Tree Fruit Maturity Report — September 17, 2025
Maturity Report
Stone Fruit
This week, we are harvesting Long John, a European plum, and Messina, one of our better peaches.
Apples
Water core is showing up in a few apples. Water core occurs when the apple cannot metabolize all the sugars that flow into it. The surplus sugars inside the apple will draw water and lead to the water-soaked appearance in the core. If customers ask, these apples are edible and have good flavor.
Because of the drought, water core may become more prevalent as the harvest progresses and night temperatures decrease. Apples with severe water core can develop internal browning in cold storage. Before putting in long-term storage, check a few apples by cutting them in half to examine the core and outer flesh. If you find too many that have water core, hold them at warm, ambient temperatures for a few days to allow the apples to fix their water core before they go into cold storage.
In years past, I have seen Honeycrisp apples with water-soaked areas in the outer flesh. This could show up later in storage as a browning disorder.
Preharvest fruit drop has been reported by some growers. Once this happens, an application of ReTain is not likely to prevent additional drop. ReTain works best when it is applied before any sign of drop. If fruit fall off the limbs with gentle shaking, it’s too late for ReTain. At this time, it is probably not too late for Cortland and other later-ripening varieties. Remember that ReTain has a 7-day preharvest interval.
Harvista may work better than ReTain under the conditions we are experiencing with the severe drought, but I don’t have enough experience to be certain.
McIntosh harvest indices for the Augusta area are listed in the table below. Maturity tests indicate that Macs are still ok for long-term storage. Gentle limb shaking did not cause any fruit drop in blocks at Highmoor Farm. The first sign of fruit drop indicates when apples are too ripe for storage, and also that fruit drop will soon begin.
Cortland maturity indicators have not changed in the last few days. It’s too early to pick for ideal long-term storage. For immediate sales, it’s just right for those customers who like them partially ripe. Ripening may be more advanced farther south in the state.
Macoun is close to being ready for short or long-term storage. For immediate sales, they can be picked anytime, but quality will improve over the next week. In my opinion, this variety has little consumer appeal when it’s under-ripe.
Honeycrisp is still suitable for long-term storage in some blocks, but may be getting too ripe in others. Check each Honeycrisp block individually because ripening is highly variable among different blocks. Fruit that are sufficiently ripe for storage will have a pale yellow-green color (see photos). When the peel turns yellow, they may be very susceptible to chilling injury in cold storage, and conditioning does not always prevent it.
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.
Baseline measurements for Empire, Fuji and Evercrisp all indicate that ripening in these varieties has not yet started.
Other varieties: At Highmoor Farm, Summerset is ripening slowly and not showing signs of preharvest fruit drop. Sweet 16 ripening is highly mixed among apples on a tree. Some are ripe while others are still green.
| Variety | Starch Index 9/2/25 | DA* 9/2/25 | Starch Index 9/9/25 | DA 9/9/25 | Starch Index 9/12/25 | DA 9/12/25 | Starch Index 9/16/25 | DA 9/16/25 |
|---|---|---|---|---|---|---|---|---|
| Honeycrisp | 2.0 | 1.21 | 5.2 | 0.97 | 5.6 | 0.77 | 6.1 | 0.75 |
| McIntosh (standard) | 3.0 | 2.02 | 4.1 | 1.88 | 3.7 | 1.72 | 4.7 | 1.86 |
| McIntosh (spur type) | 2.9 | 1.89 | 3.8 | 1.79 | 4.3 | 1.80 | 4.6 | 1.67 |
| Cortland | 1.0 | 1.87 | 1.2 | 1.78 | 1.4 | 1.69 | 1.3 | 1.69 |
| Macoun | 2.2 | 2.04 | 2.4 | 1.93 | 2.7 | 1.85 | ||
| Empire | 2.2 | 1.71 | ||||||
| Fuji | 1.6 | 1.92 | ||||||
| Golden Delicious | 1.4 | 1.52 | ||||||
| Evercrisp | 1.0 | 1.42 | ||||||
| Summerset | 2.4 | 1.08 | 3.0 | 1.01 | ||||
| Sweet 16 | 2.4 | 1.69 | 2.7 | 1.66 |
* 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. McIntosh DA has not closely followed harvest maturity in years past and remains much higher than in other varieties. Cortland and Macoun DA, in the past, has decreased below 1.5 during the harvest window. Empire DA was close to 1.0 during harvest in 2023, and Golden Delicious was 0.95.
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.
Renae Moran
University of Maine Cooperative Extension: Tree Fruits
PO Box 179
Monmouth, ME 04259
(207) 933-2100
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