University of Vermont

By Terence Bradshaw

By now virtually all orchards, including those in cooler regions, are at petal fall with only straggling bloom around on later cultivars. The cool weather has shut down concerns for continued blossom infections of fire blight. If infection did occur in your orchard during the May 18-20 warm spell (wouldn’t we love one of those again?), you should start seeing symptoms in your orchard around the middle of next week.

Figure 1. Blossom blight symptoms, 2016

Figure 2. Shoot blight symptoms, 2016

Orchards should have received a full-orchard petal fall insecticide by now or next spray. While things have been relatively quiet on the insect from this spring, a number of pests, including plum curculio (PC), European apple sawfly (EAS), and (maybe) codling moth (CM) are ready to pounce now. We have found fresh EAS and PC damaged un unsprayed or organically-managed trees at the UVM farm. If you are finding fresh damage on fruitlets in your orchard, consider application of a material that will cover both of those pests, and maybe CM too. This usually means a neonicotinoid like Assail or Actara; indoxacarb (Avaunt); or a pyrethroid, although the latter will be especially hard on predators and other beneficial insects. for organic growers, a pyrethrum application will help knock down PC that are already in the orchard but will have no residual efficacy- kaolin clay (Surround) sprays should be maintained until PC oviposition activity is complete. If you have already made you full-orchard application, then any subsequent sprays should be targeted at borders (PC, EAS) or at specific pests based on monitoring.

Figure 3. This PC damage is probably about a week old, notice the corking over and lack of sap exudate.

Codling moth are now flying in most Vermont orchards. Unless pheromone traps are checked daily, it is difficult to catch their exact first flight date, but based on captures in area orchards, I am using the following dates for sites around the state:

Brookfield: 5/23

Cornwall: 5/18

E Montpelier: n/a

Essex: 5/23

S Burlington: 5/17

S Hero: n/a

Shelburne: 5/18

Shoreham: 5/18

I would love a good catch date for some sites in southern Vermont if someone is trapping and could send them to me.

Those dates are important, because they represent the biofix that you would enter into NEWA for tracking degree day development to time CM-specific treatments. For most spray materials, timing should be targeted at about 250 degree days (base 43°F) from first catch. There is some room on either end of this, and that can account for differences between actual first flight and first catch in a trap, as well as to line up with good application weather on the other end. Based on the above assumed catch dates, most sites in the Champlain Valley have accumulated about 125 dd, and with the cool weather, we are accumulating 7-15 per day. Therefore, a targeted CM application should wait until next week anyway, we’ll follow up on that later. Specifically targeting CM sprays is a great IPM tactic for reducing impacts to non-target species, because selective materials that affect primarily lepidopteran pests (e.g., Altacor, Delegate, Intrepid) may be used at that time. However, Bt (Dipel, etc.) is relatively ineffective against CM when used as a targeted spray, its use against other lepidopteran pests is recommended but only provides supplemental management of this pest. Other ‘lep’ pests that are active include redbanded leafroller (larvae active) and obliquebanded leafroller (OBLR) (adults now flying). Your petal fall spray should have managed these for now, but if inspections of clusters are turning up larvae, a Bt spray may be warranted. For any material that has bee toxicity (e.g. most all except Bt, kaolin, or the lepidopteran-specific materials like Intrepid or Altacor), be sure to mow flowering plants in the groundcover prior to application.

For disease management, I recommend keeping at least one more fungicide on until you can scout for potential lesions from this last week’s rains. Despite NEWA’s proclamation that all overwintering apple scab inoculum was expended a week or more ago, I don’t trust it and feel it is too conservative in predicting the end of primary scab season. Scouting for detection of apple scab lesions (or lack thereof) to determine the end of scab management season should take place a couple of weeks from now to allow any infections to show.

