Tree Fruit Newsletter — June 26, 2024

In this newsletter:

  • Observations
  • Announcements

Orchard Observations

Peaches are at the pit hardening phase. Hopefully, fruit thinning is nearly complete by now. This supposedly helps with brown rot control later on. Breaking up fruit that are clustered or in close contact will also help with spray coverage, disease and pest control.

My initial thoughts on apple thinning this year were that it would be difficult to knock off enough fruit this year. This has turned out to not be the case. In some cases, crop load is great, and in others, it’s less than expected. I am seeing some clusters with no fruit and most others with 1 or 2 fruits. Thinning appears to have worked well, and none of the orchards have excessive fruit set. Set looks heaviest on Honeycrisp and relatively light on Macs. Fruit continue to drop, and this is probably June drop occurring right now.

The lower than expected fruit set could be due to the one day during bloom when temperatures were in the upper 80’s. High heat during pollination is known to reduce fruit set in vegetables. The upper limit for apples has never been studied. In tomatoes, temperatures above 85 °F will kill pollen and interfere with pollination and fertilization.

Powdery mildew has been a problem in some orchards. The cause appears to be a combination of mild winter temperatures, susceptible varieties and fungicides that have low efficacy for this disease. It generally does not hurt the fruit, but in severe cases, it will cause russeting.

Fireblight is also occurring for some growers. We had a lot of late blooming clusters this spring followed by consistent rainfall. The latest issue of Glen Koehler’s newsletter discusses what to do if you have fireblight. In addition, I am including the following from the IPM Updates for Eastern New York by Scott Cosseboom and Andres Antolinez Delgado, HVRL; Mike Basedow, CCE ENYCHP, Eastern New York.

  • Keep on the lookout for strikes, particularly in susceptible varieties that had lingering rat tail blooms. If you find strikes, Kerik recommends pruning them out as soon as you have a good cool, dry day to do so. Don’t prune in the dew, or when temps are above 75-80 °F. Prune shoots at least 12 inches back from visible infections into second or third year
    wood or older if possible. Remove the whole tree if 12” takes you into the central leader.
  • Preventative applications of copper can be used post-bloom and during the summer to protect against the spread of shoot blight infections. Copper must be applied before infection occurs as it will only reduce bacteria on the surface of tissues. It will have no effect on existing shoot blight infections and may cause fruit russet in young developing fruit. Apply with adequate drying time and use hydrated lime to reduce the potential of phytotoxicity from copper. Remember terminal shoots can outgrow protective residues of copper. A low-rate fixed copper program consists of applications on a 7–10-day schedule during high-risk weather until terminal bud set.
  • If you end up finding lots of strikes, you can also consider the rescue program of applying 6-12 oz prohexadione calcium, waiting five days, and then pruning out blighted shoots on a two-week schedule through terminal bud set.
  • We do not like to use strep for shoot blight management, however it should be applied following hailstorms or other strong storms where shoot damage occurs.
  • We continue to see Powdery Mildew strikes throughout the orchards on susceptible varieties like Honeycrisp and Cortland. We recommend keeping a good mildew material (DMI’s and QoI’s) in the mix through about third cover. Note that captan and mancozeb are not effective against this disease.


Summer Tour at UMaine’s Highmoor Farm

July 24 from 1:00 to 5:00 pm, followed by a vegetable and small fruit twilight meeting at 6 pm.

The Maine Ag. Experiment Station, UMaine Extension and the Maine State Pomological Society will be hosting the annual Summer Tour at the Highmoor Farm in Monmouth. To RSVP, call Renae Moran at (207) 713-7083 (or email at by July 20. Cost to attend the Summer Tour is $20 but is free for Pomological Society members.

Two credits offered for pesticide applicator recertification.


1:00 Welcome and Registration

1:15 Hannah Carter, Dean of Extension, UMaine

1:30 UMaine Ag. Exp. Station Director, George Criner

1:45 Guest speaker, Maria Gannett, Univ. of Mass, Managing Weeds in Perennial Crops: Perennial weeds often become difficult to manage in perennial cropping systems. Dr. Gannett will present results from trials at Cornell and UMass, attempting to manage bindweed in apple and blueberry orchards and discuss optimal times for control.

2:30 Pomological Society Announcements from Standing Committees

• Labor
• Legislative update
• Marketing
•, the website

3:15 Break

3:30 Orchard Tour with Renae Moran, Maria Gannett and Greg Koller.

• New scab resistant apple varieties, tests for predicting bitter pit in Honeycrisp and cold hardy peach varieties.
• We will look for perennial weeds at Highmoor Farm and apply what we discussed earlier to weeds we find in the field. There will be an emphasis on weed identification.
• Drone spraying demo, Active Intelligence, Rockland, ME
• Karla Boyd, Board of Pesticides Control

5:00 Dinner

Sandwiches and Highmoor farm strawberry shortcake

6:00 Twilight meeting with David Handley and Mark Hutton, Vegetable and berry variety trials.

From the North:
I95 Exit 109b, go West on Rte. 202 (toward Winthrop) for 16 miles. Highmoor Farm is on the left.

From the South:
I95 exit 86, left on Rte. 9 and continue 0.7 miles, then take a right onto Pleasant Hill Road for 0.8 miles. Continue through the stoplight where the road becomes Rte. 132 (Wales Rd. and then Pond Rd.) for 4.6 miles. Take left onto Leeds Junction Road, travel 2.9 miles to Rte. 202. Take a right onto Rte. 202 and go 1.4 miles. Highmoor Farm will be on the right.


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