Viticulture Notes May-June 2010
Total Page:16
File Type:pdf, Size:1020Kb
Vineyard and Winery Information Series: VITICULTURE NOTES ........................... Vol. 25 No. 3, May - June, 2010 Tony K. Wolf, Viticulture Extension Specialist, AHS Jr. Agricultural Research and Extension Center, Winchester, Virginia [email protected] http://www.arec.vaes.vt.edu/alson-h-smith/grapes/viticulture/index.html I. Current situation .................................................................................. 1 II. Seasonal comments and disease updates .......................................... 1 III. Question from the field: response to frost ........................................... 2 IV. Plant nutrition reminders ..................................................................... 5 V. Sustainable and organic viticulture workshop recap ........................... 7 VI. Upcoming meetings ............................................................................. 8 I. Current situation successful in obtaining federal funding through the USDA’s Specialty Crop Grapes for sale: We have provided a listing Research Initiative with a large, multi-state of Virginia-grown grapes for sale and proposal that starts October 2010. Part of updated and distributed that listing bi-weekly the funding of that proposal provides for a in recent seasons on our listserv electronic project manager, which will comprise 50% of newsletter. The Virginia Vineyards a full-time equivalent (FTE) role. The Virginia Association has agreed to provide this Wine Board simultaneously provided the service in 2010 and we will therefore not be other 50% of funding in a grant award that posting a “Grapes for Sale” service in 2010. commences July 1, 2010. We are therefore The VVA website is initiating the process of advertising and http://www.virginiavineyardsassociation.com/ hiring for this position which we hope to fill (go to the “Exchange” link in the left-hand later this year. More on all of this in future navigation pane). VN editions. Viticulture Associate: Our viticulture II. Seasonal comments and disease update associate position here at Winchester has Dr. Mizuho Nita, grape plant pathologist been vacant since Mardi Longbottom stepped down in 2008. The position was We experienced earlier than usual bud break th being funded by the College of Ag and Life this year (April 6 for our Chardonnay). As Sciences at Virginia Tech at that time. Given with other years, there have been many rain the cuts in state funding to the college, we events since bud break; however, we did not did not foresee the position being re-filled in experience a major disease event until the near-term. Two things happened this relatively recently. Many rains we had in the spring, however, that have provided financial first month of growing season were either too resources to refill the position. First, we were short or it was too cold for disease to Viticulture Notes: May - June 2010: page 2 develop. The major disease risk events were II. Question from the field rains on 5/12, 5/17, and 5/22 where we (Winchester) had 18, 55, and 19 hours of Q. The lower portion of my ‘Norton’ vineyard wet events, respectively. Temperature was frosted twice this spring; once in late- during these rain events was in upper 60’s. April, and again, more severely, on the These conditions are conducive for downy morning of May 10th. What can I expect in mildew, black rot, and Phomopsis. Our terms of crop yield and crop maturation? station has several non-treated vines to Should I have rubbed off the damaged observe the development of diseases, and shoots? some of the vines have been showing symptoms of Phomopsis since May 14th, and A. My condolences to you on the frost injury. black rot, downy mildew, and downy mildew Reports that came in after the morning of 10 since May 27th. May suggested that a number of vineyards in th th Loudoun County, parts of Fauquier and In addition, from May 24 to May 30 , we Culpeper Counties, as well as areas in the experienced humid nights (RH > 85%) for six Shenandoah Valley experienced some consecutive days. These warm humid nights degree of frost injury. What is perhaps most promote downy mildew fungus to produce surprising about our collective experience spore structures, thus, the risk of infection for with frost this spring is that there was not the next rain event will be higher. If your more injury than what was reported. We had vineyards have an issue with downy mildew a very early (as much as 2 weeks) budbreak or black rot in recent years, please spend prompted by temperatures of around 90°F time on scouting. the first weekend of April. Ultimately, April Please remember that the critical period 2010 set a record for warmest on record for downy mildew, powdery mildew, and (NOAA records); however, the later part of black rot to infect berries are from bloom the month returned to more