While we’re in that weird period between the end of ascospore release and waiting for evidence of primary scab infection to show, we can still manage a couple of other diseases in the orchard. I am expecting cedar apple rust (CAR) to be particularly problematic this year, and powdery mildew (PM) infections can still occur on susceptible cultivars. We are nearing the end of the season for mancozeb fungicides- an application tomorrow gives an earliest harvestable date of August 18 to allow for residues to degrade- but those materials have excellent efficacy against CAR and none against PM (worst on Paulared and Cortland, among common cultivars grown in VT). Captan, the ‘standard’ fungicide used against scab, fruit rots, and cosmetic summer diseases, also has no effect on either CAR or PM. The SDHI (Fontelis, Luna, etc.), strobilurin (Sovran, Flint), and DMI (Rally, Procure, etc.) are all effective against those secondary diseases, even when the local apple scab population is resistant to them. This would be a good window to consider their use. For organic growers, I am not recommending much beyond sulfur, maybe lime sulfur if you need to provide some thinning. However, if fruit finish is not a concern, some work I did in the past two seasons indicates that low-dose copper (I used Cueva, but Badge or another material labeled for summer use should work) had some efficacy against CAR (we had no PM in the trial) but did cause some fruit russeting.

Figure 4. Cedar apple rust gall on cedar sent to me by my cousin in North Hero. These ‘telial horns’ are spreading spores that will infect apple now.

Thinning- it’s still tricky this year with this cool, wet weather. Remember that thinner activity is based on promoting a short-term carbohydrate deficiency in the tree, when too many developing fruitlets are calling for the limited sugars the tree is producing. Cloudy weather reduces net photosynthesis (increasing thinning); cool weather reduces respiration (reducing thinning). Cool weather also prevents hormonal 6-BA (Maxcel, Exilis) thinners from working best. For orchards that received a thinning spray last week, you should see activity from that now- fruits that will abscise have already stopped growing. For orchards that have not thinned yet, do it asap.

General recommendations are difficult to make; where fruit remained clustered up and a previous thinners was applied, OI would consider a low rate of NAA with or without carbaryl; where no thinners have been applied yet, carbaryl + a moderate (4 oz Fruitone N / 100 gallons tree row volume) should be used. For hard to thin cultivars with heavy set (Fuji, Liberty, Gala, Macoun), a higher rate of NAA or carbaryl + 6-B,A (the latter especially on Fuji and Empire) is called for. Fruit set and thinning activity should be checked every day or two at this point, where growers are using precision thinning methods and measuring fruit to gauge thinning activity, measurements every three days should suffice.

As I said last week, good luck- unfortunately this challenging spring hasn’t gotten any easier yet, but I think good weather (and the insects it brings) is just around the corner.

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.

By Terence Bradshaw

Below are some notes I’ve taken, including my own thoughts and observations, from today’s Champlain Valley Petal Fall meeting hosted by Cornell Cooperative Extension. Thanks to Extension Associate Anna Wallis, plant pathologist Dr. Srdjan Acimovic, entomologist Peter Jentsch, plant physioloigist Dr. Poliana Francescatto, and consultant Jim Eaves for contributing to these observations and assessments of the apple crop as we shift from bloom to managing fruit.

Disease management

Pennsylvania fruit pathologist Kari Peters was reporting detection of mature scab ascospores in her state in February, which was earlier than normally expected. The Dr. Acimovic assessed leaves collected in the Champlain Valley of New York through spore towers since late March, after the blizzard snows melted. Ascospores were mature early in April. However, comparing actual spore release data with the RIMPRO model and comparing to estimated ascospore in NEWA models indicates that NEWA is likely overestimating the infection potential for early season (pre-bloom) apple scab. Despite NEWA suggesting that scab ascospores are expended for the season, actial spore releases and RIMPRO suggest 30% of ascospores are left to be expended in the North Country this season. Combined with the five infection periods which have already occurred in most orchards leading into and though bloom, this is expected to be a significant apple scab year. Growers should maintain fungicide protection going into rain/wetting events, apply a broad-spectrum kickback material such as a Strobilurin, DMI, or SDHI the next couple of sprays, and monitor orchards closely for signs of disease for the next couple of weeks.

