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UVM Fruit Blog

Preharvest orchard management

Posted: August 9th, 2019 by fruit

By Terence Bradshaw

First things first: I’m going off-line later today for a rare, two-week, no-work vacation. Please note that I won’t be responding to emails that come in during that time.

Harvest for early apple varieties is just around the corner. That brings in a few management items that should be tended to:

1. Now is the time to collect plant tissue samples for nutrient analysis in apples to best tweak fertility programs next year. If you’re applying fertilizers without tissue samples, you are doing it blind. Samples collected every two, up to three years should be sufficient, unless you are noticing or correcting a particular deficiency. Samples should be collected separately by cultivar, rootstock, and planting system/block- basically, the sample should come from a uniform set of trees. I’ve given instructions on sample collection, and refer to those now if you need them. As for timing, apples leaves are typically collected July 15 – August 15, so now’s the time.

2. Pest management: keep an eye on apple maggot and second-generation codling moth. Some orchards may also have populations of obliquebanded leafroller that warrant treatment. Each of these is really best managed on an orchard-by orchard basis, so check your traps and check NEWA for models for the lepidopteran pests.

3. It’s dry out there, so if you have the ability to water, plan on doing so. Dry hot weather also increases mite incidence, so keep an eye out for them.

4. Approaching harvest means thinking about preharvest drop control. Dr. Duane Green at UMASS recently offered some tips on drop management strategies in an issue of Healthy Fruit:
“The time is rapidly approaching for choosing the preharvest drop control strategy you will use this harvest season. The approach for each variety will undoubtedly be different. There are a number of factors to consider in making this decision including the variety, the product to use, the weather before and after application, the time from application to harvest and the intended use of the apples (immediate sale, short storage period, long storage period). A successful preharvest drop control strategy requires consideration of all of these factors.

As an apple matures and approaches the time of harvest it starts to produce the gas ethylene. The ethylene generat­ed by the ripening apple further stimulates fruit ripening. The ethylene moves through the intercellular spaces in the apple to the abscission zone which connects the spur of the apple with the pedicel of the fruit. The ethylene weakens the abscission by stimulating synthesis enzymes that destroy cells in the abscission zone and the enzymes that hold cells together. Ethylene plays a significant role in the fruit abscission process and controlling it is a key component for drop control and regulation of ripening.
Orchardist have the choice among three currently-available preharvest drop control compounds: ReTain (aminoe­thoxyvinylglycine, AVG), NAA (naphthaleneacetic acid and its many formulations) and Harvista (1-aminocyclopro­pane-1-carboxylic acid). Each compound is different. Their modes of action are different which determines in part how they are use and the responses you can expect following application.

Harvista

This is the newest drop control compound to be made available. It influences physiological responses in the apple by inhibiting the action of ethylene. As a fruit starts to ripen it produces ethylene receptor sites. In order for ethylene to in­fluence any response in an apple (ripening, fruit drop etc.) it must bind to a receptor site. Harvista works by irreversibly binding to these ethylene binding sites. As apple ripens it continues to produce new binding sites. Loss of preharvest drop control activity from Harvista is not due to Harvista being inactivate or metabolized but rather the apple continues to produce new ethylene binding sites which are then available for ethylene to attach to and stimulate fruit ripening and preharvest drop. In initial research using a different method of Harvista application we found that application of more than one low rate of Harvista was able to extend the period of drop control of Harvista. Two to 3 applications of low rates of Harvista, equal to the sum of one application at a higher rate, resulted in longer drop control. Another observation made during the early evaluation of Harvista was that loss of drop control of Harvista can occur very rapidly, within 2-3 days. The current application of this compound made is through a proprietary in-line injection system where sprayers are retrofitted to make this specialized application. Recommendations for the use of Harvista are being handled and overseen by Agrofresh.

