VT Apple IPM- Apple maggot fly traps should be prepared and hung

Assuming that you have dealt with codling moth, we’re in a calm spot between insects but it is time to hang your apple maggot fly (AMF) traps. 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.

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. 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. For monitoring 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. Remember to rotate your insecticide chemistries to avoid resistance development in pest populations. Resistance isn’t a huge issue with apple maggot fly that has one generation per year, but codling moth and other lepidopteran pests are still about and subjecting successive generations of them to the same class of materials can induce resistance. 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.

Think about including calcium in all of your foliar sprays until harvest, and on Honeycrisp and other large-fruited varieties, you may want to make some specific trips just to get more Ca on. Also, if you see any fire blight, please let me know as I have colleagues at Cornell and Connecticut Agricultural Experiment Station who are looking to sequence samples to test for streptomycin resistance.

Vermont Apple IPM

Orchards in the highest elevation and coolest areas are at or just past petal fall, so all the advice I’ve had for other growers applies there as well now. All orchards should have started or completed chemical thinning by now. Fabulous thinning weather occurred last week and those who applied the usual materials should see the effects by now. If a little more ‘nudge’ is needed to break up clusters, carbaryl , 6-BA 9 (Maxcel, etc.), and NAA (Refine, etc.) will still work so long as the fruit you’re thinning are under 15 mm diameter.

Where petal fall insecticides were applied against plum curculio (PC) and European apple sawfly, you’re probably good until another is needed for PC due to rain washoff or codling moth rears its head. As for the former, PC is only ‘programmed’ to lay eggs and cause fruit damage for about 308 degree days (base 50) after McIntosh petal fall, and we’re only about 1/2 there at the UVM Hort Farm. It would be wise to check for PC damage to fruitlets and consider reapplication at the first sign of fresh damage.

Figure 1. Plum curculio damage on a developing fruitlet. This damage is about a week old, note the dried surface and lack of sap. Fresh stings after an insecticide has been applied indicate potential need to reapply.

Codling moth have now been trapped in many orchards in the state. To best manage the first generation of this pest, calculate degree days (base 50°F) from the date of first capture in pheromone traps. Most materials should be applied at 200 degree days after catch, which should be in the next week or so. Retired Cornell entomologist Dr. Art Agnello offers the following specific recommendations for CM management the June 10, 2019 Scaffolds newsletter: “The best products for controlling both CM and OFM in apples and stone fruits are those in IRAC Group 28 (containing a diamide; i.e., Altacor, Exirel, Minecto Pro, Voliam Flexi or Besiege) or IRAC Group 5 (mainly spinetoram, Delegate; spinosad, formulated as Entrust, is an organically approved option). Two applications from either of these groups on a 10–14-day interval would be recommended starting at 220 DD50 from biofix…Products with insect growth regulator activity, such as Rimon, Intrepid or Esteem, would also be suitable options in apple sites at the lower end of these values. Other products with activity against internal leps include the neonic Assail, the biological Grandevo (also organically approved) and, in orchards where resistance has not developed to the newer pyrethroids, also Baythroid, Danitol, Endigo, and Leverage (note: I like to avoid pyrethroid use in orchards if possible sonce they can substantially disrupt beneficial insect populations- TB). Most older broad-spectrum materials like Imidan, Lannate, and the older pyrethroids, which were formerly more effective, are generally not as good choices because of insecticide resistance issues…This would also be an appropriate time for an application of a granulosis virus product in pome and stone fruits such as Cyd-X, Madex, Virosoft CP4 or Carpovirusine (apples and pears only), in addition to the larvicides discussed above. These are biological insecticides, which must be ingested to initiate the infection, after which the virus replicates inside the larva until it is killed; this releases more virus particles into the orchard. This is a very useful approach for long-term population reduction, particularly when used in at least 2 applications per generation. Madex, and now Virosoft CP4 (see “Chem News” in this issue) contain an isolate that is also effective against OFM.”

