University of Vermont

By Terence Bradshaw

Sometimes you need to check the latest weather before hitting ‘send’…

After I just sent that last missive, I double-checked conditions in western Vermont, specifically Shoreham and Bennington, and the weather prediction is indeed for warmer weather than when I last looked. NEWA is now calling for “Infection” on Monday for those two sites, but the EIP is just barely over 100 (107 and 103, respectively) and drops down the next day as cooler weather moves in. I’m going to stick with my old gut response to not worry about fire blight, with a slight caveat. If you have a history of the disease, have especially susceptible plantings (Gala, Fuji, some cider varieties), are in bloom on Monday, and things warm up over the weekend, consider applying streptomycin on Monday or Tuesday, within 24 hours of infection. Keep an eye on NEWA for further details.

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

Here’s a quick note to remind everyone that we’re in the middle of an extended wetting and apple scab infection period that is likely to peak on Monday. Every orchard in the state still has mature ascospores in the leaf litter from last year, so stay protected. We’re also still in rust season, so it’s not a bad idea to make sure your fungicide products have some efficacy against that disease. If you’ve had more than an inch or so of rain between spray events, and especially if more than 1.5-2”, you should really think about applying a DMI (FRAC 3, e.g., Indar, Rally, etc., high efficacy against rust), strobilurin (FRAC 11, e.g., Flint high efficacy against rust), or SDHI (FRAC 7 e.g., Merivon, moderate efficacy against rust) with your protectant material (captan is good, no rust efficacy; or mancozeb, good rust efficacy but only allowed four applications through bloom at 6 lb/acre rate so you may have used that up). Remember to rotate between FRAC codes to avoid resistance development, and the mix products like Inspire Super (3+9) or Luna Tranquility (7+9) or Sensation (7+11) count as both when planning your rotations. That is, if you use two back-to-back application of Luna Sensation (7+11), your next spray including one of the single-site products should be a DMI (3) or anilinopyrimidine (9, which are less effective as temperatures warm) material. More information on fungicide resistance management is available in the New England Tree Fruit Management Guide.

For organic growers, the standard is still sulfur, and possibly judicious use of lime sulfur if you’ve missed some coverage and need some protection to reach backwards. Remember though, lime sulfur is nasty stuff, so use judiciously and take all necessary precautions. For rust, sulfur isn’t very effective. I have heard reports that Regalia, a biological fungicide, has some efficacy against rust so this is as good a year as any to try it out.

One great bit of news on the disease front- fire blight should be a complete non-issue this year. That could change for late-blooming cultivars or if active cankers are leading to shoot blight later on, but for now, it’s just too cool for any activity from the bacteria that causes the disease. NEWA’s Cougarblight model shows “high” risk for Sunday and Monday, but that’s to be taken with a grain of salt. There are four conditions necessary for blossom blight to occur: open blossoms (check); wetting (check); sufficient heat, measured in degree hours, over 60°F during the infection event (maybe); and sufficient heat leading up to infection to allow the bacterial population to increase to a level high enough to cause disease (nope). Using NEWA’s fire blight model, keep an eye on the “Infection Potential EIP Value”, that should reach 100 before you need to be concerned about blossom blight. Cougarblight assumes “High” risk if three of the four conditions are met, even if the fourth necessary condition (EIP in this case) is not likely to be met. We would need temperatures a good ten degrees higher than predicted tomorrow through Monday to move that EIP into any range to worry about.

Figure 1 NEWA fire blight model for Putney, VT. Most sites in the state will have even lower risk than this. Take-home: don’t worry about blossom blight now.

