University of Vermont

By Terence Bradshaw
May 16, 2017

Okay, we’ve been hinting around about it for weeks, and the risk for fire blight will be upon us later this week. Warm weather today, and hot weather Wednesday and Thursday will allow for substantial increase in populations of E. amylovera, the bacteria that causes fire blight. Once that population is sufficiently high (characterized as the EIP or epiphytic infection potential in NEWA, 100 is considered high enough to cause infection), you need three factors for infection to occur: open wounds (i.e. blossoms or fresh pruning cuts); mean temperature above 60°F; and wetting, even a spray or dew event can be enough to move bacteria into susceptible openings.

This risk is pretty much widespread across the state. The thing to remember is that protective measures, i.e. application of streptomycin in most orchards, or caustic materials/biological controls in organic orchards, must be applied to open wounds or blossoms within 24 hours before or after infection. So if we assume that an infection event occurs in a rain event Thursday afternoon, you’ll want strep or another material (really, if your orchard isn’t certified organic, strep is the only material to consider) on by mid-day Friday. It will be hot Thursday, so blossoms will be opening all day (or petals falling on cultivars that have finished bloom already) and potential for phytoxicity will be greater. The later you can go, the better to make sure you cover any blossoms that open, but don’t delay and miss it. It’s also going to be on the windy side, so there’s that.

Harbour is the strep material available to most growers. I would recommend applying at 1-2 pounds per acre based on tree canopy volume, if in doubt, err on the lower end. I also recommend including a wetting agent like Regulaid or LI-700. If possible, apply on its own, without other fungicides or insecticides (you are in bloom, so no insecticides anyway). You will get leaf yellowing from this application, expect it and the tree will soon grow out of it. One application Wednesday PM-Friday AM should cover you. Once any particular blossom is treated, it’s protected. Temperatures are expected to drop after Friday, which lowers risk, but if high risk continues through the weekend and you keep having blossoms open, then a second application Saturday-Monday (I have no good idea of what the weather will be five+ days from now) may be warranted.

Trees that are at full petal fall are not susceptible, but straggling late blooms can be infection sites. Ideally, the whole orchard would be treated. If you need to prioritize, go first for cultivars that had fire blight last year or highly susceptible cultivars (Gala, Ginger Gold, Honeycrisp, Cortland, Paulared, etc), and of course blocks that are in bloom. Application well after Thursday’s infection event, on Saturday or later, will not give protection against it. Also, despite the wording on the Harbour label, continued treatment every 10-14 days after bloom is not recommended, and doing so is a) expensive, b) a waste, and, most importantly, c) the best way to develop antibiotic resistance in E. amylovera populations.

For organic growers, Actinovate, BlightBan A506, Bloomtine Biological, Blossom Protect, Double Nickel, Regalia, and Serenade are labeled biological controls. I can’t vouch for any of their effectiveness, and I know that some growers apply copper or lime sulfur (warning- both are very phytotoxic) during bloom to manage the disease but again, no promises are offered from me there. If you can, I would suggest Serenade or one of the other biological materials if you have it on-hand and to watch carefully for symptoms which will require cutting out.

I’ll be following up on this as things develop. The key here is to treat for this week’s infection, then relax.

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

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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 14, 2017

Orchards in the Champlain and Connecticut valleys are in full bloom now, and it looks like a good one. After my worrying comments last week about poor weather for bee flight, one grower last Monday told me, “You’re worrying too much. It’ll happen.” And it looks like Thursday and Friday the bees were flying. Although I am not trapping for native pollinators this year, I did notice some small native bees in trees in Putney Thursday afternoon. I wasn’t at the UVM orchard Friday, but my technician told me the bees were moving well. Orchards in cooler upland and inland spots will likely be flowering later this week, which also looks like a period of decent (>60° and sunny)bee weather.

