By: Bryan Hed, Plant Pathology Research Technologist, Erie County
2018 was a disastrous season for many grape growers in Pennsylvania. Excessive rainfall occurred almost everywhere below Interstate 90 and some growers have told me it was their worst crop, ever. Now, looking at various NEWA weather station locations across PA, it’s been shaping up to be another wet season in a lot of places, yet again. May rainfall was heavy in all but the Lake Erie region, with 6-9 inches of precipitation recorded across most of the state. Conditions lightened up a bit in June but were still wetter than average in most places (even in the Lake Erie region). But now, conditions in July actually appear to be drying up in a few (but not all) locations, giving some growers a break in terms of fungal disease management.
Hopefully, most premium wine grape growers have already applied fruit-zone leaf removal to open their fruit to better sunlight and aeration and better pesticide penetration. The benefits of this practice cannot be overemphasized, and in our wet, humid climate, it is one of the most effective cultural treatments we know of for reducing the susceptibility of the crop to disease of all kinds (especially bunch/sour rots), and improving coverage, and therefore efficacy, of fruit protection sprays. If you haven’t yet applied this treatment, it is not too late, though the benefits of leaf removal may be reduced the later it is applied. There is also a greater danger of sunburn on your fruit the later it is applied, and for that reason you may want to confine your leaf removal at this time to the east or north side of the trellis (depending on row orientation), especially in areas where very hot mid/late summer temperatures are expected.
And with that, let’s talk about diseases and their control for the remainder of the season. Much of this information has already been covered in previous blogs in previous years, and I have borrowed some information from those blogs here (no need to reinvent the wheel).
As you know all too well, wet years are ideal for downy mildew. At about this time, the fruit of most grape varieties are resistant to this disease, but cluster stems may remain susceptible for a couple of weeks after fruit are resistant, and leaves will remain susceptible all season. If the weather remains wet or wet weather returns, downy mildew can be a serious threat to grape canopies and ripening, until harvest. Continue scouting for the distinctive white ‘downy’ sporulation on the undersides of leaves. Growers of susceptible varieties need to keep closely monitoring their vineyards for active sporulation and use that information in combination with the DMCast model on NEWA (http://www.newa.cornell.edu/) to determine if and when infection periods occurred.
If you see active, white sporulation on the undersides of leaves, the downy mildew pathogen is capable of spreading quickly under wet conditions. Even humid nights that result in heavy dews by morning, can continue to fuel downy mildew development. Once out of control, it can strip vines of their leaves and effectively end fruit ripening for this year and shoot ripening for next year’s crop. It could also mean your grapevines will go into winter dormancy at less than optimal hardiness and more vulnerable to damage by severe cold, leading to another bout with crown gall and trunk renewal to have to deal with for years to come. All these issues are connected, and this is definitely a disease you want to keep under very tight control, especially on Vitis vinifera.
If you find yourself trying to control this disease well into the ripening period, be aware that your list of chemical control options will start to dwindle as we get within 30 (Ranman, Reason), then 21 (Ziram), then 14 (Revus, Revus Top, Zampro) days of harvest, until in the end you’ll be left with Captan, copper, and phosphorous acid products (0 day pre-harvest interval), which have their shortcomings, discussed below.
Another reason to keep this disease well under control is that products like Ranman, Reason, Revus/Revus Top, and Zampro, all contain chemistries that are prone to the development of resistance, and should not be used to put down an epidemic, which will speed up the resistance development process. Even phosphorous acid products, which are less prone to resistance development, can be lost to resistance through repeated applications on a heavily diseased vineyard. I know this is probably the last thing on your mind when your vineyard is under an attack of epidemic proportions, but still another good reason to keep downy mildew well in hand.
Conversely, Captan or copper fungicides would be least risky in terms of the development of resistance and can be an effective means of controlling downy mildew late into the growing season. Just be aware that formulations of Captan have seasonal limits, so plan ahead if you can. There are also some insecticides that should not be applied with Captan. Also, keep in mind the risk for injury by copper applications, and that copper injury will be exacerbated by application under slow drying conditions and application to wet canopies (for example, don’t make applications to dew covered canopies in the early morning). It’s also important to consider that copper is poisonous to yeasts and that excessive copper residues at harvest can interfere with fermentation, and wine stability and quality. Unfortunately, it’s impossible to predict how high residues will be on fruit at harvest; that’s going to depend on the copper formulation (fortunately some of the newer coppers utilize lower copper concentrations), rate of material used, spray coverage, and amount of rainfall from application to harvest. I am not aware of any information that establishes a nice, clean cut-off date or pre-harvest interval for avoiding excessive copper residues at harvest. There is also some evidence that late Captan sprays can cause problems in the winemaking process, in terms of delaying fermentation and negative effects on wine quality but the consequences seem less severe and irreversible. For more on this, consider this online article by Dr. Annemiek Schilder, former fruit pathologist at Michigan State University.
