By Terence Bradshaw

As has been the general case this year with the drawn-out, cool weather, we have bloom (and p-bloom) bud stages all over the place depending on elevation, proximity to the lake, cultivar, and latitude. For growers in upland sites just entering bloom, see my posts from the past couple of weeks that have been aimed at bloom-time management. Remember, no insecticides; mow flowering weeds in the groundcover to make your trees more attractive to bees; and watch for fire blight. Keeping an eye on that very weather-specific disease can be more difficult in upland areas where NEWA stations are less prevalent. However, a look at stations in East Dorset, East Montpelier, Morrisville, and Berlin (‘Montpelier’ airport) shows EIP (potential bacterial population) below infective level all week, although a warmer-than-expected Wednesday or Thursday may change that. Overall, I wouldn’t be too concerned about fire blight for those sites, but would keep an eye on things.

Growers in warmer areas, however, may need to be concerned. Shoreham was flagged as having had an infection event yesterday, and an application of streptomycin today (like, now) to open blossoms may be prudent, especially on susceptible cultivars. Remember that blossoms are pretty much done as far as disease susceptibility is concerned once the petals fall, or 80 degree days (base 40) after they open, or 3-5 days given the weather we’ve been having.

Apple scab is the main disease to stay concerned about statewide. This is proving to be a challenging year for the disease, with infection periods occurring every week since bud break and reports of numerous tractors stuck while spraying. The good news is that we’re on the tail end of the primary apple scab infection season when the overwintering spores resulting from last year’s infections on leaf litter are close to expended. If you manage to keep covered with fungicides during that window and all infections are prevented, then apple scab season ends when those spores are gone. However, any infection in the tree canopy will lead to development and release of conidial spores which creates a secondary phase of the disease. My point is, keep protected until you know that you are scab-free and the spores are all expended. Some stations (Bennington, Cornwall, Shoreham) called for the end of primary season last Thursday, many more are indication that we’re within 1-2% of the spore load left. For those orchards, I recommend maintaining a good coat of fungicide through this week, and likely next. Depending on the material you choose, this application will cover you against powdery mildew, rust, and moldy core which can be a problem in cool, wet bloom periods. In 7-10 days, get out and do a thorough assessment of foliage for scab lesions. Pick the worst-case spots- tops of trees, that corner of the orchard where you turn and can’t get good coverage on that one last tree, the shady spot where the trees stay wet longer. Only after you know you’re clean can you let your guard down.

Speaking of letting your guard down, many of us did on the insect front going into bloom because trap counts were low for most insects across the state. We’re now seeing high numbers of European apple sawfly on traps in many orchards, and I expect a petal fall spray will be warranted against them. Pay attention when making this spray- petal fall means that all blossoms are gone, your migratory bees are pulled out, and flowering weeds attractive to wild pollinators are mowed. There are a number of materials that are effective against EAS, and all are toxic to bees to one degree or another. For organic growers, now is the time to get a good, solid coat of Surround kaolin clay onto your trees to deter plum curculio. I always preferred to apply this base layer in two coats, one at ~50 lb Surround per acre followed by another 25 lb per acre to get a good build up going into petal fall and the beginning of the real incest management season.

Thinning. This is always tricky to give advice on, and the variable conditions across the state make the job even harder. Many orchards have a larger-than-normal potential crop, and pollination should have been sufficient given the handful of good ‘bee days’ where conditions were right for bee flight and fertilization. This is a good year to consider multiple ‘light coats’ of thinners. NAA + carbaryl are a typical mix to apply at petal fall on many cultivars. For smaller-fruited cultivars, 6-BA thinners may be used instead of NAA to increase cell division and final fruit size, but they need warm sunny weather to work best. NEWA has a good model (two of them, actually) for helping to determine the potential effectiveness of thinner applications based on weather before, during, and after application.

This is the most critical time to keep your eyes open out in the orchard. Stay alert for signs of fire blight and apple scab. Check traps daily for codling moths to help determine the biofix date that you’ll use for subsequent management decisions. Keep an eye on fruit clusters for signs of thinner activity (yellowing stems, sepals that don’t close up). Get you nitrogen and other nutrients on, multiple lighter coats are better in rainy years than one big one to minimize leaching and runoff. Watch for and enjoy the sunshine. This weather can’t last forever.

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.