ReTain

ReTain (AVG) has been available to growers for over 20 years. During that time it was the main drop control com­pound used by growers. The mode of action of ReTain is by blocking a key enzyme in the biosynthetic pathway, thus in­hibiting production of ethylene in apples. It requires at least 10 days following application for the drop control of ReTain to become effective.

There are several factors that growers should keep in mind when using ReTain as a drop control compound.

· The more ReTain you apply the greater the response (more drop control and a greater delay in fruit maturity) you can expect. In general the response to ReTain is linear with the amount you apply.

· The earlier you apply ReTain in the season the greater the retardation of ripening and red color development will occur.

· When one pouch of ReTain per acre is applied on McIntosh effective drop control (less than 20%) will generally last for 30 to 35 days. Supplemental application of ½ to 1 333g pouch will extend the period of drop control and contin­ued retardation of ripening.

· Split applications of ½ pouch of ReTain will have much more drop control than 1 application of 1 pouch.

· Trees under water stress, heat stress or severe mite damage do not respond to ReTain well and its use on these trees is not recommended.

· This use of an organosilicate surfactant (Silwet L-77 or Sylguard 309, 6-12 oz/100 gal) is strongly suggested. It im­proves the performance of ReTain and it imparts a certain amount of rain fastness.

· The maximum amount of ReTain that can be used per year is two 333g pouches. Maximum drop control will be achieved using this amount.

Naphthaleneacetic acid (NAA)

Since the discovery of auxins (including NAA) in the 1930s, this group of has been known to retard preharvest drop. NAA is available in many commercial formulations. It is generally applied at a rate of 10 ppm. One can expect drop control to last 7-10 days from one application. A second NAA application of 10 ppm will extend the drop control to about 14 days. Generally, it requires 2-3 days for the drop control of NAA to take effect. NAA is most effective if it is applied just prior to the start of drop. Determining this time may be difficult. The label suggests that NAA should be applied when the first few sound fruit are found under a tree. NAA is most effective when applied prior to the start of drop. Careful monitoring of the orchard is recommended. Unlike ReTain and Harvista, NAA is known to have the abil­ity to advance ripening and shorten the storage life of fruit. Advanced ripening can be accentuated when warm to hot weather follows application, harvest is delayed, used on stressed trees or applied at rates higher than 10 ppm.

NAA may be useful when applied with other drop control compounds. NAA can be used in conjunction with ReTain. Some researchers have reported that it can enhance the drop control of Retain. Some growers wish to delay the applica­tion of ReTain to 10 to 14 days prior to anticipated harvest to minimize the influence that ReTain may have on delaying red color development and ripening. In this case NAA can provide near term drop control until the drop control prop­erties of ReTain can start to take effect. There are no reports on the use of NAA in conjunction with Harvista. Another frequent use of NAA is when it is applied with ethephon to increase red color and advance the ripening of apples early in the season. In this case, NAA can be tank mixed with ethephon or it may be applied separately 2-3 days after ethephon application.

Specific Drop Control Recommendations Differ with Cultivar

Suggestions for preharvest drop control in New England were initially developed to be used on traditional New En­gland cultivars that had a preharvest drop control problem, most notably McIntosh and Macoun. However, recently the popularity and the extensive planting of Honeycrisp and Gala have presented new challenges. Both of these cultivars are low ethylene producing cultivars, thus rates used on these cultivars must be lower to minimize the inhibitory effect of ReTain on red color development.

-Honeycrisp.

Honeycrisp has a significant drop control problem that if not countered with a drop control compound, could result in preharvest drop losses of up to 50% before harvest. Frequently, 1/3 to ½ a pouch per acre is applied to minimize the reduction in red color development. The timing of this could be 2 to 3 weeks before harvest or a split application of 1/3 to ½ 333g pouch at 3 week and 1 week before harvest. Depending on the situation, a low rate of NAA may be included with the ReTain to enhance drop control. Low rates of NAA applied on Honeycrisp will probably have a limited influ­ence on adversely influencing flesh firmness and fruit quality. There is limited information available to document the effects of Harvista on Honeycrisp drop and fruit quality.