As for diseases, all sites should be nearly done with primary apple scab season. That doesn’t mean that scab management is done, you should keep covered for at least one more good infection period. Inland/cooler sites likely have inoculum left through next week, so you’ll have at least two sweeks more of fungicide coverage before backing off. Scout your orchard regularly for scab, especially in the tops of the trees, ends of rows where nozzles may have turned off, or on susceptible varieties. f you have scab, plan on maintaining some level of preventative fungicide (Captan is about all you have, sulfur if organic) for the next month or so until fruit and foliage become resistant. Do not use single-site fungicides like DMIs, strobilurins, or SDHIs (FRAC codes 3,7, 9,11) on active lesions to reduce development of fungicide resistance.

Keep your eyes out, especially in blocks that have had a history of the disease or on susceptible cultivars like Gala and Paulared, and cut strikes out as you see them.

If using nitrogen fertilizers in your orchard, plan on wrapping up applications in the few weeks to give trees time to harden off for winter. Potassium fertilizers can go on any time now.

VT Grape IPM

Vine growth is flushing out rapidly in Vermont vineyards, with many vines at or approaching 5-8” shoot growth. We are entering a critical window of disease management when anthracnose, black rot, Phomopsis, and powdery mildew can all be active. There isn’t a lot of rain in the forecast, but showers mid-week may cause enough wetting to initiate infections. Vineyards should be covered with your fungicide(s) of choice this week.

This is also a great time to apply any ground-applied fertilizers, as this period of rapid shoot growth is when plants need nutrients the most. Nitrogen need in Vermont vineyards is relatively low (but not non-existent), but most vineyards need some potassium and often magnesium. Please base your fertility applications on soil and foliar analyses (more on that next week) or visual symptoms, especially for magnesium.

And we’re off….early season orchard management in Vermont

NEW this year. Please report local apple bud stages here to make our reports more accurate: https://go.uvm.edu/22applebudstage

Upcoming weather this coming week looks warm, above freezing, anyway, for the Champlain and Connecticut Valleys. Orchards at UVM Hort Farm are at not quite at silver tip, but warm weather this weekend and early next week should advance tissues pretty rapidly. My students are wrapping up pruning today. I recommend pushing your pruning brush or flail mowing in-place for high density plantings with smaller pruning wood as soon as possible to get ready for the spray season.

Calibrate your sprayer. As soon as you can get into the orchard, an application of urea to the leaf litter (44 lbs feed-grade urea in 100 gallons water per acre directed at the ground, especially under trees) may be warranted to reduce overwintering apple scab inoculum, too. That is not an organic-acceptable practice, so if you are certified, consider applying granular lime or compost tea instead if you wish to improve leaf litter decomposition, but those need to happen sooner than later to have an effect on overwintering inoculum.

Get your early season spray materials ordered and on-hand for when the season starts. No, really, calibrate your sprayer. Be ready to properly oil the orchard if you have had any issues with mite flareups or oystershell / San Jose scale, the latter of which I have seen not only in orchards but also on fruit in grocery stores. Remember that oil should go on at full dilute or no more than 2x concentration to be most effective. So when you calibrate your sprayer, be sure to reserve a setting for high-volume applications, either by switching to higher-output nozzles, reducing travel speed, or both.

The window between silver tip and green tip is perfect for applying copper to suppress fire blight and to act as your first scab spray of the season. Dave Rosenberger pulled together an excellent summary of the use of early season copper for scab and fire blight management in the March 25, 2013 issue of Scaffolds. But, while early season copper can be an excellent management tool, copper materials can be phytotoxic. That is why the early season spray is made before much green tissue is exposed. If applied when buds are closed, however, then cold temperatures immediately before or after spraying are not a huge concern. In fact, I have in many years had my airblast sprayer fan shroud ice up while applying copper- not an ideal situation, but it can happen at 5 AM when the temperature is 31 F and the velocity of air coming through the shroud contributes to rapid cooling, much like a snow gun on the ski slopes.

Oil, however, is a different story when it comes to applications before or after freezing weather. Delayed dormant, silver tip, and green tip are common times to apply an oil spray to help manage mites, aphids, scales, and other overwintering arthropods pests. When oil penetrates cells, it causes phytotoxicity that can affect fruit development, especially when cluster leaves which supply most of the carbo0hydrates to developing fruit early in the season are damaged. Oil is often applied at dilute rates, and the goal for a grower should be to fully saturate the tree as best possible. Application of oil just after or before freezing events (24 hours either way definitely, possibly 48 hours) can cause damage, so if you have seen or are expecting freezing temperatures, put the oil away for a couple of days.