Orchards are in or entering bloom. That means a few things. First, get those blossoms and the ovules they’re attached to in good shape by applying a foliar fertilizer if you haven’t yet, I’ copying my own text from 5/5 here for that: Rates are dependent on the products used, and are intended to boost blossom vigor as the trees enter the stressful bloom period Dr. Wes Autio’s (UMASS) recommendations for Prebloom Nutrient Applications for Apple Trees: 3 lbs/100 gallons (dilute equivalent) urea; 1 lb/100 gallon Solubor (or equivalent); and label rates of zinc chelate. Ground-applied or fertigated fertilizers can also start to go on any time now. Organic growers may want to apply fish and/or seaweed products at this time.

Remember, bloom means bees, bees pollinate, and pollination = ovule fertilization = fruit. Protect them, both managed and on-managed (wild). That means avoid spraying anything, if you can, during bloom. Even some fungicides, DMIs in particular, have shown adverse effects on bees when applied to blooming orchard crops. Mow your dandelions to both force bees into the trees to work and to reduce their (the bees’) presence after bloom when you think about applying a petal fall insecticide. And for heaven’s sake, do not apply insecticides when there are flowers (apple blossoms or dandelions) in the orchard. The exception to that is Bt or other lepidopteran-specific products. On to insects…

Insect activity is really slow this season. The only insect captures of note have been European apple sawflies. If you’re at pink (i.e., ZERO blooms open) and have a population above threshold (five per white sticky trap, average), this may be a warranted application. But, application of insecticides so close to bloom is still a dangerous endeavor. Many wild bees are moving now, and since they often fly in cooler, wetter, windier conditions than managed honeybees, they may be especially important this year given the crappy weather we’re having. If you can hold off until post-bloom, I strongly recommend it.

Get your codling moth and obliquebanded leafroller traps up ASAP and check daily to set the biofix you’ll use to manage the larvae in a few weeks.

On a final note, herbicides, if used, can be applied any time, and application to weeds 6” or shorter is always more effective than waiting. Be careful with contact to trees, including mature bark, with glyphosate or glufosinate. Extra time spent is well-worth it to avoid trunk damage.

Are we having fun yet?

-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

This is a very brief message to Vermont apple growers that we are in a dry and relatively windless slot between significant wetting events and it would be wise to make sure that your fungicide coverage is maintained. I wouldn’t worry about insects now, unless you are treating for scale, but a quick reapplication of anything that may have washed off if you sprayed prior to Friday is called for. I’m heading out right now…

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

The UVM Fruit Program will host a hands-on program on apple orchard Integrated Pest Management and scouting on May 16, 2019. The program will run 1:00 – 4:00 PM. In the event of rain, we will hold the meeting on May 17. We will contact attendees the day before if we need to make that call.

This workshop will be held at the UVM Horticulture Research & Education Center, located at 65 Green Mountain Drive, South Burlington, VT. A short program may be held in the Blasberg classroom to introduce IPM concepts before heading out into the orchards with Fruit program staff Dr. Terence Bradshaw, Sarah Kingsley-Richards, and Jessica Foster.

There is no fee for this workshop, but please pre-register so that we may have an accurate counting of attendees: https://survey.uvm.edu/index.php/266459?lang=en

Thank you,

Terry Bradshaw

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

First note, please remember that we will be hosting an Orchard Scouting Field Workshop at the UVM HREC on May 16, 1-4 PM to help growers with implementing scouting programs and to discuss upcoming management strategies. I’ll have a registration link ready later this week. The event will be free, but I’m looking for a head count. Also. Don’t forget that we have hard copy New England Tree Fruit Management Guides available at: http://go.uvm.edu/netfmghc.

