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UVM Fruit Blog

Apple trees dying all over the state

Posted: September 11th, 2018 by fruit

By Terence Bradshaw

Pardon the exclamatory headline. I’m sending this message directly to the many, many people who have contacted me about the issue, and posting it as a blog post so that I can point to it when it comes up again.

Apple trees are dying all over the state. Maybe not necessarily dying, but they are looking very weak. I have had numerous calls and emails about trees with rampant leaf spots, small fruit, fruit drop, and, especially, early defoliation this year. Actually, I received quite a few last year as well. What’s up with apples in Vermont??

I have numerous photos in my inbox of trees that look like this- defoliating, often from bottom-up, leaves riddled with disease, some dead limbs, and no fruit. The most common thread among these trees is that they are all from unmanaged orchards. Backyard trees, wild trees, wildlife trees, these are generally not trees in managed, commercial orchards. So this message is not aimed at my usual commercial apple grower audience.

What we are seeing is the result of numerous environmental and biological stressors. Let’s go back to 2015. After a generally good ‘apple year’, when unmanaged trees bore relatively large crops of fruit statewide, nutrient reserves and cold hardiness going into the winter were compromised by the trees having to ripen an overabundant apple crop. The subsequent winter was normal but cold: a stretch of several nights saw weather in the minus teens below 0°F. The 2016 growing season was very dry. Both of those conditions are stressful on trees. Winter 2016-2017 was relatively mild, but the main stressor that in 2017 was the unrelenting rain in April, May, and June that resulted in rampant fungal infections, mainly of apple scab but also of cedar apple rust and other diseases. This caused major stress on unprotected trees, and although the weather turned dry by July, it shifted toward near-drought through fall, which further stressed trees. Coupled with a relatively large crop of scabby fruit which further weakened them, unmanaged apple trees were poorly-set to acclimate to a hard winter.

December 2017. Vermont apple trees were arguably as acclimated to cold winter temperatures as they were going to get, but that hardiness was questionable. I observed many trees that held onto their dry, desiccated leaves into the winter, which suggested that hardiness was marginal as the abscisic acid hormone that promotes hardiness and contributes to leaf drop didn’t have a chance to fully do its job. Then, cold weather came early (minus teens by December 15, and minus twenties by the holidays in many areas) and stayed for much of the winter, with some sites seeing -30°F or worse. That’s stressful on trees.

Finally, this spring (2018) was dry, and stayed dry through the summer for most of the state. All of the previous stressors, especially the wet spring / disease incidence of 2017; heavy cropload and dry fall; and early and intense cold led to trees that had a hard time in the drought of 2018, and many are calling it a day and dropping leaves early to rest.

Is this a major catastrophe? I wouldn’t say so- these trees have evolved functions to help them balance out their vegetative and fruiting growth to adapt to the extremes experienced in temperate regions. Will some of these trees die? Sure, but the majority will leaf out next year and keep going through their cycle. Are we going to see this again? Likely, especially as the climate gets more erratic and we continue to see greater swings in heat/ cold and rain/drought.

The best thing to do to reduce tree stress is to manage them. Prune them annually to balance out vegetative and fruiting wood and to encourage healthier 3-5 year-old wood in the canopy. Thin out the canopy to improve sunlight penetration, airflow, and to reduce disease incidence. Lime the soil if it needs it, add (judicious) amounts of fertilizer if the trees call for it. In those years when the tree is overladen with fruit, thin off 50-75% of them soon after petal drop when the fruitlets are nickel-sized to allow the tree to balance vegetative and fruiting functions. Water if it’s dry. If you’re ready to learn how to do it right and to commit to spraying, consider starting an Integrated Pest Management program for your trees. (That last step should only be undertaken after doing everything else).

Apple trees are not native to this region, despite their adaptability. More importantly, the apple as we know it was selected over millennia and is managed using the practices I mentioned to make it a regular-bearing, commercial crop. There is little about a ‘wild’ apple that suggests that, unmanaged, it will be ready to both provide quantities of high-quality fruit and survive this environment without management.