Fire blight was a significant event in Champlain Valley and other locations in 2016, which has increased potential for inoculum buildup in area orchards leading into 2017. While much of the spring has been cool this year, hot weather leading into bloom last week coupled with high blossom density and high inoculum suggests that growers should keep an eye out for fire blight infections this year. May 18-21 was a period of obvious high infection potential. Cool weather since then has reduced inoculum pressure and further application of streptomycin is not recommended at this point unless future model guidance suggests otherwise. Only where late bloom is occurring on highly susceptible cultivars where fire blight was present last year (cider varieties, maybe Gala or Fuji in cooler sites) should another strep spray be considered.

Some growers use post-infection copper to reduce spread of fire blight infection. Tis should be done with extreme caution since copper materials can severely russet fruit. Only materials labeled for post-bloom use should be used, and they should be applied under rapid drying conditions and in as little water per acre possible (30-50 gallons per acre).

Infection from last year have been observed in rootstocks, sometimes through suckers and especially on M9 and M26. Affected trees may not have died last year but could have looked weak and succumbed over the winter. Other potential factors implicated in recently observed tree death that may be noticed this spring and in recent years include: winter damage, especially from the winters of 2013-14 and 2014-15; herbicide damage to tree trunks; drought stress; borer (dogwood, black stem, and roundheaded apple are a few borers of concern) infestation; and other causes, and many of those are likely interacting with each other in any given orchard. When growing young trees in challenging environments as we have had in the past decade or so, all best management practices should be applied to reduce tree stress: best site selection, good orchard nutrition, pest management, groundcover management, painting trunks, avoiding herbicide contact with trunks and foliage, avoiding overcropping.

Apogee, a plant growth regulator used to reduce vegetative shoot growth, is often recommended to reduce incidence of shoot blight which typically occurs a few weeks after bloom. Application should happen when new vegetative shots are 1-3 inches long (i.e., now) and again two weeks later. Apogee takes 10-14 days to act, but reduction in carbohydrate demand from shoots during that time increases the fruit’s proportion of carbohydrate partitioning from leaves. That means that use of full rates of Apogee may reduce the carbohydrate deficit in trees and make thinning more difficult to attain. Therefore, thinning and shoot fire blight management may be at odds at this time of year. It is recommended to use lower rates of Apogee, i.e. 1-2 ounces per acre rather than a full rate of four ounces, so that you may achieve good thinning and disease management together.

Insect management

Management of certain insects during the prebloom period, even if only with oil, or even with Lorsban or pyrethroids, can be easier because there is no foliage on the trees to block penetration of materials into the bark and tree canopy. Most materials, especially oil, that are applied for mites and San Jose scale (SJS) management require absolutely thorough coverage, which is difficult to attain with an airblast sprayer. Movento is a material effective against SJS that works a little better than others at this petal fall to first cover stage in case good early season management windows were missed for applying oil. This is also the window for applying a post-bloom miticide like those listed in the New England Tree Fruit Guide.

Dogwood borer is becoming an increasing problem in the region, especially on dwarf trees with high numbers of burr knots that are also stressed by drought and other factors. As we shift especially to high density orchards on dwarfing rootstocks, trees remain susceptible to borer damage for up to ten years (compared to the 3-5 years we used to think trees were particularly susceptible to borer damage). Black stem borer is another emerging pest in some orchards that provides another reason for maintaining clean weed control around tree trunks, painting trunks white to reduce stress from solar heating, and applying trunk-drench insecticides when appropriate.

Codling moth (CM) is an increasingly problematic pest in the Champlain Valley. CM have just begun flying in area orchards, and we will be reporting on best timing for management of hatching larvae.

For now, assuming you are at full petal fall and no bees (including wild ones) are in the orchard, insecticides should only be targeted at those pests that are above threshold (none that I’ve seen yet), or plum curculio which will be migrating into the orchard with the occasional warm weather we’re expecting. In many cases, insecticide application can wait until next week.

Thinning

Trees are stressed from many causes: 2016 drought; borers; weed control (lack thereof or collateral herbicide injury); cool, cloudy weather during leaf development this spring; and as a result, may overthin easily.

