Terence Bradshaw

Veraison in Vermont vineyards: birds, petiole testing, disease, harvest planning

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: https://extension.unh.edu/resources/files/Resource001797_Rep2514.pdf.

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 best analytical lab for grape petiole analysis that will provide recommendation for next year’s nutrient inputs is Dairy One, which is associated with the Cornell Nutrient Analysis Laboratory . Video about petiole sampling: https://www.youtube.com/watch?v=8EHbojLfXek

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.

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 2010-2020. 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

Three to 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.

The UVM Tree Fruit and Viticulture Program is supported by the University of Vermont Agriculture Experiment Station, UVM Extension, USDA NIFA E-IPM Program, and USDA Risk Management Agency.

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VT Apple IPM: Foliar nutrient analysis, apple maggot, summer diseases

Foliar nutrient analysis – It is the time in the growing season to collect leaf samples for analysis. Samples are usually collected between July 15 – Aug. 15. The UVM Agriculture and Environmental Testing Lab can provide analysis, but at this time their output does not generate fertility recommendations. The following are potential options of labs for analysis. It is recommended that you contact the lab for instructions and costs before samples are sent. Plus, it is important to confirm that they will send recommendations along with the analysis.

University of Maine Analytical Lab: http://anlab.umesci.maine.edu/. Direct link to the leaf sampling form here.
Agro One: https://dairyone.com/services/forage-laboratory-services/plant-tissue-analysis/

Instructions on collecting leaf samples can be found here.

Wrapping up spraying – Primary insects of concern are apple maggot and codling moth. Both should be managed in high-pressure orchards. AM can often be managed with a single insecticide application based on monitoring with red sticky traps. The threshold is two flies per non-baited trap, or five flies per trap if apple volatile baits are used. Codling moth are between flights in most orchards, so management is advised later this month if this pest is a problem for you. Insecticide options are listed in the New England Tree Fruit Management Guide. Dr. Arthur Agnello discussed these summer insect pests in more detail in the July 7, 2014 issue of Scaffolds .

Summer diseases – It is important to maintain fungicide coverage to protect against sooty blotch, fly speck, and summer fruit rots. Materials should be applied after every 200 accumulated hours of leaf wetness or 2 inches of rainfall, whichever occurs first.

We ate our first peach yesterday, harvest will be here any day now.

Terence Bradshaw (he/him)
Associate Professor, Specialty Crops

Chair, Dept of Agriculture, Landscape, and Environment
(formerly Plant and Soil Science)
College of Agriculture and Life Sciences

University of Vermont
117/210 – Jeffords Hall | 63 Carrigan Dr
Burlington, VT 05405

(802) 922-2591 | tbradsha
https://go.uvm.edu/pssbradshaw

UVM Commercial Horticulture | UVM Fruit Blog
Horticulture Research and Education Center
Message me on Teams

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Climate adaptation field walk at Scott Farm, August 19th

Climate Adaptation Field Walk at Scott Farm Orchard: Dummerston, VT on August 19

WHEN: August 19, 3:30 pm – 5:30 pm
WHERE: Scott Farm Orchard, 707 Kipling Rd, Dummerston, VT 05301

Adapting to climate change looks different on every farm. This field walk will explore the range of climate risks impacting Scott Farm’s orchards and diversified production, from changing rainfall patterns to extreme temperature fluctuations. Scott Farm Orchard farm manager Simon Renault and orchardist Erin Robinson will share insights into the diverse strategies they’re using to adapt to these challenges, with a focus on business planning and preventative management.

Click here to learn more and register!

This event is sponsored by American Farmland Trust’s Planning for Adaptation & Resilience to Climate Change Program in collaboration with NOFA-VT. Thank you to our funders: NRCS-Vermont and the Vermont Agency of Agriculture, Farms and Markets.

“This message and its contents are confidential. If you received this message in error, do not use or rely upon it. Instead, please inform the sender and then delete it. Opinions in this email may only be those of the author and do not necessarily represent those of American Farmland Trust. The contents of this email do not constitute a binding offer or acceptance by American Farmland Trust unless so set forth in a separate document.”