If you are protecting a non-bearing, young vineyard from downy mildew (you’re not selling/harvesting a crop), you can continue to use mancozeb products to control downy mildew past the 66-day pre-harvest interval. You can also consider using mancozeb after harvest to keep canopies clean of downy mildew and ‘firing on all cylinders’ until that first frost. The longer your vines can continue to produce and store carbohydrates after harvest, the better prepared they’ll be to withstand winter cold.
Fluffy, white downy mildew sporulation on the underside of a grape leaf
Good control of powdery mildew is also very challenging in wet years when humidity levels remain ‘through the roof’ and cloud cover occurs for extended periods of time. Now that we are largely past the fruit protection period, our focus is on keeping leaves clean, especially on V. vinifera, for about 6-8 more weeks. I say this for many of the same reasons expounded in the section about downy mildew (ensure optimal ripening of fruit and shoots/canes, ensure optimal cold hardiness, more effectively and more easily manage fungicide resistance, etc). But there is another very important reason, demonstrated by some excellent research conducted by Wayne Wilcox, Dave Gadoury and graduate students at Cornell University, who showed that controlling powdery mildew up to about Labor Day can also go a long way to reducing overwintering inoculum and disease pressure the following spring. Why Labor Day? When powdery mildew infected leaves die by that first hard frost in fall, the mildew on those leaves stops developing and also dies…unless it has had time to form fully mature, winter resistant structures called chasmothecia. In other words, if the chasmothecia in a powdery mildew colony on a leaf, do not have time to fully mature before the leaf dies, they will not be tough enough to survive the dormant period (winter) and will not contribute to the bank of primary inoculum that infection periods draw upon the following spring. Knowing this, a grower can get a better handle on the ‘size’ of the powdery mildew problems he/she will potentially face next spring and the spring after that, and so on. If, for example, you had heavy powdery mildew development earlier in this season (on clusters and/or leaves), expect to have to deal with powdery mildew early next season and you’ll have to take appropriate action during early shoot growth stages with preventive fungicide sprays. Once again, this is particularly important if you are growing Vitis vinifera and much less important for growers of native varieties like Concord and Niagara.
Greyish-white colonies of powdery mildew growing across the upper surface of grape leaves
Botrytis bunch rot control
If you’re growing bunch rot susceptible wine grape varieties, you have already applied a Botrytis specific fungicide at full bloom and probably pre-closure (?) This is because Botrytis infections can occur during bloom and early fruit development under wet conditions (which most of us have had). These Botrytis infections of the clusters usually remain dormant, or ‘latent’, and do not result in active rot of the fruit…until after veraison, when injury to berries or high humidity, or some other factor (research has not completely determined all the factors involved) may lead to activation of a percentage of these infections and cause clusters to rot.
In varieties with very compact clusters, the pre-closure application may be extremely important as it may be your last opportunity to get protective fungicide residues onto the interior surfaces of clusters. Along with the bloom spray, this spray will also help to reduce ‘latent’ Botrytis infections that continue to accumulate throughout the ‘green’ berry development period. The pre-closure spray may also be a good opportunity to clean clusters of bloom trash (dead cap and stamen tissue that got stuck in the clusters after bloom). Bloom trash provides a substrate for Botrytis and serves as a focal point for bunch rots to develop later in the season, from inside clusters. The compactness of clusters plays an important role in not only the retention of bloom trash (the tighter the cluster, the more bloom trash retained) but also the effect of retained bloom trash on cluster rot; as compactness increases, the enhancement of bunch rot by retained bloom trash increases.
Another bunch rot control measure is leaf removal around clusters, which we’ve already discussed above. It is an expensive operation to add to your production costs and is most cost-effectively applied by machine (machinery costs aside). We have found that it can be mechanized most effectively if vines are trained to a vertical shoot positioned (VSP) or some other two-dimensional trellis system with a relatively focused and narrow cluster zone. One additional benefit of leaf removal that I haven’t mentioned yet is the fact that it can also reduce bloom trash retained in clusters: when comparing clusters of vines treated with and without leaf removal, we noted a significant reduction in bloom trash where leaves were removed, regardless of timing or method (by hand or machine).
Our next fungicide application for Botrytis is made just before or at veraison. As fruit begin to soften and skins become thinner and more easily penetrated by fungal pathogens like Botrytis, an application at this time, to rot prone varieties, is a good way to stave off bunch rot development. After veraison, fruit also becomes more susceptible and more likely to become injured by birds, insects, excess moisture/humidity, and overcrowding of berries in tight clusters. Botrytis fungicides can protect intact fruit surfaces and may help to reduce the spread of Botrytis rot on fruit, even after they have become injured.