Bud stages in Vermont orchards run the gamut, from pink and maybe even the very beginning of bloom in the south to green tip at my house at 1500 feet elevation in Washington county. At the UVM Horticulture Research Center, trees are at a solid tight cluster and will move more tomorrow. We’re in a window of relative calm, so unprotected orchards may deserve some fungicide coverage before Tuesday when enough rain is expected to cause a scab infection period. It will be cooler and drier on Wednesday, so another option would be to apply on Wednesday after the rain, assuming that you already have some coverage remaining from last spray and you’re ready to apply a site-specific fungicide (like an SDHI, QoI, or DMI material) that will have some kick-back activity and cover for the prior day’s infection. Reliance on kick-back materials speeds development of resistance in the scab pathogen, so I only recommend that strategy if you already have some coverage like from a spray last Wednesday, and I always recommend tank mixing with a multi-site protectant like mancozeb, captan, or sulfur if organic. (For growers following an organic schedule, I don’t have a good answer for a recommended kickback material. Liquid lime sulfur is a very heavy bomb that will negatively affect trees and is better saved for rescue situations; Oxidate or one of the bicarbonate materials like Kaligreen can have some post-infection activity if applied very soon after initiation of an infection period, but I wouldn’t count on getting good control if you wait any real amount of time after to apply or if there is a heavy infection period.)

Cedar apple rust galls (sixth picture) are active on red cedar and other junipers in the Champlain valley, and I recommend treating for this disease in any orchard that has had an issue with it in the past as the cool, wet conditions of last week and this week are conducive to disease development. The good news is that mancozebs (a multi-site protectant fungicide class) are effective against CAR; DMI (Indar, Rally, Rubigan, etc.) and strobilurin (Flint) fungicides are highly effective, and SDHIs (Aprovia, Fontelis)have moderate efficacy. A tank mix of those materials (one protectant and one of the other single-site classes should provide good protection. Remember, do not apply single-site fungicides with the same FRAC code more than twice in succession before rotating to another chemistry (FRAC code).

As bloom approaches, plan on completing a few activities to improve tree’s response to pollenization and fertilization. A prebloom foliar nutrient mix of nitrogen, zinc, and boron should be applied. Rates are dependent on the products used, and are intended to boost blossom vigor as the trees enter the stressful bloom period Dr. Wes Autio’s (UMASS) recommendations for Prebloom Nutrient Applications for Apple Trees: 3 lbs/100 gallons (dilute equivalent) urea; 1 lb/100 gallon Solubor (or equivalent); and label rates of zinc chelate. Ground-applied or fertigated fertilizers can also start to go on any time now.

Now is probably past time to make bee plans, but growers should certainly plan on coordinating with their beekeeper on hive delivery and placement. We are focusing on pollinator health more than ever these days, so be smart about protecting both kept and wild bees on your farm. Avoid applying insecticides right before bees are brought in, only apply after mowing or when flowering weeds are absent from the orchard, and avoid DMI fungicides during bloom as they are now recognized as harmful to bees.

On the insect front, things are quiet but the first few tarnished plant bug and European apple sawfly are flying in certain orchards. If possible, we can avoid spraying for the former (TPB); the latter is best managed at petal fall except on problematic sites or when bloom is extended. If you have been trapping for EAS, keep an eye out for the threshold of five adults caught per trap to treat; that threshold should increase to about nine per trap after bloom if no prebloom treatment was applied.

Codling moth traps should be hung at pink and checked daily until first catch is seen. That capture date will be the biofix you use when calculating degree days for subsequent management actions.

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

Well, so much for spring. Things sure cooled down this week, with apple trees pretty much parked between green tip and half-inch green bud stage, with a little more advancement in southern parts of the state. The primary scab ascospores that drive the whole disease cycle for the year and overwinter on the orchard leaf litter are maturing a decent pace, with about 15-18% of potential spores mature in the south, 10% in the cooler northern Champlain Valley, and only 2-5% in inland Vermont. Relatively warmer weather tomorrow should push things ahead a bit. Key take-home: Those warmer areas with any appreciable green tissue showing and a history of scab in the orchard last year are entering the accelerated phase of ascospore maturity and should be prepared to maintain protective fungicide coverage before rain periods until the ascospores are all released. That means that orchards should apply between rains this week, after 1-2 inches of rain, and when new growth emerges (say a move from 1-2 bud stages and increasing shoot leaf expansion, when that starts anyway). That means that in weather like we’re seeing now, maintaining a roughly 7-day schedule. Please use NEWA to track weather and disease infection periods to best plan your spraying events. It’s getting very muddy out there, so try to minimize your trips by applying tank-mixed fungicides including a protectant (e.g., captan, mancozeb, sulfur if organic) and a kick-back material (I recommend Vangard or Scala, still, at this time of year).

