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Healthy Fruit 2010 Vol. 18:7

May 18, 2010

Current (through May 17) degree day (DD) Accumulations

Location: UMass Cold Spring Orchard (CSO), Belchertown, MA

  • Base 43: 615
  • Base 50: 336

Significant upcoming orchard events based on degree days (Base 43):

  • Lesser appleworm 1st flight peak: 355-773
  • Codling moth 1st flight peak: 574-1008
  • Plum curculio oviposition scars present: 485-589+
  • Pear psylla hardshells present: 493-643
  • Redbanded leafroller 1st flight subsides: 574-882
  • Obliquebanded leafroller pupae present: 601-821

Orchard Radar insect synopsis (for Belchertown)

  • Codling moth development as of May 18: 1st generation adult emergence at 19% and 1st generation egg hatch at 0%. In most orchards, insecticide targetted against plum curculio and apple maggot prevent codling moth damage.
  • 1st generation OFM flight starts: April 15, Thursday. 1st generation - 55% egg hatch and first treatment date, if needed: May 21, Friday
  • Increased risk of Plum Curculio (PC) damage as McIntosh and similar cultivars increase fruit size:
    May 5, Wednesday. Earliest safe date for last PC insecticide spray: May 21, Friday
  • Spotted Tentiform Leafminer (STLM): 1st generation sapfeeding mines start showing: May 7, Friday. Optimum sample date is around Saturday, May 8, when a larger portion of the mines are visible.
  • 1st generation White Apple Leafhopper (WAL) found on apple foliage: May 1, Saturday

The way I see it

Notable occurrences in the last week:

  • we largely escaped frost/freeze damage, however there was some; unprotected strawberries, apples farther north and farther south, some peaches in central MA and SE NH; expect some variability in crop depending on how vulnerable you were to cold temperatures. It was a classic inversion frost/freeze at least in our area so lower spots were colder
  • rabbit damage to just-planted peaches planted into the rough, i.e. tall grass/field-like conditions; bad idea, don't do this
  • 200+/- Honeycrisp trees planted at UMass Orchard as part of a rootstock research project; these trees are gorgeous-feathered as a result of being treated in the nursery with a new growth regulator called Tiberon; expect to see improved tree quality coming out of the nurseries once they all start using Tiberon
  • herbicide injury to just-planted apple trees -- be careful! Don't underestimate the power of pre-emergent herbicides to throw young trees a hardball (hopefully they will recover). If the label says don't use on trees just planted in the orchard, they mean it!
  • black cherry aphid moving into sweet cherries despite being treated with Provado earlier! Arghhh!
  • not much sign of plum curculio although the orchards have largely been covered up with Imidan. According to the degree-day model which predicts when PC activity will be over, we are about half-way there (156 out of 308 [Base 50] from McIntosh petal fall [May2])
  • apple fruit size has shot up to about 15 mm. Later this week will be the LAST window for a traditional thinning application. I know it is a bit hard to figure out if your petal fall or any other previous applications are actually working already, but if your gut tells you you need to do some more thininng, see Duane Greene's thoughts below.

We hope you see you at one of the Tree Fruit Twilight Meetings this week. JC

2010 New England Tree Fruit Management Guide available

As a reminder, the 2010 New England Tree Fruit Management Guide is still available for purchase

Massachusetts airports on NEWA

Through a cooperative effort with the New York State IPM Program, and the Northeast Regional Climate Center, Massachusetts airport locations have been added to the NEWA (Network for Environmental and Weather Applications) website ( (Note that the map is draggable to the left wherein the Massachusetts airport locations are revealed on the map. You can also choose a location from the drop-down list.) Pests forecasts, typically based on temperature, precipitation, and relative humidity are available for various crops (fruit and vegetable). For apples, available forecasts include: codling moth, Oriental fruit moth, obliquebanded leafroller, plum curculio, spotted tentiform leafminer, apple maggot, apple scab, and fire blight.