Since we are talking bees, we need to continue to keep them in mind as we begin to think about petal fall and insect pest management. We have found extremely low levels of the usual pink/petal fall insects, tarnished plant bug (TPB) and European apple sawfly (EAS), in orchards all across the state. Some growers predicted and I confirmed a suspicion of a protracted bloom and therefore applied prophylactic insecticides at pink. In terms of bee protection, that is a valid response as long as those who applied a broad-spectrum, non-neonicotinoid material at pink use that extra protection they applied to give a little more time for all petals to drop and to clear out other attractive blooms by mowing before applying the next insecticide. This is our most dangerous timing for potentially damaging bees, because we need to get in to protect the developing crop, but there is still potential for a lot of pollinator activity in the orchard. Remember, pollinators aren’t just the honeybees you bring in to the orchard, and as we have been developing softer, more pest-specific spray programs in recent years, we are encouraging pollinator conservation in the orchards (good), which increases the number of pollinators that could be impacted when we apply that important post-bloom insecticide (not good).

I have been advising growers who are either still at pink or approaching petal fall who have below-threshold populations of TPB and EAS but who have concerns about lepidopteran pests now to consider using only a Bt spray like DiPel. Green fruitworms and obliquebanded leafroller are active now and may be monitored by inspecting 100 blossom/fruitlet clusters and terminal tips in multiple sections of the block and looking for larvae (small green caterpillars). Bt is very effective against moth larvae but has no known effect against most other insect orders, including bees.

Speaking of moths, if you have not already done so, now is the time to hang codling moth (CM) traps in the orchard. These traps are baited with either a pheromone (most common) or fruit volatile (used where CM mating disruption is used) lure and is used primarily to set the biofix date for use in the CM development model in NEWA, so daily or at least 2-4 times per week inspection is needed until the first moths are caught. Trap counts may be collected for the rest of the season to gauge population size and flight patterns. I mentioned CM mating disruption. We have been using this tactic since 2011 after suffering 65-75% damage in our organic orchards at the UVM Hort Farm. This year we have started using a Trece product, Cidetrack CMDA Meso, which reduces the needed number of applicators per acre from up to 200 to 36. This greatly affect the ability of larger-acreage orchards to hang the dispensers. Eric at CPS can provide details on availability and pricing, but growers who wish to try them must be prepared to treat the whole orchard, and should get them up as soon as possible before CM start flying and mating. A good background on using mating disruption in orchards can be found here. It’s a little bit old so the products listed may not be available or registered for use in Vermont.

Fire blight continues to be a non-issue for now, but increasing temperatures forecast for next weekend may trigger an infection, I’ll keep you posted as things develop. Keep in mind that bacteria need open blossoms to cause blossom blight, so as your petals fall, so does your risk. Scab- it’s still active, and I assume everyone is protected for today’s rain. As we get into the late bloom/petal fall window, addition of a material to the usual protectant (mancozeb/captan/sulfur if organic) schedule may be prudent. Consider a strobilurin (IRAC class 11), SDHI (7), or, if the bees are all gone, DMI (3) fungicide in your next spray or two.

Thinning is going to be interesting this year. Every orchard I have seen will need thinning, and I am going to work up some thoughts on recommendations later this week.

Finally, I have been asked to pass on to the orchard community that Dave Boyer, from Boyer’s Orchard in Monkton passed away last week. His obituary 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, a USDA NIFA E-IPM

Grant, and USDA Risk Management Agency Funds.

By Terence Bradshaw

May 5, 2017

Ugh. Vermont orchards are largely at tight cluster (inland, cooler sites and cider cultivars) to pink (most of the Champlain Valley, Honeycrisp of course is lagging) to early king bloom in a few spots and even a little full bloom in the warmest spots. Yesterday was a decent but not great ‘bee day’

for those with open flowers, but an extra 3-5 degrees would have moved their activity up a bit. My greatest concern going into the 2017 crop is this weather we’re facing as we go into bloom- gray, wet, and cool. Hopefully bud development will slow sufficiently so that by the time we get king or at least full bloom, we’ve got good bee weather. Pollen viability extends quite a bit in this weather, up to five days or more after a flower opens, so that’s a good sign as well. If you have the ability to get any extra bees in the orchard, consider doing so. And of course if you have any bees flying in the orchard, treat them right- no insecticides, especially neonics and any materials rated highly toxic to bees; lay off sterol inhibitor/DMI fungicides, at least until we learn more about their effects on pollinators; and mow competitive flowering weeds, if necessary, to funnel them to your apple blossoms. I wish I had a magic bullet that would improve pollination/fertilization/fruit set in a tough bee year, but there just isn’t any proven snake oil you can throw at the trees to compensate for this weather, so the best you can do is to promote and protect the pollinators (managed and wild) that we do have.