Lastly, an application about 2-3 weeks after veraison, especially under wet weather conditions, can reduce further rot development during the last stretch of ripening. Keep in mind that Botrytis fungicides control Botrytis and will not provide protection against sour rot organisms that often destroy the fruit of overly compact clusters, despite the application of a full Botrytis fungicide program.
And speaking of sour rot…
In case you haven’t already heard, there is some relatively new information on sour rot control that I would like to impart. It’s been included in previous blogs as well and that information was presented earlier this year at the Mid Atlantic Fruit and Vegetable Convention in Hershey PA. However, it bears repeating it here. It originated from work conducted by Dr. Megan Hall, a former graduate student of Wayne Wilcox at Cornell University, and it demonstrates how additional pesticide applications during the latter stages of ripening (beginning around 15 brix) can significantly reduce the development of sour rot, which for many premium wine grape growers in PA, is public enemy no. 1 at harvest. Her incredibly thorough work has shown a close connection between fruit flies and sour rot development. It turns out that the presence of the flies is important to the accumulation/generation of acetic acid in rotting fruit. Treatments composed of weekly, tank-mix applications of an insecticide (to control the flies) and an antimicrobial (to kill bacteria) have been found to reduce sour rots by 50-80% over unsprayed vines. So far, the best results appear to occur when weekly sprays are initiated before sour rot symptoms are observed (preventive sprays before about 15 brix). This exciting work should provide yet another effective option for sour rot control in the wet, humid parts of the eastern U.S. and we are looking forward to hearing more about this rot control option in the near future.
Lastly, don’t forget how important good canopy and fertility management is to the efficacy of your expensive Botrytis fungicide and sour rot pesticide applications. It’s always a good idea to make sure your shoots are well tucked and spaced within the catch wires, and summer pruning has removed shoots ends that may block sprays from thoroughly penetrating the fruit zone, just before you make each Botrytis fungicide application. We like to wait as long as possible to trim shoot tips because of the effect on lateral growth stimulation, but make sure excessively long shoots have not flopped over to block spray penetration into the fruit zone. Limiting shoot growth after veraison with good canopy and fertility management will also limit the supply of new green tissue that is hyper susceptible to powdery and downy mildew and will contribute to more effective late-season management of these diseases as well.
For further reading on this and many other disease management topics, refer to the 2019 New York and Pennsylvania Pest Management Guidelines for Grapes. If you don’t have a copy, you can get one through Cornell University Press. Every commercial grape production operation should have one!
By Dr. Molly Kelly, Enology Extension Educator, Department of Food Science
As we approach harvest, we should be reviewing our sanitation protocols both in the vineyard and winery. In this article we will focus on effective cleaning and sanitizing in the winery, specifically winery equipment to make sure certain objectives are met:
- To continually improve wine quality
- To reduce quality concerns
- To ultimately operate cost-effectively…by annually producing both a quality wine and reaching the targeted financial return
- To reduce food safety concerns
Stainless Steel Winery Equipment
During normal service, all grades and finishes of stainless steel may in fact stain, discolor, or attain an adhering layer of grime. What considerations should one take regarding maintaining stainless steel equipment and the related use of cleaners and sanitizers? The frequency and cost of cleaning stainless steel is lower than for many other materials and often out-weighs the higher acquisition costs. Generally, the frequency of cleaning should be determined by the objective to “clean the metal when it is dirty in order to restore its original appearance.”
So, the degree of cleaning depends on the condition of stainless steel equipment:
- Routine Maintenance – mild cleaning
- Mildly aggressive cleaning to remove minor surface dirt: use sponge or bristle brush with a non-abrasive cleaner and warm water; towel dry. To prevent compromising the integrity of the protective oxide coating on stainless steel, only soft-bristle brushes should be used in the case where scrubbing is required.
- More aggressive, for example, grease: repeat above, then use a hydrocarbon solvent such as acetone or alcohol.
- Aggressive cleaning to remove stains or light rust: use a chrome, brass, silver cleaner and mild non-scratching creams and polishes.
- Most aggressive to remove stubborn mineral deposits: use phosphoric acid (10-15% solution) – apply with a soft cloth and let stand; no rubbing. Follow with ammonia and water rinse; rinse with hot water. Note that nitric acid is effective too but tends to degrade gasket material.
General Cleaning and Sanitizing Sequence:
1. Begin with a cold water, high-pressure rinse. Cleaning with high-pressure is most effective when the spray is directed at an angle to surface being cleaned. One may also use warm water (100-109 F) in high-pressure systems; this tends to reduce time.