Neonicotinoid BMP Rule comment opportunities

The Vermont Agency of Agriculture, Food and Markets is in the process of adopting a rule required by the General Assembly that establishes Best Management Practices for the use of neonicotinoid treated article seeds and neonicotinoid pesticides. The Draft rule language was developed over the last year and a half through a public process using recommendations from the Agricultural Innovation Board (AIB).

The Draft rule language, as presented to the House and Senate agriculture committees, and approved for publication by the Interagency Committee on Administrative Rules (ICAR), is attached.

The Agency will hold five public hearings to get public comments on the Draft rule. Information on these is presented below.

Date	Time	Location	Virtual Option
8/12/2025	5pm-7pm	Virtual Only	TEAMS Link Meeting ID: 253 157 432 933 1 Passcode: UM3EW6nx
8/14/2025	5pm-7pm	Bixby Memorial Free Library (2 Main St, Vergennes, VT 05491)	TEAMS Link Meeting ID: 253 157 432 933 1 Passcode: UM3EW6nx
8/20/2025	5pm-7pm	Poulin Grain (3916 US-5, Derby, VT 05829)	TEAMS Link Meeting ID: 299 306 540 079 1 Passcode: d5m5mZ9V
8/27/2025	430-630 pm	St. Albans Free Library (1 Maiden Ln, St Albans City, 05471)	TEAMS Link Meeting ID: 239 248 720 071 2 Passcode: h34Bb7yt
9/3/2025	5pm-7pm	Brooks Memorial Library (224 Main St, Brattleboro, 05301)	TEAMS Link Meeting ID: 258 187 034 640 8 Passcode: VR3yx2gY

Please consider attending, as the state is looking for broad perspectives on this proposed rule.

The UVM Tree Fruit and Viticulture Program is supported by the University of Vermont Agriculture Experiment Station, UVM Extension, USDA NIFA E-IPM Program, and USDA Risk Management Agency.

Best Management Practices for the Use of Neonicotinoid Treated Article Seeds and Neonicotinoid Pesticides (ICAR)(4.30.25).pdf

VT Apple IPM: Summer pest management, phase 2

The time has come to hang apple maggot fly (AMF) traps in Vermont orchards. These are some of the easiest pests to manage using an IPM strategy, so there’s really no excuse. The idea is to assess the population in the orchard before applying prophylactic sprays. By using red sticky traps, you can time treatments for best effectiveness, and maybe even skip treatments if the populations are low enough. Traps are red plastic balls that you coat with Tanglefoot adhesive. Kits including traps and adhesive are available from Gemplers and Great Lakes IPM. We have some available from our program as well, if you want to swing by South Burlington. If you want to come by for traps, please email me and we’ll be sure to have some ready.

AMF traps should be hung at least four per 10-acre block, preferably at the orchard perimeter and especially near sources of the insect, like wild or unmanaged apples. (Video here: Vermont Apple IPM: Hanging apple maggot fly traps.) Placement in the tree should be about head-height, and surrounding foliage should be trimmed away- this trap is largely visual, and you should be able to see it from 10-20 yards away. The traps may be baited with an apple essence lure that improves their attractiveness dramatically. When using traps to monitor AMF populations to time sprays, unbaited traps that catch one fly per block (as an average of all the traps in the block) would warrant treatment; the lure makes them much more attractive such that you can wait until an average of five flies per trap are caught before treating. For most growers, the main insecticide used against AMF is Assail, Imidan also works but it has a long reentry interval and tends to leave visible residue on fruit. For organic growers, Surround works well, but its use in midsummer may increase European red mites, and it can be hard to remove at harvest; spinosad (Entrust) works pretty well too. First AMF treatment is still a few weeks off, most likely.