Fortunately, oil can be applied right up to tight cluster-early pink bud stages, and in fact may be more effective then. We should be out of frost risk by then (otherwise we have bigger problems than oil on fruit cluster leaves), so maybe delaying your oil application would be prudent, so long as you can fit it around Captan sprays later in the season. Oil should not be applied within 7-10 days of a Captan or Sulfur spray. For more details on spring oil applications to manage mites and other pests, including rates and spray incompatibility issues, please refer to the New England Tree Fruit Management Guide.

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, UVM Extension, USDA NIFA E-IPM Program, and USDA Risk Management Agency.

UVM Extension helps individuals and communities put research-based knowledge to work. University of Vermont Extension, and U.S. Department of Agriculture, cooperating, offer education and employment to everyone without regard to race, color, national origin, gender, religion, age, disability, political beliefs, sexual orientation, and marital or familial status.

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. At the UVM vineyard, have observed Marquette at veraison as of at least August 4, Petite Pearl and Itasca are changing color about now, and Verona is just around the corner.

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 2010-2015. 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

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.

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, UVM Extension, USDA NIFA E-IPM Program, and USDA Risk Management Agency.

UVM Extension helps individuals and communities put research-based knowledge to work. University of Vermont Extension, and U.S. Department of Agriculture, cooperating, offer education and employment to everyone without regard to race, color, national origin, gender, religion, age, disability, political beliefs, sexual orientation, and marital or familial status.

VT Apple IPM: Thinning, fire blight, scab

May 20, 2021

It’s looking pretty hot out there in more ways than one. Many orchards are at or near petal fall, but those with bloom should be keeping the streptomycin sprays on, with all this heat we’re having. Fire blight remains a concern statewide, and I would expect some infection in any orchard that has sufficient inoculum. That last part is important, and yet hard to quantify. Certainly if you’ve has the disease in the past, especially in the last two years, it’s likely that it will show up. The next disease concern is apple scab. Any promised rains keep getting pushed back in the forecast, now Saturday-Sunday looks like the most likely chance for any substantial rainfall. Whenever it comes, we should be prepared with a good coating of protective fungicide. Most growers are switching over to captan now which is fine, but be careful not to mix with Regulaid if you’re using that wetting agent to improve strep penetration into blossoms, as the combination of that, captan, and heat will likely cause leaf burn. If you’re looking at a second application of strep after one that already had a wetting agent included, you can leave it out this time. It’s also nota bad idea to put something in that would provide broader disease control, like an SDHI, SI, or DMI fungicide (take your pick from materials with FRAC codes 3, 7, 11 here, and always rotate FRAC codes after two successive applications of the same one).

Growers at 100% petal fall may want to consider adding in an insecticide against European apple sawfly, plum curculio, and early codling moth. However, if you have any blooms remaining, including in the groundcover vegetation, I recommend holding off on applying any materials harmful to bees and other pollinators. I typically include some Dipel or other Bt product in this ‘almost petal fall’ spray to help keep lepidopteran pests like green fruit worm and obliquebanded leafroller at bay while I wait until the following week to apply something more broad spectrum like Avaunt, Actara, or even Imidan if you’re still using organophosphates. Sevin applied in a thinning spray will have some efficacy as an insecticide, but not a lot.

As for thinning, it’s time to get on it. Blooms are heavy this year, and the sooner you remove resource competition and gibberellin formation from excess developing seeds, the more likely you will get reasonable return bloom next year. If you still have any bloom, or just want to stay away from it, please leave the Sevin / carbaryl on the shelf. With the hot weather, trees are going to respond well to thinner applications anyway, so an NAA or 6 BA spray should suffice. Pick one- the former is typically good on McIntosh and most large-fruited cultivars, the latter on varieties that tend to produce smaller fruit (Empire, Gala, Fuji, Macoun). See specific recommendations here.

For cider apple growers, I don’t have a great recommendation for managing biennialism on European cultivars. The need to thin for fruit size is less of a concern than for dessert cultivars, but you don’t want to overstress the tree and have no crop this year. I would plan on multiple applications of NAA, say bloom, petal fall, and at 8-10 mm fruit size, to encourage return bloom.