2. Use a strong inorganic alkaline solution; such alkaline cleaners effectively dissolve acid soils and food wastes. Examples of alkaline cleaning agents are caustic soda (NaOH), soda ash (Na2CO3), trisodium phosphate (TSP) and sodium metasilicate. Carefully follow instructions because such alkalis are very corrosive to stainless steel if used incorrectly. A mild acid (citric) will neutralize alkaline detergent residues, dissolve the mineral deposits and prevent spotting. As a rule, soda ash rinses better than caustic soda.
3. Continue with a cold water, high-pressure rinse.
4. Sanitizer Options:
a. Water and Steam
- Hot water (180 F) and steam are ideal sterilants: they are noncorrosive, penetrative of surfaces, and effective against juice/wine microorganisms.
- Use hot water for 20 minutes (at 180 F).
- If steam, use until condensate from valves reaches 180 F for 20 minutes.
b. Quaternary ammonium compounds (QACs), combined with peroxyacetic acid.
Note that “acid-anionic” sanitizers such as peroxyacetic acid are effective at lower than ambient temperatures; remove biofilms; and are effective against bacterial spores. The low foam characteristics make them ideal for Clean-in-Place (CIP) applications. Although peroxyacetic acid must be used in well-ventilated area, it is ecologically harmless by decomposing into acetic acid, oxygen, and water.
- Rinse: QAC solutions may leave objectionable films on equipment and should be rinsed off with fresh cold water, high-pressure rinse.
- Final rinse: a hot water, high-pressure rinse. Ideally, heat-sterilized water should be used for this final rinse.
- Ozone treatment (optional)
- NOTE: Remember to remove tank valves, take apart and clean prior to harvest.
There are many different barrel cleaning methods:
- High-pressure water, hot or cold
- Caustic chemicals
- SO2 (in any form: wicks, liquid, gas)
- Dry ice blasting
In selecting which method to use, consider the effects on aroma/flavor extraction, tartrate removal, microbial reductions, water usage, power usage, worker safety, and cost.
The following are recommended cleaning and sanitizing sequences, based on barrel status.
New Barrels/Fault-Free Barrels
- Cold water, high-pressure rinse, 1-3 minutes
- High-pressure steam rinse, 1-3 minutes
- Repeat cold and steam rinses twice more
- Either refill with clean wine or
- Fill with water
- add ozone, if available
- follow with water + 45 ppm SO2/90 ppm citrate
- Fill with water
- After 1-4 days, empty and refill with wine or empty and burn sulfur wick, re-bung, and store; or, if using the gas, inject SO2for three to five seconds.
- If the barrel is to be long-term stored, dissolve and add 45 grams of potassium metabisulfite (KMS) and 180 grams of citric acid; then top the barrel with water. Be sure to top the barrel with plain water every couple of weeks. When you’re ready to use the barrel, empty and rinse twice; then fill with wine.
Likely Fault-Free Barrels, but Unsure
- Sodium percarbonate washes (Proxycarb) are an excellent option for addressing potential off-flavors. Citric acid washes are then used to neutralize residual chemicals. Once the barrel has been cleaned, allow the barrel to dry completely on a rack with the bunghole facing down. Sodium percarbonate is better than hydrogen peroxide: it is more stable at application concentration (100-200 mg/L), has improved compatibility with hard water, and reduced foaming tendencies.
- When the barrel is dry, burn 10-20 grams of sulfur wick per barrel; or, if using the gas, inject SO2 for three to five seconds.
- Place either a paper cup, wooden shipping bung, or other in the bunghole.
- Check sulfur level every 3-4 weeks and re-sulfur as necessary.
Tannin and Tartrate Deposit Removal
- Removal of tannins: Alkaline solutions (soaking with 1% sodium carbonate) are most effective in removing tannins from new barrels. If further treatment is necessary, steam and several rinses should be applied.
- Removal of tartrate deposits: scraping is labor intensive and may injure wood. Instead, use a circular spray head. For stubborn deposits, soaking with 1 kg of soda ash and caustic soda in 100 L of water is effective.
- Option 1: Remove from winery and sell for non-wine uses
- Option 2: Clean, sterilize, and re-use, if worth the cost
- Use same rinse cycles as per barrels without faulty aromas or tastes.
- Fill with water, put steam wand in water and bring water to 160-180°F, steam periodically to maintain temperature for 4-6 hours and
- add ozone, if available
- follow with water + 45 ppm SO2/90 ppm citrate
- After 1-4 days, empty and burn sulfur wick, re-bung, and store.
- After 1-4 weeks, rinse and fill with clean water; after 1 week, take samples and then add 90 ppm SO2/180 ppm citrate while doing microbiological assay of samples.
- If samples are negative for spoilage microorganisms, re-use barrel, but sample periodically.
Bottling Room Equipment
The bottling and packaging function is one of the most critical steps in wine production because there are many opportunities for problems (people with different responsibilities, multiple wines to bottle, and operation and maintenance of multiple equipment stations).