That said, this may be a year to consider supplemental pollen application. We have blown pollen at the UVM orchard as long as I have been around (over twenty years), and while it’s not a commonplace practice, it’s something I’ve done partly out of tradition (it was one of the first jobs I did when I started at the UVM orchard as an undergrad in May 1995) and partly to improve our overall pollination since we don’t bring in migratory bees (but we do have seven hives on the property). I was going to skip manual pollination this year, but this bad weather had me calling Firman Pollen to order some up to apply next week. I cannot point to a good peer-reviewed study that says it works in all conditions, but supplemental pollination has, anecdotally anyway, been successful for us. Application method is a little tricky and I don’t know if Firman has the leaf blower guns anymore, but it’s worth checking with them. They also have hive inserts that you add to bee hives to increase the amount of pollen that bees are carrying as they travel through the orchard.

Thursday’s weather provided an ideal spray day between rain events, and I assume everyone took the chance to get covered up. We maintained our spray coverage at the UVM orchards- scab sprays (mancozeb + Vangard) on the IPM and cider blocks, and insecticide (Aza-Direct and Dipel) in the Vf-gene scab resistant organic block where scab isn’t a problem but European apple sawfly and green fruit worn perennially are. Those two sentences covered most of what you need to be thinking about as far as pest management in the next week. Apple scab is the primary threat now, and I expect that when it’s all over, the models will call the period from April 30 through May 10 or so one long infection period. We are entering peak ascospore maturity right now, which means the guns are loaded and each wetting event will release more spores and infection will occur unless you’re protected. Keep covered with a protectant fungicide- mancozeb, captan if you haven’t applied oil recently, or sulfur if you’re organic (and same warning with oil). Five to seven days, max, between applications, and remember that an inch or two of rain removes the coverage you just put on. If you have another perfect, dry day like we has yesterday, add in a more broad-spectrum material with kickback activity (i.e. activity after an infection has occurred but before spores penetrate the leaf cuticle) that can broaden activity against rusts or powdery mildew. Remember the tables in the new spray guide to help guide your decisions. This is a good time to use your strobilurin or SDHI materials.

Notice that I just mentioned a disease concern, but didn’t bring up fire blight. Despite my warning last week to have some streptomycin on-hand for bloom this year, the onset of cool weather has almost completely shut down concern of blossom blight infection, for now anyway. Remember that in order to have a fire blight blossom infection, you need four conditions to occur: 1) open blooms through which bacteria can enter the plant; 2) wetting events during bloom to move bacteria into susceptible tissues; 3) sufficient heat (daily average over 60°F) during an infection event to permit bacterial reproduction in susceptible tissues; and 4) sufficient levels of bacteria present going into bloom. The cold weather has shut down bacterial population growth so the last condition isn’t a concern, and I don’t see any window in the next week anyway where mean temperatures will be over 60°F in any stretch of more than a few hours. Until I say otherwise, put fire blight out of mind, but remember that a warm/hot spell during bloom could turn the situation around quickly. In the meantime, this past week’s Scaffolds newsletter from the fruit team at Cornell has a great synopsis of the fire blight situation in the region.

Insect trap captures are very low across all monitored sites, nothing that I would treat anyway. That said, we are looking like we’re entering an extended bloom period, and that means that those pests waiting in the wings can start doing damage on early-blooming cultivars while you’re waiting for petals to drop on the later ones. Growers with low tolerance for cosmetic injury or history of European apple sawfly may consider a prophylactic pink spray, but I only say that because of the drawn-out bloom. Ideally, sprays will be based on quantifiable trap data, and in no orchard have we caught even remotely enough of either to warrant a pink spray.

In between sprays, this is still a great window to get your trees in the ground, apply herbicide, and fertilize orchards. We did all three this week at the UVM Hort Farm, or at least my technician Jess and chief engineer Andy did. I had one of those days yesterday when it took me as long to spray seven gallons of material (herbicide in the vineyard() with an electric backpack sprayer as it did Jess to spray 600 gallons of materials from three sprayers in multiple orchards. The lesson here is to make sure your equipment is ready to go the day before you need it. And maybe to not let the Professor play Farmer, but I’d say I still do all right at it when I prepare properly.