Insects are still quiet, but expect tarnished plant bug and European apple sawfly to start moving with the first warm day or two.

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

At the UVM Horticulture Research and Education Center (HREC), we hit the green tip bud stage on McIntosh today. This means that, even for orchards with relatively low apple scab inoculum that carried over from last year, disease management should commence any time. Today would have been a great time to put a protectant material on ahead of the rains expected tomorrow and through the weekend. For growers who had scab last year and who are at this same or later stage of bud development who did not have a protectant applied on Monday or Tuesday this past week, plan on applying a material with some kick-back action when the rain and winds die down. Scala, and Vangard are natural options at this time, as they work better in cool weather and have relatively little effect on fruit scab so they are less useful later in the season. For those who still use or planned to use it as a spring fungicide, Syllit/Dodine is no longer registered for use in Vermont, although remaining stocks may be used up. For orchards past 1/4” green tip, it is too late to apply copper fungicides at traditional labeled rates for efficacy against apple scab without risking fruit russeting. As always, check the New England Tree Fruit Management Guide for complete recommendations (hard copy guides still available at: http://go.uvm.edu/netfmghc).

On the arthropod front, this is still a good time to apply oil for management of mites, and Esteem may be applied against San Jose (SJS) and other scale insects if they are a problem in your orchard. Notice I did not recommend Lorsban (chlorpyrifos) against SJS and other insects at this time. That’s because chlorpyrifos products are no longer registered for use in Vermont.

This is a great time to start your orchard monitoring program: keep track of phenology on all cultivars are bud emerge and develop, and start hanging traps in the orchard for weekly (at a minimum) monitoring. Insect activity is generally pretty quiet now, but tarnished plant bug will start to move as days warm up. This would be a good week to get traps up for this insect pest. We recommend four white sticky traps per block hung knee high in a visible location, often at the block edges. Traps should be checked at least weekly and treatment for TPB considered if over threshold. Thresholds are variable based on tolerance for cosmetic damage- for apples marketed wholesale, three bugs per trap before tight cluster or five before pink bud would warrant treatment; for retail and pick-your-own orchards, the recommended treatment threshold is five and eight bugs per trap, respectively, for those bud stages. TPB and other insects managed at pink are usually treated with a synthetic pyrethroid material and that is still the recommendation. In order to conserve wild pollinators, we do not recommend use of neonicotinoid insecticides before petal fall.

On the subject of scouting, we will be hosting an Orchard Scouting Field Workshop at the UVM HREC on May 16, 1-4 PM to help growers with implementing scouting programs and to discuss upcoming management strategies.

Good luck out there.

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

For as long as I’ve been in this fruit business with UVM (1995-present) and well before, the cooperating Extension fruit programs of the New England Universities have collaborated on a management guide for commercial tree fruit growers. That guide has taken numerous forms, but in 2017, we switched a on online-only platform due mainly lack of funds to prepare and print the guide every year. The online guide is still available, and should be a main resource for fruit growers: http://netreefruit.org/. That guide is formatted for both desktop and mobile devices, and will always be the most up-to-date one published.

In response to demand for a printed, hard-copy guide, we formatted the online guide into a 300-page, spiral-bound version that may be useful to keep in the truck, tractor, or spray shed. I have twenty copies available at: www.regonline.com/2019netreefruitmanagementguide. Copies are $25 postage-paid, and I plan to ship Wednesday and Friday this week. If there is demand for more copies, they may be available from UMASS or other cooperating states.

Good luck out there, at the UVM orchard, the spray season already started today.

-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.