More recently we have published work that documents the advantages of making a split application of one pouch of ReTain 3.5 weeks prior to anticipated harvest and a second 1 333g pouch application 2 weeks later. This results in a sig­nificant the delay of preharvest drop until early October. Under this scenario fruit ripen under more favorable weather conditions and red color at harvest was excellent.

-Gala.

While preharvest drop is not a malady suffered by Gala, fruit frequently experience stem-end split as they ripen, develop an undesirable “greasy” feel and internal browning may develop in storage. Under warm to hot conditions this can occur very rapidly. ReTain can delay ripening and thus reduce these maladies, but it comes at the expense of retard­ed red color development. Low rates of ReTain (1/3 to ½ pouch/ acre should be used to minimize the delay in red color development. NAA is not useful here since it does have the tendency of advancing ripening and aggravate the problem. Little information is available for the use of Harvista on the delay ripening on Gala.”

Enjoy the end of summer, this looks to be a busy harvest season ahead.

Best,

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.

Vineyard management at veraison

Posted: August 9th, 2019 by fruit

By Terence Bradshaw

First things first: I’m going off-line later today for a rare, two-week, no-work vacation. Please note that I won’t be responding to emails that come in during that time.

Veraison is on or near in Vermont vineyards, which signals the start of the ripening period. That means a few things:

1. Get your pest management in order. Diseases should be kept down to a dull roar by now, and grape berry moth or Japanese beetle treated. Your window to apply fungicides that may affect fermentation, especially captan or sulfur compounds, is closing. It’s been dry, so there shouldn’t be too much in the way of late-season diseases if you managed them well so far.

2. Finish your canopy management. Grapes need to see the sun from now through harvest, so make your final passes through to comb shoots and pull leaves where necessary.

3. Get rid of green fruit. At veraison, you can see where certain clusters from secondary buds r less vigorous shoots are behind the others. Drop those now, they will only drag down the ripeness of the others.

4. Get your nets, squawkers, scarecrows, and other bird measures ready, but wait as late as possible.

5. Collect petioles and send in for analysis to assess vine nutrient status. See this post for more details.

6. A couple of weeks before expected harvest, start assessing grapes for ripeness. 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.

Sugar level and pH are easily evaluated with simple tools (a refractometer and pH meter, respectively) available from most winemaking supply outlets. We recently published a fact sheet on Preharvest Winegrape Juice Testing.
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.

Enjoy the end of summer, and good luck as you plan for what looks to be a great vintage.

Best,

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.

Midsummer vineyard management; veraison management workshop August 6

Posted: July 24th, 2019 by fruit

By Terence Bradshaw

We will host a veraison / preharvest vineyard management workshop at the UVM Horticulture Research & Education Center on August 6th, 3:00 – 4:30. This is folded into a larger Research Open House, I sent a flyer in a previous email (also available at: http://go.uvm.edu/hrecresearchday). We will cover out latest research on cold-climate grape cultivars, management decisions to be made as veraison approaches, and preharvest juice sampling to time harvest. There is no charge for this event, just show up. The rain date will be August 9, watch this email list for word if we do move it.

Most spraying in Vermont vineyards should be wrapping up as the vines and especially fruit are becoming resistant to most diseases. However, if you have downy and powdery mildew in the vineyard, it would be wise to maintain protection against them through veraison. Vines which have not reached bunch closure may also be protected against botrytis for one last time before veraison and harvest.

Japanese beetles are probably in every vineyard in the state. Their damage can generally be tolerated on established vines, but vines under 3-4 years old should be protected. Grape berry moth are mostly in pupal stages in Champlain Valley vineyards, although in some inland/cooler areas larvae may still be feeding. Careful and thorough scouting for webbing between berries will determine the presence of the pest. The threshold for treatment against the current generation is 6% of clusters with signs of damage.

