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UVM Fruit Blog

One (or two) more things to think about

Posted: July 6th, 2018 by fruit

By Terence Bradshaw

I’ve received questions about a couple of questions about two different yet similar insect pests: grape tumid gallmaker (GTG) and phylloxera. Both of these insects cause galls that develop around larvae that feed on foliar (and fruit, in the case of GTG) tissue which can be quite concerning, but often are not an economic threat. That said, I’ve seen vines with over 50% cluster damage from GTG, and young vines with significant leaf distortions from phylloxera that overall vine growth is likely impacted. Treatment options should be the same for either pest. Although GTG may not technically be on the label for If you decide on treatment, there are a few materials of choice, which Tim Martinson outlined well in an older post that is still relevant today. Basically, Movento is the gold standard, and Dr. Ann Hazelrigg at the UVM Plant Diagnostic Clinic recently confirmed that it killed larvae inside GTG galls from one area vineyard. Admire Pro and Assail are labeled and effective against phylloxera, but have no label for GTG.

If galling is extensive, removal of damaged leaves may not reduce the damage to the plant. Galled leaves are still photosynthesizing, and, for phylloxera anyway, hatched nymphs (“crawlers”) have likely left the galls to infest younger leaves already. As those leaves expand, expect to see more galls, but not necessarily as bad as the ones on early-season leaves. I’ve seen some pretty scarred-up leaves, especially on ‘Frontenac’, that have ripened a crop just fine. If the damage is looking too severe (and I don’t have a specific threshold), then treatment with one of the systemic materials listed above is your best management option.

Where trade names or commercial products are used for identification,

no discrimination is intended and no endorsement is implied.

Always read the label before using any pesticide.

The label is the legal document for the product use.

Disregard any information in this message if it is in conflict with the

label.

The UVM Tree Fruit and Viticulture Program is supported by the

University of Vermont Agriculture Experiment Station, a USDA NIFA E-IPM

Grant, and USDA Risk Management Agency Funds.

Post-heat wave vineyard management

Posted: July 6th, 2018 by fruit

By Terence Bradshaw

It’s cooling off for a bit, time to think about activities in the vineyard. Thankfully, extreme heat isn’t good for most grape diseases, and the dry weather hasn’t been good for them either. However, berries are sizing up and bunch closure will be here before we know it, so we should consider some upcoming potential issues that might affect fruit quality at harvest.

First is grape berry moth (GBM). This moth lays eggs in developing clusters which hatch and infest fruit, causing direct damage as well as allowing rots to develop. Now is the time to start scouting 50-100 randomly selected clusters from throughout the vineyard and inspect for the characteristic webbing of GBM larvae, six percent infested clusters indicates a need to treat. If sprays are necessary to manage them, they need to be applied before the clusters close up. Bt is effective against GBM, as is Intrepid, Delegate (also good against spotted wing drosophila, more on that next week), Entrust (SWD as well, and organic), Sevin (good against Japanese beetles), and Avaunt (also JB). Notice I’m not recommending pyrethroids like Danitol, as they tend to be harsh on predators and may increase mite populations as a result.

Next is Botrytis. This disease is increased by prolonged wet periods and moderate temperatures (60-75° F), not what we’ve had recently. Still, if you have tight clustered cultivars (anyone still growing Vignoles?) or a history of the disease, an appropriate material may be called for if a long rainy week ever appears in the forecast. Downy mildew can infest leaves and clusters, and, like with botrytis, an effective material may need to be applied ahead of any rainy period that may come up in the next few weeks. Finally, keep an eye out for powdery mildew on foliage. If you’re relatively clean, this disease may not pose a problem for the rest of the season, but if there is incidence of the disease, it may spread given appropriate weather.

All diseases will be much better-managed with an open canopy, and your fruit quality will increase as well. Soon, if not already, the bases of shoots will lignify (get ‘woody’) and will be tough enough to comb shoots downward and separate them in order to expose fruit to the sun. This is an absolutely critical practice to attain highest quality fruit, as well as to allow for sufficient hardening off of shoots and other tissues heading into next winter. If the heat continues too much, I would avoid pulling leaves around the clusters at this time, the combing should expose them enough to develop some thicker cuticles on berries that will resist sunburn. A final leaf pulling can be debone a few weeks before veraison.