It is summer lepidoptera season, and monitoring and treatment should be on everyone’s minds, especially for codling moth (CM) and obliquebanded leafroller (OBLR). CM are active and eggs are likely still hatching across the state, so growers who have caught CM in their traps or who often have issues with this pest (that’s most everyone) should apply something effective against them at the appropriate time. Most orchards saw CM first trap captures in late May and peak at the beginning of June. Optimum spray timing for CM is 250 degree days (base 50°) after first catch with a follow up spray 10-14 days later. Very specific materials like insect growth regulators (Intrepid, Rimon) or granulosis virus (Madex, Cyd-X) can be used that are very safe to non-target insects. One or two applications of a material should suffice for first generation.

OBLR are just showing up in traps but generally at low levels compared to previous years, and treatment should be timed at 360 degree days (base 43°F) after first catch. There is a NEWA model for this pest, and a material like Bt (Dipel, etc.) is effective (but not against CM). Other good materials targeted at this lepidopteran pest include Intrepid, Rimon, Delegate, and Belt.

I have seen one pretty bad case of European red mites already, and hot, dry weather is also conducive to mite flare-ups. A weekly or, if the numbers indicate, bi-weekly scouting will help to indicate if there are high enough mite numbers to consider treatment. Information on monitoring: https://netreefruit.org/apples/insects/mites. Mites should be treated based on the following thresholds: in June, 1-2 mites per leaf; July, 5 mites per leaf; in August, trees are more tolerant of feeding so treatment should only be applied if there are over 7.5 mites per leaf.

Diseases: keep checking on your scab, if you have none (I mean none), then it’s okay to relax. That said, the summer diseases sooty blotch and flyspeck are of concern now, but they require 270 hours of leaf wetness for lesions to form, so fungicide coverage between that period should be maintained. I am also seeing more leaf spot diseases (here’s a great article on the different leaf spots you may encounter) this year that may warrant continued coverage to reduce potential defoliation and/or spread to fruit rots. Recommendations from our colleagues at Cornell suggest including a FRAC group 3, 7, or 11 fungicide with your captan cover to reduce incidence of these diseases. Keep in mind that one inch of rain washes off half of your coverage, after two inches, it’s gone.

It’s time to wrap up any ground-applied nitrogen fertilizers, but potassium and magnesium fertilizers can be applied any time in summer. It’s also a good idea to start your regular foliar calcium sprays, especially on bitter pit-prone cultivars like Honeycrisp and Cortland.

The UVM Tree Fruit and Viticulture Program is supported by the University of Vermont Agriculture Experiment Station, UVM Extension, USDA NIFA E-IPM Program, and USDA Risk Management Agency.

VT Apple IPM- Codling moth

This will be a fairly brief newsletter today as I am away all week at a conference in Chicago. Feel free to e-mail or text me if you have specific questions, I will keep up the best that I can. -TB

We are entering into what I consider early summer insect management season. The main insect of concern at this point is codling moth, although plum curculio may still be active in some orchards. Two times sprays against codling moth, pheromone baited wing traps would have been hung prior to bloom and the date of first sustained capture recorded. From that point degree days are calculated using a base of 50°F and hatching larvae are best treated when 220° days have accumulated. For the UV orchard where we had sustained moth capture on May 17th, that would put us at good timing to manage our first generation of codling moth this week. Our orchard has a relatively high population and this emergence is earlier than I have seen in other orchards in the region, so your site may be able to be treated next week in the Champlain Valley or even later in the cooler inland orchards. Cottonmouth should best be managed with a material that specifically has high efficacy against that particular pest. Some good options are presented in this table Apple Insecticide Efficacy : New England Tree Fruit Management Guide : UMass Amherst (best seen on a computer or tablet screen, it doesn’t render well on a smaller phone screen).

Even though primary apple scab season is done for virtually all orchards in the state, I still recommend applying at least 1/2 rate of captan as we continue to have wet weather and some are diseases and fruit rots can get out of control if not managed. This is also the time to be applying calcium in every spray, especially on Honeycrisp.

The UVM Tree Fruit and Viticulture Program is supported by the University of Vermont Agriculture Experiment Station, UVM Extension, USDA NIFA E-IPM Program, and USDA Risk Management Agency.