-TB

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

As many growers know, we are rolling out an expanding orchard scouting program at select sites this year in cooperation with Eric Boire from CPS. This week I got to my sites, both ‘inland’ in Washington and Orange counties, and things were, as expected, behind the main production regions (half-inch green vs tight cluster). Growers in cooler sites still have time to apply oil at 1% by volume, maybe 1.5% if you’re really showing nothing past half-inch green. We are seeing a flare up of San Jose scale in Vermont orchards (just check out some apples from the grocery stores, they’re not hard to find), and a good coating of oil will go a long way toward managing them as well as the mites that we’ll inevitably see come summer.

Insect activity has been relatively low, although the higher temperatures yesterday afternoon may have incited a bit more activity than our traps have caught. Right now we’re looking mainly at tarnished plant bug, and of 40 traps across the state, we’ve only caught one on a TPB trap and another couple in nearby EAS traps- nowhere near treatment threshold. Green fruitworm is a pest that might flare up (and which we have no traps for) and a dose of soft material like Dipel or another Bt product would be good to have on-hand. One nice thing about Bt at this time of year is it’s very safe on bees, but as a lepidopteran (caterpillar)-specific material, it also has no activity against TPB or European apple sawfly, when (if) that one becomes a problem later on.

Apple scab season is here for everyone- keep protected with a protective fungicide going into any rains. Mancozebs, Captan (if no oil has been applied for 7 days before or after), sulfur if organic. Plan on using one of the ‘bigger gun’ materials at pink or petal fall, or immediately after a missed wetting event if that material has good kick-back activity (strobilurins, sterol inhibitors, or SDHIs). There is some evidence of toxicity of sterol inhibitors (Indar, Inspire Super, Procure, Rally, Vintage) to pollinators, to it is best used well before or after bloom when bees (managed and wild) are not visiting flowers.

My main reason for writing today is to get everyone thinking ahead about fire blight. Not panicking, not spraying indiscriminately, but preparing for the event should infection conditions arrive. In that case, you’ll need streptomycin (Harbor, applied at 2 lbs per acre) on-hand since you’ve got 24 hours to apply it after an infection event. Sorry organic growers, strep isn’t approved any more, but Serenade and some other biologicals that I don’t have experience with (Blossom protect, etc.) have some efficacy when applied during an infection event in bloom but not nearly as effective as strep. I expect bloom as early as mid-late next week, so you have time to get some on-hand but if you wait and the big orchards in northeastern New York order up enough material to cover their 2500+ acres (remember they had a FB outbreak last year), it will be in short supply. Any grower who had even a small amount of fire blight last year should have enough on-hand to hit those infected blocks plus susceptible cultivars (Cortland, Paulared, Gala, Honeycrisp) at a minimum, and ideally enough to treat thew whole orchard.

My recommendation to have strep on-hand is different than my recommendation on how to use it, so no one should be spraying strep right now or without consulting a model or hearing otherwise. The fire blight bacteria requires heat prior to and during a potential infection event to multiply and infect, and also requires fresh open wounds (or blossoms) and a few other factors. Until all of those pieces are in place, leave it on the shelf.

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

April 25, 2017

Expected showers beginning this afternoon through Wednesday may trigger an apple scab infection period in Vermont orchards. There has been relatively little buds development or and not enough rain in the last week or so to wash off protective residue, so any orchards that received a full-dose protectant fungicide in the past seven days should be protected through this event. However, any rain that does come will add up to sufficiently wash off residue, and warm temperatures Thursday through Saturday should advance bud development substantially. For orchards that are3 at tight cluster now, this may be your last window to apply oil (1% solution, full soaking coverage) before buds advance too far. If you couldn’t get an oil application on and mites are an issue in your orchard, there is a number of different miticides options available now that may be used pre- or post-bloom. Those can be found in the spray tables at netreefruit.org.