Where trade names or commercial products are used for identification,

no discrimination is intended and no endorsement is implied.

Always read the label before using any pesticide.

The label is the legal document for the product use.

Disregard any information in this message if it is in conflict with the

label.

The UVM Tree Fruit and Viticulture Program is supported by the

University of Vermont Agriculture Experiment Station, a USDA NIFA E-IPM

Grant, and USDA Risk Management Agency Funds.

Cooling off orchard activities

Posted: July 6th, 2018 by fruit

By Terence Bradshaw

Now that we have a respite from the heat wave, I imagine growers are thinking about what needs to be managed in Vermont orchards. As a rule, there aren’t any across-the-state IPM issues that I expect every grower will be facing. In warmer areas, it’s still a decent time to apply a second codling moth spray if your trap capture were high, say consistent 7-10 or more per trap during the peaks, In cooler regions, this is a good time to cover for emerging larvae, again, if your trap catches were high. It’s early to treat for obliquebanded leafroller, and apple maggot traps were just barely deployed last week on most farms. That said, I’ve seen at least one orchard with very high trap catches, and remember that an average over five flies per baited red sphere (or one per unbaited trap) indicates a need to cover. Most growers are using Assail against apple maggot, and it is also effective against codling moth and several other secondary pests.

Mites are likely to be an increasing problem with the heat we experienced, especially where pyrethroids or organophosphates have been used. Use this chart to guide mite scouting. The threshold in July is five European red or two-spotted spider mites per leaf. There is a number of materials available for use against mites, see the New England Tree Fruit Management Guide for details. If mites are a problem, consider a thorough oil application next spring and moving away from broad-spectrum insecticides. You may need to reintroduce predators from an orchard with a good population of them, but it can be well-worth it.

Diseases are pretty quiet. For the few that have scab, keep maintaining some captan coverage, between that and the heat (more is on the way for Monday), it should burn out. I’ve heard few reports of fire blight, but if you have it, keep cutting it as you see it. Sooty blotch and flyspeck are still awaiting another 100+ hours of wetting. Powdery mildew should have been shut down by the heat wave, but if you have it on susceptible cultivars (e.g. Cortland, Honeycrisp), sulfur, a strobilurin, or a DMI fungicide should take care of it. I’d aim for the first, given its low cost and lack or issues with resistance, and save the others for late-0season rots or summer diseases if it ever gets wet enough.

Speaking of wet, I don’t need to tell anyone that it’s dry out there. Water if you can, and remember that consistent moisture is better for trees than infrequent flooding. Also remember that inadequate soil moisture is linked to poor calcium (and other nutrient) uptake in trees and can exacerbate bitter pit, so every spray should include calcium and you may consider going out just top put that nutrient on to susceptible cultivars (again, Cortland, Honeycrisp).

Where trade names or commercial products are used for identification,

no discrimination is intended and no endorsement is implied.

Always read the label before using any pesticide.

The label is the legal document for the product use.

Disregard any information in this message if it is in conflict with the

label.

The UVM Tree Fruit and Viticulture Program is supported by the

University of Vermont Agriculture Experiment Station, a USDA NIFA E-IPM

Grant, and USDA Risk Management Agency Funds.

Spraying and hot weather

Posted: June 28th, 2018 by fruit

By Terence Bradshaw

This is just a quick note to urge caution for anyone planning to spray grapes or apples ahead of the upcoming hot spell which is expected to start tomorrow. Meteorologists are calling already saying that this may be the most intense heat event seen in Vermont in recent history, particularly in terms of duration. Temperatures in much of the state are expected to hit the upper 90s by Sunday July 1, with a slight reprieve into the 80s mid-week, followed by another jump into upper 90s. We are expected to see 100-degree weather in some parts of Vermont over the next ten days.

Heat and crop spraying do not mix well, especially when accompanied by high humidity that limits transpiration and the cooling it brings. Many spray materials are phytotoxic under certain conditions, especially when intense heat follows application. I would be very careful spraying anything until this weather subsides. Especially dangerous materials include sulfur compounds (including lime sulfur), copper, oil, captan, foliar fertilizers, and most emulsifiable concentrates and similar liquid products that contain potentially damaging solvents.

