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Healthy Fruit 2009 Vol. 17:10

Jun 9, 2009

Current (through June 8) degree day (DD) accumulations

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

  • Base 43: 956
  • Base 50: 556
  • Plum curculio model: 316 (Base 50 from petal-fall, 05-11-09; 308 is the 'end')

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

  • codling moth first flight peak: 593–1017
  • obliquebanded leafroller 1st catch: 827–939
  • obliquebanded leafroller 1st flight peak: 843–1139
  • dogwood borer 1st catch: 759–1503

The way I see it

I guess the most prominent comment on the past week is June drop is starting to kick-in and we are seeing some more decent thinning of apples. Golden-type apples are still heavy, and it may still be worthwhile to try some 'rescue thinning' as described here. Cover sprays should include calcium to reduce the incidence of cork spot and bitter pit, and in another week or two it will be time to begin an Ethrel spray program to enhance return bloom next year. Early cherries are starting to ripen, but alas, the birds are already eating them. I am convinced that to grow cherries successfully (i.e., profitably), they need to be netted and rain-covered to prevent cracking. Otherwise, don't forget brown rot sprays on ripening cherries. It's not too soon at all to start hand-thinning peaches if you can find the time or have the help. In fact, the sooner the better. Good luck.

J. Clements

Entomological comings and goings

Plum curculio: We are approaching the end of the curculio season based on the degree-day model that predicts when spray coverage is no longer needed. Many orchards that have some spray coverage into this week should be all set.

Oblique-banded leafroller: Adult flight should be starting soon. Ideally, you should be monitoring adult flight with pheromone traps to set a BIOFIX date for when the newly hatched larvae are most susceptible to control with insecticides.

Dogwood borer: Adults should be flying now. They soon start to lay eggs on apple trunks and the exposed portion of rootstocks, particularly where burr-knots are present. Towards the middle-end of June is a good time to treat trunks of dwarf apple trees with a Lorsban spray. Most generally, one application of Lorsban (several formulations) can be applied post-bloom to apple tree trunks only. (Not the foliage or fruit.) For more information on dogwood borer control, see guest article below..

J. Clements

Timely and updated fact sheets available on the UMass Fruit Advisor website

F-129R--2009 Late Season "Rescue" Thinning with Ethephon

Summary recommendation for "rescue" thinning with ethephon:

  • Treat when temperatures are 70-80 F (day of treatment + 2 days).
  • Do not treat when below 70 F or above 80 F (day of treatment + 2 days)
  • Fruit 15-25 mm diameter (0.8-1 inch)
  • McIntosh and Macoun 200-300 ppm (0.7 - 1 pint Ethrel per 100 gallons dilute spray, with 0.5 lbs carbaryl a.i. and a surfactant)
  • See the fact sheet noted above for more precautions and details

F-131--2007 Enhancing Return Bloom on Apple with Plant Growth Regulators

Summary recommendation for enhancing return bloom with ethephon

  • Begin 4 to 6 weeks after full bloom and after 'June drop'
  • Use Ethrel at 0.5 pint per 100 gallons dilute spray -- can be combined with cover sprays
  • Make 2 to 3 weekly applications depending on variety (1-2 on early maturing cultivars)
  • Avoid applying at high temperatures and/or too early as ethephon can cause significant fruit thinning under the right conditions
  • See the fact sheet noted above for more precautions and details

J. Clements

Guest Article: Dwarf Apples and Dogwood Borer

by Win Cowgill, County Agricultural Agent, Rutgers Cooperative Extension

reprinted from Rutgers Cooperative Extension Plant & Pest Advisory, Fruit Edition, June 2, 2009

Apple trees on size controlling rootstocks should be periodically checked for infestation by the dogwood borer. We have caught moths in Northern NJ orchards since the end of May and the begin- ning of June and populations are on the increase. Apple growers in our NJ IPM scouting program have traps placed to monitor the adult moth. Infestations of this clearwing moth in apple are almost always located in burrknots or graft unions that are planted above ground level. Burrknots are aggregations of root initials that can develop on the above-ground portion of the rootstock. All commercial dwarfing and semi-dwarfing rootstocks have a tendency to develop burrknots. After infesting the burrknot the larvae continue to feed in other tissue and can severely weaken and even kill the tree.

It is important that we plant dwarf apples with the graft union at least four inches out of the ground to avoid self-rooting of the scion. The trade off, however, is the development of burrknots, which are susceptible to the dogwood borer. Mark rootstock is known for this. The adult dogwood borer moth seeks out these spots (burrknots) to lay eggs, particularly if they are surrounded by vegetation or protected by something, such as mouse guards or weeds. Moreover, mouse guards and

weeds shield the lower trunk from exposure to insecticide cover sprays. Sustained feeding by dogwood borer at the graft union may severely weaken the tree at this juncture, or girdle the trunk and cause a slow decline in tree health. Orchards in which mouse guards are used should be examined for signs of damage. The tight spiral plastic guards provide a perfect place for the borers to get established and are not recommended for this reason.


Lorsban (several formulations) is labeled for dogwood borer control on apple. Since Lorsban remains in the tissue you will also control the larvae from any egg laying that occurs in the months of June and July as well as any that has occurred to date. The best control is a dilute trunk application done with a handgun, and an insecticide with good residual activity to provide control of established infestations.

Lorsban 4E now has a supplemental label for apples and is the most effective material for control. Application should be made between late June and the end of July, bearing in mind the specific pre-harvest intervals. Where heavy infestations are present, then make the application in late June. The following directions and restrictions are from the label:

Mix with water and apply directly to trunk from a distance of no more than 4 ft using low volume handgun or shielded spray equipment. Rate is 1 and 1/2 quarts/100 gallons Do not allow spray to contact foliage or fruit.


● Treat only the lower 4 feet of the apple tree trunk.

● Do not make more than 1 application per year for borer control.

● Do not apply when wind speed is greater than 10 mph.

● Do not apply within 28 days of harvest (watch your PHI on early maturing cultivars)

White latex paint brushed/sprayed on the exposed portion of the rootstock will help prevent new infesta-tions of the borers, and also protect against southwest injury to the bark. We utilize a white-wash of about 50% white latex with low acrylics and 50% water to spray all dwarf rootstocks in the fall to prevent southwest injury.