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UVM Fruit Blog

Borers and moths, plus a little on orchard diseases

Posted: June 26th, 2017 by fruit

By Terence Bradshaw

June 26, 2017

There’s pretty much no question that apple scab ascospore release is done now, and only lesions from that primary scab season that became established in the trees can continue to spread the disease. There is a bit of scab out there; if you have any, then keep covered with Captan for about four weeks until those lesions are finished spreading secondary spores. Sooty blotch and flyspeck are going to be active this year, and if you’ve had more than 2” of rain since a fungicide, it would be prudent to apply one soon against those diseases.

Apple maggot traps should be up now in Vermont orchards. These red sticky spheres should be hung in a very clearly visible location at the corners of a block and baited to better attract flies to them- see last week’s message for more details. Codling moths may need management if you haven’t yet done so, but the window to manage the first generation is closing rapidly. Another set of insects to consider targeting soon are dogwood borer (DWB) and roundheaded apple borer(RAB). The former is a clearwing moth that looks like a wasp upon first sight, and its larvae tunnel in trunks, especially in burr knots on rootstocks, and cause a general decline in tree health. The latter is a beetle whose larvae tunnel into trunk tissue and hollow out trees, especially those between 3-8 years of age, and can eventually kill the tree. Infestations can be found by looking closely for a roughly 1/4” drill hole low on the trunk with frass coming out. If you see that, the larvae is either in there or has already done the damage and left. RAB tend to affect low-spray orchards most, especially those surrounded by woods and with brushy undergrowth. For both insects, a directed trunk spray right about now is the best option. Older (>7 year-old) trees may not be as susceptible to damage; young trees should be protected if you have ever had problems. Many growers aren’t familiar with either- in a typical orchard in which insecticides are applied, RAB is typically controlled, DWB is more subtle however, and we have caught the adult moths in every orchard we have monitored in the state this year. The Cadillac material for effectiveness is chlorpyrifos (Lorsban, also sold as a generic), but it is one of the old, highly toxic organophosphate materials that we would rather see left to history. That said, especially on young, high-density (and thus high-investment) orchards, it could greatly improve tree health moving forward. Chlorpyrifos can only be used once per year, and after bloom, only in a directed (i.e., handgun-applied) trunk spray with no contact to fruit or foliage. Cultural practices that can improve control include maintaining clean ground under the trees (you should be able to clearly see all trunks) to reduce refuge sites and increase biological control from birds, etc; removing solid trunk guard like the white spiral wraps during the growing season to expose the trunks; or (conversely) maintaining tight weave window screen trunk guards and closing the tops with elastic bands to prevent intrusion from above.

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.

Disease management still critical in grapes

Posted: June 26th, 2017 by fruit

By Terence Bradshaw

June 26, 2017

No one needs me to tell them that this has been a wet spring and now early summer. Most grapes are approaching, in, or maybe just exiting bloom across the state, and disease pressure continues to be possibly the highest of the season. Fungicide coverage should be maintained on 7-10 day intervals, depending on rainfall (1” removes about half of a material from the canopy, 2” and you’re no longer covered at all). The diseases of concern right now include all of the major ones: black rot; phomopsis; powdery mildew; downy mildew; anthracnose; and botrytis, so make sure any materials you apply cover the whole spectrum. Spray choices should include a contact material like Captan or a mancozeb (probably the last chance to use the latter, and watch the long preharvest interval); plus a second specific activity toward Black rot, downy mildew, and/or powdery mildew, like an SDHI (Luna Experience); strobilurin (Flint or Sovran); DMI (Rally, Tebustar); or a combo material like Revus Top, Pristine, or Inspire Super. Be sure to rotate between fungicides, never applying anything other than sulfur, copper, Captan, or mancozebs in more than two back-to-back sprays.

For organic growers, this is going to be a difficult season. Sulfur may be used now but will really only manage powdery mildew; copper materials may be the most effective against downy with a little activity against powdery and black rot, which will continue to be very hard to manage on an organic schedule in this wet year. Sanitation must be performed regularly to reduce disease inoculum in the canopy, that means pulling every leaf with visible lesions as it develops and destroying it. In a year like this, you may face significant vine defoliation using this method, but it will be your first line of defense.