The good news is that most fungal pathogens do not thrive in such hot conditions. Keep an eye out for fire blight in apples (which you can’t spray for now anyway, so just cut it out as soon as you see it) and keep monitoring for any insect and mite populations that you may need to treat after this heat is over.

Where trade names or commercial products are used for identification,

no discrimination is intended and no endorsement is implied.

Always read the label before using any pesticide.

The label is the legal document for the product use.

Disregard any information in this message if it is in conflict with the

label.

The UVM Tree Fruit and Viticulture Program is supported by the

University of Vermont Agriculture Experiment Station, a USDA NIFA E-IPM

Grant, and USDA Risk Management Agency Funds.

Vineyard management, June 25

Posted: June 24th, 2018 by fruit

By Terence Bradshaw

Things haven’t changed all that much in Vermont vineyards since the last posting here. Despite the showers over this past weekend and a pretty good rain last Monday, the predominant weather feature has been dryness. That’s good for most diseases, and as we shift into the postbloom period, we need to also shift our thinking of the predominant fungal diseases that are likely to affect Vermont vineyards. Phomopsis (PH) is becoming less of an issue with each passing day, and leaves and fruit will increase their resistance to black rot (BR) in the next few weeks. Downy mildew (DM) is increasing in importance, and this past wetting event is likely to have triggered infection. Botrytis (Bot) will be an issue soon, and powdery mildew (PM), which needs only high humidity and not necessarily rain (unlike most fungal diseases) will continue to affect unprotected vineyards through the summer and into harvest.

This has been a good season to stretch fungicide coverage because of the lack of rain (or to get away with more lackadaisical management than a wetter year would allow), but it is important to keep vigilant as we enter the heat of summer. This is the time that I generally suggest growers shift over to fungicides targeting PM, DM, and (less importantly, unless it’s really wet or your vines are a tangled mess or in a foggy hollow) Bot. This may mean using multiple materials if necessary. Captan is a pretty solid material to use to cover the emerging DM and the waning but still important BR and PH. Addition of a strobilurin (e.g., Flint) or DMI (e.g., Rally) would give great protection against BR and PH as well as PM. For organic growers, copper is probably your best bet now, as it is fairly effective against DM and PM.

I’ve received a few questions about potassium fertilization, which is commonly needed in bearing Vermont vineyards and is appropriate to apply now. If vineyards show deficiencies in both potassium and magnesium, then sulfate of potash magnesia (Sul-Po-Mag) is a great material that is available in both organic and non-organic forms. If potassium is needed (based on petiole and soil tests) but not magnesium, potassium sulfate is also available in both organic and non-organic forms. There is a great section in Appendix A of the Wine Grape Production Guide for Eastern North America (which every grower should have a copy of on the bookshelf, ready to grab with short reach) which helps to guide fertilizer application rates based on soil and petiole samples. If you have a copy of those to send to me, I’d be happy to help you with the numbers as well.

I think it’s still a bit too early to do much canopy management in the vineyards, as the bases of shoots are still too tender to hold up to much wrangling without breaking off. But plan on combing and shoot positioning soon, around the July 4 holiday.

Finally, for anyone looking for stimulating discussion this week, I’ll be part of a public panel with a number of my colleagues discussing Farming Practices and Ideologies this Tuesday at the UVM Davis Center. Information can be found at: https://www.facebook.com/events/187470125292645/. There is no fee for admission and we expect a lively discussion amongst the panel and the audience, so I encourage the Vermont orchard community to participate and weigh in. I’ve included specific information on the panel in another posting.

Where trade names or commercial products are used for identification,

no discrimination is intended and no endorsement is implied.

Always read the label before using any pesticide.

The label is the legal document for the product use.

Disregard any information in this message if it is in conflict with the

label.

The UVM Tree Fruit and Viticulture Program is supported by the

University of Vermont Agriculture Experiment Station, a USDA NIFA E-IPM

Grant, and USDA Risk Management Agency Funds.

