By STAN MADDUX

Indiana Correspondent

EAST LANSING, Mich. — They won’t turn mushy once picked from trees overnight, but the record late September heat wave across the Midwest and East Coast could noticeably limit the shelf life of apples.

There are things growers can do to keep their heat-stressed fall crop from going to waste. Bill Shane, a tree crop expert from Michigan State University, explained a long stretch of extremely hot weather like the one just experienced causes the metabolism in apples to “rev up.”

Heat builds up and they ripen quicker, but getting them off the trees sooner doesn’t solve everything. Shane said overheated apples, through respiration, produce more carbon dioxide (CO2) than normal and must be cooled as quickly as possible once picked to limit any damage to their consumer lifespan.

Storage should be in a well-ventilated area to help the process along. Closed or cramped storage restricts not just how fast the heat inside the apples escapes but puts sort of a “lid” on the already higher volumes of CO2 the stressed crop is releasing – and it is exposure to elevated CO2 levels that directly impacts shelf life, said Shane.

Under ideal conditions, he said apples once picked can remain crisp for 2-3 months but improper storage of an overheated crop means having to take it out of circulation, perhaps, within a month or less.

Some growers with Mother Nature-baked late-season apples try compensating by getting them into the stores quicker, but that can be a losing venture if too many wind up on the market all at once, Shane said.

“That’s why there’s such an important emphasis on getting the temperature of fruit down once they’re picked,” he added.

Overheating can also negatively impact taste, from some of the natural sugars inside evaporating, he said.

MSU also suggests growers add a skid of lime to a storage room to help reduce CO2, and leaving fruit outside with the nights getting cool, then filling the rooms in the morning. Avoid stacking bins tightly together until the apples have cooled, to allow heat to more freely escape.

According to MSU, using 1-MCP products such as Harvista and SmartFresh to slow down metabolism could be more important than usual this year. Ideally, application should occur right after picking but growers should make sure the crop isn’t too warm when applied, or a ghosting on the fruit’s surface will form.

In 2016, Michigan ranked third in the nation for producing 8.5 percent of the nation’s apples, and just ahead was New York at 9.2 percent, according to USDA. Washington far and away was first, producing 69 percent of the country’s apples.