Vineyard Management at Veraison

August 4, 2020

Grapes are at or near veraison in Vermont vineyards, which signals the start of fruit ripening. This is an important time of year for a few activities. First, bird damage can be expected to begin and increase as fruit ripen. Birds will harvest your berries just a day or two before you’re ready to, so if you don’t have damage yet, don’t think you’re out of the woods. Netting is the best method of protection. Auditory scare calls, propane cannons, and inflatable ‘used car lot’ balloons are sometimes used as well, but their effectiveness is questionable and their annoyance factor significant. Dr. Alan Eaton from the University of New Hampshire wrote a good guide on prevention of bird damage in fruit plantings, available at: Marquette veraison, 8/3/2020. UVM Catamnount Vineyard, S. Burlington, VT.

Disease management: as fruit ripen, they will become more susceptible to the various bunch rots, including botrytis, ripe rot, and sour rot, and canopies can be affected by late-season downy and powdery mildew. Good cultural management for all of these includes keeping the canopy open, ensuring that clusters can ‘see the sun’ by shoot combing / thinning, removal of leaves, and pruning of laterals. There may be a few sprays warranted at this time, with some big caveats. Copper, sulfur, and captan should be avoided as we approach harvest, as they can either inhibit fermentation of contribute to off-flavors in the finished wine. Consider preharvest intervals, too. Visible downy mildew can be  managed through leaf removal, or application of one of the various Phosphorous acid products (e.g., Rampart, Fosphite). Some other materials that have efficacy against DM may be found in the New England Small Fruit guide. Be sure to rotate fungicide resistance classes (FRAC codes). There may be a bit of powdery mildew in the vineyard as well, that can typically be managed with a thorough application of stylet oil, applied as soon as it is observed in the vineyard. Botrytis can be specifically managed with fungicides, but it will be difficult to get into any closed clusters like Petite Pearl, and that disease is best managed during the immediate postbloom window. Remember that not all varieties are equally susceptible to disease, and loose-clustered varieties tend to have less issues with botrytis overall. There is some concern regarding spotted wing drosophila (SWD) and its potential to damage ripening fruit, which leads to sour rot infections. This invasive pest has been seen in high numbers in the region this year, but that does not suggest cause for alarm among the vineyard community. SWD have lower preference for grapes than for other soft fruit, and winegrapes that will be processed immediately after harvest are less prone to damage from secondary diseases. Still. Good vineyard sanitation is key in managing this pest. Any damaged clusters with cracked fruit should be removed from the vineyard in the weeks between veraison and ripening, as these attract SWD and other rot-bearing fruit flies. SWD have a preference for protected, shady areas in the canopy, so, again, keeping clusters exposed to sun is a helpful practice. While there are many insecticides labeled for control of SWD, I do not recommend their use in vineyards in any but the most specific cases.

Now is the time for plant tissue testing as well. Petiole samples may be collected at bloom or veraison, and comparisons between years or blocks should be based on the same time of collection. Samples should be collected separately for each cultivar or block. In each sample, a random collection of 75-100 petioles should be collected from throughout the planting. Petioles should be collected from the most recent fully expanded leaf on the shoot, not across from the fruit cluster as is collected for a bloom sample. Just remove the whole leaf and snip the petiole (the leaf ‘stem’ off with your pruners. Gently wash each sample in water with a drop of dish detergent, then rinse fully and place in an open-top paper bag to dry. The closest analytical lab for grape petiole analysis is the Cornell Nutrient Analysis Laboratory . Please note that they now have partnered with Agro-One Services. It is recommended that you contact them before you send any samples to confirm that recommendations will be sent along with the analysis and to confirm costs.
Video about petiole sampling:

Start making plans for harvest and crush now. This may be a good time to thin out any lagging ‘green’ clusters that developed from secondary buds and are lagging in ripeness. Remember, you’re looking for crop uniformity. You can estimate yield by counting clusters on a few representative vines and multiplying by the typical cluster weight for your vineyard. If this is unknown, use 0.25 pounds (113 grams) per cluster, which is the average we have recorded at the UVM vineyard for Minnesota cultivars from 2010-2015. Your formula should look like this:

Estimated tons/acre = average # clusters/vine * 0.25 lbs/cluster * # vines per acre /2000 (pounds per ton)

For the UVM vineyard, where we have 726 vines per acre [43560 sq feet/acre / (6 feet between vines * 10 feet between rows)] = 726, the crop estimate for 50 clusters per vine is:

4 tons/acre = 50 * 0.25 * 726 / 2000

Four tons per acre is a good crop for mature, healthy vines for most cold climate cultivars; some vigorous vines in good health may support higher crop yield but I wouldn’t push mush more than 5.5 tons per acre lest you compromise ripening. If you have too many clusters, thin out the smallest and greenest ones to get your target cluster number. This exercise will help you plan lugs, bins, and tank space, as well as allow you to communicate that information to any wineries you plan to sell to.

