University of Vermont

June 7, 2020

I had a chance to visit some orchards late last week in Southern Vermont. We should remember that the lower Connecticut River Valley has traditionally been a major center of apple and peach production in the state. While there are fewer acres of trees than in the past, that’s true across the state. I am always impressed by the landscape down there, it really feels like another place compared to the Champlain Valley or interior highlands. What I saw is likely pretty indicative of orchards around the state.

Fruit set looks pretty heavy, and I have been seeing evidence of thinners applied early last week working. We are entering another window of good thinning weather, so if your crop id still clustered into doubles and triples per cluster (or worse), plan on another thinner this week before it warms up again. Grower who use Apogee for shoot growth management should keep applying on a 10-14 day schedule until terminal bud set. That’s still a solid month away. Get your nitrogen, potassium, magnesium, and boron fertilizers (plus anything you need if your foliar analysis from last year indicates it) on now. Any time, you can start applying calcium sprays to developing fruitlets, especially Honeycrisp and other large-fruited varieties.

Diseases: scab? What scab? This spring has been easy to manage for apple scab, as rains have bee intermittent, spread out, and fairly short. NEWA suggests that most of the ascospores at our orchard in South Burlington have been ejected, but I don’t really trust that yet. Growers should maintain fungicide coverage ahead of any rain events for the next couple of weeks. Fire blight: I started seeing symptoms on Friday in one of our blocks that was intentionally inoculated as part of Dr. Kerik Cox and Anna Wallis’s fire blight trials I am hosting. So, I know conditions were ripe for infection. Keep an eye out in your orchards and be ready to cut out any strikes as they appear. Haste is good on that front. Sooty botch / flyspeck will be managed with your scab sprays.

Insects: Things are hopping on that front. Plum curculio remains active and I have seen injury. We’re only about halfway through their oviposition period at this point, so keep covered. Organis corchards should plan to keep Surround on for another couple of weeks anyway. Codling moth are active. If you didn’t trap them in your orchard, use the NEWA models to guess, but it’s always best to use an actual catch date from your farm when calculating degree days for managing this pest. I’ve played around with a few capture dates for various orchards in the warmer sites and all are calling for treatment sometime this week. If CM  are a problem in your orchard, I would plan on a spray specific to them with a selective and efficacious material like Intrepid, Rimon, Belt, or Madex. As always, see the New England Tree Fruit Management Guide for recommendations.

June 17, 2020

It’s dry, I know. If you have the ability to irrigate, you should be. At a minimum, newly planted trees should be watered regularly. This dry weather has been great for management of most diseases- apple scab, plus rusts and some of the other ‘minor’ diseases should be pretty low in abundance in managed orchards. It’s not hard to find scab lesions in unsprayed orchards, even at the especially-dry UVM Horticulture Research & Education Center (HREC), so the potential is there. This dry weather is slowing the end of scab season, though. Ascospore development follows a fairly predictable curve in years with normal precipitation patterns. However, in dry conditions, the fungus enters a dormant state, so development slows. We’re not entirely sure how extended the dry window needs to be for the inoculum to die out rather than just wait it out until rains come and re-energize it. Most orchard’s NEWA models indicate that the primary scab season is over, but others who are using the RIMpro model indicate another infection period is waiting in the wings. I would feel better with one fungicide protection going into next week when rains are expected. I don’t know if any of the models adequately plan for weather conditions like this.

The disease of greater concern to me is fire blight. Weather during bloom was hot this year with pretty high potential for infection. However, wetness events were rare, and inoculum isn’t guaranteed in all orchards. We have some active fire blight research going on at the HREC, and I can assure you that trees that were inoculated have plenty of the disease. We also have other sections of orchard with little FB history where I have found a few strikes. Everyone should keep an eye out and do a thorough scouting of your orchards for signs of infection and plan to cut it out ASAP. This dry weather we’re having is conducive to cutting while minimizing disease spread. Dan Cooley and others wrote a nice fact sheet on fire blight management that can be found at: https://ag.umass.edu/sites/ag.umass.edu/files/fact-sheets/pdf/f-133.pdf. I have also recorded a video on removing strikes that I’m posting to my YouTube channel (https://www.youtube.com/user/UVMOrchard). My rural DSL upload capability is taking quite a while to get it there, so check back later today.
Insect management is key in orchards now. Where codling moth has been a problem, application of a CM-specific material is warranted most any time now, depending on your biofix (the date of first catch in pheromones traps in your orchard). For upland and inland sites, you may be a week away. Plum curculio are likely still active in cooler sites, but I have not seen fresh damage in the warmer sites (Champlain / Connecticut Valleys) so if a suitable material was applied in the last week or so, you’re probably covered there. 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.

