I grow weary of hearing people in our industry complaining about "that damn university" and how they can't relate to our problems. The "ivory tower" effect is a vicious cycle. A group of talented scientists endeavors away at their respective fields of expertise, which don't necessarily mesh with those of the industry group that ostensibly supports them. Scientists reach out for guidance and funding, and the industry group: a) rebukes them, saying, "What do you know about our problems anyway?" b) keeps their money in their pockets and c) stays home when they should be listening to what the scientists have to offer them. Scientists, who can't get funding by their industry group, look elsewhere for support and work in other areas, like corn biology and dairy effluent management (I'm just making those up). And there you have it. Another brick in the Ivory Tower wall.

Fortunately, I see some of those ivory bricks being replaced with windows, though the process is plodding along slowly. I would hope that members of our industry step up their efforts to bridge the communication gap. It is far too easy to dismiss the whole concept.

I have been pleased to see improvements in the past couple of years simply in the numbers of attendees at the annual Recent Advances in Viticulture and Enology (RAVE) held by UC Davis' Department of Viticulture and Enology. Attendance has been huge and the presentations very germane to the issues facing the grape and wine industry.

On Feb. 18, 2009, I attended a symposium entitled "Wine and Grape Research 2009" at UC Davis. The symposium was convened by Deborah Golino, director of the funding bodies Viticulture Consortium West and California Competitive Grant Program for Research in Viticulture and Enology. The symposium was also supported by and featured work supported by the American Vineyard Foundation, California Grape Rootstock Improvement Commission, California Grape Rootstock Research Foundation, California Raisin Marketing Board, the California Table Grape Commission and the Oregon Wine Board.

The forum was also supported by Jerry Lohr of J. Lohr Vineyards & Wines, who has been a tireless proponent of research and a board member of the National Grape and Wine Initiative. The speakers were from several different institutions, though primarily from various UC Davis departments, which differentiates this forum from RAVE, which is conducted by UC Davis' V&E faculty. The symposium was open to the public, but Golino told me that the majority of attendees were invitees, like me, who serve on review committees for the various funding agencies.

I would hope that this venue is repeated on an annual basis and that general attendance increases. I will make brief mention of several presentations given at this symposium. There are plenty of others that I will not have room to mention, but that is not to downplay their importance.

Sauvignon Blanc Clones

Glenn McGourty, UC Cooperative extension farm advisor for Mendocino County, talked about his Sauvignon Blanc clonal trial he is conducting at Fetzer's Valley Oaks vineyard in Hopland. Clones are one of my pet peeves, primarily because most of what we think we know about them is due to anecdotal folklore from one experience here and a different experience there. Because clonal differences can be quite subtle, oftentimes the fruit and wine characteristics of the location and its viticultural practices override the clonal contribution. Notwithstanding some great work in France by ENTAV-INRA, controlled clonal research trials are few and far between.

McGourty's trial comprises 12 clones of Sauvignon Blanc in a randomized complete block experimental design (hurray!). The fact that all clones are grown on the same site with replicated plots means that his results will actually be meaningful. I'd like to see more clonal research being conducted in this manner. Vines in his trial are still reaching maturity, so it is premature to talk about any results at this time.

Petiole Nutrient Content

G. Stuart Pettygrove, from the department of Land, Air and Water Resources department of UC Davis, reported results from a study on spatial variability of petiole nutrient content within a vineyard. He found that there was variability among the several people he had taking samples in the vineyard. Most of the variability among sampling personnel had to do with petiole weight. Samplers that tended to take smaller, lighter petioles had vastly different results than the others. Petiole weight was negatively correlated with petiole potassium concentration. In other words, smaller, lighter petioles had higher potassium concentrations. Petiole nitrogen was also correlated with petiole weight, but phosphorus content was not.

This indicates the importance of consistent sampling. Sampling at bloom requires very little decision making on the part of the sampler. The petiole opposite the cluster is chosen at bloom, but at veraison, the proper petiole selection is from the most recently fully expanded leaf.

This creates room for error, but good training, including testing of samplers' skills, is essential for accurate results. By the way, they also found tremendous variability in nitrate-nitrogen but much less variability in total nitrogen levels. This is something that I have seen in dramatic fashion and is why I favor total nitrogen levels for the determination of nitrogen nutritional status of vines.