Vineyard Management at Bloom

June 17, 2020

I’ve visited some vineyards from the higher-elevation interior of the state to the Champlain Valley in the past week. Champlain Valley grapes are entering or even well-into bloom, upland and inland are around 5” shoot growth stage. Bothe are at key management points, so it’s best to spend some time in the field in the coming week. If it hasn’t been done, now is the time to thin your shoots out to 3-5 per foot of canopy length. That’s a pretty gross rule of thumb, it might be better to adjust down to a per acre target and go from there, especially if your vines aren’t completely linear. I’ve seen a couple of instances where established VSP / mid-wire cordon vines are being shifted to a top wire cordon training system. Those vines have plenty of vigor to hold a decent crop, but the canopy is in a middle-stage and shoots originate from all over the place. In that case, consider a target harvest per acre and count back from there. Day you want 3.5 tons, or 17,000 lbs per acre. You have 800 vines per acre on a 6 x 10 foot spacing. (Calculating vines per acre = 43,560 square feet/acre / (in-row spacing (ft) * between row spacing (ft) or 43,560/(6*10) = 796). That means you’ll want 21.25 clusters per vine. If your clusters average about 1/3 lb each, that’s 60 clusters to keep per vine. Then, you’d thin out shoots to select the most uniform and appropriately-spaced ones to get to that number. In many cases where vines give you two clusters per shoot, that would leave five shoots per foot of canopy (or 30 shoots on our six-foot vine).

Just as important as getting your shoots and cluster numbers in order is disease management. We’re blessed to be in such a dry spell during this critical period for disease, and I’ve seen remarkably little disease even on minimally-sprayed vines. But we’re in the prebloom and soon, postbloom window where all of the major grape diseases are primed to infect. Chances of rain are increasing as we move into the weekend and beyond, so it’s important to get things covered this week. Be careful spraying in hot weather, for two reasons. First, a properly-protected spray applicator (Tyvek suit, gloves, goggles, etc) is at risk for developing heat-related health problems, so spraying at dawn or even at night can help. Second, some of the more phytotoxic materials like captan, sulfur, and copper can cause more plant damage when applied just before a heat wave. Spray material choice is dependent on your management system, I recommend our Initial IPM Strategy for Grape Growers fact sheet in general, and specifically for non-organic growers. Regardless of system (organic or non-organic), this is the time to use your best tools available. For non-organic growers, that would be a protectat and single-site fungicide combination, like mancozeb or captan plus a strobilurin (e.g., Flint) or DMI (e.g., Rally) or SDHI (e.g., Aprovia). Note for that last part of the mix, there are also some good pre-mix combinations like Luna Experience (SDHI + DMI) and Pristine (Strobilurin + DMI) that can cover a lot of bases while reducing resistance development in the target pathogen.

For organic growers, I’d also consider a two-part mix. Regalia has been getting a lot of interest lately and it does appear to have good efficacy against downy and powdery mildews. It needs to be applied 1-2 days before infection, and requires sunlight to activate resistance in the plant- spraying the night before a wetting event won’t do it. Regalia can be mixed with sulfur or copper (more on those two later). Serenade is another biological product which is approved for organic production. Its mode of action is as a microbial antagonist to the pathogen, so it must get established and colonize susceptible tissue before wetting and infection events. Because of this, Serende is not compatible in a tank mix with sulfur or copper, but it could be rotated with them in separate sprays. Serenade has most efficacy (good but not excellent) against powdery and downy mildews. However, it does not protect against some key diseases that affect grapes during this window- anthracnose (especially important on Marquette), Phomopsis, and the most difficult to manage organically, black rot. For those diseases, copper has a bit more efficacy, so this is one spray that should include it, if the vines aren’t sensitive to it. Cold-hardy hybrids with considerable labrusca in their parentage (e.g., St Croix, Brianna, other Swenson varieties) are more sensitive to copper than some others. However, copper damage can be reduced by avoiding application during slow drying conditions (there goes my recommendation to spray at dawn…). As always, spraying should be about your fourth  line of defense when managing grapes organically- first consider; then strict weekly sanitation and removal of all diseased tissue; maintain a training system that ensures good air flow; and finally fit a spray program to help manage within that greater IPM (yes, organic systems are IPM too) program.