For what it’s worth, here’s the tank mix I plan to apply tonight or tomorrow morning: Captan (5 lbs/ac), Merivon (5oz), Dipel DF (1 lb), Refine (8 oz), Harbour (24 oz). This is to a very mixed orchard of ~50 varieties in all stages of bloom to petal fall.

Webinar tomorrow: NEWA 2.0: Project upgrades for 2021

Here’s a reminder that tomorrow, Tuesday March 30, we will host the final New England Winter Fruit Seminar of the season: NEWA 2.0: Project upgrades for 2021. More information and registration at: https://ag.umass.edu/fruit/events/newa-20-project-upgrades-for-2021. Please plan to register at least 30 minutes prior to the webinar, which will run from 12:00 to 1:30 PM.

The webinar will feature Dan Olmstead. Dr. Olmstead is an Extension Associate with the New York State IPM Program at Cornell AgriTech. He is the program coordinator for NEWA, the Network for Environment and Weather Applications. NEWA is an online platform that provides decision support information for insect pests, plant diseases, and crop management in fruit, vegetable, and field crop commodities. These resources are accessible at http://newa.cornell.edu free of charge to all producers in any of NEWA’s 15 member states in the US.

Important changes to UVM Fruit website, and upcoming winter educational opportunities

As we shift into winter, I’d like to highlight some changes among the UVM Fruit program, and to present a number of opportunities for learning and networking this season. First, our website which has been operating since 2013 was retired on fairly short notice when the background sofytware was retired by . Thanks to the Extension Web Team, we now have a new site shared with the Vegetable Program, now together known as UVM Commercial Horticulture. The site is not completely migrated yet, but is largely in-place at: https://www.uvm.edu/extension/horticulture/commercial. Please update your bookmarks, but save the “…this link is broken…” emails for a bit until we can get things squared away. The complementary UVM Fruit Blog is still available, but will likely be tweaked a bit this winter to make specific material easier to find. Consider the website as the main site for static information, and the blog as a place where I post more time-sensitive material, particularly an archive of all emails sent to our mailing lists.

One of the key outputs of our program is the annual Vermont Tree Fruit Grower Association meeting held every February. Obviously, that is not going to happen this year. On the other hand, we do have a number of online meetings and webinars that will provide opportunity for learning, collaboration, and to acquire pesticide applicator’s recertification credits. These will happen under different banners, so I’ll summarize them below. All of these require preregistration, and each platform has a different sign up.

2020 Vermont Vegetable and Berry Grower Webinar Series registration (all use same link, on right side of page)

  • 12/2/2020: Bags, Liners, Containers – So Many Options – Chris Callahan
  • 12/9/2020: Adding Tree Fruit to a Diversified Farm – Terry Bradshaw
  • 12/16/2020: VVBGA Meet and Greet. Lisa McDougall, Justin Rich, Andy Jones

2020 UVM Fruit Program / VT Tree Fruit Growers Assoc Annual Meeting.

  • 2/18/2021: Meeting hosted by UVM Fruit Program on Zoom; VTFGA will handle registration (watch for details)

2020-2021 New England Winter Fruit Meetings registration page (not all meetings set up for registration yet)

A collaboration among the New England Tree Fruit Extension Professionals. Most of these meetings will qualify for pesticide recertification credits.

  • 1/12/2021: Harvista and SmartFresh on Honeycrisp and Other Varieties; CA Storage Techniques Presenter: Jennifer DeEll, OMAFRA and Randolph Beaudry, MSU
  • 1/19/2021 : Training and Pruning Strategies for Healthy and Productive Peach Trees Presenter: Bill Shane, MSU
  • 1/26/2021: Blueberry Twig Blight Diseases Presenter: Mark Longstroth, MSU
  • 2/9/2021: Cider Apples in 2021: Where Do We Stand? Presenters: Terry Bradshaw and Liz Garofalo
  • 2/16/2021: Invasive Insect Pests: Spotted Wing Drosophila, Brown Marmorated Stink Bug and Spotted Lantern Fly Presenter: Jaime Piñero, UMass
  • 3/3/2021: Managing a Trickster: Adventures in Apple Maggot Control Presenter: Suzanne Blatt, Ag Canada
  • 3/10/2021: Research Update on Early-Season Insect Pests Presenter: Jaime Piñero, UMass and Glen Koeher, UMaine Extension
  • 3/17/2021: Honeycrisp Bitter Pit and Soft Scald Management Presenters: Renae Moran and Glen Koehler, UMaine Extension
  • 3/23/2021: Tree Row Volume: What it is, why it matters and when to use it Presenter: Terry Bradshaw, UVM
  • 3/30/2021: Network for Environment and Weather Applications (NEWA) 2.0 – Project Upgrades 2021 Presenter: Dan Olmstead, NEWA

There are more details to come on all of these, and each will be outlined in later posts. I look forward to a productive winter, and wish everyone the best during this holiday season.