UVM Farming Practices Panel, Tues June 26

Posted: June 24th, 2018 by fruit

By Terence Bradshaw

Panel on Farming Practices
Tuesday June 26, 6-8 PM
Sugar Maple Ballroom, 4th floor
Davis Center,
University of Vermont

Dissecting Competing Philosophies in Vermont Agriculture

Organic – Maddie Kempner, NOFA-VT
Conventional – Dr. Terence Bradshaw, UVM Plant and Soil Science
Regenerative Agriculture – Corie Pierce, Bread & Butter Farm
Permaculture – Keith Morris, Prospect Rock Permaculture
Agroecology – Dr. Ernesto Mendez UVM Agroecology and Livelihoods Collaborative – ALC

Moderator: S’ra DeSantis, UVM Farmer Training Program

Livestream at: https://www.youtube.com/user/universityofvermont/live

The event will be archived on the UVM YouTube channel.

Have you ever wondered what distinguishes organic agriculture from conventional agriculture or permaculture from agroecology and regenerative ag? We hear these words often in the agricultural community and it can be confusing to distinguish one from the other. Come join us for an evening of intellectual and practical discussion as we hear from five experts in these fields and work to dissect the meanings of these important concepts and practices. Our panel will speak to the significance of these agricultural practices in both their personal careers and in agriculture as a whole.

Sponsored by UVM Farmer Training Program, UVM Catamount Farm, NOFA-VT, UVM Agroecology and Livelihoods Collaborative – ALC

For more information please contact S’ra DeSantis, 802-324-3073, sra.desantis@uvm.edu

Where trade names or commercial products are used for identification,

no discrimination is intended and no endorsement is implied.

Always read the label before using any pesticide.

The label is the legal document for the product use.

Disregard any information in this message if it is in conflict with the

label.

The UVM Tree Fruit and Viticulture Program is supported by the

University of Vermont Agriculture Experiment Station, a USDA NIFA E-IPM

Grant, and USDA Risk Management Agency Funds.

Orchard IPM, June 24

Posted: June 24th, 2018 by fruit

By Terence Bradshaw

Things are a bit quiet in the orchards right now. Primary scab season is done, and there is little of it in commercial orchards where dry conditions and easy spray windows have allowed for decent disease management conditions. Fire blight- a minor annoyance in some orchards and absent in most, but keep an eye out for an errant strike here and there. Sooty blotch and flyspeck- these diseases require an accumulated 270 hours of leaf wetness to incubate between infection (e.g., a wetting event post-bloom in which you had no fungicide protection going in) and disease symptoms. We’re only halfway there, even if you had no fungicide coverage after bloom. That does mean, however, that summer fungicide protection may be needed in the next couple of weeks to manage these cosmetic diseases as well as the worse fruit rots (black, white, and bitter). See the New England Tree Fruit Management Guide for recommended materials, but generally, strobilurins, SDHIs, captan, and topsin are among those recommended. For organic growers, an application of a low-dose copper like Cueva or Badge may reduce fruit rots based on some preliminary work I did a few years ago, but watch your rates and don’t spray under slow drying conditions as fruit finish (russeting and lenticel blackening) may suffer. Maintaining trees via pruning, training, and appropriate rootstock/scion combinations to begin with can help to keep the canopy open to facilitate drying and reduce disease substantially.

Insects are relatively quiet. Mites (not an insect, but close enough for this sake) are nearly non-existent, even in a few of the hot spots I’ve seen over the years. Codling moth (CM) flight and egg hatch is still happening, and the timing for managing hatching larvae is now, either for your first or second spray for this generation. We’ve been trapping CM in every orchard we’re in this year, and while there’s no set threshold for when to spray, the general rule of thumb is that 5 or so moths per week in a pheromone trap is a light population, and more than ten indicates a larger problem. Where orchards are on the latter end of that spectrum, I recommend a second application during the first generation. Dr. Art Agnello at Cornell is recommending IRAC Group 28 (containing a diamide; i.e., Altacor, Exirel, Minecto Pro, Voliam Flexi or Voliam Xpress/Besiege) or Group 5 (spinetoram or spinosad) insecticides as the best options. For resistance management, it is best to use one IRAC class for the first generation, even if in two successive sprays, then switch to another class for the second generation.

Obliquebanded leaf roller still need some time to develop; I would plan to manage them along with apple maggot fly (AMF) or second-generation CM. Speaking of AMF, now is the time to hang red sticky traps in the orchard to monitor their populations. Baited traps placed four per block at the outside rows (to catch in-migrating flies) and checked regularly would indicate a population that needs management when a cumulative total of five flies is caught; unbaited traps are less effective at catching flies so an average of one fly caught per trap would indicate a need for treatment. We typically hit threshold at the UVM orchard in mid-July, but flies will start emerging from their pupae in the soil any day now. That also highlights an important management practice for this pest- removal or chopping (via flail mower) of dropped fruit to prevent pupation. Traps can be found at Gemplers and Great Lakes IPM.