For more information, see the Cornell Guide to Growing Fruit at Home.

Good luck,

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.

Craft Cidery Startup Workshop in Oregon, Nov 4-8

Posted: September 5th, 2018 by fruit

FYI for anyone interested. -Terry

From: Aronoff, Greg
Sent: Wednesday, August 29, 2018 4:53 PM
Subject: Question

I’m with Oregon State University and we have an upcoming cider workshop that fills a current gap.

To help apple growers, farmers and entrepreneurs successfully start their own craft cidery, OSU created a cidery startup workshop that levels the playing field for success.

The Craft Cidery Startup Workshop starts Nov. 4 and teaches folks about sourcing, marketing, and creating a viable business plan (which will be vetted by the expert instructors).

Here’s the link for more information – https://pace.oregonstate.edu/cider-startup.

Due 9/ 7: Short, important survey for cider apple growers

Posted: September 1st, 2018 by fruit

By Terence Bradshaw

Cultivation of specific cider apple cultivars, including European bittersweets, heirloom North American cultivars, and other dual-purpose fruit is a small but growing component of the New England apple industry. I am collaborating with faculty from UMASS and University of Maine to conduct a short-medium term research and education project supporting increased or improved production of specialty cider apple cultivars on New England farms. We will submit a grant shortly, well before the end of the harvest season, and wish for grower input to rank specific research goals that we’ll address in the project.

The survey is quite short, as is out turnaround time- we would appreciate all responses to be submitted by Friday, September 7.”

https://www.surveymonkey.com/r/BFD6LQ7

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.

Preharvest thoughts for Vermont vineyards

Posted: August 24th, 2018 by fruit

By Terence Bradshaw

Pardon my absence these past few week- a trip to beautiful Istanbul, where I presented some of our research from the past couple of years on cider apple management, and both wrapping up and starting a new course have kept me a bit distracted. Grapes in Vermont vineyards are some of the best quality I’ve seen in recent years, as that dry summer facilitated low disease pressure and fabulous growing conditions. Veraison has come and gone, hopefully all who need it have bird nets up and are now starting to arrange the logistics of moving that fruit into ready fermenters (or customers’ baskets, for the table grape growers out there).

As harvest approaches, it is critical to track ripening in the vineyard to best achieve the juice chemistry values to optimize wine quality. Sampling should be methodical and regular (at least weekly, or more often as harvest approaches). Generally a 100 berry sample is sufficient to ascertain general ripeness. Berries should be randomly selected, but should come from a diverse distribution in the vineyard: from all parts (top, shoulder, bottom) of the cluster, and from clusters well-distributed through the canopy. Fruit can be collected into a plastic bag, crushed lightly, then a corner of the bag cut off to squeeze juice into a sampling jar. Juice should then be assessed for pH, sugars, and titratable acidity (TA). Remember that for most popular cold climate grapes, TA is a primary determinant for ripeness; for reds (Frontenac, Marquette), a target TA of 1.5% or lower is preferred; for whites, 1.2% should be considered the upper end, although La Crescent may frequently have higher values. Ideally, all grapes for winemaking should have TA below 1%, but that is not always possible for the cultivars that we grow. Work with any wineries you plan to sell grapes to to determine their preferred juice chemistry levels before harvest.

Dr. Imed Dami at Ohio State has a good fact sheet on evaluating grape ripeness at: http://ohioline.osu.edu/factsheet/HYG-1436

Sugar level and pH are easily evaluated with simple tools (a refractometer and pH meter, respectively) available from most winemaking supply outlets. TA test kits are typically available from the same vendors. A procedure for measure TA through titration is available at: http://www.extension.iastate.edu/wine/titratable-acidity

It’s not too late to perform petiole sampling, which is the best method for assessing nutrient status in plants. I’m copying my instructions below from a previous post, as that information is still relevant:

Petiole sampling
Growers may ascertain overall nutritional status in their vineyards at two times through petiole analysis: bloom and 70-100 days post-bloom. Now is the time for late (post-veraison/pre harvest) petiole sampling for plant nutrient status. Dr. Joe Fiola form the University of Maryland has posted some good recommendations in his latest Timely Viticulture newsletter:

· Grape petiole analysis is recommended along with soil samples and visual observations as part of a complete nutrient management program.