For more information on how to use NEWA, see 'Pest Forecasts in Real Time -- NEWA' in the April 19, 2010 issue of Scaffolds. I urge you to look at the NEWA website and give us your feedback. This is the future of IPM information delivery! JC

Duane Greene thinning thoughts for week of May 18

The period of time when apples can be thinned using traditional postbloom thinners will soon end. Fruit size in some varieties is approaching or has reached 15 mm. This week may be your last opportunity without resorting to more drastic thinning measures. Fruit have not been exposed to very stressful weather so far this postbloom season, thus there remains a very good possibility that adequate and appropriate thinning can be achieved now. Weather for the next two days will be unsettled, damp, cool, and thus it is unsuitable for thinner application. Starting on Thursday there appears to be coming a favorable period for thinners to work. I suggest that thinners should be applied as early in this period as the weather permits.

All traditional postbloom thinners (except AmidThin) can be used at this time. However, with the fruit size as large as it is I favor the use of MaxCel, carbaryl or MaxCel plus carbaryl. MaxCel appears to work more effectively when applications are made at the larger fruit sizes (as opposed to the 7-10 mm size). MaxCel is a relatively mild thinner when applied by itself. When it is applied with carbaryl it is much stronger. Research at the UMass Cold Spring Orchard has indicated that the carbaryl does not have to be tank mixed with MaxCel. A synergistic effect with carbaryl can be achieved if carbaryl and MaxCel applications are separated by as much as 7 days. MaxCel is an indiscriminate thinner whereas carbaryl is reported to aid in breaking up clusters. If trees contain significant percent of clustered spurs, the addition of carbaryl in your thinning spray may be helpful. Application of MaxCel on trees that have previously been sprayed with NAA is not a problem, with two notable exceptions. Application of NAA and MaxCel on Delicious and Fuji during the same thinning season may result in pygmy fruit or a reduction in fruit size.

NAA can be an effective thinner when applied at the 14 to 16 mm fruit size stage but its use comes with some potential peril. If very warm temperatures follow application fruit size may be reduced. Even if very warm temperatures do not follow application, there is the possibility that increased fruit size normally seen when crop load is reduced will not occur even if thinning is achieved. Use of NAA on varieties that tend to be naturally small may result in small fruit size at harvest.DG

Editor's note: on Orchard Radar - Belchertown, MA, there is a very useful 'Thinning weather synopsis chart' that gives " Thinning weather estimates that are based on the influence of night time temperatures and daytime cloud cover on sensitivity of young apples to postbloom thinning agents." It is updated daily. Below is a sample output for Tuesday, May 18, but you should check out the full page on Orchard Radar. JC


Pest watch

  • although primary apple scab season is largely over based on the ascospore maturity model, you should continue fungicide coverage until you are sure you have no developing scab on foliage from previous infection periods; other apple diseases are ongoing too, such as powdery mildew, rust diseases, and black rot. See the Guest Article 'Apple Diseases Targeted by Early Cover Sprays.'
  • expect plum curculio to become very active (again?) during the next period of warmer, more humid and wet weather (this weekend?) so be prepared with an insecticide spray
  • bacterial spot of peaches and nectarines is still active, so if you are growing susceptible varieties, antibiotic (oxytetracycline) sprays should be ongoing
  • cherry leaf spot is active too: cover sprays of Pristine, Gem, or Adament are excellent for control of cherry leaf spot
  • it's probably not too early to consider trunk application of Lorsban to control dogwood borer in apples. (I have been finding more larvae in burr-knots of my dwarf trees than I would like at the UMass Orchard. I will get my herbicides down first.) Honeycrisp and Macoun seem especially susceptible. Lorsban 75WG at 2 lb/100 gallons in a directed, good and wetted, trunk spray should do it.

Useful links

UMass Extension Fruit Program

UMass Cold Spring Orchard

Scaffolds Fruit Journal

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