On another note, for anyone looking for stimulating discussion this week, I’ll be part of a public panel with a number of my colleagues discussing Farming Practices and Ideologies this Tuesday at the UVM Davis Center. Information can be found at: https://www.facebook.com/events/187470125292645/. There is no fee for admission and we expect a lively discussion amongst the panel and the audience, so I encourage the Vermont orchard community to participate and weigh in. I’ll include specific information on the panel in another posting.

Where trade names or commercial products are used for identification,

no discrimination is intended and no endorsement is implied.

Always read the label before using any pesticide.

The label is the legal document for the product use.

Disregard any information in this message if it is in conflict with the

label.

The UVM Tree Fruit and Viticulture Program is supported by the

University of Vermont Agriculture Experiment Station, a USDA NIFA E-IPM

Grant, and USDA Risk Management Agency Funds.

Early summer orchard considerations

Posted: June 14th, 2018 by fruit

By Terence Bradshaw

I’m not sure if everyone reads all the way to the bottom of my postings, or if things are going fine in Vermont orchards. If you recall, I was away working with apple growers and aspiring cider makers in Lebanon May 26-June 10, and was mostly unreachable. That I heard very little from growers suggests that either things are pretty quiet or I’m not needed. I’ll assume the former. I’ll also plan on presenting a trip report at the winter VT Tree Fruit Growers Association meeting, There are quite a few lessons we can learn from where the Lebanese apple industry id now, compared to our own situation now and especially over the past several decades. Stay tuned.

This week I’ve been getting caught up at the farm, in class, and with some upcoming research reports. Orchards are generally looking good. Primary apple scab is done, and if you missed infection periods, you’ll see lesions now. If you have scab in the orchard, keep covered with captan (sulfur if organic) and watch for lesions to burn out during hot/dry periods. It’s been dry and looks to stay that way (mostly) outside of rain expected on Monday. The next diseases to think about, assuming you have scab under control, are the summer tots and sooty blotch/flyspeck. Those all need substantially more moisture than we have had or are expecting, so sit tight. You can hold off on the fungicides for a while.

Monday I saw one single fire blight strike. That is important for two reasons. First, it confirms the predictions in Maryblyt that infections from the infection periods that may have occurred around May 25. Second, this strike was found in a Crimson Gold tree in our organic block. We do not use antibiotics in that block, and have suffered from substantial infections in most years. That we found one strike, and none on our most sensitive cultivar, tells me that that infection period was indeed relatively weak. Keep an eye out for strikes in your orchards and prune out when you see them, but I’d say we’re generally done worrying about fire blight for 2018.

Insects are another matter of course. Plum curculio (PC) are largely done in most orchards except inland/upland cooler sites- keep an eye on developing fruitlets for fresh damage and treat if needed. Perimeter sprays should be sufficient there. Codling moths (CM) are active and the eggs from the first flights are hatching. If you have had issues with this pest in your orchard, we’re in a good window to manage them. A broad-spectrum material could manage both CM and PC, but if you’re only concerned about the former, consider using one of the softer, lepidopteran specific materials like granulosis virus (e.g., Cyd-X) or an insect growth regulator (e.g., Rimon, Esteem, Intrepid) which are much safer on beneficial insects. Esteem is also effective against San Jose scale which are susceptible now if you’ve had a problem with those insects recently.

Obliquebanded leafrollers are just starting to fly now, there are a couple of weeks before we need to worry about them. As the weather turns hot and dry (trust me, it’s coming), keep an eye out for mites. Ideally, newer ‘soft’ IPM programs will help to maintain mite predator populations such that pest mites don’t require treatment beyond spring oil application.

Horticulturally, think about getting on any last nitrogen fertilizers before it gets too late and risks reducing cold hardiness. Where needed, magnesium and potassium may be ground-applied. Make sure to keep training new trees. As for thinning, the window to chemically thin has mostly closed. That said, if you still have too many fruit set, rescue thinning with Ethephon is an option that may be used cautiously.