Insect pressure is usually pretty low at this time, but we have seen an uptick in tarnished plant bug on buds. If you are trapping with white sticky traps, the threshold before requiring an insecticide application is three or five per trap (wholesale and retail orchards, respectively) at tight cluster and five or eight per trap at pink bud stage. Fruit grown for cideries do not need to be treated for pre-bloom insect pests since their damage is largely cosmetic.

If applying a prebloom insecticide, consider a synthetic pyrethroid material if possible. The jury is still out on the potential for neonicotinoid residue to carry over into pollen and nectar and adversely affect both managed and wild pollinators. And although news was recently made that EPA would not cancel uses of chlorpyrifos (Lorsban and some generics), we would be best to move away from that product as a canopy spray and save it for its use as a trunk spray to manage borers. There is only one use allowed per year, and if a canopy spray is made pre-bloom (the only time allowed for a canopy spray), then its use later on trunks when borers are more active will not be allowed.

Now is a good time to get your first soil-applied nitrogen fertilizer down. In many cases. Split applications are more useful than a single application, timed at tight cluster to pink and a second application at petal fall. Without a foliar analysis (which is always the gold standard for developing fertilizer recommendations), growers should err on applying a total of 30-40 pounds of actual nitrogen per acre whether in one or two applications. This is also a good time to apply the foliar tonic of urea (3#/100 gallons), boron (1# solubor or 0.1-0.2 lb actual B/100 gal) and zinc (many materials, use label rates). I wouldn’t mix this tonic with oil, do one and then the other in this next spray or two if needed.

It’s great weather for planting trees. If you have them in the cooler, get them in the ground.

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 doesn’t take too much fancy software to tell that we are in the middle of a pretty good apple scab infection period in most every orchard in Vermont. Ascospore maturity is estimated at 4-8% for today, and up to 14% in some orchards by the end of the weekend with showers and rain expected for the next four days. Orchards that were covered with copper or another full-rate before April 12 may still have protection, but if more than one inch of rain falls, reapplication during a break in the weather would be warranted. Addition of Vangard or Scala in that spray (in combination with at least a half-rate of EBDC or Captan) will help to manage any infections that slipped though if poor coverage and/or washoff is a concern.

However, in cooler orchards with less tissue showing (and potentially low inoculum from last year), a postinfection material may not be warranted. Use your judgement here and err on covering up if in doubt. This is a good time to put on some oil (2%, good full coverage) but not if using Captan or sulfur in the next or previous 7-10 days.

Organic growers: ignore my suggestion for adding a postinfection fungicide if that means using liquid lime sulfur at this time. The scab risk isn’t great enough to offset the negative impacts that LLS has on orchard ecology and tree health. Save that ‘big gun’ for later in the season. If you feel like you need some retroactive coverage, consider Oxidate or one of the potassium bicarbonate products. Either of those must be applied shortly (<24 hours) within the onset if infection.

I’m away through the weekend, so good luck on this. In between worrying about scab (which, in the big picture, isn’t a massive threat right now), start planting trees and getting other spring activities in order. You can expect to fertilize soon when the soil warms up a bit. And of course everyone is done with pruning and pushing brush, right?

-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

Warm weather over the weekend advanced bud stages, pretty much everything in the Champlain and Connecticut Valleys are at green tip and some orchards are bordering on half-inch green. If you haven’t gotten copper out yet, now is the time, tomorrow (Tuesday 4/18)v looks like a good day wind-wise. We’re also out of any frost risk for the foreseeable future (but not necessarily done for the season so don’t plant out your tomatoes), so you can apply oil any time. At this point I would apply 2% (volume/volume) oil and soak it down real well with 100+, preferably 200 gallons of water per acre. After tight cluster, 1% oil should be used to avoid phytotoxicity.

As temperatures cool down this week, bud development will also slow. However, scab ascospores will continue to mature and by mid-week we can expect 5% or more of ascospores to be available for release during the expected rains and wetting events. This is another reason to cover your trees Tuesday prior to the rain. If you put on a full copper rate Friday or later, you are probably good for now, but if you had spotty coverage or have had substantial bud development, and therefore emergence of new susceptible tissue, since you sprayed, then another preventative fungicide may be called for.

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 trapes 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. TPOB 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.

1Tarnished plant bug trap (lower left) in tree. Right picture: TPB on trap.

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.