"Oak" Root Fungus

Kendra Baumgartner of the USDA-ARS and Department of Plant Pathology at UC Davis discussed her recent work with the fungus Armillaria mellea, commonly called Oak Root Fungus. She prefers not to refer to it by this title since the fungus infects numerous native tree and shrub species. This fungus is particularly annoying since it seems to appear out of nowhere. Vines just collapse and seem to die overnight even though the infection process is actually much slower than that.

While the disease seems to move from one vine and kill the neighbor vines a year or two later, Baumgartner explained that the disease does not really move from vine to vine like that. It really doesn't travel in the soil, but roots coming in contact with infected remains of old roots become infected themselves. The problem is not correctable. Pre-plant fumigation only knocks it back but doesn't kill all spores. Replanting vines is not really an effective solution. It is nearly impossible to remove all of the infected root debris from a site.

There are no Armillaria-resistant rootstocks, though Baumgartner has tested several in controlled studies. The most resistant current rootstock is Freedom. Too bad, since Freedom is a highly vigorous rootstock and is generally not suitable for high-end viticulture. Next most resistant was St. George although its resistance was far less than that of Freedom. On the other hand, the most susceptible rootstock she found was 3309C.

To further discover and develop Armillaria-resistant rootstocks, she has been developing rapid culture assays, culturing tiny plants in plastic boxes. This allows her to test resistance of a selection in about half a year, compared to about three years that are required for potted, greenhouse-grown plants. Using current technology, including a laser confocal microscope and DNA-based PCR methods, she can quickly determine the level of Armillaria colonization on the roots to determine susceptibility.

Pictured is a typical pie-shaped canker found in wood infected with one of various species of wood-rotting fungi. While typically diagnosed by viticulturists as Eutypa lata, other fungal species are even more likely to be the causal organism.

Eutypa by any other name is …

... still something that rots wood! Doug Gubler, from the Department of Plant Pathology, UC Davis, talked about wood-rotting fungi and their "friends." Interestingly enough, what we typically refer to as Eutypa dieback disease is more often than not caused by something other than the fungus Eutypa lata. In fact, he found that only 17 percent of wood rotting diseases in California can be attributed to E. lata. Of the others, 40 percent are caused by various Botryosphaeria species, 15 percent by Diatrypacea species, 7 percent by Phomopsis, 11 percent by Botryosphaeria accompanied by either Eutypa or Phomopsis, and the remaining 10 percent by other fungi. Disease from Botryosphaeria is commonly referred to as Bot Canker, which is more aggressive than Eutypa. In fact, it moves so quickly and causes disease so rapidly that, unlike Eutypa, there are no foliar symptoms because the spurs die before budbreak occurs.

The best control for any of these canker diseases is double pruning or late pruning. Double pruning involves pre-pruning of vines to long spurs and following up with a final pruning about the time that the apical buds begin to push. The fungi cannot travel more than about five inches through a pruning wound during the winter, so leaving a long stub on each spur will prevent the fungus from reaching the basal part of the cane used as a spur.

Of course, this does not pertain to cane-pruned vines, but that system is less prone to wood fungi anyway as the prior years' wood is removed each winter. Prophylactic pruning wound treatments include the antagonistic fungus Trichoderma, available commercially as a product called Vinevax. Timing is critical, and the treatment requires about two weeks for colony development to be effective against an infection.

Gubler stated that lime sulfur provides good protection against many different pathogenic fungi, including Esca, which is responsible for young vine decline as well as black measles. For canker diseases, Gubler also mentioned a product called B-lock (active ingredient is boric acid), which cannot be recommended since it is not registered for this purpose on grapes. Nevertheless, Boric acid has been found to be effective at a 5 percent concentration, especially when combined with a 1 percent concentration of Topsin-M.

Syrah Decline Associated Virus Identified?

Speaking of diseases, Maher Alrwahnih of the UC Davis Department of Plant Pathology discussed his lab's use of high-throughput DNA sequencing, which has enabled them to discover disease-causing organisms (mainly viruses) within plant material very rapidly and with a very high yield. They recently analyzed plant material from Syrah vines that showed symptoms of Syrah decline. Within those tissues, they found DNA from a multitude of viruses known to be pathogenic to grapevines.