Canopy management is critical at this time of the year- every fruit cluster should see at least some direct sun. However, if opening up congested vines at this time, be careful not to fully expose clusters that have been heavily shaded, as the risk for sunburn increases when a shaded cluster is exposed to full sunlight in midsummer.

Get your bird netting ready.

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 orchard management

Posted: July 24th, 2019 by fruit

By Terence Bradshaw

High summer is here, the time that apple growers can relax (a little), maybe go away for a few days, and just get ready for money to fall off the trees. While that’s a bit of an exaggeration, this has always been one of my favorite times in the apple season, as we watch the fruit size up with a lot less work than earlier in the season.

Pest management: thinks are pretty simple now. Insects drive your fungicide sprays, as there is room to stretch the latter out on a 2-3 week schedule depending on rain. If you still have active scab in the orchard, captan every 10-14 days is still on the menu, but leaves and fruit are becoming more resistant to new infections, and existing lesions should be burning out. Sooty botch. Fly speck, and fruit rots should be the main targets, select your material of choice based on the New England Tree Fruit Management Guide.

As for insects, that really depends on things farm by farm. Some orchards have already seen sufficient trap captures to trigger an apple maggot fly spray, check your traps and be ready to treat when average trap captures hit one per block for non-baited traps or five for baited traps.

Second generation codling moth are just flying now, so egg hatch is still a few weeks away. Obliquebanded leafroller, if they are a problem in your orchard, could be treated any time now but I’d plan on scheduling that with your maggot spray.

Every spray tank should include some calcium product at this time of year. For Honeycrisp and Cortland especially, you may need to make some passes with just calcium to keep bitter pit at bay.

Now through mid-August is the time to collect leaves for foliar nutrient sampling. 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, anyone interested in seeing what we’re up to in our research orchards can attend the UVM Hort Farm research day on August 6. I sent a flyer in a previous email this morning. We’ll only be covering apples from 10:30-11:15, but there will be plenty to see along the tour route and you can always chat with me before/after, at least until I need to get ready for my next stop. http://www.uvm.edu/~hortfarm/documents/20190806_UVM_HREC_ResearchDay.pdf

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.

UVM Horticulture Research & Education Center Research Open House August 6, 2019.

Posted: July 23rd, 2019 by fruit

By Terence Bradshaw

Since 1952, the UVM Horticulture Research & Education Center has hosted projects that have furthered production of apples, small fruit, vegetables, and ornamental specialty crops in Vermont and the surrounding region Join UVM faculty, staff, and student researchers on August 6 (rain date August 9) as we show off our current research projects at the UVM Hort Farm. The agenda will follow projects via a walking tour across the landscape of the 97-acre facility throughout the day from 9:00 am – 4:30 p. Attendees are encouraged to come and go to fit your interests. Pack a lunch and make a day of it, or attend just the sessions you’re most interested in. The tour is designed so that attendees can join and leave at any point to suit their interests.

A tour agenda is attached and can be found at: http://go.uvm.edu/hrecresearchday

A research synopsis can be found at: http://go.uvm.edu/catfarmresearch

No RSVP is needed, but if accommodations are required, please email Hort Farm Director Dr. Terence Bradshaw at: tbradsha.

Please distribute to your contacts as you feel appropriate.

See you on the 6th,

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.

20190806_UVM_HREC_ResearchDay.pdf

Grape canopy management

Posted: July 11th, 2019 by fruit

By Terence Bradshaw

High Summer is here, and this period from after July 4 through early August is the perfect time to apply some canopy management to the vineyard. By thinning and positioning shoots; removing unwanted clusters; and cleaning up trunks, we can significantly increase penetration of sunlight into the canopy and especially into the fruiting zone. This will make for measurably better juice and wine quality, improved winter hardiness, and less disease pressure.

