Tree Fruit Newsletter — September 21, 2023
Maturity Report
McIntosh: Not much change in maturity indicators in the spur type strain, but flavor and texture have improved. Both strains are still ok to pick for storage based on the lack of fruit drop during limb shaking. McIntosh is susceptible to superficial scald when stored longer than three months. If applied within five days of harvest, 1-MCP products will prevent this browning disorder.
Cortland: Cortland will be ready to pick for storage, soon. They are susceptible to superficial scald and should be treated with an antiscald material such as 1-MCP (SmartFresh) and DPA (No-Scald). 1-MCP is not fully effective by itself.
Honeycrisp: This variety ripens unevenly, so spot pick according to the green ground color changing to light green or greenish yellow. Some are ripe enough to be highly susceptible to chilling injury and should be conditioned prior to cold storage. To condition, hold apples at 50 to 70 °F for five to seven days before putting into cold storage at 36 to 38 °F. If you have purchased Honeycrisp apples from another grower, there is a good chance that they have not been conditioned and are susceptible to chilling injury (soft scald and soggy breakdown). Honeycrisp can develop soft, brown spots on the surface in as little as three weeks in cold storage if they have not been conditioned first. Dr. Renae Moran did the rapid induction test to measure relative risk of bitter pit in several different blocks. Much less bitter pit showed up this year, the worst block having 14%. This is far less than last year.
Gala: Based on Delta readings, Gala is over-ripe for storage and should be sold soon. Our block has a very light crop and may be advanced in ripening compared to other farms.
Empire: This variety is normally late to ripen.
| Variety | Starch Index | Delta Absorbance meter reading* |
|---|---|---|
| Gala | 5.8 | 0.33 |
| McIntosh standard Strain | 4.7 | 1.80 |
| McIntosh spur type | 6.3 | 1.81 |
| Honeycrisp | 4.7 | 0.99 |
| Cortland | 2.0 | 1.54 |
| Empire | 1.8 | 1.53 |
*Delta reading is a measure of chlorophyll breakdown in the peel and change in ground color from green to yellow. Starch index is a measure of starch breakdown, so the index number increases as fruit ripen.
Renae Moran
UMaine Cooperative Extension Tree Fruits Program
University of Maine Cooperative Extension
PO Box 179
Monmouth, ME 04259
(207) 933-2100
rmoran@maine.edu
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