Matthew Clark, Assistant Professor
About 65 people attended the annual Grape Fall Tour hosted on September 10 at the Horticultural Research Center. The 2 hour event included sampling grapes from the research vineyards, learning about insect and disease pests, demonstrations in the field, as well as a short lecture on soil nutrition as it relates to winemaking.
Attendees were welcomed at the registration table and given a new copy of “Growing Grapes in Minnesota”, which was hot off the press that morning. The updated manual published by the Minnesota Grape Growers Association is a modernized version of the best practices guide, complete with spiral binding, color images, updated tables, new content, and web resources.
The event started with a brief introduction of the staff and a review of the year’s events. Dr. Clark described research findings on wine making, genetic work for disease and insect resistance, the release of the ‘Itasca’ grape in 2016, and plans for the future which include additional focus on breeding table grapes.
An open grape tasting was held which allowed the attendees to try a curated collection of fruit grown at the HRC. Jenny and John Thull selected samples to reflect unique attributes of the fruit that are important in wine making and targets for the breeding program. This included Vitis vinifera samples that are familiar to wine drinkers worldwide. In addition there were high tannin varieties to help the tasters experience how the juice (and later the wine) interacts with the mouth. There were also samples of Vitis labrusca hybrids and cultivars, primarily from Elmer Swenson breeding material. Additional, a table we set with ‘muscat’ varieties, which have unique flavors and aromas that are different from the other hybrids and are often desirable in table and wine grapes. A selection of table grapes were often shown. Unfortunately, many of these do not perform well in Minnesota without protection or growing strategies to reduce winter injury (such as burying the vines). Of course, the common wine cultivars grown in Minnesota were available for tasting. Some new breeding selections were also on display.
Professor and Department Head, Carl Rosen, of the Dept. of Soil, Water, and Climate, gave a short lecture on vine nutrition and its effects on wine and juice. This was a brief report at the conclusion of the Northern Grapes Project (northerngrapesproject.org).
The HRC staff demonstrated new bird netting equipment that was donated by Plantra which allows for easy over-the-vine netting to be deployed with three laborers. The pull-behind device uses a reusable, soft knit net called AviGard® Flex™ Diamond Mesh Net. Also on display were bins and other equipment from MDT and Associates. Finally, the attendees were able to walk through some of the vineyards and see young plantings of ‘Itasca’ and ‘Marquette’ grown in VSP.
John Thull, Vineyard Manager
Matt Clark, Assistant Professor, Extension Specialist
Tracking the weather conditions at each vineyard site is something that growers should be doing over the winter months. Despite most of the grape varieties being ‘cold-hardy’, winter injury can come in many forms and cause damage. Winter injury can result from large shifts in temperature (more common in South Dakota), low temperature injury, repeated low temperature injury, bare soils, wind damage, and late spring frosts. Not only are vines impacted, but winter conditions also have a role in insect population life cycles.
The snow that most of the state received this past weekend (12/10-12/11) is well timed to provide insulation for the roots and bases of the vines. However, most of the vine is still above the snow-line and therefore these parts (trunks, cordons, canes) will be exposed to the low temperatures coming during the next couple of months. A pending polar vortex this week is predicted with lows in the negative single digits (Fahrenheit), something most cold-hardy hybrids should be able to endure if they had sufficiently acclimated for winter by responding to the shorter days and cooler temperatures.
How much cold a vine can endure depends on the state or condition of that vine going into winter. Stresses and environmental conditions from that growing season (rainfall amounts, growing degree days, solar radiation intensity, crop load, etc.) vary from year to year. Therefore, the cold temperature minimum that a vine can tolerate before suffering little cold injury will naturally change every season as well. For example, some years Frontenac can see -30°F with little or no damage and other times we may see Frontenac getting damaged already in the -20's range.
Without snow cover, the roots of the vines may see some damage, especially on newly planted vines, which can lead to symptoms of stunted growth and/or nutrient deficiencies in the next season. With a delivery of snow, the temperature drop below zero for a few days should have less of an impact. However, this may also favor Japanese beetle grubs which will also benefit from the insulation effects of the snow.
Monitoring the weather and vine health throughout the winter may seem like a chore, but it can help to set the vineyard manager up for success for the coming spring. For example, monitoring bud survival through the winter can inform pruning in the spring. Weather monitoring (all season long) is one of the best tools for understanding the yearly variation and to help in predicting insects, diseases, and also injury during the dormant season. Keeping these events in mind will help growers understand why their vineyards behave as they do during the upcoming growing season.