Other than disease management, this is a great time to work on weed control and training young vines to the top wire. Canopy management should take a back seat for now, at the shoots are not lignified at their bases and thus are quite brittle.

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.

Orchard management- June 18, 2017

Posted: June 18th, 2017 by fruit

By Terence Bradshaw

June 18, 2017

I am doing some last minute preparations for my summer cold-climate viticulture course which starts this week (and still has a few slots if you’re interested), so this will be relatively brief. Codling moth (CM) should be tended to in most orchards in the warmer valleys this week if you have any question about them being a problem- and they are an increasing problem. candidates to use. Plum curculio and European apple sawfly should be all done doing their damage by now, so it’s just CM and some other leps that you’d be managing. This should be a great week to target first generation egg hatch, and CM-specific materials like granulosis virus (effective against CM only, with some efficacy against Oriental fruit month OFM), growth regulators (Intrepid, Esteem), and reduced-risk materials like Altacor and Assail would be good candidates at this time.

We are trapping all sorts of other moths, including lesser apple worm and OFM, which may be managed similar to CM, generally.

Apple maggot traps should be hung soon. These red sticky balls can be purchased from Great Lakes IPM or Gemplers. Buy the inexpensive ones and throw them out, we have spent countless hours over the years scrubbing the old wooden spheres in various solvents and the (literal) headache just isn’t worth it. Traps should be hung at least four per managed block, preferably at the corners of the orchard adjacent to woods or other overwintering areas. Organic growers with small plantings may ‘trap out’ by using a (much) larger number of traps as described here. Most growers find it easier to use the traps to monitor the flight of the flies and time a spray application, which may (hopefully) be timed to manage second generation codling moth as well later in July.

Diseases: this is the week to scout you orchard carefully for apple scab; if you have more than 1% of leaves affected, you’ll need to keep a protectant like Captan on until the terminal buds set and leaves become less susceptible. Fire blight is popping up, we are finding it in the usual trees at the UVM Hort Farm and cutting it out. Please let me know about anything bigger than a sporadic infection in the usual hot spots. Sooty blotch and flyspeck aren’t a problem right now. Frankly, unless you find scan, I’d put the fungicides away for now.

Water if you need to; apply calcium in most every spray and extra calcium in Honeycrisp. You can apply potassium-based fertilizers any time, that large crop this year will draw a lot out of the tree/soil. Of course your cation (calcium/potassium/magnesium) applications should be based on soil and, even better, foliar samples. Those will be ready to take in mid-July.

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.

Wild grape bloom starts the clock for grape berry moth management

Posted: June 12th, 2017 by fruit

By Terence Bradshaw

June 12, 2017

There is a wild grape that overhangs the South Burlington bike path just east of the UVM Hort Farm that I run by several days per week. Last Friday, June 9, it went into bloom (it was not blooming on my run the day before). Why is this important?

Grape berry moth is likely the most injurious pest of grape fruit in northern New England and New York. It is relatively easy to manage, often with a single application of a lepidopteran (caterpillar)-specific material. 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 ten 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.

Remember, however the important components of Integrated Pest Management (IPM): cultural controls such as sanitation and good canopy management can reduce disease inoculum and insect pests while reducing canopy moisture and humidity; and most cold-climate grape cultivars are more resistant to the main diseases of black rot, powdery mildew, phomopsis, and downy mildew than V/ vinifera or even older French American and other hybrids with a substantial amount of vinifera in their parentage. So a ‘clean’ vineyard will have less need to spray when a model says a disease infection occurred, and a vineyard of cold climate cultivars is even better off. Remember the basics from our basic spray strategy for cold-climate grapes in Vermont: keep covered immediate prebloom and post bloom, plus another application or two 7-10 days apart after that. Build up from there as needed based on your vineyard history or unique cultivar susceptibility.

-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.

EAS, FB, CG…observations from this week.

Posted: June 10th, 2017 by fruit

By Terence Bradshaw

June 10, 2017

CPS crop consultant Eric Boire sent me this picture yesterday of what, on first glance, looks like a first generation codling moth larvae burrowed into an apple at about 10-12 mm growth stage:

Figure 1. European apple sawfly damage posing as codling moth injury.