seasonal highs to 4-5 weeks after bloom. Please be on and lows, as did much of May. This of course set the stage for frost problems and top of the situation during this critical period. th After this critical time, you can relax a bit in by the 10 of May, shoots of early budding terms of the berry protection. varieties were 18 inches or longer. Another consequence of the early, widespread heat Also, we have seen a development of wave is that it essentially nullified our normal mealybug population in our field, and I have latitudinal difference (and much of the been receiving reports of sighting of this varietal difference) in vine phenology; vines insect. If you have seen mealybugs in your in Loudoun County were as advanced as vineyards, please let me know, so that I can those in the southern Piedmont by the end of visit your place to sample them. It is very April. Neither of these observations address important for us to find out which species of your questions, but they do put your mealybugs we have in VA to determine experience with frost injury in perspective to whether we have a high risk of spread of leaf what else was happening in the state (and a roll disease, which is caused by a group of large part of the eastern US). viruses. In addition, if you have a reasonable suspicion that some of your On to your questions: To answer your vines are showing leaf roll disease, please second question first, No, I don’t believe that contact me. We are offering free virus you should have rubbed off injured shoots, testing as a part of my research program. If although there could be a justification for this you want to know what mealybugs and leaf under specific conditions. Vineyardists have roll disease look like, please visit my blog dealt with the consequences of frost since (http://grapepathology.blogspot.com/). weather and vineyards have existed, so it’s not surprising that someone took a methodical approach to looking at various vine management strategies following a frost Viticulture Notes: May - June 2010: page 3 event. Frost is rarely even-handed in the totally scorched (“A”). Would the stripping of injury it causes, especially when air damaged shoots benefit the vine? With temperatures are at, or just below, the critical vines that have total loss of shoots (“A”), temperature required to initiate freeze there would likely be no benefit to this events. Some shoots are totally scorched. strategy. Work in California (Winkler, 1933; Others are unscathed. Still other shoots may Lider, 1965; Kasimatis and Kissler, 1974) have their tips or only a portion of leaf area suggests that while a positive response frosted, with the basal portions of the shoot, (slight crop increase) to stripping damaged including inflorescences escaping injury. To shoots might occasionally be observed with simplify the response discussion here, let’s some varieties (such as ‘Tokay’ in the just consider these three scenarios: A) totally Winkler study), the overriding result was no destroyed shoots; B) healthy shoots, and C) significant increase in yields. Furthermore, if shoots with injury to the tips and/or some the shoots were partially lignified at their degree of leaf area, but with apparently point of attachment to older wood when the unaffected flower clusters. As I discussed at stripping was done (18- to 24-inch shoots), the vineyard meeting on 19 May (see the manual breaking out of damaged shoots additional Upcoming Meetings at end of this often damaged the base buds. newsletter), a first course of action would be to survey the frosted vineyard and determine What about vines that have long shoots (24 the classification of injury and the pattern of inches or longer) that had their tops/tips injury within the vineyard. As you illustrated frosted, but which appear to have unaffected in your question, topography would obviously flower clusters (what I called scenario “C”, affect the pattern or incidence of injury within above). The consequence of this damage is the vineyard, but also the severity of injury difficult to accurately predict, but let’s try. A on a given vine. damaged shoot will initiate one or more lateral shoots at nodes proximal (below) to In areas where a significant portion of the the point of frost injury. We’ve all seen this shoots are “A” (totally destroyed), most response with shoots that were decapitated (possibly 75% or more, but varies by variety) from grape cane girdlers, periodical cicada of the current season’s crop potential of egg-laying, hedging, wind damage, or from a these vines will have been lost. New shoots host of other reasons. The new leaf area of will emerge in time from base buds on the lateral shoot(s) will compensate in time cordons or from secondary buds in the for the primary shoot leaf area lost to frost. compound bud of cane-pruned vines. Some However, the lateral leaf area may not of these new shoots will bear some crop.