Drew Horton, Enology Specialist
Matt Clark, Assistant Professor
No doubt about it, one of the worst things that can happen with a wine is re-fermentation in the bottle. Instead of a beautifully-colored wine with brilliant clarity, you discover a once-perfect wine has become cloudy and bubbly, or even worse, numerous "bottle bombs" are exploding in the cellar or on winery or retail shelves, or at the least, corks are pushing out of the bottle. This is a disaster.
Whenever there is any amount of unfermented sugar in a bottle of wine, the wine risks re-fermenting. This article is really about sweet white or rosé wines, but also applies to any non-dry red wine as well.
There are a variety of methods, techniques and additions that can help eliminate or reduce this risk.
Firstly, overall winery sanitation is the most important. Each and every surface; tank, pump, hose, valve, bottle-filler, or corker that comes into contact with wine must be clean and sanitized. There are many ways to sanitize, but none of them will work unless the surface is first cleaned. Cleaning is the removal of dirt or other residue from a surface, sanitizing is the killing of all microbes on a surface. A wine maker needs to do both when handling any sweet wine.
When preparing a wine for bottling, the first step after blending (if any blending is to be done) is to treat the wine with bentonite, which removes excess protein and keeps the wine heat stable. A complete and exhaustive article on the use of bentonite is available on the internet, posted by Purdue University Extension: https://www.extension.purdue.edu/extmedia/fs/fs-53-w.pdf
After the bentonite treatment, some method of achieving cold-stability must also be done. Traditional cold-contact treatments are the norm, but they do require the wine be super-chilled. This means bringing the wine close to, or just at, freezing for a period of 5 to 15 days, depending on the amount of excess tartaric acid in the wine, among other variables. It should be noted that there are new preparations of manno-proteins and cellulose that can provide almost instant cold-stability, but they lack the often-beneficial side effect of traditional cold-contact stabilization which can reduce the overall total acidity in a wine by precipitating excess tartaric acid in the form of crystals. See this link to the Laffort website for alternate cold-stabilization methods and products: http://laffort.com/en/products/stabilisation
Electrical conductivity tests can be done by a laboratory to confirm that cold-stability has been achieved. In the Midwest, Iowa State University's Midwest Grape & Wine Industry Institute can conduct this testing quickly and for a small fee, see this link to their Lab services order form: http://www.extension.iastate.edu/wine/sites/www.extension.iastate.edu/files/wine/PriceList-May%202016.pdf
The addition of a sweetener (sugar, sweet reserve juice, or concentrate) should happen late in the wine preparation process, usually between a nominal rough and polish filtration step is best. Any extra time a wine is in storage with any sugar it risks re-starting fermentation. During the aging and storage period for a wine with existing natural residual sugar, you are advised to pre-filter the wine and keep the wine at a cold-enough temperature (45F degrees or less) and with sufficient free sulfur (based on wine pH) in order to inhibit re-fermentation.
So, with this now blended, heat and cold stabilized wine, you are ready to start final filtration and any final sweetening. Keep in mind when discussing filtration that there are both "nominal" and "absolute" filtration equipment and techniques. Nominal filtrations are achieved by the use of sheet or pad filtration, sometimes used with DE (diatomaceous earth), in a plate and frame type of filter. Cross-flow filtration, though it does not require DE or filter sheets, is also to be considered a nominal filtration and not "absolute".
Nominal filtration (sometimes called depth filtration) will remove 99.9% of bacteria and yeast cells. Only absolute (aka sterile membrane) filtration will keep the wine 100% free of bacteria and yeast cells. Sterile membrane filter cartridges and housings are not inexpensive, and they must be integrity-tested both before and after use. If a wine is not pre-filtered well, membranes will plug quickly. Here is a link to the bubble-point method to test sterile cartridge membrane integrity: http://www.scottlab.com/uploads/documents/downloads/25/ScottCart%20Bubble%20Point%20Test%20.pdf
In lieu of the use of absolute sterile membrane filtration, and the use of strict chemical or heat sterilization of all bottling/capping/corking equipment, you can consider the use of a yeast fermentation inhibitor such as Sorbic acid, usually used in the form of powdered Potassium Sorbate. The big issue with sorbate is that it does not guarantee stabilization, and it must be used properly and in conjunction with proper levels of free sulfur. Also, if used in large amounts, or in a wine that may undergo spontaneous malo-lactic fermentation, there is a risk of "geranium-smell taint." Also, above a certain level, some consumers will notice the smell and taste of sorbate. Here is a link to an article on the nature and proper use of sorbate : http://www.extension.iastate.edu/wine/sites/www.extension.iastate.edu/files/wine/SorbicAcid1.pdf
If you are able to produce a sweet wine with alcohol at or above 13% and a pH below 3.5, then sorbate may be an option to help stabilize the wine without the use of absolute sterile membrane filtration, and without the risk of geranium taint. A low alcohol wine (say 11% or below) with high pH (above 3.6) and any amount of residual sugar is virtually impossible to stabilize and guarantee stability without the use of a high-speed bottling line utilizing integrity-tested absolute sterile membrane filter equipment.