There are a number of practices that should be performed, but the most important is shoot positioning (also known as “combing”). This practice includes separating each shoot from its neighbor and directing the growth into the vertical plane: usually down, for high-wire cordon vines, or up for those on a low wire, vertical shoot positioning system. Once shoots are pointed in the right direction, it’s easy to see where runty secondary or tertiary shoots are in the canopy, and where smaller clusters that are behind in development compared to the main crop are- those can both be removed.

(Retired) Iowa State Extension Specialist Mike White presents a good overview of the concepts and practices behind canopy management in his February 8, 2012 newsletter found here.

There’s a video of some UVM staff doing some (silent) canopy management here.

Ohio State Extension has a nice video here.

While I have you, it’s worth mentioning that we’re not out of the woods as far as disease management is concerned. It has been a difficult year so far with all of the rain, and the frequency of it, to maintain fungicide coverage but I have been seeing mostly clean fruit and foliage in vineyards which have maintained an appropriate spray schedule of 4-5 well-selected and –timed fungicides since prebloom. At this point, phomopsis is pretty much done, and black rot will soon be winding down. Powdery and downy mildews (PM?DM) should be the main focus for disease management, as well as botrytis a few weeks down the road. If this wet weather continues, I would recommend a specific botrytis material such as Flint, Rovral, Vangard, Endura, or Pristine before bunch closure (the point where berries size up to the point where spray material cannot penetrate the cluster to protect fruit from infection). As always, check your Pest Management guide (New York & Pennsylvania or New England guides) and the label, rotate fungicide classes to reduce resistance likelihood, and follow all safety precautions when spraying. Organic disease management spray options include copper (DM, a little PM), sulfur (PM), stylet oil (PM, do not spray before or after a sulfur spray), and possibly some of the biologicals but I don’t know enough about them in regards to their performance against these late-season diseases.

Next week would be a good time to scout clusters for grape berry moth (GBM) webbing which could suggest a need to treat for that insect pest. The threshold for treating this generation is 6% of clusters showing damage, which appears as small bits of webbing in between berries up inside the cluster. GBM is the primary insect pest of established vineyards in Vermont, and if it is the only pest insect need to manage, then some very specific materials with low potential for non-target effects may be used, including lepidopteran-specific materials like Bt, Intrepid, Delegate, or Altacor (the latter has some activity against Japanese beetle). Bt (DiPel and others) and Entrust would be effective materials against GBM for organic growers- the former affects only lepidoptera, while the latter would have some activity against Japanese beetle and some other insects as well.

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.

Vineyard management at bloom

Posted: June 30th, 2019 by fruit

By Terence Bradshaw

Many vineyards are in bloom across Vermont, and inflorescence looks good and bodes well for a promising year. As I’ve been saying all along, be sure to maintain spray coverage for the next couple of weeks; to remove any diseased tissue as you find it; and to do your best to maintain an open canopy (more on that in a minute). All of the main diseases, including downy mildew, should be active now, so fungicide choice should cover all of the bases. That likely means applying a mix of materials that have multiple modes of action, like mancozeb (watch the 66-day preharvest interval) or captan and a strobilurin (Flint, Abound) or DMI (Rally, Elite, etc.). There are some good premix materials available that cover two modes of action, like Inspire Super and Pristine, but even they could use some protectant activity from mancozeb or captan to improve efficacy and reduce resistance development. The New England Small Fruit Management Guide has a good table that outlines the efficacy of the main fungicide materials available to growers. For organic growers, a rotation of sulfur and copper is pretty common now, but be sure to watch for signs of phytotoxicity. Coverage maintained for the next few weeks will pay off by allowing you to relax a bit for the second half of the summer.

Wild grape bloom occurred on June 19 in South Burlington, which sets the clock for grape berry moth management. The first overwintering generation is rarely significant enough to warrant a management spray except in vineyards that have had extreme damage in previous years. Each generation requires about 820 degree days (base 47°F, or DDb47°F) to complete, and the first generation typically emerges around the time of wild grape bloom. So if we use June 9 as our ‘biofix’ and track DDb47°F, we can estimate the best time to treat for the more damaging later generations.