Are sterile bottling rooms necessary? No, but the bottling area should be screened-off from fermentation areas and excessive air movement, and the room itself should have easily sanitized floors, walls, and ceilings.
General Cleaning and Sanitizing Sequence:
- Cold water, high-pressure rinse
- Mild alkaline detergent solution
- Cold water, high-pressure rinse
- Quaternary ammonium compounds (QACs), combined with peroxyacetic acid.
- Cold water, high-pressure rinse
- Sanitization: Hot water and steam used to sanitize bottling line
- 80-90F for 30 minutes
- 180F for 20 minutes; or
- Ozone for 20-30 minutes; or
- Use of iodophors (iodine-based sanitizers): broad-spectrum – active against bacteria, viruses, yeasts, molds, fungi. Follow instructions carefully to avoid potential TCA problems; follow with a hot water, high-pressure rinse.
Prior to bottling, add enough SO2to ensure enough free SO2for 0.8 ppm molecular SO2. Add a little bit extra – to account for free SO2loss during bottling. Generally, target a free SO2that is 10 to 15 ppm higher than the level of free SO2needed for 0.8 ppm molecular SO2. Also, target more or less depending on trauma of bottling method (O2pick up)
Recommendations during operation of the bottling line:
- Wine spills as a source of contamination should be countered by regular and proper cleaning
- Filter-pad trays should be emptied often, and related wine spills quickly rinsed away with a sanitizing agent
- Fill bowls: Mist filler spouts with 70% ethanol to inhibit microbial growth
- Corker: will likely have spilled wine, so use ethanol misting of corker jaws during bottling
- Floor drain gutters should be kept clean by frequent rinsing
- Activity: Limit number of people around the filling/corking area
- Daily sanitation…hot water or steam…20 minutes at 180F
- At least weekly, clean with caustic cleaners followed by hot water sanitation.
- Collect bottles for analysis hourly and immediately after start-up and breaks.
Butzke, C., Barrel Maintenance, Dept. of Food Science, Purdue University, 2007.
Carter, James, There’s a Right Way to Clean and Sanitizing your Facility, Food Quality.com
Donnelly, David M, Airborne Microbial Contamination in a Winery Bottling Room, Am. J. Enol Vitic, Vol 28, #3, 1977
Fugelsang, Kenneth; Edward, Charles G. Wine Microbiology, 2nd Edition, 2010. Springer-Verlag New York Inc. (Chapter 9, Winery Cleaning and Sanitizing)
Marriott, Norman G.; Gravani, Robert B. Principles of Food Sanitation, 5thEdition, 2006. Springer Science + Business Media, Inc. (pp 361-367)
Howe, P., ETS Laboratories, SOWI “Current Issues” Workshops March 2011.
Menke, S., Cleansers and Sanitizers, Penn State Enology Extension, 2007.
Tracy, R. and Skaalen, B. Jan/Feb 2009. Bottling-last line of microbial defense. Practical Winery and Vineyard
Worobo, Randy W., Non-chlorine Sanitizer Options for the Wineries, 33th Annual New York Wine Industry Workshop
Zoecklein, B. et al, Wine Analysis and Production, Aspen Publishers, 1999.
Barrel Care http://www.boswellcompany.com/barrel-care/
Maintaining and Cleaning Stainless Steel http://www.evapco.eu/sites/evapco.eu/files/white_papers/40-Cleaning-Stainless-Steel.pdf
Stainless Steel – Cleaning, Care and Maintenance http://www.azom.com/article.aspx?ArticleID=1182
Taking Care of Your Barrels https://barrelbuilders.com/wp-content/uploads/2016/06/06-16-Barrel-Care.pdf
Dr. Michela Centinari, Assistant Professor of Viticulture, Department of Plant Science
Another growing season has started for many Pennsylvania grape growers. Unfortunately, but not surprisingly, we are seeing and hearing of situations of vine winter injury across the State. This past winter, the lowest temperatures occurred at the end of January and during the first two days in February, with values around -5 °F (-20.6 °C) here in State College (central PA) and even lower temperatures were recorded at other locations.The injury seemed to have mainly affected Vitisviniferavarieties with reports of bud kill up to almost 100% for the most cold-sensitive varieties and, in some cases, trunk splitting.Growers also noticed uneven /nonuniform budburst which is typical of winter-injured vines. We ask that more growers share their experiences with us; in particular, we would like to know if growers made any pruning adjustments and what the results are/have been.
Since winter injury is a reoccurring issue for the eastern US, during certain years, we have covered topics related to vine cold hardiness, injury assessment, and pruning techniques for winter-injured vines at Extension meetings. Also, we have posted an announcement that focused on Pruning strategies for cold climate viticultureon the Penn State Viticulture and Enology Facebook page in January 2019, just before the “Arctic Vortex” event hit our region. Please do not hesitate to contact us if you have questions on how to manage cold-injured vines.
