Apple storage advice for 2016 - a warm year at harvest
Growers should pay extra attention to temperature of fruit going into controlled atmosphere storage.
Fruit are ripening ahead of normal harvest dates this year in all regions following this warm summer. My recommendation is to push through harvest to the extent possible, as weather is likely to deteriorate soon. One important consideration is the temperature of the fruit going into controlled atmosphere (CA) storage. Gala and other fruit harvested in the early days of fall are now going in warm, so extra attention needs to be paid to temperature monitoring.
In terms of temperature prior to CA storage, we usually like to see the temperatures of the warmest fruit at about 45 to 50 degrees Fahrenheit, but lower temperatures are better to be sure. Temperature control is your number one friend when it comes to preserving apple fruit quality.
Another reason temperature control is important in warm years is that the fruit coming in at high temperatures respire much faster than cool fruit, leading to a rapid build-up of CO2 (carbon dioxide) in the storage environment. In a room with a closed (not sealed) door, CO2 levels can reach 5 percent overnight! For CO2-sensitive varieties (e.g., Honeycrisp, Empire, Jonathan, McIntosh), this can be disastrous. For these varieties, Michigan State University Extension recommends putting a half- or a quarter-skid of lime in the room during loading, especially if the fruit are coming in warm. CO2 scrubbing may also be an option.
Cooling fruit is important, but even warm fruit are responsive to 1-MCP. For most varieties, there is no reason to delay the application of 1-MCP. Our work has shown that 1-MCP is similarly effective from 32 to 70 F, and keep in mind multiple applications are just fine. There is no harm to treating the same fruit twice if room loading is stretching out due to waiting on color (also a problem some warm years) or labor or weather issues.
With regard to treating fruit at higher temperatures, an exception might include Golden Delicious, which, during warm harvest seasons, seems to be susceptible to a surface discoloration when treated with 1-MCP while still warm. I’ve not seen this disorder on Michigan fruit, but I have on Ohio Goldens in 2012.