Finally, this is a good time to consider applying micronutrients to the vineyard. Boron is very often deficient in Vermont soils, and is needed for fruit development at bloom. The best way to assess need and amount to apply is with a recent petiole sample analysis (last year’s, although you could sample at bloom and make a quick correction). Without that, I feel safe recommending 1 lb per acre actual boron (5 lbs per acre Solubor, an OMRI-certified boron source with 20% B) applied in your spray water. The only caution I make there is that boron and water soluble packaging materials (like Rally bags) do not mix- you’ll gum up your sprayer and ruin your day. Apply those separately. Also, this is a pretty low rate of boron I’m recommending, as you can overshoot pretty easily so I do recommend a petiole analysis to tune your application rate before adding any more.

Finally, Wild grape bloom occurred on June 5 in South Burlington, which sets the clock for grape berry moth management. The first overwintering generation is rarely significant enough to warrant a management spray except in vineyards that have had extreme damage in previous years. Each generation requires about 820 degree days (base 47°F, or DDb47°F) to complete, and the first generation typically emerges around the time of wild grape bloom. So if we use June 5 as our ‘biofix’ and track DDb47°F, we can estimate the best time to treat for the more damaging later generations.

This is made easy by the Network for Environment and Weather Applications (NEWA) system, which I coordinate for Vermont. The network includes twelve on-site weather stations (all located at orchards) and six airports, and imports data in near real-time for use in pest models. It is free to use, and growers can locate the site nearest them and develop a best-guess of phomopsis, black rot, and downy mildew infection periods as well as a sense of the grape berry moth generational development.

Pre-Harvest Juice Testing For Ripeness

August 30, 2020

Heat accumulation is up overall this year, and we are about ten days ahead of ‘normal’ in South Burlington. As harvest approaches, it’s important to keep and eye on three important parameters of juice chemistry: soluble solids (sugar), pH, and titratable acidity. These values should be checked at least weekly against your target levels for the wine style you are aiming for. Last year, we published a fact sheet the details the methods for completing these tests:

Good luck with the harvest.

Early Summer Vineyard Management

June 29, 2020

July 1 brings a number of early summer vineyard tasks to think about. First, be sure to keep up with your disease management: sanitation, especially in organic vineyards, and sprays as needed. We’re still in that critical window where all or the main diseases (except maybe Phomopsis) are active. See our initial diseases management guide, or the New York guide for details. Also, the material in Cornell professor Katie Gold’s early season disease management recommendations is still relevant.

As for horticulture, there are a number of activities to stay on top of. Petiole samples to assess vine nutrient status may be collected now where vineyards are in bloom, or at veraison. Stick to the same timing in your vineyard if you are going to compare samples year to year. Details here. Keep vines, especially young or struggling ones, watered during this drought. Manage weeds, especially, again, on young vines. Established vines tend to compete better for water and nutrients, but tall weeds growing up into the canopy will increase disease pressure.

Finally, shoots will soon lignify at their bases and be strong enough for combing without breaking them off. The goal, for vines on a high wire cordon system, is to separate each shoot and direct it downward, thus exposing fruit to sunlight and making a more manageable canopy. Once shoots are pointed in the right direction, it’s easy to see where runty secondary or tertiary shoots are in the canopy, and where smaller clusters that are behind in development compared to the main crop are- those can both be removed.

(Retired) Iowa State Extension Specialist Mike White presents a good overview of the concepts and practices behind canopy management in his February 8, 2012 newsletter found here.

There’s a video of some UVM staff doing some (silent) canopy management here.

Ohio State Extension has a nice video here.