Take care,


Buds are bursting- 2020 season is on a roll

By Terence Bradshaw

Growth in the UVM vineyard ranges from bud burst to 2-3 shoots emerged; a few shoots are nearing three inches in length. It’s time to really be thinking about protecting vines from early season disease infections. Most cold-climate cultivars will not need disease protection until 5-8” of shoot growth, but any vineyards with heavy disease pressure last year and organic vineyards may wish to begin earlier, especially if inoculum reduction through thorough removal of diseased wood and mummy berries and/or dormant application of lime sulfur was not performed. I still recommend our fact sheet, An Initial Integrated Pest Management (IPM) Strategy for New Cold Climate Winegrape Growers as the best resource to boil the decisions down to a simple ‘prescription’, with the caveat that since it was written some new pest management materials have been released and inoculum may have increased in your vineyards which could lead to increased disease pressure. Growers should have an up-to-date copy of the New England Small Fruit Management Guide (on-line and hard copy versions) and/or New York and Pennsylvania Pest Management Guidelines for Grapes as a reference for specific materials, their efficacy, and use considerations. Remember however that the guidelines are written largely for vinifera and less disease-resistant hybrids, so the specific spray programs recommended may be overkill in Vermont vineyards.

The warm weather in the past few days may have increased emergence of grape flea beetle or cutworms. Grapes are susceptible through about the one inch shoot growth stage, so vines will eventually outgrow the threat. However, cooler temperatures this coming weekend may hold the vines at this susceptible stage long enough for damage to increase to unacceptable levels. A scouting of your vineyard for feeding on swelling buds or developing shoots may be warranted. If damage is evident on more than 2% of buds, an insecticide treatment may be warranted. But if shoots expand rapidly over the weekend, don’t worry about this pest. More information may be found here.

Since buds at ground level have begun to emerge, applications of systemic herbicides should either be halted or very carefully controlled to prohibit contact with green tissue. Now is an appropriate time for cultivation in vineyards to manage weeds. It’s also a good time to keep water on newly planted or young vines. With soil warming and growth beginning, nitrogen fertilizer applications, if needed based on foliar analyses or observed low vigor last year, may also be made now.

I’d say any time now is good to get your shoots thinned down to 3-5 shoots per foot of canopy. Keep more on more vigorous vines, less on weaker ones.

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


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.

Petal fall

By Terence Bradshaw

I know that some orchards are still in bloom, so the thinning and insect management portions of this message may not pertain. Hopefully everyone with any hint of risk for fire blight has treated sometime during this heat spell. Cooler weather this weekend and rapidly dropping blossoms will decrease risk, but until then, the pump is primed. Everyone also needs to keep an eye out for blossom blight symptoms, and for the shoot blight that will follow. Growers can apply Apogee (4.5-9 ounces per 100 gallons dilute**) any time now to reduce shoot blight incidence. Apogee treatments will reduce shoot elongation and thicken cell walls for about 2-4 weeks post-application, so retreatment may be necessary every 1-4 weeks until terminal bud set.

All set on FB? Okay, we have some big fish to fry this week. Let’s cover them one by one.

