Tree Fruit Newsletter — May 24, 2025

May 27, 2025 Tree Fruit Newsletter

In this newsletter:

  • Thinning Strategies
  • Peach Leaf Curl
  • Announcements

Thinning Strategies for 2025

The prolonged cool weather during full bloom has me concerned about pollination in Honeycrisp and other varieties that bloomed after McIntosh at Highmoor Farm. Temperatures in the forecast for the Augusta area look favorable for some pollination Monday assuming that it is not too late. Honeycrisp and Golden Delicious still had a few blossoms unopened as of Friday afternoon. McIntosh was at petal fall Friday. Pears, peaches and sour cherries are at petal fall. Sweet cherries are showing signs of fruit set. Balaton cherries do not look healthy and are probably stressed from the severity of last year’s leaf spot disease.

Information for Cherry Leaf Spot can be found in the New England Tree Fruit Management Guide.

Warm temperatures improve the effectiveness of chemical thinners, so weather should be ideal for thinning this week. Thinning strategies will likely be based on your confidence in how well the orchards have been pollinated.

For orchards that had good pollination prior to this cold spell, this week is a good opportunity to apply thinners. After June 1, the forecast is uncertain, and could be too cold for good thinning, so I am recommending not waiting to see that fruit set is certain where you know your trees have been adequately pollinated. Low rates of NAA or 6-BA combined with carbaryl or just carbaryl by itself may be sufficient this year for most varieties. As the week progresses, leaves will develop a thicker cuticle and may need higher rates of NAA or 6-BA. Accede® can be applied to fruits that have reached the 15 mm diameter stage.

  • NAA products: Fruitone, PoMaxa, Refine
  • 6-BA products: Maxcel, Rite-Way, Exelis
  • ABA: Protone, a new thinner that is OMRI listed

For orchards that have uncertain pollination, I recommend waiting to see how the rest of bloom goes. McIntosh at Highmoor Farm may have had king bloom pollination at the start of the cold spell, but fruit set is uncertain. Honeycrisp still has a few blossoms not yet open and may still have a chance. Waiting to see signs of early fruit set could put us in a situation where weather is too cold for thinners, so this strategy comes with a risk of having to apply thinners in cool weather. It may be a good year to try Accede which is reported to thin fruit at the 15 mm diameter stage.

For information on thinning different varieties, see the Specific Apple Variety Thinning Recommendations section of the New England Tree Fruit Guide.

To view the Accede® product label, visit the Accede® Plant Growth Regulator Liquid Concentrate, Valent webpage.

 

Peach Leaf Curl

Peach leaf curl disease is starting to show up in orchards that were not sprayed last year. Look for large, orange spots on foliage and puckering of the leaves. Leaf buds were infected at budbreak, and new infections will not occur till next spring. Infections may look more severe in the coming days, but fruit infection is uncommon. There are no signs of peach leaf curl in orchards that received fungicides last year.

 

Announcements

Summer Tour

According to my notes, the date of the Maine Pomological Society Summer Tour is July 9. Details about the location and program will be finalized in June.

 

Cornell Cooperative Extension Newsletter (CCE ENYCHP)

For those of you who subscribe to Cornell University newsletter for fruit growers, here is the announcement for how to sign-up or renew your subscription. If it has not been coming to your email inbox, check your spam folder.

Cornell Cooperative Extension’s Eastern NY Commercial Horticulture Program (ENYCHP) is happy to be the agricultural educational resource for your fruit and vegetable businesses. We appreciate the support of 17 Cornell Cooperative Extension Associations that provide the bulk of the financial resources required to allow resident growers access to affordable, highly-specialized agricultural production and business management information. In addition, this support allows the ENYCHP team of 10 specialists to conduct on-farm research of problems pertinent to you.

Below is the link to the 2025 CCE ENYCHP Subscription form and donation request. For questions or comments, please contact Chuck Bornt at 518-859-6213 or cdb13@cornell.edu.

 

Renae Moran

University of Maine Cooperative Extension: Tree Fruits

PO Box 179

Monmouth, ME 04259

(207) 933-2100

rmoran@maine.edu

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