We heard from several PA growers in southern and central PA that budburst occurred earlier this year, a week to 10 days is what has been typically reported, than in 2018. This was also true for the hybrid varieties grown at the Penn State research farm at Rock Springs (central PA). I checked the growing degree days (GDD), a widely used index of heat accumulation, data calculated by the Network for Environment and Weather Applications (NEWA Cornell) for weather stations located in North East, Erie (northwestern PA), Biglerville (south-central PA), and Reading (southeast PA). Although historic data are not available, I compared the average GDD accumulated from January 1 to May 15 for 2013-2017 to those accumulated for the same period in 2018 and 2019 (Figures 1, 2 and 3).
Trends across locations/regions
Not surprisingly, it was cooler in Erie compared to south-central and southeastern PA between January to Mid-May, not just in 2019 but for each year analyzed. In 2019, approximately 158 GDD accumulated between January 1 to May 15 in Erie, while GDD were at least double in south-central and southeast PA. Differences in temperatures across regions and locations explain why budburst typically occurs much earlier in southeast PA compared to the northwestern part of the state.
Difference between years
In Erie, the GDD accumulated between January to mid-May 2019 (red line) were slightly lower than those for the same period in 2018 (blue line) and for the 2013-2017 average (black line). Also, note that there was no accumulation of GDD for a few days in May 2019 due to cool temperatures (Figure 1). The trend, however, was opposite in south-central and southeast PA, at least at the locations reported in this post. April was warmer (higher GDD) in 2019 compared to 2018 and the 2013-2017 average. While warmer spring temperatures favor earlier budburst they also increase the chance of freeze injury to green, tender plant tissues (Figure 4).
At several locations across PA, temperatures were below freezing in the early morning of April 29 and some varieties were close to or already passed budburst. Below freezing temperature does not necessarily mean freeze injury as many factors affect the temperature at which the plant tissue is damaged or killed. However, the freeze event on April 29 did cause freeze damage to vines at several locations, while others avoided the damage by using frost protection methods, such as frost dragons. Some of the varieties grown at the Penn State research vineyard at Rock Springs, chiefly Marquette and young LaCrescent vines, sustained freeze injury. It is too early to estimate crop losses, but at least we are seeing some secondary shoot development (Figure 5).
How to recognize a secondary from a primary shoot
A relatively easy way, especially for caned pruned vines, is to check the angle of projection from the cane. Primary shoots typically grow with an angle of 45°, while secondary grow at an angle of 90° (figure 5).
You can learn more about the basics of spring freeze injury and methods of protection at https://extension.psu.edu/understanding-and-preventing-spring-frost-and-freeze-damage
It is almost time for some early season canopy management practice. Please check the following articles if you need information on shoot thinning or early leaf removal:
On March 5, 2019, Penn State researchers and Extension personnel presented research findings and provided five-minute overviews of upcoming studies at the 2019 Wine Marketing & Research Board Symposium, held in conjunction with the Pennsylvania Winery Association Annual Conference.
In this post, we have included short summaries of what each presenter discussed during their session along with a PDF/access to their presentation.
Under-vine cover crops: Can they mitigate vine vigor and control weeds while maintaining vine productivity?
Presented by Michela Centinari, Assistant Professor of Viticulture, Suzanne Fleishman, Ph.D. Candidate, and Kathy Kelley, Professor of Horticultural Marketing and Business Management
Michela, Suzanne, and Kathy discussed research conducted at Penn State related to the use of under-vine cover crops as a management practice alternative to herbicide or soil cultivation. Michela reviewed potential benefits of under-vine cover crops, such as reduction of excessive vegetative growth, weed suppression, and reduced soil erosion. She showed how the selection of cover crop species depends on the production goals of a vineyard, climate, vine age, and rootstock. Suzanne presented results from her research project. She is investigating above- and belowground effects of competition between a red fescue cover crop and Noiret grapevines, comparing responses between vines grafted to 101-14 Mgt vs Riparia rootstocks. Surveys will be administered to Pennsylvania grape growers and wine consumers in the Mid-Atlantic region. Growers will be asked to respond to questions about interest in using cover crops and benefits that could encourage their use. The consumer survey will focus on learning whether cover crops use would impact their purchasing decision and if they would be willing to pay a price premium for a bottle of wine to offset additional production costs.
Impact of two frost avoidance strategies that delay budburst on grape productivity, chemical and sensory wine quality.