Keep in mind, though, that an absolute sterile membrane is only a doorway, with dirty on one side and sterile on the other. Any downstream equipment (i.e., post-membrane), such as valves, hoses and bottle-filler that are not also completely sterile, can allow even a few bacteria or yeast cells to enter the bottle, and can lead to re-fermentation. If you have ever spent a few hours, or days, "de-corking" and attempting to re-treat and re-bottle a wine that has become unstable or is re-fermenting, you will take the preceding to heart.
Drew Horton, Enology Specialist
Matthew Clark, Assistant Professor
Each wine harvest season as the picking ends and the last wines are completing primary yeast fermentation, it is often asked about how to know when your secondary or "malolactic" fermentation has completed? "MLF", as it is known, is a bacterial fermentation that can occur naturally, or as an addition, in a wine, which converts most of the stronger or harsher malic acid into the softer and "rounder" lactic acid. Think of malic as the "green apple" acid and lactic as the weaker acid in dairy products; cream, butter, cheese, and etc. as the names imply. MLF can change the sensory perception of the wine (less sour due to lower TA and higher pH) as well as changes in the mouthfeel with the development of additional compounds that add to a wine’s body such as glycerol.
99% of the red wines made in the world are allowed or encouraged to complete MLF as one of the beneficial effects of MLF is to lower total acidity in a wine. Its use in white wines is mostly limited (to Champagne and white Burgundy wines) as it can negatively mute and/or alter the fresh fruit flavors and aromas in most white wines.
Paper Chromatography is an easy and inexpensive method used to determine if MLF has finished, or completed. A kit with solvents and paper for analyzing 50 wine samples can be purchased on-line through various vendors including www.piwine.com, who have a kit for $60: http://www.piwine.com/chromatography-test-kit-vertical-paper.html
Testing is easy to do and the results are simple to read. Figure 1 is a sample of a test executed on four red wines here at the UMN Horticulture Research Center. Three standards are utilized (tartaric, malic, and lactic acid) to show their migration and serve as a reference to the wine samples. In this case, all 4 wines have undergone MLF, as there is very little malic acid evidence on the chromatograph.
Follow the manufacture directions carefully. Special consideration should be taken as the solvent used does require a place with adequate ventilation. The paper can be dried overnight in a garage or shed or other place with sufficient ventilation.
There are other options available from commercial labs to test your MLF, but they can start to get expensive if you are doing multiple wines and if you include shipping time and cost.
Figure 1. Paper chromatograph showing the three acid standards (tartaric, malic, and lactic acid) and 4 wine samples. The reference standards show the relative migration of the compounds in each sample in the direction of the solvent. You can see that lactic acid moves the farthest on the chromatograph. There is little evidence for malic acid remaining in the wine samples as shown in the rectangle. However you can see that tartaric acid remains.
Volatile Acidity in Wine Making
Drew Horton and Matthew Clark
Dept. of Horticulture, University of Minnesota
Volatile Acidity, or "VA", is caused by a type of bacterial spoilage which produces large amounts Acetic acid (vinegar) which is a serious wine fault, the metabolization of acetic acid and alcohol (ethanol) can produce ethyl acetate which smells like nail-polish remover and is also a serious wine fault.
The legal limit of VA in finished wines is: 1.2 gram/liter in whites, 1.4 g/l in reds, 1.2 g/l in dessert wines and for late-harvest wines picked at 28 °Brix or above it's 1.5 g/l for whites and 1.7 g/l in reds.
High VA wines can only be brought within legal limit by "blending away" with low VA wine, or by the use of specialized reverse osmosis filtration.
Most or all of the following can be considered "best practices" in all wine making, but are especially important when working with poor condition or otherwise "compromised" or degraded fruit.