Vermont Grape IPM: Immediate Prebloom disease management

Passing this on from Bethany again. -TB

Hi there again folks,

I’m writing in to you on the eve of the most important disease prevention period of our grape systems! Over the past two weeks we have had several Phomopsis and black rot infection events according to our NEWA models. As we enter pre-bloom it is essential that we are using our most powerful disease prevention and suppression tools against black rot, Phomopsis, and maybe even powdery mildew in vineyards where this is a particular concern.

Part of why there have been so many infection events is because we are experiencing so much rain. Both Phomopsis and black rot infections are spread by rain splash and are encouraged by humid and warm temperatures over 60 degrees. While we can’t do much about the weather, other management strategies will include:

Cultural methods (EXTREEMELY important for organic growers)

Making sure you’ve thinned shoots! By removing excess plant material you not only better balance the vine, but also allow for better spray penetration and airflow both now and into the summer months.
Remove any woody material that has not flushed out by now. This material will act as a disease reservoir if not removed promptly. It is worth taking a walk through the vineyard to find what you may have missed

Chemical Methods

Check available NEWA models to track possible infection periods. The model uses climatic data such as rainfall, temperature, and hours of leaf wetness to predict infection events. Be sure to enter the shoot stage and use the closest station to you for the most accurate predictions. Contact Terry if you are interested in hosting a station!
Because pre- and post- bloom is THE MOST IMPORTANT infection window for diseases such as black rot and powdery mildew we should all be applying our best and most reliable materials. Recs from Terry: “Every vineyard should be covered with the full suite of disease management products this week. That means mancozeb or captan plus a DMI, SDHI, or strobilurin (group 3, 7, or 11, respectively) material for non-organic vineyards; and sulfur plus copper (watch for incompatibilities on certain varieties, page 9 here) on organic vineyards. This would also be a good time to add biologicals, since we’re at ‘all hands on deck’ right now. Some materials, like Lifegard and Howler, are systemic acquired resistance promoters and need to go on a few days prior to infection. Others, like Serenade and Double Nickel, are biological extracts but can be mixed with other materials. Either way, these applications should be made a before infection, so spraying in the next day or two is a good idea.”

That’s all for now- I myself have to prep for a spray tomorrow. I will be in touch soon to introduce our good friend Downy Mildew and talk about weed and canopy management!

Signing off,

Bethany Pelletier & UVM Fruit Lab

Terence Bradshaw (he/him)
Associate Professor, Specialty Crops

Chair, Dept of Agriculture, Landscape, and Environment
(formerly Plant and Soil Science)
College of Agriculture and Life Sciences

University of Vermont
117/210 – Jeffords Hall | 63 Carrigan Dr
Burlington, VT 05405

(802) 922-2591 | tbradsha
https://go.uvm.edu/pssbradshaw

UVM Commercial Horticulture | UVM Fruit Blog
Horticulture Research and Education Center
Message me on Teams

Vermont Apple IPM: Thinning, codling moth, general IPM

Orchard video covering this week’s material is here: YouTube 5/30/2025

Vermont orchard are at petal fall (inland and upland) to generally 10-12 mm fruit size in the lower elevation valleys. Primary apple scab ascospore release is complete for all orchards, so apple scab is not a major management consideration only if you know the disease is managed well in your orchard. That means taking a very careful, methodical walk through the orchard and checking high up in trees and at the ends of rows where coverage may have been spotty to ensure that you don’t have active scab in your orchard. I recommend keeping at least some captan on for the next week or so anyway, and adding a single-site fungicide material if you have questions about your spray efficacy and go into tomorrow’s rains without appropriate coverage.

If you applied full-orchard petal fall insecticide, you are likely between insect pests now. Codling moth still needs some time for mating females to lay eggs and eggs to hatch. For more information on ecological codling moth management, consider attending this Cornell Zoom meeting on the topic next Tuesday June 3 at 2:00 PM. Plum curculio will still be active in orchards for another week or two, but if you applied a block-wide insecticide at petal fall, you can manage PC with boerder row sprays.