· A three year cycle of sampling all of the varieties in a vineyard is typically recommended.

· Tissue/petiole analyses reveal the actual nutrients in the vines.

· Spring tissue sampling is a good time to sample, as you can make nutrient adjustments to the vineyard that will influence this year’s crop quality.

· Nitrogen status is best evaluated with tissue sampling not soil sampling.

Some specifics on sampling:

· Each sample should be less than 5 acres; less if there are major changes in soil or topography

· Sample different varieties separately. Samples should represent plants that are planted on the same soil type and are of the same age, variety and rootstock.

· Vines should represent that portion of a block that is maintained under the same cultural practices, i.e. fertilizer, irrigation and vigor control practices. For example, irrigation blocks are not to be combined with non-irrigated blocks even if they are on the same soil type.

· Do not sample vines on the border of the block or near dusty roads.

· For the late-season sampling period, sample the petiole of the most recent- FULLY EXPANDED leaf (NOT the one across from the first blossom cluster as during bloom).

· About 75-100 (depending on size) petioles are needed as they are typically smaller at the end of the shoot.

· Gently wash petioles with water and gentle detergent, pat dry and place in OPEN paper bag (lunch, #6 size) to dry for a few days.

· The closest analytical lab for grape petiole analysis is Dairy One, which is affiliated with the Cornell Nutrient Analysis Lab. It is recommended that you contact them before you send any samples to confirm that recommendations will be sent along with the analysis and to confirm costs.
Video about petiole sampling: https://www.youtube.com/watch?v=8EHbojLfXek

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.

Apple maggot, the calm before harvest

Posted: August 24th, 2018 by fruit

By Terence Bradshaw

Pardon my absence these past few week- a trip to beautiful Istanbul, where I presented some of our research from the past couple of years on cider apple management, and both wrapping up and starting a new course have kept me a bit distracted. Nonetheless, we have continued to scout in Vermont orchards, and overall, things are looking good. Rains came when needed (although more growers need irrigation for summers like this), thinning was decent so fruit size is good, scab is minimal. For growers who haven’t yet applied a stop-drop material, there is still time to get some Retain on. See my August 2016 post for more instruction on its use to help reduce drop and delay maturity to help manage the harvest.

Of greater concern is the seeming invasion of apple maggot fly (AM) this summer. In every orchard we’re scouting, these insects have been caught at above-threshold numbers, and, in a few2 places some pretty alarming numbers. I’ve seen a little damage on some early varieties but by and large not a massive outbreak of damaged fruit- yet. I’ll be looking into this more as the season commences and may tap some orchards for spray records to get a handle on this. AM used to be fairly easy to kill with organophosphate insecticides, which also persisted on the fruit for a good while and thus were very effective against this pest which may have a long emergence period over the majority of the summer in some situations. As we’ve shifted away from OPs for pest management in Vermont orchards (and that’s not a bad thing), I think that this pest is slipping through the cracks a bit. Growers are relying on Assail as the default material, and I am starting to question how effective that material really is, or if there is possibly an issue with resistance development in the AM population to that material.

For orchards with sustained, very high populations (10+ flies per baited trap), a final application against AM may be called for, especially if your last spray was some time ago or you have late cultivars. Materials are listed in the New England Tree Fruit Management Guide, and in addition to that table, Delegate and Entrust (the latter is organic certified)may be reasonable choices, especially if you want to rotate chemistries but still avoid using OPs. However, watch your preharvest intervals.

Generally, late-season (September-October) AM flights aren’t thought to lead to significant egglaying and subsequent fruit damage, so don’t sweat it too much as we get into harvest. I’ll work with the best experts in the region over the winter to see how we can better develop a management program for this pest.

Good luck with harvest, 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.