This is made easy by the Network for Environment and Weather Applications (NEWA) system, which I coordinate for Vermont. The network includes twelve on-site weather stations (all located at orchards) and six airports, and imports data in near real-time for use in pest models. It is free to use, and growers can locate the site nearest them and develop a best-guess of phomopsis, black rot, and downy mildew infection periods as well as a sense of the grape berry moth generational development.

Plant tissue sampling is one of the best ways to plan fertility management in your vineyard, and now is one of the important times for collecting samples. Petiole samples may be collected at bloom or veraison, and comparisons between years or blocks should be based on the same time of collection. The benefit of a bloom sampling is that it gives you time to make corrections, if needed, during the present growing season.

Samples should be collected separately for each cultivar or block. In each sample, a random collection of 75-100 petioles should be collected from throughout the planting. Petioles should be collected from the most recent fully expanded leaf on the shoot, not across from the fruit cluster as is collected for a bloom sample. Just remove the whole leaf and snip the petiole (the leaf ‘stem’ off with your pruners. Gently wash each sample in water with a drop of dish detergent, then rinse fully and place in an open-top paper bag to dry. The closest analytical lab for grape petiole analysis that also provides pretty comprehensive management recommendations is the . There is a great section in Appendix A of the Wine Grape Production Guide for Eastern North America (which every grower should have a copy of on the bookshelf, ready to grab with short reach) which helps to guide fertilizer application rates based on soil and petiole samples. If you have a copy of those to send to me, I’d be happy to help you with the numbers as well.

Finally, I have two events to mention. First is a reminder of the July 9 Canopy Management Workshop we will hold at Ellison Estate Vineyard in Grand Isle. Please preregister here to attend.

The second is a UVM Horticulture Research & Education Center Research Open House that we will hold at the farm in South Burlington on August 6. Researchers with projects across the farm and working in multiple disciplines will showcase our work. I will host a tour of the research vineyard, and will have a pre-harvest management workshop at which we will discuss bird protection, late-season canopy and crop management, and preharvest sampling procedures to optimized juice quality at harvest. Watch for details on that event in the next week or so, but plan on it happening in the later afternoon around 3:00.

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 fly traps

Posted: June 29th, 2019 by fruit

By Terence Bradshaw

The time has come to hang apple maggot fly (AMF) traps in Vermont orchards. Last year, we saw higher populations state-wide, for which I don’t really have a good explanation. These are some of the easiest pests to manage using an IPM strategy, so there’s really no excuse. The idea is to assess the population in the orchard before applying prophylactic sprays. By using red sticky traps, you can time treatments for best effectiveness, and maybe even skip treatments if the populations are low enough. Traps are red plastic balls that you coat with Tanglefoot adhesive. Kits including traps and adhesive are available from Gemplers and Great Lakes IPM.

Traps should be hung at least four per 10-acre block, preferably at the orchard perimeter and especially near sources of the insect, like wild or unmanaged apples. Placement in the tree should be about head-height, and surrounding foliage should be trimmed away- this trap is largely visual, and you should be able to see it from 10-20 yards away. The traps may be baited with an apple essence lure that improves their attractiveness dramatically. For monitoring to time sprays, unbaited traps that catch one fly per block (as an average of all the traps in the block) would warrant treatment; the lure makes them much more attractive such that you can wait until an average of five flies per trap are caught before treating. For most growers, the main insecticide used against AMF is Assail, Imidan also works but it has a long reentry interval and tends to leave visible residue on fruit. For organic growers, Surround works well, but its use in midsummer may increase European red mites, and it can be hard to remove at harvest; spinosad (Entrust) works pretty well too. First AMF treatment is still a few weeks off, most likely

