Tree Fruit Maturity Report — September 9, 2025

Maturity Report

Peaches

Peach varieties we picked this week include: PF23, Blushingstar, Veteran, Contender, Harrow Beauty and Glowingstar.

We have only a few varieties left to pick: Messina, Autumnstar and Selena.

Plums

European plums are in the process of ripening. We picked Castleton and Rosy Gage. Long John will be ready next.

Apples

McIntosh harvest indices are listed in the table below. Some starch and chlorophyll breakdown has occurred in the last week indicating that ripening is beginning. They should be ready to pick for long-term storage soon. For pick-your-own and immediate sale, they can be picked anytime, depending on customer taste.

Honeycrisp in one of our blocks is ready to pick today, but a nearby block (see table below) needs another week based on Delta Absorbance (DA) readings. This is in reference to harvest for storage. This variety had a lot of starch breakdown in the last week, but some of this maybe due to the recent rain diluting the starch. Check each Honeycrisp block individually because ripening is highly variable among different blocks.

Bitter Pit

I expect bitter pit in cold storage this fall. Apples still on the tree are showing it, and this has been an indicator of more bitter pit showing up in storage.

• For blocks considered to be low risk, I am recommending harvest later this month rather than now because some additional ripening reduces the severity of bitter pit.
• For blocks with an expected high risk of bitter pit, fruit can be sold immediately but bitter pit may develop during the marketing window. It can develop as early as two weeks after harvest. Another option is to store them three weeks to sort out the bad apples before marketing.

Honeycrisp apples that will be cold-stored longer than two weeks should be conditioned first. Hold them at temperatures in the range of 50 to 70 ºF for five to six days before placing in cold storage. Temperatures can be warmer than 70 ºF, but shorten the conditioning period to three or four days. Gradually lowering the storage temperature is another option, but hold apples at 50 ºF for at least four days.

Storage temperature recommendation is normally 38 ºF to prevent chilling injury, but this year I am recommending 35 ºF to lower the risk of bitter pit. This applies to apples that have been harvested at a maturity appropriate for long-term storage and have been conditioned. For apples harvested late, storage at 38 ºF following conditioning is recommended because they are more prone to chilling injury.

* DA is a measure of chlorophyll breakdown in the peel which parallels ripening. Numbers decrease as fruits ripen. Gala and Honeycrisp readings between 0.8 and 0.3 indicate sufficient maturity for storage. Mac and Cortland generally have much higher numbers than Honeycrisp and show a small decrease in DA as they ripen.

The following is a rough guide to what the starch index numbers mean for apple ripening:

1 – 2: indicates lack of starch breakdown and generally unripe.

3: partially ripe, but prone to disorders in long-term storage.

4: typically ready to pick for long-term storage.

5 – 6: indicates good flavor and ready for general harvest or harvest for short-term storage.

7 – 8: indicates fully ripe, too ripe for long-term storage.

Honeycrisp Storage Guidelines

Summary by Chris Watkins, Yosef Al Shoffe, Craig Kahlke, and Mike Basedow, Cornell University.

The 2025 Cornell Apple Storage Meeting was held in Geneva on August 19, 2025. Below are some of the main storage suggestions for a few of the varieties discussed during the meeting.

Honeycrisp

• Condition fruit at 50⁰F for 7 days. However, if fruit have high bitter pit potential based on peel sap or passive prediction tools, a strategy to reduce losses is to not condition the fruit, but keep them at 38⁰F for a month to allow bitter pit to be expressed before marketing.
• Storage at 38⁰F
• Controlled Atmosphere (CA) storage in 2-3% oxygen and 2% carbon dioxide has provided consistently good storage outcomes.
• Many storage operators use diphenylamine (DPA) treatment as it protects fruit against carbon dioxide injury.
• If DPA is not used, a delay of 3-4 weeks in air storage before CA, and /or maintaining carbon dioxide concentrations below 1% (and preferably close to 0.5%) is necessary. Concern about carbon dioxide is greatly reduced if fruit are treated with DPA.

For more information, visit the 2025 Storage Meeting Take Home Messages – CCE Eastern NY Commercial Horticulture Program

 

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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