PGR helps stone fruit growers hit marketing windows, cut fruit drop
By Vicky Boyd
A plant growth regulator that helps prolong fruit firmness and quality in apples is gaining a following among stone fruit growers, who say it helps them hit profitable marketing windows.
We were looking at it for timing on the marketing end, says Joy Cline, farm manager at Bear Mountain Orchards in Aspers, Pa., who tried the PGR, ReTain, on about 30 acres of peaches and nectarines in 2004. If you can hold that fruit an additional two or three weeks in storage when the market is flooded and then sell it when the people are out, it's going to be a help.
ReTain, from Valent BioSciences, has been federally registered for use on apples since 1997 and gained federal registration for stone fruit, except cherries, in 2004. It is not yet registered for use on stone fruit in California.
AVG, or aminoethoxyvinylglycine, the naturally occurring active ingredient in ReTain, blocks ethylene production in plant tissue. Ethylene, a plant hormone, controls fruit maturity, ripening, firmness and abscission, or fruit drop.
The product is approved by the Organic Materials Review Institute for use in organic production.
Can you hold, please
In apples, growers apply a single spray of ReTain about four weeks before the anticipated start of harvest. Because it prohibits ethylene production, ReTain allows growers to hold apples on the tree longer without softening or dropping. In the meantime, the fruit can color and size.
If apples enter storage firmer, chances are they will be better quality and firmer when removed and repacked, says Ricardo Menendez, Valent BioSciences global business manager for PGR products.
Cline first became acquainted with ReTain when she used it on red delicious, galas and Rome apples.
We use it mostly as a harvesting tool, she says. We wanted to delay the reds long enough to get a little bit better color. With all of our other varieties, we wouldn't get to our Romes quick enough, and we used it for drop-control problems.
Since the Romes remained on the tree two to two and one-half weeks longer, they also increased in size.
With the galas, she used the PGR to help gain size and color and was able to harvest in one picking.
In this case, it's a great harvesting tool, because we don't lose time pulling out of our peach harvest and we gain quality on the gala, Cline says.
Less drop in stone fruit
For stone fruit, ReTain should be applied seven to 14 days before anticipated harvest.