It is summer lepidoptera season, and treatment should be on everyone’s minds, especially for codling moth (CM) and obliquebanded leafroller (OBLR). CM are active and eggs hatching or soon to hatch across the state, so growers who have caught CM in their traps or who often have issues with this pest (that’s most everyone) should apply something effective against them soon. Very specific materials like insect growth regulators (Intrepid, Rimon) or granulosis virus (Madex, Cyd-X) can be used that are very safe to non-target insects. One or two applications of a material should suffice for first generation. OBLR are just showing up in traps, and treatment should be timed at 360 degree days (base 43°F) after first catch. There is a NEWA model for this pest, and a material like Bt (Dipel, etc.) is effective (but not against CM).

Mites are a no-show statewide. Keep scouting leaves, as their populations can grow very quickly, especially as the weather heats up.

Diseases: keep checking on your scab, if you have none (I mean none), then it’s okay to relax. The summer diseases sooty blotch and flyspeck are of concern now, but they require 270 hours of leaf wetness for lesions to form, so fungicide coverage between that period should be maintained. Keep in mind that one inch of rain washes off half of your coverage, after two inches, it’s gone.

Enjoy the holiday this week and remember that trees shouldn’t be sprayed when it’s over 80-85, and application of sulfur, captan, and other potentially phytotoxic materials should be avoided when hot weather is in the forecast for the next couple of days.

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.

July 9 UVM Grape Canopy Management Workshop

Posted: June 19th, 2019 by fruit

By Terence Bradshaw

Summer canopy management is one of the most important tasks for producing high-quality winegrapes, especially in cool/cold regions where ripening can be impacted by low heat unit accumulation. The tasks taken to open and manage canopies aren’t necessarily intuitive, and are often overlooked by beginning fruit growers.

Join the UVM Fruit Program on Tuesday, July 9, 2019 for a hands-on workshop on managing canopies in cold-climate hybrid grape vineyards. The workshop will run 9 AM – Noon at Ellison Estate Vineyard 69 East Shore North Grand Isle, VT 05458 United States. There is no fee for this workshop, but please pre-register by completing this very short survey.

https://survey.uvm.edu/index.php/187557?lang=en

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 pest management, June 19

Posted: June 19th, 2019 by fruit

By Terence Bradshaw

June 19, 2019

It’s always impressive to me how fast grapevines can go from zero to full foliage in a matter of a couple of weeks. Vines at the UVM Horticulture Research & Education Center are generally at 16-24” shoot growth. We’re not quite at “Immediate Pre-Bloom” stage, but not far off, either. Now is a critical time for disease management. As we mention in our initial IPM strategy for winegrapes, all of the major diseases save for late-season fruit rots are sensitive to management right now. That means that fungicide applications should be made, using a material or materials with broad range of coverage against powdery mildew (PM), downy mildew (DM), black rot (BR), anthracnose (Ant), and that last bit of phomopsis (Ph) for the season. Generally, this means a combination of materials, including a protectant (mancozeb, most effective against Ph, BR, PM, or captan (Ph, DM)) plus a systemic or more narrow-spectrum material. Those may include Vivando / Quintec (PM only); a DMI material like myclobutanil or tebuconazole ((BR, PM); or a strobilurin (BR, PM, also excellent against botrytis so save until later in the season in July if you have issues with that disease). I’ll mention other materials with excellent efficacy against DM and botrytis later when those diseases are of greater relative concern.

For organic growers, be sure to maintain your copper and/or sulfur sprays, watch for phytotoxicity, and remove diseased leaves and clusters as soon as you see them. It’s been a wet spring, although a bit drier since grape budbreak that earlier in the year. I expect diseases will be pretty significant problems for growers this year, so stay alert.

Insect activity is usually pretty quiet at this time of the season. Keep an eye out for bloom on wild grapes, as that sets the clock for the degree day model used to time management of grape berry moth (GBM). We typically add BT (Dipel, Javelin, etc.) or another material specifically active against lepidopteran pests soon after bloom at the earliest, so there’s time before we consider managing for this pest. GBM isn’t always a problem in every Vermont vineyard, we’ll talk about scouting for that pest in an upcoming bulletin.

