Tree Fruit Newsletter — June 23, 2026
Reducing Biennial Bearing in Honeycrisp Apples
It is time for NAA (naphthaleneacetic acid) summer sprays to enhance repeat bloom in Honeycrisp and other varieties. NAA will no longer thin apples and can be applied at this time to stimulate flower bud formation for next year’s crop. Three applications at roughly two-week intervals will cause a modest increase return bloom. See product label (Pomaxa, Fruitone, Refine) for rates. Rate per acre can also be found in the New England Tree Fruit Management Guide’s section on Return Bloom Enhancement. These sprays are not recommended for summer apples because they can interfere with normal ripening.
NAA sprays at the same rate and timing may also reduce the risk of severe bitter pit in Honeycrisp apples, but this effect is based on only a few years of research.
Peach Diseases
New England Tree Fruit Management Guide has a Summer Spray Table for peaches.
Bacterial leaf spot causes small yellow spots in the foliage that eventually fall out and create a ‘shot hole’ appearance. Some defoliation will occur, but this has not been an issue because peach tree shoots have an overabundance of foliage. Varieties in our collection that are most susceptible are Desiree and Summer Serenade. Plums will also develop bacterial leaf spot.
Peach scab is not often seen in orchards that receive fungicides but can show up where fruit are set in tight clusters that prevents thorough fungicide coverage. Many fungicides are effective at control including Captan, sulfur and Pristine. Chlorothalanil products should not be used after the shuck-split stage which has already passed. Thinning fruit early to prevent clustered fruit can help prevent peach scab.
Brown rot will likely be more severe this year because of the frequent rains. Sulfur has only fair efficacy at control, and Captan has fair to good efficacy. Fungicide FRAC groups 3, 7 and 11 (Luna Sensation, Flint Extra, Inspire Super, Merivon, Pristine) have good to excellent brown rot control. Guidance from the Penn State Extension website indicates, “Apply fungicide sprays at 18 days, 9 days, and 1 day before peach harvest to limit rots pre- and postharvest. Captan used as a cover spray has been shown to decrease the available spore load leading to harvest. To reduce the risk of resistance, alternate fungicides by FRAC Group.” These specific timings may be difficult to time because most of our peach blocks have varieties ripening at different times. If an insecticide will be tank-mixed with fungicide, pay close attention to the preharvest interval (PHI). Many insecticides have PHI’s of 7 to 14 days.
As in years past, aphids have been prevalent in the peach block at Highmoor Farm. Symptoms are leaf curling and distortion. Infestations appear more severe this year.
Lesser and Greater Peachtree Borer can be a problem in organic or unsprayed orchards. More information on monitoring for these pests can be found in the New England Tree Fruit Management Guide’s section on Lesser Peachtree Borer (LPTB).
Agritourism Webinar Series
The Maine Department of Agriculture, Conservation and Forestry is hosting several agritourism webinars for Maine farmers (but others are welcome)! To register, visit the Maine Agritourism Webinar Registration page.
Webinar topics and dates are below.
If people cannot attend live, we encourage them to share their email address so we can send them the recordings and gather their questions.
- Marketing & Promotion – July 15, 4 pm
- Hospitality & Customer Service – July 28, 4 pm
- Risk & Regulation – August 12, 4 pm
- Financial Access – August 25, 4 pm
- Collaboration & Partnerships – September 16, 4 pm
- Discussion & Q&A – October 6, 4 pm
Maine Pomological Society Summer Tour at Highmoor Farm in Monmouth
July 29, 2026 (rain date July 30).
1:00 p.m. to 5:00 p.m., followed by a vegetable and small fruit twilight meeting at 6:00 p.m.
For more information and to register, visit the Summer Tour at Highmoor Farm for 2026 webpage.
Renae Moran
University of Maine Cooperative Extension: Tree Fruits
PO Box 179
Monmouth, ME 04259
(207) 933-2100
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