We have seen this a lot in the UVM orchards, especially the organic section. What we are looking at is European apple sawfly (EAS) damage. You can see the characteristics squiggly scar right below the hole, but sometimes larvae aren’t content feeding on one apple and will exit one fruit and enter an adjoining one- all the more reason to thin your fruit down to singles per spur early. There isn’t a lot to do to manage them at this stage except hand-thin the affected fruitlets and remove them from the orchard to lower nest year’s population-we’ve done this with seemingly millions of these in the organic orchards at the Hort Farm. The maddening thing about seeing this damage now in a commercial orchard is that we have caught very few EAS in our traps all over the state, including in this orchard. Traps used for monitoring EAS are unbaited white sticky cards that are designed to mimic a large blossom.

Figure 2. EAS trap.

We have used a trap for decades at the UVM farm that have been quite effective, but this year, we started using a smaller, more inexpensive trap that has less surface area and less ‘sticky’ and seems to be missing these pests during aa time when monitoring would help deliver actionable recommendations for their management. Long, extended bloom periods like this year’s make EAS management more difficult as well.

Codling moth will do similar damage but always later in the season, usually when fruit are over 20 mm in size. CM larvae are just starting to hatch now in the Champlain and Connecticut Valleys, so a targeted application at them would be prudent, as I’ve mentioned in recent posts.

Another oddity that came to me was the presence of crown gall in some trees at a commercial orchard that prompted me to check some dying trees we have at the UVM orchard on the same rootstock from the same nursery:

Figure 3. Crown gall on apple.

Notice the warty growths on the roots. This tree was dead, and had little to no root growth since it was planted in 2016. The affected rootstock was Geneva 935; keep an eye out for declining trees on that (or any) rootstock. Crown gall is caused by a bacterium, Agrobacterium tumefaciens, which affects many types of plants. It is not uncommon, but generally becomes pathenogenic when plants are damaged, e.g., from cold (commonly seen in grape) or from nursery digging. The best defense is to use disease-free plants. A careful inspection of roots at planting time should be performed to make sure you’re not putting a dying tree in the ground to start with. A. tumefaciens is one of nature’s original agents for horizontal gene transfer, a natural GMO, if you will, as it inserts its own DNA into the host plant which responds by growing the galls or ‘tumors’ as shown in the picture. AAs an aside, early GM breeding used this characteristic of the bacterium to transfer genes to new plants, although more precise methods are typically used these days for that task. There is no chemical management for crown gall in apple, basically we need to plant clean trees and keep them healthy through good cultural practices. A good fact sheet on the disease is available at: http://ohioline.osu.edu/factsheet/plpath-fru-19

If you were affected by fire blight from the May 18-20 potential infection period, you should start to see blossom infections now- scout orchards carefully and be prepared to cut out as you see it. Prime targets will be trees that had the disease last year, and highly susceptible cultivars like Cortland, Paulared, Gala, Fuji, and Honeycrisp. Damage will be evident on fruit clusters, and should be accompanied by oozing or water-soaked vascular tissue below the affected area. Some damage that looks like FB can often be attributed to other damage to blossom clusters, often from feeding by various shoot boring lepidopteran larvae. In that case, there will be an abrupt ending where the damage stops and clean tissue starts, often accompanied by an entry hole and a tiny larvae in the shoot.

Figure 4. Possible fire blight on an organic fruit spur. UVM orchard, 6/9/2017.

Finally, I get reports that sometimes my pictures do not come through on email postings. If that’s the case, my posts are always copied to my UVM Fruit blog, http://blog.uvm.edu/fruit/.

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 tumid gall maker- curiosity and management

Posted: June 8th, 2017 by fruit

By Terence Bradshaw

June 8, 2017

One of the great things about growing grapes in Vermont is that, by and large (and compared to my other crop, apples), the pest management is relatively simple- four or so well-timed fungicides sprays, and an insecticide aimed at grape berry moth. There are other considerations for unique situations: wet years or susceptible cultivars that need an extra botrytis spray; Japanese beetle or phylloxera on young vines. And then there’s the potentially weird, and maybe damaging, like grape tumid gall maker (GTGM).

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

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.