Grape berry moth, spotted wing drosophila, and summer wrap-up

Posted: July 30th, 2018 by fruit

By Terence Bradshaw

I had an email come in tonight that I imagine includes a question on many people’s minds. That is, as we near veraision (I saw my first Marquette changing color today), what do we need to worry about as far as spotted wing drosophila (SWD) is concerned? SWD (Drosophila suzukii) is an invasive species of fruit fly with the unique ability to lay legs in intact (i.e., undamaged) fruit, thanks to its serrated ovipositor. Mated female adults use that tool to lay eggs into developing fruit. The ovipositor puncture is a great site for rots to move in; the eggs in the fruit hatch into maggots that eat out the insides of fruit and lend to more rot. This isn’t a fun pest, read more about it at: http://fruit.cornell.edu/spottedwing/.

In general, cultural measures are the first and best line of defense against SWD. There are many practices that can reduce SWD populations and reduce susceptibility in grapes. One really nice thing is that the practices that make for high-quality (ripe) grapes also help to reduce SWD infestation.

The best thing is that grapes are not a ‘top’ preferred host for SWD- they’ll go for many other crops first. Generally, they come in after working over other more desirable crops, including wild choke cherry, elderberries, and similar soft fruit. Of course, raspberries and blueberries are the most preferred cultivated crops, and netting is becoming a more common practice used on those crops. Less so on grapes- the tight weave needed to keep out SWD would reduce the critical sunlight that is needed to fully ripen winegrapes, and as you get to larger acreages, the cost becomes prohibitive. Where a grower is not limited by organic certification, there are more tools available to manage SWD and other pests, but pesticides should not be the first defense against this pest. You’ll be playing a losing game and find yourself doubling down with increasing regularity

The scent of fermenting/rotting fruit will bring SWD into the vineyard more quickly, so do everything to maintain fruit quality and to prevent damage. That includes managing for disease, maintaining an open canopy, shoot thinning / positioning, cluster thinning, leaf removal, you know the drill. The higher quality (and the more defect-free) the crop, the less likely they will be to draw in SWD.

Sanitation should be a first line of defense against SWD. Any fruit that are decaying need to go, not on the vineyard floor, but buried into a compost pile. If you do feel a need to treat (spray) for them, I would recommend doing so as a secondary pest when spraying for grape berry moth (GBM). That is, treat for GBM (more on that shortly), but instead of using a lepidopteran-specific material like Intrepid or Bt, use something with activity against diptera as well. Delegate (spinetoram) is the preferred material, Entrust if you’re certified organic. Do Not get into the game of spraying either of these materials on a 7-10 day basis until harvest, it’s a losing game. Not only will you likely build up resistance in the SWD population to your pesticide of choice, but you’ll kill any potential predators that may fee on SWD in the vineyard. One, maybe two shots are plenty, and remember to time them against grape berry moth. Notice I’m not suggesting using pyrethroids (e.g., Danitol) or carbamates (e.g., Sevin) against these insects, as they are generally too harsh on predator insects.

GBM are starting to show up in Vermont vineyards- some sharp-eyed students of mine scouted our vineyard and found that we were over threshold and need to treat for that insect. We’re also running up against the bunch closure window after which it gets much more difficult to manage GBM (or SWD, for that matter) that are tucked up in the cluster happy. Protected, and fat on your ripening and rotting grapes.

So this is it- time to get out there and optimize the conditions for what looks like another fabulous vintage. Manage that canopy, expose those clusters, treat these couple if insects, and get your netting ready. Harvest will soon be upon us.

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.