How to minimize VA production in the winery
Clean, clean, clean and SANITIZE your winery and all surfaces and equipment that come into contact with wine as effectively, thoroughly, and as often possible. Pay particular attention to keeping floors and drains as clean as possible.
Harvest fruit as quickly, cleanly and as cool as possible, and proceed to crushing/de-stemming and/or pressing as soon as possible. Do not attempt to use obviously damaged, degraded or rotted fruit. Sorting of fruit prior to processing is advised if it can be done cool, quickly and cleanly.
Use a 50 ppm "shock" dose of sulfur (SO2, aka potassium meta bisulfate (KMBS)) on all juices or musts as soon as possible just prior to or during initial grape-reception and processing to reduce the bacterial "load'. This dose should be sufficient to eliminate native yeast fermentation or other microbes being transported into the winery. Do NOT use "cold-soak” methods or encourage 'wild" or "native" yeast fermentations when VA risk is high.
Encourage healthy and fast-starting fermentations through proper yeast hydration strategies that include the use of a yeast hydration nutrient. A yeast hydration nutrient is DIFFERENT from a yeast fermentation nutrient, and the difference is important. The ultimate goal is to reduce any fermentation stresses and encourage a quick and complete fermentation by the use of adequate yeast nutrition and managed temperature control. Each yeast has a preferred temperature range that you should be aware of and will be indicated on the original packaging or in the supplier catalog.
Choose and use pure strains of yeast that are proven to be low producers of volatile acidity, including: "BC" (a Bayanus yeast), Lalvin "C" and "DV10", and ICV "OKAY”. These yeast do not actually lower VA, rather they are proven strong fermenters with a fast start and completion. All commercial "pure" strains of yeast are chosen based, among other things, on the fact that they are naturally low producers of VA.
Eliminate or control the population of fruit flies by keeping all fermentations covered with a physical barrier (even thin plastic sheeting held in place by string and a bungee cord) and the use of fruit fly traps in the winery (a glass or jar with an ounce or two of sweet or red wine in it with a drop of dish soap makes a cheap and effective trap, or commercial "fly strips" or "tape" can also help).
Keep all winery waste (stems, skins, lees, and pressed grape pomace) as far away from winery as possible, at least 100 yards away from winery, or further if possible, do not keep grape-waste near the winery for extended periods.
Avoid cross-contamination of different lots of wine, sanitize all sample devices, valves, and wine thieves with a sulfur/citric acid solution or 40 per cent ethanol solution (i.e. cheap vodka, which is an inexpensive, available and effective surface sanitizer).
The recipe for effective SO2/citric acid solution is 3 grams of citric acid and 0.5 gram of KMBS per liter of water. This should produce a solution with a pH of 2.2, and active SO2 level of 250 ppm.
Other acid-based, iodine-based, or quaternary ammonia based sanitizers are highly-recommended.
Minimize oxygen exposure during all phases of production and storage by eliminating or reducing head space in vessels.
Minimize oxygen exposure during processing, settling, racking or transfers and during storage by "sparging" (i.e., displacing the air) all tanks and hoses with a food- grade, inert gas (CO2, nitrogen or argon) prior to use and/or filling. Keep any headspaces sparged with inert gases at least twice a week.
Dry ice can help in minimizing oxidation by its evaporation into carbon dioxide gas which displaces air/oxygen during processing, pressing, and prior to filling tanks. One should be careful with the handling of dry ice and be aware of the safety hazards of using this product, including its storage.
Minimize or eliminate any head space in storage vessels, and if necessary, spray a mixture of sulfur (SO2 aka KMBS) and water on the exposed surface of stored wine by mixing 0.5 gram of KMBS with one liter of clean water, this 250ppm SO2 solution can be sprayed directly on to the surface of wine in storage, especially if the presence of a "film yeast" is noticed. If large amounts of film yeast form, attempt to siphon or rack the clean wine under the film yeast to another container, leaving the contaminated "film" behind. “Early” sterile filtration may be used to reduce or eliminate bacteria load prior to storage or maturation.
At ALL times, keep the stored or maturing wines at an appropriate Free SO2 level, which should be checked and adjusted at least once per month.Keep all wines in barrels topped monthly at least and at an appropriate free-SO2 level, based on the wines pH (Molecular SO2 chart: http://srjcstaff.santarosa.edu/~jhenderson/SO2.pdf)
All white wines, fruit wines, and sweet wines should be maintained at 0.8 molecular SO2. Only dry red wines can be maintained at the lower 0.5 molecular SO2 level.
