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Volume 21, Number 4. April 23, 2013.


Current degree day accumulations

Current bud stages

Upcoming pest events

Upcoming meetings

The way I see it

2013 New England Tree Fruit Management Guide available



New Fungicides: Balancing Resistance Management and Disease Management


Strategies to Increase Fruit Set of Apples in Situations Where Frost Damage Has Occurred

Useful links

Current degree day accumulations

Location: UMass Cold Spring Orchard, Belchertown, MA

22-April, 2013
Base 43
Base 50

Current bud stages

Location: UMass Cold Spring Orchard, 22-April, 2013

Honeycrisp apple early half-inch green
McIntosh apple half-inch green
Rainier cherry still swollen bud
PF-14 Jersey peach very swollen bud+
Gold Bosc pear early bud burst

See pictures of current bud stages here: http://flic.kr/s/aHsjEPF5Ef

Upcoming pest events

Coming events
Degree days
(Base 43)
Green fruitworm flight peak
Redbanded leafroller 1st catch
Spotted tentiform leafminer 1st catch
Green apple aphid present
Rosy apple aphid nymphs present
Obliquebanded leafroller larvae active
McIntosh tight cluster

Upcoming meetings

May 8 (Wednesday): University of New Hampshire/UMass Tree Fruit Growers' Meeting, Brookdale Fruit Farms,41 broad Street, Hollis, NH.

May 14 (Tuesday): UMass Fruit Team Twilight Meeting, UMass Cold Spring Orchard, 391 Sabin St., Belchertown, MA. 5:30 PM. 1 pesticide re-certification credit will be available. $20/25 meeting charge.

May 16 (Thursday): University of Rhode Island/UMass Fruit Twilight Meeting, Location TBA.

The way I see it

Could the weather be any different than last year? At this point in 2012 we were well into McIntosh bloom. Most would agree this is a good thing, however, we have a long way to go. In fact, I had a report of isolated (but significant) frost/freeze injury to apple buds already. Thus, the Strategies to Increase Fruit Set of Apples in Situations Where Frost Damage Has Occurred by Duane Greene is very timely.

Because of the cool weather it is otherwise pretty quiet. We have yet to have a scab infection period at Belchertown. New Fungicides: Balancing Resistance Management and Disease Management by Dan Cooley is still very relevant. Insect activity is next to nothing. As you know, it will heat up real fast, real soon (well, most likely) so get all those other jobs like tree planting out of the way. JC

2013 New England Tree Fruit Management Guide available

The 2013 New England Tree Fruit Management Guide is available here: http://www.umassextensionbookstore.com/store.php?crn=238


Pheromone traps for Oriental Fruit Moth should be placed to determine the first catch of overwintering moths:




New Fungicides: Balancing Resistance Management and Disease Management
Daniel Cooley

This year, we have new fungicide products on the market, based around a new chemistry, the succinate dehydrogenase inhibitors, or SDHI’s. There are several new fungicide products registered for apples based around these materials, including Fontelis, Luna Sensation, Luna Tranquility and Merivon.

Three of these new products are pre-mixed combinations of an SDHI with another type of fungicide. Only Fontelis is not pre-mixed. The companies that produce the pre-mixes market them as better for resistance management and covering a broader spectrum of diseases than the SDHI alone. Pre-mixing also can, in my opinion, waste fungicides. They may even lead to problems, as both the SDHIs and the fungicides they are mixed with are site-specific. That means there’s a relatively high risk that resistance to either fungicide can develop. Theory says that putting two fungicides together, even two site-specific fungicides, decreases that risk. I agree with the theory in principle, but I’m not aware of much actual data that backs that idea up. I think it would be more prudent to mix a site-specific fungicide with a multi-site protectant, specifically captan or one of the EBDCs (mancozeb or Polyram). There has never been a case of apple scab resistance to multi-site fungicides to my knowledge.

