. Preplant fumigation is helpful, but it will not completely eliminate the nematodes. You may also treat existing vineyards with the fumigants fenamiphos and sodium tetrathiocarbamate (Enzone), but these treatments have only temporary effects. There are some new biological materials being tested, but at this time they are not evaluated well enough to know how effective they are, and for which nematode species. Similarly, there is probably some benefit from resting ground and cover cropping with rye grass, certain mustards and vetches that will suppress nematode populations but not eliminate them. Here are some of the most problematic nematodes to have in your vineyard: Dr. Andy Walker from UC Davis has released five rootstocks, numbered GRN 1-5, which all have different parentages broad resistance against all nematodes, but individual stocks show enhanced resistance to dagger, citrus, ring, lesion and root knot nematodes. More testing is definitely needed. Proliferation of shoots at a node is charac- teristic of fanleaf degeneration. based on native grapevine species from the United States. Nematode-resistant parents in the group include Muscadinia rotundifolia, Vitis rufotomentosa, Vitis champinii (Dog Ridge and Ramsey) and Vitis monticola. Propagation of some of the new rootstocks can be tricky—especially GRN-1, which has a high amount of Muscadinia rotundifolia in its parentage. No one rootstock has 2. Fanleaf degeneration Xiphenema index transmits the fanleaf de- generation virus and is a scourge once the virus and nematode are found in a vine- yard. Infected vines produce very poorly if at all. Infestations of both problems often came from contaminated nursery stock many years ago, before the disease was un- derstood (another reason to be very careful where you source budwood and rootstock materials for new plantings.) It is mostly a problem where multiple generations of vine- yard have been planted. Presently, only one rootstock is known to impart resistance: 039-16, an old hybrid between Muscadinia rotundifolia and Vitis vinifera (Almeria.) The rootstock evidently allows feeding by the nematodes and infection by the virus, but somehow the symptoms are not mani- fested. O39-16 is only recommended for fanleaf sites, as it tends to invigorate what- ever scion is grafted to it, and it also may cause increases in potassium in the fruit, making winemaking more difficult. Addi- tionally, there is some concern about phyl- GrapeParts4Less.com Paying Too Much For Picking Rods? Now You Have A Low Cost Source! GrapeParts4Less.com supplies quality American made picking rods, closures, and parts for all major grape harvester brands. Call 559-277-7382 or visit our website. Mastercard or VISA accepted. Se habla Espaňol. GrapeParts4Less.com Your Low Cost Source For Quality Harvester Parts 54 Wines & Vines APRiL 2012 GP4L_W&V_April_2012.indd 1 2/27/12 11:59 AM G.P. MartElli/ OntariO MiniStry Of aGriculturE fOOd & rural affairS