ReTain could be useful for managing harvest

The new growth regulator ReTain could be useful in helping owners of large apple orchards harvest their crops at the right maturity, Joyce Thompson, manager of the Washington Apple Maturity Program, said during the Washington Tree Fruit Postharvest Conference.

ReTain (aminoethoxyvinylglycine) inhibits ethylene production and slows maturation of the fruit.

"We have lots of large orchards in the state now, and we have to look at the possibilities of having better control over the maturation of the fruit and better control over harvest management," she said. "I think, eventually, our harvest crews will become a bit smaller, and we're going to have to figure out how to keep those people moving at a nice steady rate instead of bringing them in and trying to harvest the fruit all at once. If we have more control over maturation, we will have more control over how we manage our harvest crews and still have nice fruit coming off the tree that we can store for a long time."

The Apple Maturity Program has been comparing fruit treated with ReTain and untreated fruit for the past three seasons.

Apples treated with ReTain tend to have slightly lower sugar levels at harvest and less advanced starch hydrolysis, but after seven months in storage, the sugar levels are the same as in untreated fruit.

Fruit firmness tends to be higher in treated fruit both before and after CA storage, and it does not drop off as rapidly after the fruit comes out of storage. However, this effect has varied from year to year. In 1995, the increase in firmness was not dramatic, Thompson said.

Color of the fruit does not seem to be affected. If ReTain-treated fruit was harvested at optimum maturity for CA storage, its color was about the same as untreated fruit harvested at the right maturity for CA storage. In other words, if half the orchard was treated, and the other half was not, the orchardist could harvest the untreated fruit at optimum maturity, and, one to two weeks later harvest the treated fruit also at optimum maturity, and all the fruit would have about the same amount of red color. However, leaving the fruit on the tree one to two weeks longer did provide a gain of about one box size on average.

Fruit treated with ReTain had less watercore and less internal browning during storage.

The fruit was treated four weeks before anticipated harvest at a rate of 50 grams of active ingredient per acre, applied in 100 gallons of water per acre. Thompson said some orchards responded to the ReTain treatment better than others.

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ReTain could be useful for managing harvest

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