Two of the pre-mixes, Luna Sensation and Merivon, are combined with a strobilurin. Strobilurin-resistant population of the apple scab pathogen have been identified in Michigan and NY, and scab from a few orchards in Massachusetts and other parts of New England have been identified as shifting towards resistance. Luna Tranquility is mixed with an anilinopyrimidine, the active ingredient in Scala. This is a reasonably good fungicide against scab prior to pink, but as temperatures warm, and particularly once fruit has formed, it is not as effective as most other scab fungicides. With these issues in mind, the wise thing to do, in my opinion, is mix a multi-site fungicide, captan or mancozeb, with these fungicides if you’re going to use them. It reduces the risk of failure and resistance development.

In general, the strobilurins and the AP in the pre-mix products are marginally useful. So, if one wants to use the new chemistry, why not simply buy Fontelis and mix it with a multi-site proctectant?

In addition to resistance management, there are other disease issues that need to be managed beginning around bloom, most importantly rusts and powdery mildew. Powdery mildew in particular has been more of a problem in MA in recent years.

Because the options for apple fungicides up to first cover have become more complicated this year, I’ve suggested five different schedules that try to balance the many factors important to effective disease management in apples including resistance.

Scab sanitation using urea and/or leaf chopping, and a green tip copper application, are recommended in all schedules. They will reduce the risk of resistance development, as well as reduce overall risk of scab.

Half-inch green and tight cluster sprays should be captan and/or mancozeb, except where risk of scab is high, or a systemic is required to help with extended wetting. In those cases, either an AP (Scala or Vanguard) or Syllit (dodine) should be used with captan or mancozeb. Where oil is being used, growers should not use captan within a week of an oil application; use mancozeb instead.

The DMI, QoI and SDHI fungicides are reserved for use from pink through first cover. This targets the time when disease pressure is highest. It is not be necessary to use the systemic fungicides in low-inoculum blocks, or on cultivars that are more resistant to scab, as the captan/mancozeb protectant program will work fine. However, where scab pressure is high, or if extended wetting periods are predicted, then adding a systemic to captan or mancozeb is recommended. As an extra safeguard against resistance, these programs do not use fungicides from the same FRAC group in two consecutive sprays.

If using a systemic from pink through petal fall is recommended, when considering just scab, the choice of which ones to use will largely depend on cost. All of these fungicides are very effective against scab, unless resistance is developing.

The DMI’s are also excellent against rust and mildew. SDHI’s are also effective against both rust and mildew, though less effective than the DMI’s against rust. The QoI’s are effective against rust and mildew, but less effective than the DMI’s against both. Mancozeb is about as effective as the QoIs against rust, but has no effect on mildew. If mildew is a concern, two other options to consider are sulfur or Topsin-M, but avoid using sulfur with oil.

There are certainly other combinations of fungicides that could be used to effectively manage apple diseases through first cover. The five programs suggested here focus on resistance management, as it is critical to IPM and disease management in general that the efficacy of the broadest number of fungicides be maintained for as long as possible.


Strategies to Increase Fruit Set of Apples in Situations Where Frost Damage Has Occurred

Duane W. Greene, University of Massachusetts

            The abnormally early warm weather last year resulted in very early bloom.  Some orchards escaped unscathed with little or no frost damage but others were far less fortunate.  The weather patterns so far this year are much closer to what we consider normal resulting in a later bud break and presumably a later bloom period when frost is far less likely to occur.  Since weather has been very erratic, there still exists the potential for frost damage especially if weather patterns change.  Since the weather last year is still fresh in our minds, it seems like a good time to review the options you may have available this year if a frost event does occur during bloom.  Orchardists have three options to cope with frost damage; two of which are available for the first time this year.  

Promalin® Application

            Promalin® has a special registration this year to allow it to be used on apples to increase fruit set in the event of a frost.  Many of you have read articles in the popular press by Dr. Steve McArtney about the success he had at increasing fruit set following a rather severe frost in North Carolina in 2012.  He applied Promalin® at rates of either 1 pt or 2 pts/ acre at 11:00 am on the morning of a frost event where the temperature dropped down to 25° F.  He made a second application at the same time of day the following morning after a low temperature of 28° F was recorded.  The yield in this orchard was substantially increased as a result of the Promalin® treatments but yield was not restored to the projected level if no frost had occurred.  Fruit were seedless but otherwise quite normal.  Very similar experiments were also done in New York by Terence Robinson and in Massachusetts.  There was a small but significant increase in fruit set in New York but no treatment effects were observed in Massachusetts.  The conclusion from these series of experiments is that Promalin® can increase fruit set in frost damaged trees but complete reversal is unlikely, and in some instances it just is not effective.  However, it may be the best option available and certainly worthwhile considering the low input.  In the experiment in North Carolina the crop value was increased by nearly $4,000, and this increase was totally attributed to increased fruit set. 

