Tree Fruit Newsletter — September 23, 2024
Maturity Report and Storage Reminders
Peaches and Plums
Peach harvest was completed this week.
Long John plums will be ready to pick soon. If you need to store them longer than a few days, they can be picked now.
Apples
McIntosh has reached a stage where it is ok for short-term storage. If you still need to harvest for storage, 1-MCP (SmartFresh®, Hazel®) applied after harvest will help them maintain good condition. Fruit drop is evident after the limb shaking test. This indicates that McIntosh is too ripe for long-term storage and that fruit drop will increase.
ReTain® (or Harvista®) Macs should still be ok for long-term storage, particularly with post harvest 1-MCP (SmartFresh®, Hazel®).
Cortland ripening has not yet reached a stage that is best for long-term storage, but is ok for immediate sale. This variety is prone to superficial scald and bitter pit, both of which are more severe when fruit are harvested too soon.
Gala at Highmoor Farm is fully ripe. This variety is not susceptible to storage scald, chilling injury or bitter pit, but will develop some internal browning if stored longer than six months.
Honeycrisp has reached a stage of maturity where they are suitable for long-term storage. The risk of bitter pit decreases when the starch index passes 5 and the Delta Absorbance readings decrease below 0.8. Honeycrisp has reached the stage where they are highly susceptible to chilling injury in storage, so conditioning is critical now. To condition, hold apples at 50 to 70 °F for five days before putting into cold storage at 36 to 38 °F. You could also do a stepwise decrease in temperature during the first week of storage to lessen the risk of chilling injury after a shorter conditioning period. Don’t skip the conditioning.
Reminder: Honeycrisp is sensitive to the elevated carbon dioxide that occurs in controlled atmosphere storage. Other varieties are also sensitive when treated with SmartFresh® or Hazel®. Be sure to include enough lime in your CA rooms. Diphenylamine (No-Scald®) will increase tolerance to carbon dioxide in CA storage, but it’s best to keep carbon dioxide below 1% in the first month of CA storage.
When conditioning Honeycrisp in an enclosed room, the oxygen concentration can decrease to the point where human suffocation can occur. Ventilate these rooms before entering.
| Variety | August 26 | August 30 | September 5 | September 10 | September 16 | September 24 |
|---|---|---|---|---|---|---|
| Zestar! | 3.4 | 4.8 | — | — | — | — |
| Gala (Fulford) | — | — | 2.2 | 3.2 | 3.0 | 4.7 |
| McIntosh (Roger’s) | 2.4 | 3.1 | 3.6 | 4.5 | 4.7 | — |
| Macspur | — | — | 3.9 | 4.5 | 4.8 | 5.9 |
| Honeycrisp | 1.0 | 1.2 | 2.8 | 4.2 | 4.8 | 7.5 |
| Cortland | — | — | — | — | 1.5 | 2.4 |
| Royal Red Cortland | — | — | — | — | 1.2 | 1.4 |
| Macoun | — | — | — | — | — | 2.4 |
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 – 4 indicates some sweetness developing and generally partially ripe.
5 – 6 indicates good flavor and ready for general harvest.
7 – 8 indicates fully ripe.
| Variety | September 5 | September 10 | September 16 | September 23 |
|---|---|---|---|---|
| Gala (Fulford) | 0.76 | 0.70 | 0.55 | 0.11 |
| Honeycrisp | 1.12 | 0.88 | 1.04 | 0.56 |
A measure of chlorophyll breakdown in the peel and change in ground color from green to yellow. Numbers decrease as fruits ripen. Gala and Honeycrisp readings between 0.8 and 0.3 indicate sufficient maturity for storage. Standards for other varieties have not been determined.
Renae Moran
University of Maine Cooperative Extension: Tree Fruits
PO Box 179
Monmouth, ME 04259
(207) 933-2100
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