A "cool" or cold cellar is better than a "warm" cellar, acetic acid bacteria produce faster in a warm environment. A very clean and very cool (50-56°F / 10-13 °C) cellar/work area is a great help in slowing and reducing bacterial spoilage.
The website "vinoenology.com" is an excellent resource for various wine making "calculators" including: SO2 additions, acid additions, pH adjustments, blending, copper sulfate additions and fortifications, etc.
IN SHORT: KEEP IT CLEAN, KEEP IT COOL, PROPERLY AND TIMELY MANAGE THE USE OF SO2, AND MINIMIZE OXIDATION/OXYGEN EXPOSURE AT ALL TIMES.
Articles of interest:
Alert: Spotted Wing Drosophila (SWD) in Grapes
Matthew Clark1, Eric Burkness2, Drew Horton1, and Bill Hutchison2
1Grape Breeding & Enology Program, Dept. of Horticulture, University of Minnesota
2MN Extension IPM Program, Dept. of Entomology, University of Minnesota
Typically, when grape berries have intact skin, female SWD are not able to penetrate the berry skin to lay eggs. However, despite the relatively low susceptibility of grapes to being infested by SWD, as grapes age, skins become thinner and there is a greater risk for splitting and other fruit injury to occur (hail, birds, disease, general deterioration). With the very wet growing season in 2016, we have observed increased berry splitting in tight cluster cultivars. In varieties like Marquette and the Frontenac series, we have observed fruit breakdown. This degradation in berries (skin and pulp) could likely be attributed to the increased berry water content. Additionally, we have been observing necrosis on Marquette rachis leading to some berry decay but have not been able to determine if this is pathogenic or a stress response. In most years, harvest of Frontenac can be delayed as a benefit to juice chemistry as it often “hangs well” allowing acids to decline. This is not recommended in 2016.
Once fruit skin is compromised, or the fruit skin has deteriorated sufficiently, female SWD will begin laying eggs in the fruit. Despite typically low populations of adult flies, relative to other fruit crops, if fruit becomes susceptible to egg lay, populations can grow exponentially in a few short weeks reaching thousands per trap per week (http://www.fruitedge.umn.edu/swdtrap#grapes). With the limited success and/or options for insecticide use, the best options for managing SWD populations in grapes is to use production practices that minimize fruit splitting, disease, bird damage, and fruit deterioration. If fruit starts showing high levels fruit damage or deterioration, growers should consider harvesting fruit as soon as possible.
Vineyard monitoring can help inform the grower if and when the SWD are present. Although grape is not a preferred host, SWD may be present in other fruits adjacent to vineyards, including in gardens, greenhouses, composting fruit, and native plant populations. These SWD are opportunistic and will exploit damaged or deteriorating grape berries. Through monitoring, the grower can determine what steps are needed to use insecticides, although there is inconclusive evidence that insecticides are effective. Weekly monitoring will help determine what insect pests are a problem, and if their is increased presence of SWD or other pests.Traps can be purchased from catalogs such as Great Lakes IPM (http://www.greatlakesipm.com/2016%20Catalog%20Web.pdf) or traps can be constructed using the following instruction sheet (http://www.ipm.msu.edu/invasive_species/spotted_wing_drosophila/monitoring)
Vineyard sanitation is also critical to minimize fallen fruit or missed clusters during harvests. Most wine makers are familiar with fruit flies in the winery and in discarded grape must. One should consider strategies to restrict the fly movement. Consider covering waste must with fine mesh or tarps until all fruit has been harvested from the vineyard as this compost could serve as a source of continued fly infestation. Small amounts of damaged fruit/must can be placed in clear plastic bags where heat from the sun will kill larvae and flies, although this may have limited success in the fall as temperatures decline. Do not compost or bury the material as neither of these methods have been shown to eliminate SWD. Winter conditions in Minnesota are not favorable for SWD as the insects are not able to survive.
In the Winery
Fruit flies, including SWD, are adept at transferring microbes including acetobactor from berry to berry in the vineyard and from juice to wine and to equipment. These microbes are responsible for the volatile acidity (VA) that taints the wine with aromas of acetic acid and ethyl aldehyde. You will smell and taste this in the vineyard, and these berries should be discarded (although not to the vineyard floor). The use of traps in the winery fermentation area can help eliminate flies that either enter the winery on their own or those that come in with fruit at harvest. The traps used for monitoring are suitable. Simple vessels with a small volume of vinegar, sweet wine, or red wine, and a drop of unscented dish detergent are cheap, effective traps that can be set out daily. Removing must and waste regularly and sanitizing winery surfaces will help to reduce fruit flies and microbial problems.