            Specific recommendations for the use of Promalin®

  1. Apply 16 to 32 oz/acre.
  2. Apply within 24 hours of a frost event.
  3. Apply prior to or after a frost.  In New York the label allows application only after a frost event. 
  4. Apply between early bloom and full bloom in 75 to 150 gal/acre.
  5. Do not apply with a surfactant.
  6. Apply only after the tissue has completely thawed out.

ReTain® Application

            The ReTain® label has been revised to allow the use of ReTain® to increase fruit set.  This is a new use for ReTain® that was just added this past year.  Unfortunately, ReTain® will not be labeled for this use in Massachusetts until next year.  I have used ReTain® or the active ingredient AVG over the past few years.  It generally does increase set on nonfrosted flowers.  Frequently the fruit are smaller on the treated trees compared with the untreated trees.  Therefore, I suggest that you proceed carefully with the use of this treatment until you become familiar with the response under a number of different environmental conditions and in different years. 

Specific Recommendations for the Use of ReTain® to Increase Fruit Set

  1. Application may be made between pink and full bloom.
  2. Apply at a rate of one pouch of ReTain® per acre.
  3. Apply in a water volume of 100 gal/acre.
  4. Do not apply with a surfactant.
  5. Only one application is allowed in the spring but a pre-harvest drop application can be made on these trees prior to harvest.  

Apogee® to Increase Fruit Set

            Apogee® is a growth retardant that has been available for a number of years and the majority of fruit growers have used it successfully to retard vegetative growth.  We soon learned that when this was applied at the recommended timing (1 to 2 inches of terminal growth at or soon after petal fall) it could make thinning more difficult.  We also learned that Apogee® did not initially increase fruit set per se but it did retard June drop, thus negating some of the fruit abscission responses hoped for following a chemical thinner application.  Consequently, a basic recommendation for Apogee® is to use initial rates of 2 to 4 oz/100 gal to avoid/minimize the reduction in thinning.  However, if the desire is to increase fruit set, application of Apogee® at the normal timing for growth retardation is appropriate, but the use higher rates may be appropriate.  These higher rates of Apogee® use also may aid in fire blight control.  Although the evidence is not overwhelming, there is a good indication that higher rates of Apogee® will control fire blight better than lower rates.  Therefore, application of Apogee® to increase fruit set may also provide increased protection from fire blight.  

            I have not applied Apogee® specifically to frost damaged flowers so extrapolation of results from application of Apogee® on undamaged flowers to frost damaged flowers may be a little dangerous.  If a frost does occur at bloom I would probably suggest applying Apogee® as soon as there is sufficient leaf area to absorb the compound, and that may be by early petal fall.       

            We hope that a situation will not arise this year where you must consider one of the above treatments to reduce frost damage.  The good news is that you do have options available if specific conditions warrant it.    

Useful links

UMass Fruit Advisor: http://umassfruit.com

Scaffolds Fruit Journal: http://www.nysaes.cornell.edu/ent/scafolds/

Network for Environment and Weather Applications (NEWA): http://newa.cornell.edu

Follow me on Twitter (http://twitter.com/jmcextman) and Facebook (http://www.facebook.com/jmcextman)

UMass Vegetable & Fruit IPM Network (on Facebook, http://www.facebook.com/umassipmteam)

The next Healthy Fruit will be published on Tuesday, April 30 or thereabouts, 2013. As always feel free to get in touch with any member of the UMass Fruit Team (http://extension.umass.edu/fruitadvisor/team-members) if you have questions or comments.