Commercial Cider Making Workshop August 24 in Walden

Posted: July 24th, 2018 by fruit

By Terence Bradshaw

Commercial Cider Making Workshop

Presented by UVM Extension & Center for an Agricultural Economy

Getting serious about cider marking? Come learn quality control best practices and latest equipment recommendations for handling, storing, and processing of apples after harvest. Learn how food-safe practices can ensure quality control. Discuss potential value-added products with food safety experts, including the safety of shelf-stable acidic and acidified foods, cider pasteurization, UV cider processing, and the laws around hard cider production. This workshop is intended for people interested in pursuing commercial value-added apple products (cider, jams, vinegars, etc.). Participants should come with questions about specific products, designs and processes that they are considering. This event is free but registration is required. Signs for Parking will be posted. Lunch will be provided. REGISTER HERE

Date and Time

Fri, August 24, 2018

11:30 AM – 3:30 PM EDT

Add to Calendar

Location

Walden Heights Nursery & Orchard

120 Route 215

Walden, VT 05873

View Map

Daniel Keeney

Center for an Agricultural Economy

140 Junction Rd. Hardwick, VT 05843
(802) 472-5362

www.hardwickagriculture.org

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.

Midsummer vineyard management

Posted: July 19th, 2018 by fruit

By Terence Bradshaw

Sorry grape growers, you just received my comments on orchard activities for the immediate time being. The good thing, as my predecessor Dr. Lorraine Berkett used to say when discussion apples and grapes, is that it’s the same story with different characters. So, here we go with Act One:

Weather has been as dry in vineyards as it has in orchards, although some sites got a good soaker on Monday. We are expecting rain next week, and the fruit clusters are at ‘berry touch’ stage and we’ll soon see bunch closure when it will be more difficult to get protective materials into clusters. The main diseases of concern are spot outbreaks of powdery mildew, downy mildew, and possibly botrytis as we approach veraison/harvest. The good thing is that primary infection of all of these were low, so there’s little secondary inoculum out there to cause problems. However, good IPM suggests not only reducing pesticide applications unless the biology says they are absolutely necessary, but also targeting critical management points so that diseases may be managed “one and done” and not have to fight them longer through the season. I’ll summarize that point later.

Our main insect of concern is grape berry moth (GBM), which is also difficult to manage after bunch closure. The threshold for this pest is evidence of webbing between berries on 6% of inspected clusters, but I would be a little more conservative if that window is due to close. Bt is an effective and low-impact material for use against GBM, as are Delegate, Altacor, and other lepidopteran-oriented materials.

Japanese beetles are a concern for young vines, they can be managed with numerous materials including carbaryl, Assail, and Avaunt; or Surround and Pyganic for organic growers. Note that those are more broad-spectrum materials than the ones I suggested for GBM, and I generally steer clear of them unless necessary. Really, most vineyards can tolerate any Japanese beetles that they get.

Spraying summary- I’d lean toward applying something in the next 7-10 days against GBM if you’re seeing damage, and consider a downy mildew fungicide at the same time. That might be it for the season unless things get wet and we’re seeing the mildews (downy and powdery) showing up on foliage.

Canopy management: this should be priority #1 now, get those shoots combed first, but don’t really worry about leaf removal given the high amount of sunlight we’ve been getting. This is also a time to think about final crop load, I’ve received a question or two about estimating the crop to plan harvest or to help with dropping excess crop. The concept here is that you can fairly easily guesstimate the potential crop by knowing three variables: average number of clusters per vine, average cluster weight at harvest, and actual vines per acre. This is when past records are helpful for determining average cluster weight at your vineyard. If you don’t have them, I’ve used numbers from Cochran and Smiley’s Review of Cold Climate Grape Cultivars in the past, but I’ve also way overestimated doing that. Another estimate that is used is the lag phase method, which assumes that grape clusters are about half their final weight during the midsummer window when berry growth slows. Despite its use by Oregon Pinot Noir growers, the timing of the lag phase is difficult to determine on newer cold climate cultivars and so I don’t recommend using it for estimating crop yields unless you have good empirical data from your vineyard. Ohio state has a nice guide with appropriate formulas and worksheets for crop estimation.

This is a good time to apply potassium and/or magnesium fertilizers, based ideally on petiole and soil analyses from the last year or two.

Coming up: veraison and petiole analysis…

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.