Thinning applications should be based on tree row volume. We haven’t discussed this much recently, Tree row volume is a calculation method which determines orchard canopy size and the theoretic al amount of water required to saturate that canopy with an airblast sprayer, generally ranging from 100-400 dilute gallons per acre (DGA). No one is planting 400 DGA trees any more, these are the big (20+ foot) old standard trees on wide spacings; most small/high density plantings are about 150 DGA; a typical mature M.26 orchard is about 250. Do not use more than 200 DGA as a basis for determining rates. Many materials will call for a rate based on xx/100 DGA. So if your material calls for 2 oz/100 DGA and you have a mature block of M7 trees, apply 4 oz per acre. No one sprays at the full dilute gallons per acre, so if you use 50 actual gallons of water on a 200 DGA block, you are concentrating your spray 4X. 100 gallons of water applied per acre is best for thinners, definitely don’t go lower than 50.

Some other notes to consider when applying thinners:

· Trees on large rootstocks thin easier, because there is more shading in the canopy.

· Leaves formed in low light like this spring will be more responsive to thinners.

· That said, cool temperatures in the next week will reduce activity of most thinners.

· Trees less than four years old will overthin easily.

· Options for each cultivar and more specifics on thinning are, again, in the Guide.

My thoughts:

Essentially all Vermont orchards should receive a petal fall thinner application this year, it’s our best chance to break the biennial bearing habit that many of our trees are in and to produce fruit of reasonable size and quality. Where you can (no bees, no accounts that disallow it), I would start with an application of carbaryl at 1 pint or 1 pound per acre, plus a moderate (5-7.5 ppm) rate of NAA. I would not use Maxcel or other 6-BA now, until temperatures warm up. One exception, and this comes with caveats that it’s not fully tested for effectiveness, is to replace carbaryl with 7.5 ppm NAA in a mix with Maxcel. However, I just learned of this today and have not evaluated it myself.

I will follow up in a few days after we see the weather and crop develop further. Keep good notes on what you have done and, if possible, try to skip a tree or two to compare against as you evaluate your thinning program. Remember that you’re trying to remove maybe 85% of the fruit from the tree, assuming strong bloom and good fruit set, not 50 nor 95%.

Organic growers: liquid lime sulfur applied (2% solution) in combination with 1% oil (watch for phytotoxicity) can help with thinning by stressing the trees while also giving some scab control. Otherwise, start hand thinning as early as possible to get the best results on increased fruit size and return bloom.

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.

By Terence Bradshaw

Sorry folks, I’ve advertised a tour that doesn’t exist. The Tuesday, May 23rd petal fall meeting will be held at 3:00 at Rulf’s Orchard in Peru, NY. There is no pre-meeting tour.

3PM: Thinning Meeting, Rulfs Orchard, 531 Bear Swamp Rd, Peru

Cornell Fruit Program Champlain Valley Petal Fall Meeting

Tuesday May 23, at 3PM

Rulfs Orchard

531 Bear Swamp Rd

Peru, NY 12972

Agenda:

Brief Introduction & Program Announcements – Wallis & Donahue, CCE ENYCHP

Fire Blight Survey – Liz Higgins, CCE ENYCHP

ENY Entomology Update – Peter Jentsch, HVRL

ENY Pathology Update – Dr. Srdjan Acimovic, HVRL

Thinning, Panel Discussion –

– Dr. Poliana Francescatto, Cornell NYSAES

– Jim Eve, Eve Farm Services LLC

– Dr. Greg Peck, Cornell University

– Dr. Terence Bradshaw, UVM

– Dan Donahue, CCE ENYCHP

– Anna Wallis, CCE ENYCHP

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.

By Terence Bradshaw

May 21, 2017

Most Champlain, Connecticut, and Taconic valley orchards are at petal fall or quickly approaching it, which means the management needs will ramp up quickly- insect and disease management; nutrient application, mowing/herbicide/cultivation; and, of course, thinning. I’ll be wrapping my head around thinning options in the next few days, but for now, virtually every orchard should receive a petal fall application of carbaryl or, if organic, lime sulfur to aid in thinning. Like every odd-numbered year since 2011, this looks like a heavy crop, and your best bet for a good crop next year is to take 80+% of it off now. This is not a year to be shy with thinners, but also recognize that foliage that developed during cool, cloudy weather, as well as trees that were drought-stressed last year, will respond more to thinners than non-stressed trees. On the other hand, sunny to partly cloudy, seasonably warm (not hot) weather like we’re expecting this week reduces the carbohydrate deficit in trees which is what drives thinning treatments, so we really can expect a fairly ‘normal’ thinning season overall.