The main management consideration that I am getting a lot of calls and emails about is thinning. The crop is all over the place, from well-thinned single fruitlets; to unthinned six-fruit clusters with intact king fruit; to unthinned clusters with no king fruit as king blooms were open during the wettest, coldest, most bee-unfriendly weather of the spring. Fruitlet size also runs the gamut from petal fall (~5 mm) to up to 15-20 mm.

Thinning is complicated, but it needs to be done. Dr. Renae Moran has a good summary of chemical thinning materials and strategies in the New England Tree Fruit Management Guide: Apple Fruit Thinning : New England Tree Fruit Management Guide : UMass Amherst. I’ll post some general thoughts in bullet point:

Fruitlets whose sepals have not closed and/or whose stems have begun to yellow are likely to thin off.
Fruitlets will be most susceptible to the older thinners (NAA, NAD, 6BA) at 10-12 mm in size. Carbaryl at 1 pint per acre increases their activity, and I suggest including it if using those materials.
Once fruitlets are over 18 mm those thinners no longer work sufficiently to warrant their application. A newer material, Accede, is available and labeled in Vermont for thinning apples and peaches. It is much more preferable to the old ‘rescue thinning’ standby, Ethephon (which I would no longer recommend now that there is something netter on the market).
Thinners are more effective when warmer / hotter weather comes before (2 days) or especially after (4 days)n application.

It’s hard to make blanket recommendations across multiple sites, elevations, fruit set levels, cultivar, tree ages, and all the other interacting aspects that we see across the state, so I won’t even try. If you have a specific scenario you’d like to run by me, reach out and I’ll do my best to help. My plan for our UVM orchard is to go in Sunday or Monday with 1 pint per acre of carbaryl and 100 ppm of Maxcel.

The UVM Tree Fruit and Viticulture Program is supported by the University of Vermont Agriculture Experiment Station, UVM Extension, USDA NIFA E-IPM Program, and USDA Risk Management Agency.

VT Apple IPM: 2025 Petal Fall

This was meant to be sent out with some field pictures yesterday morning, but my teaching job and administrative duties all collided into a backup of worktodo this week. Hopefully it’s timely enough to be useful. -TB

After a few decent days of pollination during bloom last week in between the cold, cloudy, showery weather, I saw good fruit set on most cultivars at the UVM orchard over the weekend. Short of measuring and tracking the diameters of individual fruitlets to those which are continuing to grow, a very effective way to see if a fruit has been set is to look at the sepals on the calyx end of the fruit which were at the base of the blossoms when it was a flower. These five pointed, modified leaves will close up a bit on a blossom that was pollinated, fertilized, and is developing into a fruit.

Management considerations at petal fall are a bit more difficult than usual given the relatively low blossom density we had this year after substantial crops around most of the state last fall, questionable pollination weather for much of the bloom period, and continued cloudy, cool wet conditions. All of these would suggest that growers should be cautious with applying thinner applications this year. However, in most situations aside from an off-year on biennial cultivars or orchards with very poor fruit set, I recommend application thinning this year (and really every year). The weather this week is not conducive to application thinners that increase cell division, e.g. MaxCel, Exilis, etc. Those materials should be left on the shelf until temperatures after application will hit 75 to 80°F. That leaves the auxin-based thinners (Fruitone, Refine, etc.) as the best option for thinning the crop at petal fall. That said, even those materials do not work well in these 50° temperatures. Fruit are also growing extremely slowly, and will remain at the ~5mm “petal fall” window through the weekend. This will allow us to wait a bit until warmer weather is expected and will also allow late blooms to drop and minimize pollinator exposure to sprays. Dr. Terence Robinson from Cornell recently recommended relying a bit more on cabaryl to increase thinner activity this year. Where there is complete pedal drop and wildflowers have been mowed or otherwise controls, I recommend addition of carbaryl (Sevin XLR alone or generic carbaryl plus a surfactant) at one pint per acre, which will help to increase the effectiveness of thinning materials. Carbaryl is a relatively mild insecticide, but will provide some protection against insect pests that have had free reign of the orchard in the last few weeks if used at two pints per acre. I do recommend getting in with a more effective fall insecticide as soon as you are able for control of plum curculio, European apple sawfly, and some of the generalist lepidopteran pests that I have observed in various orchards. Codling moth have just begun to be trapped in area orchards, which means they are still flying and mating, and therefore have not laid eggs nor those eggs hatched into a stage where a targeted pesticide would be most effective. We will likely manage those pets next couple of weeks.