Codling moth and other pest management in apples

Posted: June 6th, 2017 by fruit

By Terence Bradshaw

Codling moth (CM) management is just around the corner in many Vermont orchards. This is an increasing pest in the state- many orchards never had a problem until recently, and some still don’t. Adults begin flying around bloom, and our monitoring program is designed to catch the first flight to tie later management applications. Mated females lay eggs in the tree canopy and hatched larvae burrow into fruit causing significant damage in some orchards. It is the larvae that are generally targeted for control. Materials effective against larvae include many broad spectrum pesticides that may also have substantial non-target impacts on beneficial insects. If you need a late petal fall cover effective against plum curculio (PC) or European apple sawfly (EAS), then a broad-spectrum material may be needed. However, if targeting CM specifically, then a more specific material may be called for. As I mentioned last week, there are a number of materials that have high efficacy against CM and low non-target impacts, including granulosis virus, insect growth regulators like Intrepid and Rimon, and some more lep-specific materials like Delegate and Altacor. Applications should be made about 250 degree days (base 50°F) from first trap capture. In South Burlington, current DD since the first capture is 193 as of today, with 250 predicted by Sunday. So the next spray application should include a CM-specific material if they have been a problem in your orchard and you are located in a warmer area like the Champlain or Connecticut Valleys.

San Jose scale is another insect which is increasing in Vermont orchards. Crawlers emerge about 500 DD base 50 from March 1; that should occur mid-late next week in the warmer sites and a bit later in the cooler ones. Some scale-specific materials include Esteem, Movento, and some of the neonicotinoids like Assail and Admire Pro, which may have activity against other pests, especially Assail which is fairly effective against CM, PC, EAS, and a number of other insect pests.

Disease: I recommend one more fungicide cover until we can get a handle on what the scab situation is next week. Captan (sulfur if organic) is fine, adding a DMI, stroby, or SDHI will cover for rusts and/or powdery mildew.

Fertilizers: I haven’t discussed them much this season. Nitrogen applications should be wrapping up by the middle of the month. Calcium applications, both ground (gypsum or calcium nitrate in that last N application) and foliar, should start now. If needed, magnesium and potassium applications can also begin any time now. Consult your leaf analysis for determining these.

Thinning: most orchards should know the fruit set, thinning, and general crop load status by now. If you need additional thinning, the window will start to close after this weekend. Maxcel and other 6-BA thinners will finally start to work given the upcoming heat. Also, remember that the leaves are soft and trees will thin easily, so don’t overdo it.

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 approaching bloom

Posted: June 6th, 2017 by fruit

By Terence Bradshaw

Grapes are at 10-12” growth in most Vermont vineyards, and combined with the wet, cool, rainy weather, are at prime susceptibility for phomopsis, black rot, and anthracnose. Fungicide coverage should be maintained on 7-10 day intervals during this extended rainy stretch; if it dries out as expected at the end of the week, spray intervals may be stretched to 10-14 days. Best material options are captan or mancozeb with or without a DMI (e.g., Rally, Tebstar), although I would recommend the DMI given how wet it’s been. Strobilurins (e.g. Flint, Sovran, Quadris) are also effective, but best saved for later when Downy mildew is a concern.

Inflorescence is well-developed, and we can see the potential for the 2017 crop now, so this is a good time to continue shoot thinning, removing the shoots with the weakest clusters if possible. This is also an important time to maintain good weed control, as the period of most rapid growth coincides with a need for moisture and nutrients. It won’t necessarily stay this wet for the whole summer, and if weeds aren’t managed early, the vineyard can become a jungle later in the summer. I do not recommend glyphosate herbicide at this point of the season, there is just too much chance for causing vine damage. Postemergent contact herbicides like glufosinate or paraquat (be extra cautious applying the latter) can be effective in knocking back annual and (to some degree) perennial weeds. Cultivation also works well if the proper equipment is used, but is likely difficult to perform on wet soils. The time period needed for good under-vine weed controls isn’t long; by July, the vines begin to slow growth and shift resources toward developing fruit so a little weed growth is okay by then. But for now and in the next week or so, think about getting those weeds under control.