Presented by Michela Centinari, Assistant professor of Viticulture
Crop losses and delays in fruit ripening caused by spring freeze damage represent an enormous challenge for wine grape producers around the world. This multi-year study aims to compare the effectiveness of two frost avoidance strategy (application of a food grade vegetable oil-based adjuvant and delayed winter pruning) on delaying the onset of budburst, thus reducing the risk of spring freeze damage. Our objectives are to: i) evaluate if the delay in budburst impacts grape production and fruit maturity at harvest, as well as chemical and sensory wine properties; ii) elucidate the mechanism of action of the vegetable oil-based adjuvant through an examination of bud respiration and potential phytotoxic effects; and iii) assess the impact of the two frost avoidance strategies on carbohydrate reserve storage and bud freeze tolerance during the dormant season.
Toward the development of a varietal plan for Pennsylvania wine grape growers.
Presented by Claudia Schmidt, Assistant Professor of Agricultural Economics, and Michela Centinari, Assistant Professor of Viticulture
Claudia Schmidt is a new Assistant Professor of Agricultural Economics with an extension appointment at Penn State. Claudia used the opportunity of the symposium to introduce herself to the industry. In her presentation, she first gave an overview on what and where Pennsylvanians buy their wines and spirits. She then talked about the research needed to develop a varietal plan for the Pennsylvania grape and wine industry to match existing and future grape production and variety suitability with anticipated consumer demand. The immediate next steps on her research agenda are to develop a baseline survey of grape production in Pennsylvania and, in collaboration with Michela Centinari, region specific cost of production of grapes.
Survey for grapevine leafroll viruses in Pennsylvania: How common is it, and how is it effecting production and quality?
Presented by Bryan Hed, Research Technologist
This is a continuing project funded by the PA Wine Marketing and Research Board, that has focused on the determination of the incidence of grapevine leafroll associated virus 1 and 3 (the two most economically important and widely distributed of the leafroll viruses) in commercial vineyard blocks of Cabernet franc, Pinot noir, Chardonnay, Riesling, and Chambourcin, across the Commonwealth. Over two years, the survey has shown that grapevine leafroll associated viruses 1 and/or 3, were present in about a third of the vineyard blocks examined. Infection of grapevines by grapevine leafroll-associated viruses can have serious consequences on yield, vigor, cold hardiness, and most notably fruit/wine quality. Bryan also discussed a second phase of the project, anticipated to continue for at least another two years within 6 vineyard blocks of Cabernet franc, identified in the survey. In these vineyards, we plan to plot the spread of these viruses, examine and report their effects on grapevine vegetative growth, yield, and fruit chemistry, and characterize the influence of inter- and intra-seasonal weather conditions on virus-infected grapevine performance.
Integrating the new pest, spotted lanternfly, to your grape pest management program.
Presented by Heather Leach, Extension Associate
Spotted lanternfly (SLF) is a new invasive planthopper in the Northeast U.S. that threatens grape production. Heather covered the basic biology, identification, and current distribution of SLF. She also presented on the economic impact of SLF in the grape industry and ways to manage SLF in your vineyard. SLF can feed heavily on vines causing sap depletion in the fall which has resulted in death of vines, or failure of vines to set fruit in the following year. While biological controls such as pathogens and natural enemies along with trapping and behaviorally based methods are being researched, our current management strategy relies on using insecticides sprayed in the vineyard. Heather showed results from the 2018 insecticide trials conducted against SLF, with efficacy from several products including bifenthrin, dinotefuran, thiamethoxam, carbaryl, and zeta-cypermethrin. You can read more about the results from this trial here: https://extension.psu.edu/updated-insecticide-recommendations-for-spotted-lanternfly-on-grape
Five-minute research project overviews
Impact of spotted lanternfly on Pennsylvania wine quality.
Presented by Molly Kelly, Extension Enologist
The Spotted Lanternfly (SLF) presents a severe problem both due to direct damage to grapevines as well as their potential to impact wine quality. Insects are known to produce or sequester toxic alkaloid compounds. The objectives of this study include characterizing the chemical compounds in SLF and production of wines with varying degrees of SLF infestation. We can then provide winegrowers with recommendations for production of wine from infested fruit. Toxicity studies will be conducted to determine the levels of toxic compounds in finished wine, if any, using a mouse bioassay.
Exploring the microbial populations and wild yeast diversity in a Chambourcin wine model system.
Presented by Chun Tang Feng, M.S. Candidate, and Josephine Wee, Assistant Professor of Food Science
In Dr. Josephine Wee’s lab, we are interested in the microbial population and diversity associated with winemaking. When it comes to wine fermentation, not only are commercial yeasts involved in this process, but also many indigenous yeasts. Our research goal is to isolate the wild yeasts and assess their feasibility of wine fermentation. We are expecting to explore the unique yeast strains from local PA which are able to make a positive impact on wine flavor.