  1. This will all be said in light of the heat that we’re experiencing in the next couple of days. If you can avoid spraying anything (streptomycin excepted) when the weather is >85°, that’s a good thing. Then again, don’t ignore the very real threat of the following pests that need to be protected against. I have an inkling that many of us will be up pretty late/ early tonight/tomorrow morning to get things covered while dodging the heat.
  2. We are all headed for a pretty big apple scab infection period starting tomorrow Thursday 5/28 or Friday. Make sure you are covered going into it, I would not count on any material’s kick-back activity to handle this kind of scab load. As I’ve mentioned before, some materials (captan, sulfur) can cause leaf burning when applied ahead of hot weather. But, given what looks like an extended wetting period and an ample load of mature ascospores, I’d take the chance of a little leaf burn over a major scab outbreak. If you want to put on a lower rate now and follow up Sunday or so with a kick-back material (SDHI, strobilurin, or DMI, see here for more discussion, also mixed with a protectant like mancozeb or captan). Everyone should plan on phasing out mancozeb soon, as it it toxic to beneficial predatory mites that do some great biological control or European red mite and two-spotted spider mite, and we’ll soon have to be thinking about its 77-day preharvest interval. Organic growers, I would apply sulfur before and after the rain event, and maybe consider lime sulfur (LS) for the second spray to provide some post-infection control. LS is caustic, nasty stuff, so use it wisely, wear all the appropriate gear, and wash everything down well as it is very corrosive to steel and other materials.
  3. If you’re at total petal fall, then it’s time to start thinking about insect pests, especially plum curculio (PC). PC love this heat and will be ready to oviposit on fruit as they reach 7-10 mm diameter. Organic growers should plan on getting a coating or Surround on trees asap, and maintaining that coverage for about 400 degree days (base 50°F) after petal fall (NEWA has a good model for this). This is a longer window of coverage than for non-organic orchard management (308 dd base 50°F), because Surround does not kill the insects and so must be maintained longer until the biological urge to oviposit has completely subsided. For non-organic orchards, effective materials include Imidan, Actara, Avaunt, Voliam, and Agri-Flex. Carbaryl, if used for thinning (see below), will have some efficacy, but probably shouldn’t be your primary material of choice given the weather that is very conducive to PC activity. Thinning rates of carbaryl are about half the insecticide rate, and I would plan on using just that lower rate as a thinner and use a separate material for my insect management. Any of these materials will help to manage the other petal fall insects, including European apple sawfly and the various lepidopterans (obliquebanded leafroller, Oriental fruit moth, codling moth, etc) that may be emerging at this time.
  4. Thinning. Okay, this is always a tricky one. First, anything applied in the next 40 hours will be highly active because of the heat, so I’d err on lower rates and a lighter touch. A second application may be needed after this weather breaks. Now, I haven’t been in orchards all across the state, but where I have seen bloom from Connecticut valley, Addison county, and our own orchard in South Burlington, it was good to downright heavy. Pollination and fertilization conditions have been just about perfect, so I’d expect trees to need a decent thinning this year. The New England Tree Fruit Management Guide has some good variety-by-variety recommendations, so I recommend starting there. A good, standard petal fall spray of 1 qt/acre of carbaryl and 8 oz/acre Fruitone N or L (I did the TRV adjustment for you) should do the trick for most orchards. For organic orchards, it’s time to start hand thinning. A lime sulfur spray used for scab can help to knock some fruit off, but it’s not labeled specifically for that use.

I think that covers it for now.

**This reference to amount per 100 gallons dilute refers to Tree Row Volume (TRV), which is a somewhat out-of-vogue method for adjusting spray rates to compensate for canopy volume. I describe it some here, but in simple terms, it calls for measuring the tree canopy volume and estimating the number of gallons of water to saturate the canopy to wetness (dilute gallons per acre, DGA). No one sprays at full dilute, that wastes time, money, and water. For a good rule of thumb, large, standard trees 20 feet tall planted at 30 feet x 40 feet spacing had (notice the past tense) about 420 DGA. A more typical ‘large’ semidwarf orchard on M.7 or similar with 12 foot tall trees planted at 12 ft x 18 ft would have 200 DGA. DGA decreases down to around 100 and stays there pretty consistently for tall spindle and similar high density, narrow-canopy systems. BUT, we often do not recommend reducing TRV below 150, maybe 120 if you have excellent coverage and an easily sprayed canopy. And this TRV is only used to determine the rate of material used per acre, not how much water you put in the tank. So. Let’s just say use 200 DGA for semidwarf trees, 150 for trellised trees. Back to the Apogee example, let’s use 8 ounces per 100 DGA for simplicity’s sake, that would be 16 ounces per acre to the big trees, 12 ounces to the smaller high density trees. Then figure out how much to put in the tank based on the amount of water you spray per acre, which is likely 50 (or less?) to 150 gallons.

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