Insects are a relatively minor concern for Vermont vineyards, with a few exceptions. We are seeing a bit of grape tumid gall in the UVM vineyard this year. This is an infrequent pest that causes visually striking but relatively insignificant damage to the vines, and management practices are not recommended against them. Grape berry moth is the next insect to note in vineyards, although it likely won’t be active for another couple of weeks. Traps are available from Gemplers or Great Lakes IPM to assess flight patterns in the vineyard. Generally, one application of a narrow-spectrum material effective against lepidopteran pests such as Intrepid, Delegate, or Altacor (see other options in the 2017 New York Pennsylvania Grape IPM Guidelines), applied 10-14 days after bloom followed by another application 10-14 days after that will generally manage that pest for the season. Better management may be performed by scouting clusters and applying one of those materials or a Bt product immediately upon the first signs of larval feeding. There is also a good grape berry moth degree day model in the NEWA system that may be of use in your vineyard.

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.

Registration for summer 2017 Cold Climate Viticulture course

Posted: May 31st, 2017 by fruit

This viticulture course is an opportunity for new and aspiring growers to receive a comprehensive knowledge base for establishing or maintaining a vineyard for anyone who is seriously considering winegrape production in Vermont or surrounding regions. The course is guaranteed to run based on present enrollment, but won’t be offered again until 2019.

Tuesdays and Thursdays, 9:00 am – 3:45 PM

June 20 – July 13, 2017

University of Vermont Horticulture Research & Education Center
South Burlington, VT

Information and registration

Students will learn principles and practices of commercial cold-climate grape production, including: site selection and preparation; varietal selection; vine training; nutrient, water and pest management; harvest; and introductory winemaking considerations. Special emphasis will be placed on environmental and economic sustainability of the vineyard operation. The class will apply knowledge of integrated horticultural and pest management practices in a real vineyard setting. The class format will consist of a combination of classroom lectures, hands-on fieldwork, and visits to local commercial vineyards. Students are responsible for their own transportation to the UVM Horticulture Research and Education Center.

For more information contact Terence.Bradshaw

Orchard management at fruit set

Posted: May 31st, 2017 by fruit

By Terence Bradshaw

By now virtually all orchards, including those in cooler regions, are at petal fall with only straggling bloom around on later cultivars. The cool weather has shut down concerns for continued blossom infections of fire blight. If infection did occur in your orchard during the May 18-20 warm spell (wouldn’t we love one of those again?), you should start seeing symptoms in your orchard around the middle of next week.

Figure 1. Blossom blight symptoms, 2016

Figure 2. Shoot blight symptoms, 2016

Orchards should have received a full-orchard petal fall insecticide by now or next spray. While things have been relatively quiet on the insect from this spring, a number of pests, including plum curculio (PC), European apple sawfly (EAS), and (maybe) codling moth (CM) are ready to pounce now. We have found fresh EAS and PC damaged un unsprayed or organically-managed trees at the UVM farm. If you are finding fresh damage on fruitlets in your orchard, consider application of a material that will cover both of those pests, and maybe CM too. This usually means a neonicotinoid like Assail or Actara; indoxacarb (Avaunt); or a pyrethroid, although the latter will be especially hard on predators and other beneficial insects. for organic growers, a pyrethrum application will help knock down PC that are already in the orchard but will have no residual efficacy- kaolin clay (Surround) sprays should be maintained until PC oviposition activity is complete. If you have already made you full-orchard application, then any subsequent sprays should be targeted at borders (PC, EAS) or at specific pests based on monitoring.

Figure 3. This PC damage is probably about a week old, notice the corking over and lack of sap exudate.

Codling moth are now flying in most Vermont orchards. Unless pheromone traps are checked daily, it is difficult to catch their exact first flight date, but based on captures in area orchards, I am using the following dates for sites around the state:

Brookfield: 5/23

Cornwall: 5/18

E Montpelier: n/a

Essex: 5/23

S Burlington: 5/17

S Hero: n/a

Shelburne: 5/18

Shoreham: 5/18

I would love a good catch date for some sites in southern Vermont if someone is trapping and could send them to me.

