Happy (official) summer. We’re still in peak diseas management mode on Vermont vieyards, but things are starting to shift a bit. Phomopsis management should be done, but black rot is still a concern as fruit won’t develop resistance to that disease for a couple more weeks. More importantly, ‘the mildews’ (downy and powdery) are a concern. For powedery mildew, which only requires high humidity to cause infection, sulfur, Regalia, and stylet oil are options for organic vineyards; those and the strobilurin (FRAC class 11), DMI (3), SDHI (7), and AP (9) are options for non-organic vineyards. Downy mildew is in another whole biological class of diseases, and organic options for management include the copper materials, Serenade Max, and various potassium bicarbonates; non-organic producers may use a strobilurin, phosphite product, captan, or Revus. The New England Small Fruit Management Guide summarizes these options in a pretty easily-digestible table.

I am deep in the midst of teaching two summer courses now, including my Cold Climate Viticulture course. Tuesday I gave the students a tour of the UVM vineyard, which I hadn’t walked in a good week or so, and was taken aback by the amount of Phomopsis and black rot I saw on some vines. Closer examination revealed that the diseases were restricted to the bottom 2-4 leaves on the shoots. This generally indicates that there was an issue with application when those leaves were sprayed, as I checked my spray records against the NEWA grape disease models and I was pretty well-covered. Last year we installed a new exclusion netting system that we left up on the wires, which my tractor with spray cab won’t fit under. So, we pretty quickly set up an old sprayer for use on one of our other tractors, and while spraying that first time, I was tweaking many aspects of the operation while making my spray– travel speed, fan speed, nozzle orientation, etc. I also noticed that one nozzle had some grit in it and likely wasn’t getting material on like I should have. Lesson learned: calibrate your sprayer and check coverage before you start the season.

We also noticed that my vines were a little yellow, and pretty much begging for some nitrogen. This is a good time to get a last, light dose of nitrogen on your vines before putting it away for the summer so vines can adequately shut down before winter. This is also a great time to apply potassium and magnesium as your soil and petiole tests call for them.

Any time now the bases of shoots will start to lignify and we can start shoot positioning in earnest. Vermont summers are short and relatively cool, and developing and ripening fruit clusters need as much sun as you can give them. That starts with getting the clusters exposed by combing shoots down on high-wire trained vines so fruit are exposed and leaves are more or less under the fruit zone. Low-wire or vertical shoot positioned vines need their shoots directed up and away from developing fruit, again to minimize shading. Make sure shoots aren’t breaking off as you work with them, and if they are, wait a bit to do this. We’ll post more information on this shortly.

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.

Happy summer:

Apple scab should be pretty much done by now, but be sure to look carefully to ensure that you haven’t had any slip through, as it was certainly windy during a couple of the infection periods this season. If you find no scab in a thorough evaluation of the orchard, that disease is done for this year. Sooty blotch and fly speck (SBFS)would be next on the management agenda, and typically require 270 hours of accumulated wetness starting at 10 days from petal fall. For reference, accumulated wetness in Shoreham (according to NEWA) is about 125, with similar values for other Vermont orchards. Keep an eye on this and apply an appropriate material ahead of any rains as we near the threshold. Honeycrisp growers in particular should also plan on applying a material with efficacy against black rot, which that cultivar is uniquely susceptible to. Common summer fungicides targeted against these diseases include captan in combination with Topsin, a strobilurin (Flint / Sovran), or a DMI (Pristine, Inspire, etc); organic growers may consider Regalia, sulfur, or Serenade, but I am not really sure of theis efficacy. I will say that in 12+ years of managing an organic orchard with a primarily sulfur-based program, I saw almost no SBFS, but plenty of black rot on Honeycrisp especially. Take that as you will.

We’re in a calm spot between insects, but it is time to hang you 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. 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.

Forwarding from Ollie Cultara at VT Agency of Agriculture, Food, and Markets- TB

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A good question came up today regarding my recent recommendation on codling moth management: “Saw your note on Codling Moth and was wondering if Assail or Leverage or Belay would work as well as what you listed (Intrepid, Altacor, Belt, Rimon)?”