We are seeing a bit of grape tumid gall (GTGM) in the UVM vineyard this year. This is an infrequent pest that causes visually striking but (usually) relatively insignificant damage to the vines, and management practices are not recommended against them. However, serious cases can affect fruit clusters, especially in La Crescent and Marquette, so any signs of them in clusters may warrant treatment. I discussed this pest in a post on June 8, 2017:

This insect is similar to phylloxera in that the larvae feeds on leaf tissue which responds by forming a protective gall around it. GTGM is different in that it also affects rachises and fruit, and when the galls become fully engorged, can look pretty dramatic.

Figure 1. Grape tumid gall on a fruit cluster in midsummer. UVM vineyard, 2009.

GTGM is an midge insect (small fly) that lays eggs on grapevines. Flies are ephemeral and only live a day or so; management should not be targeted at adults. Hatching larvae burrow into vine tissue and are thus protected from contact insecticides. In most vineyards, GTGM is considered a minor pest or even a curiosity as the galls can be quite drastic-looking. That said, I have been hearing reports of high levels of GTGM in vineyard this year, and some of these vineyards reported them last year under different management, so I suspect that certain vineyards have increasing and potentially problematic populations.

Figure 2. GTGM on Marquette, UVM vineyard, 2010..

Vineyards should be scouted before assuming you have a problem with this pest. There is no threshold established, as most growers tolerate low levels of damage. However, I have heard reports of 50% or more leaves affected in some vineyards, and I can’t imagine how that wouldn’t negatively affect vine productivity.

Figure 3. GTGM on inflorescence. UVM vineyard, 2011.

Sanitation is an important method of reducing GTGM populations and may be enough in low-pressure situations. Galls can be crushed if seen on leaves, or severely affected leaves removed and destroyed. In organic vineyards, as always, this should be the first line of defense since spray options are minimal. If the extent of damage is beyond physical removal, an application of Movento is the best (only) recommended option I can find. Movento is a systemic insecticide with a unique mode of action and is listed as posing low risk to wildlife, and as non-toxic to fish and birds. It is best used at first sign of galls, practically speaking, as scouting for hatching larvae (which hatch from microscopic eggs) is difficult under normal field conditions.

GTGM may be distinguished from phylloxera by the gall surface, which is smooth compared to phylloxera which is bumpy or warty. Movento is effective against phylloxera as well as GTGM and has a long residual control period, so may be a good material if either or both of those pests are common in your vineyard.

More information on GTGM may be found in this Cornell fact sheet: https://ecommons.cornell.edu/bitstream/handle/1813/43134/tumid-gallmaker-FS-NYSIPM.pdf?sequence=1&isAllowed=y

Horticulture: There are two good times to collect petiole samples to assess vine nutrient status, bloom and veraison. Generally, you should stick with whichever timing you have been using so that you may compare to past tests. Dr. Joe Fiola at University of Maryland has a good fact sheet on petiole sampling. We recommend the Cornell Nutrient Analysis Laboratory for petiole sampling, as they have extensive experience in providing nutrient recommendations for grapes. Should nutrient applications be needed, this is a good time to apply boron, magnesium, and nitrogen as they are needed during this period of rapid shoot and fruit growth.

Other activities that I don’t need to tell you about: shoot thinning can continue, but shoots aren’t lignified at the base enough to comb them, they’ll just break off. Keep the vineyard mowed to improve airflow, but a golf course mowing regime isn’t necessary unless that’s your aesthetic choice. Keep the in-row weeds down however you can, but most herbicides should be put away for now because of likelihood of vine damage.

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.

Contact Us ©2010 The University of Vermont – Burlington, VT 05405 – (802) 656-3131
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