However, most interestingly, they found one novel virus that they have tentatively named Grapevine Syrah Virus-1 (GSyV-1). This virus is not the same as the Syrah strain of rupestris stem pitting-associated virus. To confirm pathogenicity of the new virus, they must re-inoculate a plant with the isolated virus to see if it produces symptoms and then re-isolate it from the plant (per Koch's postulates). So, it's premature to announce that a cause for Syrah decline has been discovered, and it is possible that the disease is caused by a combination of viruses--but this looks like progress to me.

This Disorder Makes me Unhappy

Ken Shackel, from the UC Davis Department of Pomology, has been conducting research with Mark Matthews of the Viticulture and Enology Department on a disorder formerly referred to as "berry shrivel." The berry shrivel disorder was one of many that caused berries to, well, shrivel. But, unlike other causes of shrivel, such as water or heat stress or bunchstem necrosis, the berry remains acidic and largely devoid of sugar. Furthermore, the berry fails to color properly. Fruit in this condition must often be culled as it does not contribute positively to wine quality. Shackel and Matthews have renamed this disorder "Sugar Accumulation Disorder" or SAD, and the disorder seems to be associated with a dysfunction of the phloem vasculature's connection to the berry.

I wrote about this disorder in August of 2006, following a presentation by Mark Krasnow, a post-doctoral scholar working with Shackel and Matthews (see "ASEV Highlights: Vine Pests and Disorders" article in the August 2006 issue of Wine Business Monthly. It can be found at www.winesbusiness.com). To make a long story short, they have recently discovered that SAD-expressing vines can transmit this disorder to non-SAD-expressing vines. They determined this graft transmissibility through reciprocal grafting of buds from vines of each category with host vines also from each category. Their current hypothesis is that SAD is caused by a pathogen. Future work will be directed toward testing of this hypothesis and isolation of the purported pathogenic microorganism.

A Few More Briefs

Vaughn Walton from the Department of Horticulture at Oregon State University discussed issues with Eriophyid Mites and their infestation of dormant buds. These mites are not spider mites and are commonly called rust or bud mites, with the bud mites seemingly being the more detrimental of the two. The mites overwinter in the buds and produce a stunting of the young shoots. The symptoms include scarring of the shoot, which is often confused with Thrips damage. Sulfur as well as miticides are effective controls. However, repeated use of sulfur may kill predatory mites and may exacerbate the situation for the following season.

David Smart from the UC Davis Department of Viticulture and Enology discussed some research into comparison of "drought-tolerant" versus "drought-intolerant" rootstocks, namely 1103P (tolerant) and 101-14 (intolerant). He found that the hydraulic resistance of 101-14 tended to be higher than that of 1103P and that 1103P's resistance declined between spring and fall. The resistance of 101-14 did not change during the growing season. He also found that 1103P produced more roots during the summer below 60cm of depth than 101-14. On the other hand, 101-14 tended to produce its roots during the spring and winter. He suggested that the production of roots during the summer months may contribute to 1103P's drought tolerance.

Rodrigo Almeida from UC Berkeley's Department of Environ­mental Science, Policy and Manage­ment discussed mealybug transmission of leafroll virus. He thinks that any mealybug species can transmit any strain of leafroll-associated virus. First instar stage insects are more efficient transmitters of disease than adults, but mother insects do not pass the virus on to their progeny. However, he has found that acquisition of the virus can occur within one hour of feeding after which each insect remains infective for three to four days. He is beginning to think that most mealybug transmission of leafroll-associated virus occurs during the September to November window.

There were more presentations of research, and I'm already well out of room to discuss those. Needless to say, forums like these prove that there's a lot of good work going on that will benefit our industry. I hope that this briefing will whet your appetite for more and keep you in touch with the research community. If not, I'll do it for you. wbm

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UPDATE:

Though water shortages likely to remain, tillage no longer necessary

Recent winter rains have alleviated concern for early spring water deficits in Northern California vineyards. However, shortages in public reservoir storage are likely to remain after this rainy season is over. Flow in the Russian River may be severely limited by late summer, making it important for vineyard owners to conserve water this year. Consequently, it is important to minimize the use of overhead sprinklers for frost protection this spring to preserve public and private reserves for late-season irrigation.

Last month, I suggested that growers consider tilling their cover crop in order to reduce frost risk. In light of recent weather events, that recommendation is no longer applicable. Keep cover crops and other floor vegetation mowed very low to reduce frost risk. But, tillage for the sole purpose of raising vineyard temperature is not necessary or advised.