It’s helpful to have someone read your words back to you. The materials I mentioned are all pretty targeted, if not specific to, lepidopteran pests, and are all effective against codling moth. My unspoken statement was that if you are only targeting CM and want to use a ‘softer’ material, these fit the bill. But certainly, if you still have fresh curculio activity, or just have another material ready to go in the shed, a more broad-spectrum pesticide is fine to use. Assail, Delegate, Imidan, Voliam Flexi, and Danitol are other materials rated at high efficacy against CM in the New England Tree Fruit Management Guide. By all means, use them. Managing CM in high-pressure orchards is pretty critical now.

Take care. I’ll be out tomorrow morning with a tank of Intrepid and Calcium at the crack of dawn tomorrow morning. Were I in the commercial business, I might consider one last fungicide before calling it good for apple scab, but it’s important to get the fire blight I’ve seen out of the orchard and the 4-hour REI on Intrepid is pretty key to getting that done.

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.

I apologize for this overdue communication. Some grapes at the UVM Vineyard in South Burlington were starting bloom yesterday, and we are in peak disease management season. I’ll keep this brief:

1. Pretty much every major disease is likely active now, including black rot, Phomopsis, powdery and downy mildew, and anthracnose. Vines should be protected with the best materials in your toolbox. For non-organic growers, that means mancozeb or captan plus a DMI (FRAC code 3, e.g., Rally, Vintage, Inspire super) or strobilurin (FRAC code 11, e.g., Flint, Sovran, etc) material. Rotate those FRAC codes and do not use materials with the same code more than twice in a row.
2. For organic growers, this is the window to be using whatever copper material you choose.
3. Keep fungicide coverage on at 7-14 day intervals, shorter as there is more rain.
4. Keep an eye out for grape tumid gallmaker to be popping up. If these have been a problem in your vineyard, Movento or Assail are your best materials. I don’t know any organic option, so you’ll need to remove them by hand.
5. Shoot thinning is still critical now, the sooner it’s done, the more resources you will leave for the remaining shoots. Shoots have not lignified enough to do any combing.
6. If you suspect any nutrient deficiencies, this is a good time to collect petiole samples for analysis. I prefer the veraison timing, but bloom sampling allows for correction this season if somethings comes up particularly low. Details on petiole sampling can be found here.

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.

Category [tree fruit; IPM]

June 8, 2021

Sorry- I’m late on getting anything out, so I’ll cover the high points that are important for managing Vermont orchards in the next few days / week:

1. It’s time to get a codling moth spray on for many orchards. CM is best managed by using the NEWA degree-day model. For your site, enter the first pheromone trap capture (Biofix) or, with less certainty, let the model predict emergence (that’s the default). Most materials should be applied between 100 and 200 degree days (base 50°F) from that date. For most orchards, that is now. A lepidopteran-specific material like Intrepid, Altacor, Belt, or Rimon (latter two should have been on a few days ago) is best against this pest.
2. Plum curculio still has some activity left in it for this season in most orchards. If you covered the orchard with a relatively broad-spectrum insecticide at petal fall, border sprays will suffice to keep late-season damage down.
3. Apple scab primary season is done pretty much everywhere. Scout the orchard meticulously for signs of scab, if you have it, keep up a Captan program until things are burned out. Otherwise, fungal diseases are probably good for a little bit.
4. Fire blight- Streptomycin works!! We have tow partial rows at the UVM orchard with many dead trees that I plan to rip out (that’s another story), so I haven’t bothered spraying them this year. They are right in our Fire Blight-riddled cider block, which is 95-98% clean right now, but those Spitzenburgs are toast. Scout your orchard carefully for signs of the disease and plan to prune out ASAP, on a dry day. Except in the case of hail, do not apply streptomycin to an orchard that shows symptoms of the disease.
5. Fertility- If you’re applying nitrogen, start making plans to back off and shut it down soon. This is a great time to apply magnesium, potassium, and other cations if our soil or foliar analyses calls for them.
6. Every spray this time of year should include some calcium. On Honeycrisp, calcium should go on even if another spray material isn’t needed.
7. Keep an eye on thinning. This has been one of the most inconsistent years I have seen in my time with this crop (25 years) and I’m seeing and hearing of fruit densities all over the place. It’s getting late to apply thinners, so while scouting for Fire Blight, keep an eye out for trees that need a little hand thinning.
8. Water, if you can. Many areas of the sate are running dry, and we’re still in the window of maximum cell division that determines fruit size and quality.

All for now,

Terry