AMF, midsummer orchard management

Posted: July 19th, 2018 by fruit

By Terence Bradshaw

Despite localized rains early this week, it’s still really dry out there. That means running irrigation if you can, and considering what it will take to get it in the future because I expect we’ll be seeing more of these extreme dry summers. That also means that summer diseases haven’t been much of a concern. But wet weather is expected for next week and may be enough to trigger infection of sooty blotch/flyspeck or summer rots. It may be worth thinking about your (first?) summer fungicide in the next week or so.

While you’re thinking about coverage in the orchard, the main target to consider should be apple maggot (AMF). We’ve seen very high numbers in virtually all monitored orchards in Vermont and colleagues to the east, west, and south (and I wouldn’t be surprised about the north) are saying the same thing. Of course, use trap catches on your farm to guide management of this pest, but I expect that many will be treating (and maybe re-treating). Codling moth (CM) remains between generations for all Vermont orchards, and applications aimed at AMF, as long as the material has some efficacy against CM, will take care of any stragglers. CM trap captures are high in most monitored orchards would plan to treat with a CM-specific material like Rimon, Intrepid, Delegate, granulosis virus, or other material with high activity against lepidopterans (except Bt, which isn’t very effective against CM) in the next 7-14 days. Check NEWA for insect model development.

Horticulture: add calcium in every spray, the lack of water will certainly be minimizing uptake from the soil. If you haven’t yet, consider applying potassium fertilizers based on foliar or soil analysis (foliar preferred). If you don’t have a previous foliar analysis, figure on a rate of 50 lbs actual potassium per acre as a rule of thumb.

On the topic of foliar nutrient analysis – It is the time in the growing season to collect leaf samples for analysis. Samples are usually collected between July 15 – Aug. 15. The UVM Agriculture and Environmental Testing Lab can provide analysis, but at this time their output does not generate fertility recommendations. The following are potential options of labs for analysis. It is recommended that you contact the lab for instructions and costs before samples are sent. Plus, it is important to confirm that they will send recommendations along with the analysis.

(1) University of Maine Analytical Lab: http://anlab.umesci.maine.edu/
(2) University of Massachusetts Soil and Tissue Testing Lab: http://www.umass.edu/plsoils/soiltest/
(3) Cornell Nutrient Analysis Lab: http://cnal.cals.cornell.edu/

Finally, terminal buds have set on most trees so you can think about summer pruning any time. Remember, you’re only looking to get some light into the canopy and onto fruit, not to reshape the tree. Judicious trimming mostly of this year’s watersprouts is most all that you’ll need. I tell my help to spend no more than 1-2 minutes on an M7 tree.

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.

One (or two) more things to think about

Posted: July 6th, 2018 by fruit

By Terence Bradshaw

I’ve received questions about a couple of questions about two different yet similar insect pests: grape tumid gallmaker (GTG) and phylloxera. Both of these insects cause galls that develop around larvae that feed on foliar (and fruit, in the case of GTG) tissue which can be quite concerning, but often are not an economic threat. That said, I’ve seen vines with over 50% cluster damage from GTG, and young vines with significant leaf distortions from phylloxera that overall vine growth is likely impacted. Treatment options should be the same for either pest. Although GTG may not technically be on the label for If you decide on treatment, there are a few materials of choice, which Tim Martinson outlined well in an older post that is still relevant today. Basically, Movento is the gold standard, and Dr. Ann Hazelrigg at the UVM Plant Diagnostic Clinic recently confirmed that it killed larvae inside GTG galls from one area vineyard. Admire Pro and Assail are labeled and effective against phylloxera, but have no label for GTG.

If galling is extensive, removal of damaged leaves may not reduce the damage to the plant. Galled leaves are still photosynthesizing, and, for phylloxera anyway, hatched nymphs (“crawlers”) have likely left the galls to infest younger leaves already. As those leaves expand, expect to see more galls, but not necessarily as bad as the ones on early-season leaves. I’ve seen some pretty scarred-up leaves, especially on ‘Frontenac’, that have ripened a crop just fine. If the damage is looking too severe (and I don’t have a specific threshold), then treatment with one of the systemic materials listed above is your best management option.

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.

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