Where trade names or commercial products are used for identification,

no discrimination is intended and no endorsement is implied.

Always read the label before using any pesticide.

The label is the legal document for the product use.

Disregard any information in this message if it is in conflict with the

label.

The UVM Tree Fruit and Viticulture Program is supported by the

University of Vermont Agriculture Experiment Station, a USDA NIFA E-IPM

Grant, and USDA Risk Management Agency Funds.

Immediate prebloom in grapes

Posted: June 12th, 2018 by fruit

By Terence Bradshaw

Grape bloom is looming in many Vermont vineyards, and this is a critical time for disease and vine management. As we mention in our initial IPM strategy for winegrapes, all of the major diseases save for late-season fruit rots are sensitive to management right now. That means that fungicide applications should be made, using a material or materials with broad range of coverage against powdery mildew (PM), downy mildew (DM), black rot (BR), anthracnose (Ant), and that last bit of phomopsis (Ph) for the season. Generally, this means a combination of materials, including a protectant (mancozeb, most effective against Ph, BR, PM, or captan (Ph, DM)) plus a systemic or more narrow-spectrum material. Those may include Vivando / Quintec (PM only); a DMI material like myclobutanil or tebuconazole ((BR, PM); or a strobilurin (BR, PM, also excellent against botrytis so save until later in the season in July if you have issues with that disease). I’ll mention other materials with excellent efficacy against DM and botrytis later when those diseases are of greater relative concern.

For organic growers, be sure to maintain your copper and/or sulfur sprays, watch for phytotoxicity, and remove diseased leaves and clusters as soon as you see them. The good thing is that it has been relatively dry this season, so disease pressure should be manageable. That said, in this vulnerable period, spray coverage should be applied prior to expected wetting events.

Insect activity is usually pretty quiet at this time of the season. Keep an eye out for bloom on wild grapes, as that sets the clock for the degree day model used to time management of grape berry moth (GBM). We typically add BT (Dipel, Javelin, etc.) or another material specifically active against lepidopteran pests soon after bloom at the earliest, so there’s time before we consider managing for this pest. GBM isn’t always a problem in every Vermont vineyard, we’ll talk about scouting for that pest in an upcoming bulletin. While we’re on the subject of insects, I haven’t seen much / any grape tumid gallmaker (GTGM) at the Hort Farm vineyard this year, but it has been a somewhat unlikely yet injurious pest in local vineyards in the past couple of years. I do not want to get into recommending treatment for minor pests of likely little economic importance, but if yours is one of the handful of vineyards which as suffered from extensive damage in recent years, consider using Movento or Assail if you see the first stages of galling by overwintering midges as they are hatching out now. There are only a very few vineyards where I’m even suggesting treatment for this- if you don’t remember this pest and its’ damage, then don’t worry about it on your farm. For more information on GTGM check the link above or my previous bit on them here.

Horticulture: There are two good times to collect petiole samples to assess vine nutrient status, bloom and veraison. Generally, you should stick with whichever timing you have been using so that you may compare to past tests. Dr. Joe Fiola at University of Maryland has a good fact sheet on petiole sampling. We recommend the Cornell Nutrient Analysis Laboratory for petiole sampling, as they have extensive experience in providing nutrient recommendations for grapes. Should nutrient applications be needed, this is a good time to apply boron, magnesium, and nitrogen as they are needed during this period of rapid shoot and fruit growth.

Other activities that I don’t need to tell you about: shoot thinning can continue, but shoots aren’t lignified at the base enough to comb them, they’ll just break off. Keep the vineyard mowed to improve airflow, but a golf course mowing regime isn’t necessary unless that’s your aesthetic choice. Keep the in-row weeds down however you can, but most herbicides should be put away for now because of likelihood of vine damage.

Where trade names or commercial products are used for identification,

no discrimination is intended and no endorsement is implied.

Always read the label before using any pesticide.

The label is the legal document for the product use.

Disregard any information in this message if it is in conflict with the

label.

The UVM Tree Fruit and Viticulture Program is supported by the

University of Vermont Agriculture Experiment Station, a USDA NIFA E-IPM

Grant, and USDA Risk Management Agency Funds.

