Issue link: http://winesandvines.uberflip.com/i/235959
S M Aw iT n V MT A K IN T U R E R e I ICULG patches gradually grow. New symptoms can occur on isolated vines down-wind, spread by spores •Trunk cankers and internal staining/ dead tissue are common. •Staining at the base of last year's spur may be seen. •Sometimes early season shoot growth is inhibited, and in late season the vines may show mild chlorosis and apoplexy, the latter with wilting of shoots and fruit. For newly planted vineyards, the symptoms are: •Vine growth will be variable in the first year, and in general, some vines will fail to thrive. This variability will continue for the life of the vineyard, and the least vigorous vines will die first. • Poorly performing vines, and even some healthy ones, may show internal staining. This may be black (indicating Phaeomoniella, Phaeoachremonium or Cylindrocarpon) or light brown (Botryosphaeria). The staining may be seen at the rootstock base, or under the graft union, or above the graft union. •Some vines may not grow, others may fail in the first year, and some fail to grow during spring in following years. Depending on the degree of initial infection, "clumps" of infected vines may appear in subsequent years. Conclusion My review of recent research presented here, my other reading and widespread vineyard observations suggest to me that the vine and wine world may be facing a new disease crisis, which can be compared to phylloxera in the late 19th century. American readers may have a different perspective about phylloxera than vine growers elsewhere in the world. Why? Because phylloxera is native American, as are downy mildew and powdery mildew (Oidium). These two fungal diseases and the insect pest phylloxera almost brought European viticulture to its knees by the 1890s. The situation for phylloxera was resolved eventually by grafting to native American vines, or their hybrids, as rootstocks. This is now a world-wide practice. The phylloxera problem was solved because a source of genetic resistance was found. Now compare phylloxera and trunk diseases. Both are vine killers — in fact phylloxera the more quickly. Trunk diseases spread more slowly and are insidious; that is why they have escaped observation for so long. I would guess that trunk disease is 12 p r actic al w i ne ry & v i ne yard JANUARY 20 14 Production practices have changed (including spur-pruning in various trellis systems), varieties have changed, chemical controls are different, according to Paul Verdegaal. "Arsenite took care of a lot of problems, as did copper, lime sulfur, parathion, weed oil, etc. Propagation methods have gone more to centralized nurseries. "During the last planting boom there was undoubtedly lots of poor quality (and/or infected) wood used for propagation to meet the demand. Nurseries are more careful now (maybe more care is needed?), and growers are more careful, but problems persist. Agricultural bankers like to see full production sooner rather than later. Legally or otherwise, plant material is moving faster and farther than ever before. "We do have a relatively dry climate in California, compared to many other areas of the U.S., and other more traditional districts in the world, but also areas such as Missouri, Arkansas, Pennsylvania, Michigan, Kentucky, even New York, etc. are only beginning to see local commercial vinifera vineyards and wine-growing districts 'mature,' and with that more problems. "We have limited chemical options right now with Rally, Topsin M, BrotoMax and VitiSeal. They cost money, require timely access; they and their application all come under regulatory scrutiny. Late pruning and/or cane pruning, with shoot thinning and reducing number and size of cuts if possible, along with protectants are standard suggestions. Variable weather patterns and the diverse array of pathogens make for a complex problem and don't make management easy or cheap." more widespread now than phylloxera. Remember that phylloxera is limited by quarantine in Australia, and most vineyards are own-rooted; Chilean vineyards are all own-rooted. So phylloxera is not everywhere, as in Washington state. There is a cure for phylloxera which is cheap, environmentally friendly and sustainable: That is grafting to resistant rootstocks. There is no such cure for trunk diseases. There are no known sources of genetic resistance. We also have a situation where the majority of the world's nurseries are spreading trunk diseases; that is not the case for phylloxera. These problems with trunk disease are not insurmountable. They can be overcome, as was phylloxera. The "cure" for trunk diseases will involve removal of infected vines, replanting with healthy material, and likely some pruning-wound treatment. Developing a cure will require increased recognition by growers and regulatory authorities and more research. Final words about two paradoxical situations One of my overseas clients is importing "high health" virus-free grafted vines from California. The photos (page 9) show trunk disease symptoms, but the California nurseryman assures my client there is "nothing to worry about." Humbug! The second paradox also involves imported vines. Growers in the UK, where I now live, import "virus-free" but trunk disease-infected grafted vines that typically grow very poorly. The UK growers could much more cheaply propagate own-rooted vines, as they do not have phylloxera in their vineyards! But they are told (by the nurseryman's agents!) that they need rootstocks. Humbug! I hope this column helps raise some awareness about trunk diseases. To solve the problem first requires recognition. I would be pleased to hear from others who might share my view, and may be concerned about the insidious spread of trunk diseases in North American vineyards. PWV In writing this column, I acknowledge the excellent scientific work of Dr. José ÚrbezTorres and his Spanish colleagues David Gramaje and Josep Armengol. Were it not for Dr. Doug Gubler of UC Davis and his Ph.D. students, our knowledge of grapevine trunk diseases in the U.S. and contiguous countries would not be nearly so complete. Congratulations to all of you! I would also like to acknowledge the helpful reviews made on drafts of this column by Don Neel, Steve Thomas, Paul Verdegaal, Lucie Morton and José Úrbez-Torres. However, I take responsibility for the final text.