For most Vermont orchards, the apple scab ascospore maturity model predicts that all overwintering inoculum has been released and if the disease adequately controlled during the primary phase of the disease, then management for that best may be finished for the 2025 year. However, I strongly recommend maintaining fungicide coverage for the next 10 to 14 days. That is because apple scab is not the only disease of concern. Some of the summer fruit rots can get established early in the season, cedar apple is likely still a consideration, and in the case of low spray orchards or orchards where protection completely washed off, Marssonina leaf spot could become a serious disease given the constant wet weather we are seeing. We also cannot know that we have fully controlled for apple scab until we give enough time to see any lesions that may have broken through during these long infection periods.

Fire blight may not be a huge consideration this year, unless you had open blossoms that were not covered with streptomycin during the potential infection that occurred on Friday and / or Saturday of last week. The temperatures are just too cool now the bacteria to build to an infective population, and most orchards are at petal fall anyway which means that blossoms are no longer susceptible to the disease. Keep an eye out in the coming weeks for the development of any potential blossom or shoot blight symptoms. In orchards that have had a history of fire blight, I recommend maintaining low dose prohexadione calcium (Apogee, Kudos, etc.) applications for the next several weeks to help stiffen up cell walls in developing shoes and which will reduce the trees susceptibility to fireplace shoot infection.

Here’s what we’re doing for pest management and thinning in the UVM orchards this week: fungicide (captan plus Rally) tomorrow Wednesday morning to provide coverage through the next round of wetting on Thursday and Friday, then a weekend application of carbaryl plus eight ounces of NAA per acre for thinning, Avaunt insecticide for curculio and other petal fall pests, and possibly another fungicide depending on how much rain fell since the last application. That thinning application will be timed to coincide with the necessary low wind conditions and hopefully just ahead of any expected warm up we get early next week.

Good luck and let me know if you have any questions.

Terry

—

Terence Bradshaw

Associate Professor and Chair

UVM Agriculture, Landscape, and Environment

Sent via mobile app. Please excuse typos.

Terence Bradshaw (he/him)
Associate Professor, Specialty Crops

Chair, Dept of Agriculture, Landscape, and Environment
(formerly Plant and Soil Science)
College of Agriculture and Life Sciences

University of Vermont
117/210 – Jeffords Hall | 63 Carrigan Dr
Burlington, VT 05405

(802) 922-2591 | tbradsha
https://go.uvm.edu/pssbradshaw

UVM Commercial Horticulture | UVM Fruit Blog
Horticulture Research and Education Center
Message me on Teams

VT Apple IPM: Fire blight alert

With welcome, warm, sunny weather, we are seeing epiphytic infection potential rise in virtually all orchards around the state. We are expecting by Thursday or Friday to have high enough populations of bacteria to cause fire blight infections on trees with open blossoms. That will include most orchards in the state which may either be just beginning to bloom or starting to end their bloom. Growers should plan to apply streptomycin to all blooming orchards on Thursday or Friday this week. Streptomycin works best when applied with a non ionic surfactant. There is also good potential for apple scab infection this weekend, so application of an appropriate fungicide would also be prudent. Next week we’ll discuss options for insect management and thinning at petal fall.

The UVM Tree Fruit and Viticulture Program is supported by the University of Vermont Agriculture Experiment Station, UVM Extension, USDA NIFA E-IPM Program, and USDA Risk Management Agency.