That said, I will reserve specific recommendations until after Tuesday’s Petal Fall/Thinning meeting in New York, which all are invited to and which was discussed in a previous message. Wednesday looks like a decent spray day anyway, so I expect we’ll have a better handle on things by then.

I hope to see many of you in the Chazy/Peru (NY) area Tuesday,

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.

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.

By Terence Bradshaw

May 19, 2017

An short, extremely intense line of thunderstorms passed through the state last night, accompanied with damaging high winds and, in some cases, hail. I was cutting trees out of our road soon after to make it passable, a neighbor lost 24 around his relatively small yard, many uprooted. That type of weather event can trigger trauma blight, where fire blight bacteria is moved to new abrasions and other wounds resulting from the storm damage.

Although the storm brought cooler temperatures, which will drop the bacterial inoculum levels in most orchards, that high inoculum of E. amylovera was around right before the storm. Many growers applied streptomycin in the past couple of days to protect against the infection that likely occurred to open blossoms as a result of last night’s wetting. Now I’m going to suggest, especially in high-risk blocks that had fire blight last year, getting out there again and putting on a second strep spray ASAP (as in, between now and tomorrow morning) to protect against trauma blight.

If you had hail or other damaging weather, make sure to contact your crop insurance agent within 72 hours.

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.

By Terence Bradshaw

It’s hot today, it doesn’t take an expert to tell you that. Bees should be moving; orchards all over the state including in the inland, cooler regions are at least in king bloom. Hopefully you got a fire blight spray on if you’re at all concerned about that disease in your orchard. We found a short window of relatively calm weather this morning to treat the UVM orchards.

Next Tuesday, Anna Wallace and the rest of the Eastern New York Commercial Horticulture Program will host tours of orchards in the morning and a thinning meeting in the afternoon. I strongly recommend anyone who can make this meeting do so, there will be a lot to talk about and you’ll have the experts there to cover all of your questions, From Anna:

Hello everyone-

The Champlain Valley Petal Fall Meeting will be next week Tuesday 5/23 at 3PM.

Here is the approximate agenda for the morning orchard tour and the meeting agenda. I hope you will all be able to join us for the morning tour. If not, please be in touch and we will meet with you when you are able to join us. Addresses are approximate, so please be in contact with me if you’re arriving late. My Cell: 518-410-6823.

Morning Tour – approximate agenda

9-10AM: Chazy Orchards, 9486 U.S. 9, Chazy

10:30AM: Everett Orchards, 345 Pleasant St (22B), Peru

11:30AM: Forrence Orchards, 86 River Rd, Peru

12:30 Noon: Quick Lunch, TBD

1PM: Northern, 537 Union Rd, Peru

2PM: Hart (if time allows), 2327 Rt22, Keeseville

3PM: Thinning Meeting, Rulfs Orchard, 531 Bear Swamp Rd, Peru

Champlain Valley Petal Fall Meeting

Tuesday May 23, at 3PM

Rulfs Orchard

531 Bear Swamp Rd

Peru, NY 12972

Agenda:

Brief Introduction & Program Announcements – Wallis & Donahue, CCE ENYCHP

Fire Blight Survey – Liz Higgins, CCE ENYCHP

ENY Entomology Update – Peter Jentsch, HVRL

ENY Pathology Update – Dr. Srdjan Acimovic, HVRL

Thinning, Panel Discussion –

– Dr. Poliana Francescatto, Cornell NYSAES

– Jim Eve, Eve Farm Services LLC

– Dr. Greg Peck, Cornell University

– Dr. Terence Bradshaw, UVM

– Dan Donahue, CCE ENYCHP

– Anna Wallis, CCE ENYCHP

Again if you have any concerns or questions, please let me know.

Thank you again for assisting with this meeting!!

Anna

Also: I will be along for the whole tour and meeting, so if you have any questions about where we are at any time, feel free to call me during the day at: (802)922-2591. –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.

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.