Vineyard Management

June 7, 2020

First, sorry about lumping the grape growers in with my last apple email. I do know that you’re (mostly) separate entities with separate needs. That said, the importance of staying on top of disease management now is just as much there. We’re entering the critical immediate prebloom period in vineyards, when they are susceptible to pretty much all of the major diseases we face: black rot, Phomopsis. Powdery mildew, and early downy mildew. For non-organic growers, and combination of a protectant (captan or mancozeb) and a systemic / ‘kickback’ active material like a strobilurin, DMI, or SDHI would be warranted now and in the next application 7-10 days fr4om now. Be sure, especially with that latter group of materials, to rotate fungicide resistance classes so that you’re not using any class (e.g., 3 for DMIs, 7 for SDHIs, and 11 for strobilurins)  more than twice back-to back. Some materials have more restrictive seasonal application  caps- always check your label. For organic growers, I would recommend rotating copper and Serenade or bicarbonate (like Armicarb O or equivalent) on a fairly tight 5-7 day schedule. Then again, the dry weather has been nice for managing diseases. Organic growers need to really pay attention to sanitation and removed any diseased tissue as soon as it’s seen, and scouting should be done weekly.

I saw a good bit of grape tumid gallmaker in our UVM vineyard last week, enough that we treated for it. Usually, this insect is a curiosity, but we have seen and had others report that losses can be as high as 50% of fruit clusters ruined by the insect. Keep an eye out for it (pictures in the link posted) and consider treatment if more than 5% of fruit clusters or 15% of leaves are affected. Organic growers will need to crush galls by hand, non-organic can treat with Movento or Assail.

Get your shoots thinned. This will make life so much easier later this summer.

Seeking Information: 2020 Perennial Crop Losses

June 3, 2020


I have been asked by the USDA Risk Management Agency for information on potential weather-related losses of perennial crops in Vermont in 2020. This is not a system to report insurable losses. If you have a loss, be sure to contact your insurer asap. Rather, this is a high-level assessment of loss events. Please contact me as soon as possible (reply to this email) with a brief note on the status of any weather-related crop damage on your farm. If you have had a loss, please indicate:  Issue or event of loss; Date of damage; Area (county or region); Estimate percent of damage or crop loss.

Thank you,


Pick-your-own and Farmer’s Market Guidance for COVID-19 Safety

By Terence Bradshaw

The Vermont Agency of Agriculture, Food, and Markets (VAAFM) has released guidance on Farmers Markets and Pick-Your-Own operations that must be followed until further notice. The Farmer’s Market guidance was posted earlier last month and is viewable on the VAAFM website: All farms that operate their own farm stands should plan on following these guidelines.

Pick-your-own guidance was just released today. Those rules are in the attached document, and copied below. VAAFM COVID_19 information can be found at:


Agency of Agriculture, Food & Markets                                                                          Office of the Secretary

116 State Street

Montpelier, VT 05620-2901

(802) 828-5667

June 1, 2020


Pick-your-own agricultural producers, including berry farms and orchards, shall adhere to the Agency of Commerce & Community Development’s Phased Restart Work Safe Guidance for retail operations and follow the best practices identified in this Pick-Your-Own Restart Plan.

MANDATORY HEALTH & SAFETY REQUIREMENTS FOR ALL BUSINESS, NON-PROFIT & GOVERNMENT OPERATIONS: All businesses must follow Vermont Department of Health and CDC guidelines outlined in the Phased Restart Work Safe Guidance and all health and safety and training requirements enumerated in Addendum 12 to Executive Order 01-20.

BUSINESS CUSTOMER & GENERAL PUBLIC MASK USE: Customers, and the public in general, are encouraged to wear face coverings any time they are interacting with others from outside their household.  Businesses may require customers to wear facial coverings over their nose and mouth.


Non-essential retail operations are limited to 25% (twenty-five percent) of approved fire safety occupancy; or 1 customer per 200 square feet; or 10 total customers and staff combined, whichever is greater. Operators must POST their temporary occupancy limit, and which method was used to determine it, prominently on all entrances. Posting templates are available at 

Cashless/touch-less transactions are strongly preferred. 

Curbside pickup remains the preferred method of operation. When possible, retailers should take steps to schedule or stage customer visits, such as waiting in cars or outside, to ensure lower contact operations.

Organized outdoor markets, such as flea markets, shall adhere to the farmers market guidance issued by the Agency of Agriculture, Food & Markets.