Think about applying calcium in all of your sprays now, especially on Honeycrisp, Cortland, and other large-fruited cultivars, and especially especially on those cultivars if they have a relatively small crop this year.

Many growers, myself included, have observed poor fruit set or over thinning this year. That warm spell around June 4-6 and again 10-12 seems to really have activated thinners, and there may have also been some frost damage going into bloom. I hope your crop has turned out okay, please let me know if there are issues. I’m not sure if weather events contributed to overthinning is an insurable loss under most crop insurance policies, but it’s worth looking into.

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July 15, 2020

It’s been a while since our last check-in. One of the things I was surprised by when I started in orchard work was the relative slowdown in urgency after July 1. Having grown up on a dairy farm, where there’s no break, and summer means haying season on top of all the other chores, a chance to take a breather in summer is welcome.

But that doesn’t mean there’s nothing to do in the orchard, and activities done (or not done) now can greatly affect your crop. Here are some of the things to keep in mind right now:

Insects: Apple maggot fly (AMF) is active in most Vermont orchards. Red sticky traps should have been hung at the beginning of the month, and five flies per baited trap, or one if not using baited lures, should indicate a need to treat. Assail is the most common material that growers are using these days, although many others are also effective. As always, see the New England Tree Fruit Management Guide for specific details. Organic growers may have success using Surround at this time, although the residue will need to be removed from fruit at harvest. Entrust has some efficacy against AMF, but should be used with a feeding stimulant like sugar to increase feeding by flies. Codling moth (CM)second generation egg hatch is still a bit away, we usually aim for treatment around 1260 degree days (base 50F) after the first trap capture biofix (we’re at 907 in South Burlington as of today). Obliquebanded leafrollers should be active soon as well, and I’d imagine that materials applied to target CM (unless using very specific materials like codling moth granulosis virus) will take care of hatching larvae.

Mites aren’t really insects, but I’ll include them here. The hot, dry weather has been very conducive to mite population flare-up, both for European red mite and for two-spotted spider mite. These pests are worth scouting for, and an average of over 5 mites per leaf (choose mid-aged leaves on terminals) may warrant treatment. The best ways to avoid mite problems are measure to protect beneficial mites and insects that eat them. That means avoidance of pyrethroid, carbamate, and organophosphate insecticides in general, as well as a thorough oil treatment in spring. Still, if you are in mite trouble, there are many materials available to help manage them.

Diseases: Apple scab should be done, it was a pretty easy year on that front. Sooty blotch and flyspeck are now the main cosmetic diseases, along with bitter rot and black rot that can destroy fruit. Although it’s dry, maintaining a minimum residue of a fungicide like Captan, Topsin, or a strobilurin will help to keep diseases at bay until harvest. We’re on a three-week schedule at the UVM orchards, but it’s really dry there and we do not wholesale fruit so a little cosmetic damage from SBFS is acceptable. Finally, keep looking for and cutting out fire blight.

Horticulture: Now is the time to start summer pruning to get some sunlight into vigorous trees and improve airflow and spray penetration. In most cases, summer pruning may not be necessary except to correct for occasional broken limbs or branches growing out into the drive row. But in many Vermont orchards where semi dwarf trees are still common, a light haircut can improve light penetration, red fruit color, and overall pest management and fruit quality. I tell my pruners that I want to see the whole trunk- that means removing vegetative shoots tat are blocking light from penetrating into the tree canopy. Fruit don’t need to be 100% exposed, dappled light is okay, but they can’t be in the shade.

It’s important to be maintaining calcium sprays, especially on large-fruited cultivars and doubly especially on Honeycrisp. Four to eight applications are recommended, especially on Honeycrisp, to reduce bitter pit. That may mean making extra trips through the orchard just to spray calcium. Most times, it can be mixed into the tank with other pesticides, as long as any pH requirements are met for the materials you’re using.

Keep running water if you can. It’s really dry out there, not that you need me to tell you that.

COVID-19: As harvest nears, I’ll get more materials out regarding impact of the pandemic on farm operations. For now, I’ll point you to Verm Grubinger’s excellent resource list for vegetable and berry growers. You will need a plan this year, whether harvesting for wholesale, selling retail, or opening for PYO.