Early season vineyard management

Posted: May 24th, 2018 by fruit

By Terence Bradshaw

Grapes are moving fast in Vermont vineyards, with most cultivars in the UVM vineyard at about 3” shoot growth. Shoot thinning now will give best results before the vines waste energy on growth that you won’t keep. We typically aim for 4-6 well-spaced shoots per foot of canopy, selecting for the most healthy/vigorous and those with appropriate orientation for our downward training system (high-wire cordon).

Figure 1 Before shoot thinning

Figure 2 After shoot thinning

This is a typical time to start a spray program to manage disease. First, a warning- do not spray anything in the heat we are expecting tomorrow May 25. Application of many materials just prior to and most anything during heat over 85°F can cause phytotoxicity to vines. The primary disease of concern at this point is phomopsis, as rachis infection at this point in the season is may cause significant fruit loss at harvest. Anthracnose may also be active at this point , given the warm/hot weather. Most growers would do best to cover early this week with a contact fungicide like mancozeb or captan.

Organic growers are in for a bit more work. The standard fungicides, copper and sulfur, have only fair efficacy against this disease at best, and in a couple of weeks when black rot becomes the next disease of concern, those materials will have even less efficacy against that disease. The first line of defense in an organic vineyard is a strict sanitation program. This includes removing all mummies still in the canopy (not dropping on the ground, but actually removing them from the vineyard) as well as any obviously diseased wood. Phomopsis and anthracnose both overwinter largely on infected wood in the canopy, and removing this wood during dormant pruning or now is essential to reducing disease pressure. Stubs left at the ends of spurs should now be removed since you can see where this year’s shoot growth will resume (at the developing shoot)- these stubs will die and may become infected with phomopsis this season (or were last season) .

Figure 3 Removing stubs at end of retained spurs.

It is worth noting that both copper and sulfur (including lime sulfur) can cause phytotoxicity on certain cultivars. Dr. Patty McManus summarized her research on copper and sulfur sensitivity in cold-hardy grapes in the 2/8/16 Northern Grapes newsletter, and I’ll summarize it to say that Brianna should receive no copper; and Frontenac (all types), LaCrescent, Leon Millot, Marechal Foch, Marquette, and St. Croix should receive no more than 2-3 copper sprays per season. Dr. McManus also suggests no copper or at most a limited trial on Louise Swenson, as it has similar parentage as Brianna which showed substantial phytotoxicity to that material. Save limited applications of copper for later in the season when black rot and downy mildew become bigger concerns. Sulfur sensitivity was observed on several cultivars, and its use (including lime sulfur) is discouraged on Foch, Millot, Brianna, and Louise Swenson; with limited (2-3) applications suggested on LaCrescent and St. Croix.

So, if you have removed all diseased wood and are ready to cover your vineyard for protection against phomopsis and anthracnose, the best choices is likely lime sulfur applied at two quarts per acre in sufficient water (25-30 gallons should do it) to wet the canopy. Lime sulfur is hot stuff: caustic, corrosive, and noxious. Use appropriate personal protective equipment and spray in cooler weather to reduce phytotoxicity. Powdered sulfur may also be a good choice, I would suggest 3-5 pounds per acre at this stage.

Finally, a word of warning:
Starting Saturday May 26 and for two weeks I’ll be away on a USAID assignment helping some farmers in Lebanon (the country) to set up cider operations to improve the profitability of their orchards. Some of these sites are pretty remote, and as such, I expect I’ll be out of contact for a bit. By the time I return, all vines should be shoot thinned, another fungicide or two applied (and we’ll be well into black rot season by then), and weeds controlled by whatever method you choose to use. Here are links to some past postings that are relevant to this time of the season and should give some advice on management as we enter the bloom period:
http://blog.uvm.edu/fruit/2017/06/06/vineyard-management-approaching-bloom/
http://blog.uvm.edu/fruit/2016/06/03/vineyard-disease-management-june-3/
http://blog.uvm.edu/fruit/2015/05/28/prebloom-disease-management-and-frost-prevention/

Best of luck and I’ll drink a glass or two of Lebanese wine for you all,

Terry

Where trade names or commercial products are used for identification,

no discrimination is intended and no endorsement is implied.

Always read the label before using any pesticide.

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Disregard any information in this message if it is in conflict with the

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University of Vermont Agriculture Experiment Station, a USDA NIFA E-IPM

Grant, and USDA Risk Management Agency Funds.

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