Pick-your-own agricultural producers, including berry farms and orchards, shall adhere to retail guidance, and follow the best practices identified in the Agency of Agriculture’s Pick-Your-Own Restart Plan.


  1. Customer Face Covering. In accordance with Executive Order guidance, customers are encouraged to and should wear face coverings over their nose and mouth any time they are interacting with others from outside their households. Individual farms may require their customers to wear face masks.
  1. Limited Outdoor In-Person Picking. PYO farms shall admit no more than one customer per 200 square feet of the crop space that is available for harvest/picking at the time of admission. All employees and customers in the harvest area must practice social distancing and follow all related safety requirements. If customer demand significantly exceeds available space, PYO farms should pre-schedule customer visits to limit the number of people on site.
  1. Social Distancing and Customer Flow. PYO farms must manage customer flow to ensure a distance of at least 6 feet between all employees and customers at all times, including ensuring that all customers either wait in their vehicles or remain at least 6 feet apart while awaiting entry to the harvest/picking area.
  1. Containers and Tools. Picking containers must either be clean containers provided by customers who maintain exclusive control over them, disposable containers provided by the PYO farms for customers to take home, or reusable containers that employees thoroughly clean and disinfect before each use.  All tools or other devices that customers may share must be thoroughly cleaned and disinfected by employees before each use.
  1. Retail Stations. All in-person sales should be conducted at an outdoor retail station whenever possible, and all retail stations must include a sneeze guard, be regularly cleaned and disinfected, and have a hand-washing station or hand-sanitizer containing at least 60% alcohol on site.  Transactions should be conducted in advance whenever possible, and in-person sales should be conducted by electronic transaction without utilizing cash. 
  1. Additional Requirements. To limit in-person contact and the risk of contamination, the on-site consumption of food—including crops being picked—is not allowed. In addition, customers are not permitted to congregate on site before, during, or after picking. PYO customers are prohibited from areas of the farm not involved in the PYO farm operation.  
    1. All employees and customers will follow all safety practices and always maintain a distance of at least 6 feet between all employees and customers.
  • Online or telephone orders and transactions are encouraged because they are accomplished without in-person contact with customers. All employees engaged in this work shall practice social distancing.
  • Sales should be conducted outside whenever possible. Indoor retail operations are limited to 25% (twenty-five percent) of approved fire safety occupancy; or 1 customer per 200 square feet; or 10 total customers and staff combined, whichever is greater.  Operators must POST their temporary occupancy limit, and which method was used to determine it, prominently on all entrances. Posting templates are available at  
  • All harvest areas are limited to a maximum of no more than one customer per 200 square feet of the crop space available for harvest at the time of picking. All employees and customers must practice social distancing and follow all related safety requirements. The designated health officer employee will ensure compliance.  The customer waiting, harvest, and retail area shall also be marked for one-way access wherever two-way access would require employees or customers to be closer than 6 feet apart, and whenever a crop row provides less than 10 feet of open space for foot traffic.
  • Outdoor space will be further monitored to ensure that all customers awaiting access to a harvest site remain in their vehicles or maintain sufficient separation while awaiting entry.  The designated health officer employee will ensure safety compliance for traffic flow and customer spacing while awaiting access to a harvest site.
  • Employees shall not have more than two persons in a vehicle and should have a single employee per vehicle whenever possible.
    1. Internal for Employees. All PYO farms shall distribute a concise internal document to all employees that explains all social distancing and related safety requirements. 
  • External for Customers/Visitors. All PYO farms shall employ a designated health officer employee to ensure ongoing and simultaneous compliance with all safety requirements in each sector (parking/waiting, harvesting, retail) of the PYO operation. 
  • Postings/Signs. PYO farms shall post visible signs that include the following information: a) pre-ordered sales transactions are prioritized and preferred; b) identifying the maximum number of customers permitted in indoor retail spaces and outdoor harvest sites; c) the protocol for maintaining separation while awaiting entry, d) that all customers should wear appropriate facial coverings, and e) customers with COVID-19 or COVID-19 symptoms are not allowed on the premises.  Instructions for minimizing contact shall also be posted adjacent to each retail station, which shall be conducted in an outside area whenever possible. 
  • All PYO farms shall adopt a written plan to ensure that all safety, health, and sanitation requirements are followed in each facet of their operations. 

Anson Tebbetts Secretary

Vermont Agency of Agriculture, Food & Markets