Rotundone as a potential impact compound for Pennsylvania wines
Presented by Jessica Gaby, Post-Doctoral Scholar and John Hayes, Associate Professor of Food Science
This study will examine Pennsylvania consumers’ perceptions of rotundone with the goal of determining whether a rotundone-heavy wine would do well on the local market. This will be examined from several different perspectives, including sensory testing of rotundone olfactory thresholds, liking and rejection thresholds for rotundone in red wine, and PA consumer focus groups. The ultimate aim of the study is to determine the ideal concentration of rotundone in a locally-produced wine that would appeal to PA consumers.
Defining regional typicity of Grüner Veltliner wines
Presented by Stephanie Keller, M.S. Candidate, Michela Centinari, Assistant Professor of Viticulture, and Kathy Kelley,
Grüner Veltliner(GV) is a relatively new grape variety to Pennsylvania, and while climatic conditions are favorable to its growth, the Pennsylvania wine industry is still becoming familiar with the varietal characteristics of GV grown and produced throughout the state. This study focuses on defining typicity of Pennsylvania-grown GV wines. Typicity is described as the perceived representativeness of a wine produced from a designated area, and defining typicity can improve wine marketing strategies. This study uses multiple experimental sites across the state to create wines from a standardized vinification method. The wines will be analyzed using both instrumental and human sensory methods.Surveys will be administered to Pennsylvania grape growers and white wine consumers in the Mid-Atlantic region. Growers will be asked their interest in growing GV and what perceived and real barriers may impact their decision to grow the variety. The consumer survey will focus on understating how to introduce them to a wine varietal they may be less aware of and what promotional methods may encourage them to purchase the wine.
Boosting polyfunctional thiols and other aroma compounds in white hybrid wines through foliar nitrogen and sulfur application?
Presented by Ryan Elias, Associate Professor of Food Science, Helene Hopfer, Assistant Professor of Food Science, Molly Kelly, Extension Enologist, and Michela Centinari, Assistant Professor of Viticulture
The quality of aromatic white wines is heavily influenced by the presence of low molecular weight, volatile compounds that often have exceedingly low aroma threshold values. Polyfunctional varietal thiols are an important category of these compounds. This project aims to provide research-based viticultural practices that could lead to increases in beneficial varietal thiols in white hybrid grapes. The expected increase in overall wine quality will be validated both by measuring the concentrations of these desirable compounds (i.e., thiols) in finished wines using instrumental analysis and by human sensory evaluation, thus providing a link between the viticultural practice of foliar spraying and the improvement of overall wine quality.
By Bryan Hed, Andy Muza, and Michela Centinari
For this week we would like to devote our blog to Jody Timer, our grape insect pest specialist at the Lake Erie Regional Grape Research and Extension Center in North East, PA, who retired at the end of February.
Jody came to work at the Penn State research center in August of 2004, filling a position long since vacated by her predecessor, Sudha Nagarkatti. With an M.S. degree in Biology and many years of experience monitoring water quality and chemistry for a company in the North East area, Jody was hired to work at the North East lab as a skilled technician for Dr. Michael Saunders of the Entomology Department at the University Park campus. From day one, Jody was a passionate researcher for grape growers in the Lake Erie Region and eventually the whole state for almost 15 years (how the time flies!). Her main research has always focused on control methods for the grape berry moth and how this knowledge can be applied to management programs. In that regard she and her technician, Mike Schultz, have spent countless hours each season monitoring berry moth populations on several local commercial farms in the Lake Erie region, and working closely with Andy Muza, Erie County extension, to provide real-time updates on pest pressure for local juice grape growers.
She has also played key roles in the study of a number of invasive pests like Japanese beetle, Multicolored Asian Lady Beetle, Brown Marmorated Stinkbug, Spotted Wing Drosophila, and most recently, Spotted Lanternfly. One of my most memorable moments in working with Jody was my involvement in one of her experiments to taste test stink bug tainted Concord grape juice; one of the reasons I shudder at the mere mention of ‘cilantro’.
Jody’s position was mostly devoted to conducting research but she often played the part of teacher through extension presentations of science-based recommendations for grape growers at regional meetings like the Mid-Atlantic Fruit and Vegetable Convention in Hershey, PA; statewide meetings like the spring grape disease and insect pest workshop; and local extension meetings such as coffee pot meetings and the mid-summer chicken BBQ in the Lake Erie region. Jody is also a world traveler and, having been to many exotic places across the world, she has a unique and heightened perspective that most people only experience through TV and books. I’m sure that she is looking forward to seeing many more places with her husband, Rich, after her retirement. For those of us who worked closely with Jody over the years, she will also be remembered for her hard work ethic, devotion to her family, and her great sense of humor. Jody’s retirement will leave a large hole in our grape team and our efforts to serve the grape growers of Pennsylvania. We wish her well in her retirement.