Those dates are important, because they represent the biofix that you would enter into NEWA for tracking degree day development to time CM-specific treatments. For most spray materials, timing should be targeted at about 250 degree days (base 43°F) from first catch. There is some room on either end of this, and that can account for differences between actual first flight and first catch in a trap, as well as to line up with good application weather on the other end. Based on the above assumed catch dates, most sites in the Champlain Valley have accumulated about 125 dd, and with the cool weather, we are accumulating 7-15 per day. Therefore, a targeted CM application should wait until next week anyway, we’ll follow up on that later. Specifically targeting CM sprays is a great IPM tactic for reducing impacts to non-target species, because selective materials that affect primarily lepidopteran pests (e.g., Altacor, Delegate, Intrepid) may be used at that time. However, Bt (Dipel, etc.) is relatively ineffective against CM when used as a targeted spray, its use against other lepidopteran pests is recommended but only provides supplemental management of this pest. Other ‘lep’ pests that are active include redbanded leafroller (larvae active) and obliquebanded leafroller (OBLR) (adults now flying). Your petal fall spray should have managed these for now, but if inspections of clusters are turning up larvae, a Bt spray may be warranted. For any material that has bee toxicity (e.g. most all except Bt, kaolin, or the lepidopteran-specific materials like Intrepid or Altacor), be sure to mow flowering plants in the groundcover prior to application.

For disease management, I recommend keeping at least one more fungicide on until you can scout for potential lesions from this last week’s rains. Despite NEWA’s proclamation that all overwintering apple scab inoculum was expended a week or more ago, I don’t trust it and feel it is too conservative in predicting the end of primary scab season. Scouting for detection of apple scab lesions (or lack thereof) to determine the end of scab management season should take place a couple of weeks from now to allow any infections to show.

While we’re in that weird period between the end of ascospore release and waiting for evidence of primary scab infection to show, we can still manage a couple of other diseases in the orchard. I am expecting cedar apple rust (CAR) to be particularly problematic this year, and powdery mildew (PM) infections can still occur on susceptible cultivars. We are nearing the end of the season for mancozeb fungicides- an application tomorrow gives an earliest harvestable date of August 18 to allow for residues to degrade- but those materials have excellent efficacy against CAR and none against PM (worst on Paulared and Cortland, among common cultivars grown in VT). Captan, the ‘standard’ fungicide used against scab, fruit rots, and cosmetic summer diseases, also has no effect on either CAR or PM. The SDHI (Fontelis, Luna, etc.), strobilurin (Sovran, Flint), and DMI (Rally, Procure, etc.) are all effective against those secondary diseases, even when the local apple scab population is resistant to them. This would be a good window to consider their use. For organic growers, I am not recommending much beyond sulfur, maybe lime sulfur if you need to provide some thinning. However, if fruit finish is not a concern, some work I did in the past two seasons indicates that low-dose copper (I used Cueva, but Badge or another material labeled for summer use should work) had some efficacy against CAR (we had no PM in the trial) but did cause some fruit russeting.

Figure 4. Cedar apple rust gall on cedar sent to me by my cousin in North Hero. These ‘telial horns’ are spreading spores that will infect apple now.

Thinning- it’s still tricky this year with this cool, wet weather. Remember that thinner activity is based on promoting a short-term carbohydrate deficiency in the tree, when too many developing fruitlets are calling for the limited sugars the tree is producing. Cloudy weather reduces net photosynthesis (increasing thinning); cool weather reduces respiration (reducing thinning). Cool weather also prevents hormonal 6-BA (Maxcel, Exilis) thinners from working best. For orchards that received a thinning spray last week, you should see activity from that now- fruits that will abscise have already stopped growing. For orchards that have not thinned yet, do it asap.

General recommendations are difficult to make; where fruit remained clustered up and a previous thinners was applied, OI would consider a low rate of NAA with or without carbaryl; where no thinners have been applied yet, carbaryl + a moderate (4 oz Fruitone N / 100 gallons tree row volume) should be used. For hard to thin cultivars with heavy set (Fuji, Liberty, Gala, Macoun), a higher rate of NAA or carbaryl + 6-B,A (the latter especially on Fuji and Empire) is called for. Fruit set and thinning activity should be checked every day or two at this point, where growers are using precision thinning methods and measuring fruit to gauge thinning activity, measurements every three days should suffice.

As I said last week, good luck- unfortunately this challenging spring hasn’t gotten any easier yet, but I think good weather (and the insects it brings) is just around the corner.

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