Winery practices to control VA with sulfur dioxide (SO2) are really no different than controlling wild yeast and other bacteria that come in on the berries and are controlled through managed fermentations. However, tainted juice prior to fermentation will be difficult to manage unless it falls below detection thresholds after winemaking through blending. During primary fermentation, racking and pressing may eliminate some of the VA in addition to more SO2. Other advanced techniques include reverse osmosis and filtration to reduce the microbe population. During and after fermentation, some of the bacteria may live in a film on the juice/wine surface and not be effected by the dissolved SO2. Again, best practices to reduce oxygen at the surface in the vessel will reduce the chances for VA. Select vessels with minimal head space and consider sparging with inert gases.
Some Follow up from the event can be found here with links to important documents.
The MGGA has put together a one day MDA class with local MDA officials to help alleviate your concerns.
What: MDA Mock Inspection Class with Inspectors and Q&A sessions.
When: April 29th from 9:30am-2:30pm
Cost: $10 MGGA Members/ $40 non MGGA members
Where: Two Rivers Vineyards and Winery
6111 Us Hwy 10 Ramsey, MN 55303
Two Rivers Vineyard & Winery
Schedule: 9:30-10 Registration
10-12 Mock Production area and Tasting Room Inspection with Open Q&A with Inspectors
12-12:30 Lunch (provided)
12:30-2:30 Winery Processing with MDA Inspectors and more Q&A
Register at the following link:
On 2/19/2016, buds were chopped for winter survival measurements on 7 sentinel varieties at the University of Minnesota research vineyards at the Horticultural Research Center. The data represented here are just an example using a small sample number of canes, buds, and cultivars. Only 4 canes, 8 buds each were evaluated (32 total buds). We urge you to begin sampling your own vineyards as there is some evidence of damage. At this point, no changes would be needed to pruning based on these results at this location. More complete data will be presented in coming weeks.
Cultivar Primary Bud Survival
Frontenac gris 97%
Frontenac blanc 84%
La Crescent 91%
St. Croix 91%
Some Early images from a grafting ‘experiment’ with Ampelopsis as the scion wood (top part as a cultivar), and a hybrid rootstock from the UMN breeding program.
Starting to see callus formation at the graft union. We use the Ryset grafting tool which just like cutting puzzle pieces.
On the bottom we see callus where roots will soon start to form. The next step for us is to dip the top of the plants in melted wax (covering the bud and graft union) to prevent excessive evaporation, and to stick them in a potting media for rooting in the greenhouse. We will also likely remove the wire ties to prevent girdling as the stems begin to grow radially.
We are feeling pretty optimistic, but only time will tell if these grafts are compatible.
Winter is Minnesota can be one of the most challenging times for the grape plants. It's the main reason V. vinifera varieties aren't grown here. Learn a little bit about whats going on in the vineyard in winter.
Wine making is a rewarding career, but is not free from headaches. A wine maker's nightmare is the re-fermentation of sweet wines and the instability of some wines. This blog entry addresses the topic and offers some strategies to avoid and mitigate a potential devastating re-ferment.
Are you curious if your wine is finished with malolactic fermenation? Here is a quick reminder on how to test with paper chromatography.
ALERT: September 27, 2016. Spotted Wing Drosophila (SWD) in Grapes: A short memorandom on SWD in Minnesota and associated volatile acidity. Read more here.
Fall vineyard managment should focus on managing insects, vertebrate pests, rots, and diseases that will impact the vines in the next growing season. Making quality wines requires disease intervention and sorting, as infected fruit will impact wine quality. Read more here.
“From Vine to Glass: Understanding the Flavors and Aromas of Cold-Hardy Grapes and Wine”
Tuesday, May 17th*, 2016
12:00 Noon Eastern (11:00 am Central)
7:00 pm Eastern (6:00 pm Central)
*Please note this is a date change from the original date of May 10th.
Join Anne Fennell of South Dakota State University, Adrian Hegeman of the University of Minnesota and Somchai Rice of Iowa State University as they discuss their research conducted on Marquette and Frontenac as part of the Northern Grapes Project.
Friday April 29, 2016
This Saturday April 16, 2016
The University of Minnesota releases its news wine varieity 'Itasca' on April 4, 2016
Experimenting with different grafting techniques including grafting Ampelopsis with a hybrid rootstock.
Early bud chop counts on cold-hardy cultivars at the HRC