Matt Whiting (right) discusses results of his research with the reflective material Extenday with Oregon State University Extension educator Lynn Long (center) and Steve Agidius.
For Oregon cherry grower Steve Agidius, laying a reflective fabric in the alleys between his Rainier trees can make the difference between hitting the market in time for the Fourth of July or trying to sell his cherries in the glut that follows that critical holiday.
A combination of using the dwarfing Gisela 6 rootstock, summer pruning, and an Extenday ground cover can advance maturity of the cherries at his orchard at The Dalles by as much as four to five days, he has found. Typically, he harvests his Rainiers, just before his Bings, in the first part of July.
“When you get into the Rainier peak, the price goes down,” he said. “You still make okay money, but it’s definitely much more profitable if you can bump it up four to five days.”
As well as advancing maturity, he’s seen improvements in size and color. He figures he gains perhaps half a row size just from the cover, and the cherries have a darker blush. The Extenday he uses is designed to reflect 80 percent of the light up into the trees with the other 20 percent going into ground to warm the soil. He thinks this warmth also helps promote fruit maturity.
The cost when Agidius bought the Extenday several years ago was $2,000 for the one acre he has covered and he’s planning on covering another one or two acres next season.
He lays the cover between the tree rows at bloom or slightly after, covering the entire alleyway. He has a machine to roll and unroll it, and can cover the one-acre block of cherries in about 1.5 hours with three people. It is attached to bungee cords stapled to the tree trunks, which allows the wind to move it around and reflect more light on the cherries, he said.
In the rest of his Rainier cherries, he puts four-foot-wide strips of Mylar polyester film down under the trees. The labor involved in putting down either Extenday or Mylar is about the same, he said, because the Mylar is kept in place by shoveling dirt on top of it. The Mylar is disposed of every season, whereas the Extenday is rolled up and stored in his shop and can be reused for several years.
During the growing season, he sprays the trees with the Extenday down. His Blueline sprayer draws in air from the sides and the bottom, so he covers the bottom intake with cardboard to avoid it sucking the fabric into the machine.
At harvest, he used to unhook the Extenday and slide it to the sides of the drive rows, but he now leaves it in place so that when he does multiple picks the later-maturing cherries can continue to benefit from the increased light reflected into the trees. He’s noticed that with Extenday he can harvest around 75 percent of the cherries in the first pick, versus about 50 percent in blocks where he has Mylar polyester film instead.
Agidius works as a field horticulturist for Diamond Fruit Growers cooperative and thinks that Extenday has resulted in longer extension growth in the trees and less of the blind wood that normally develops in trees on Gisela 6 rootstocks.
“That’s an observation I made last year,” he said. “I get to see a lot of different orchards, and you see a lot of Gisela 6 blocks that have a lot of blind wood, and this block has zero. I think it’s just getting the light up underneath the tree and keeping that wood that’s typically shaded out in the light.”
Dr. Matt Whiting, horticulturist with Washington State University in Prosser, said he began doing research trials with Extenday eight years ago. During four years of trials on Bing, the only consistent difference he found between tree rows with Extenday and those without was advanced maturity, although some years, there would be slight increases in soluble solids and fruit size.
He did notice, however, that with a full-season treatment of Extenday, it was possible to leave a larger crop on the tree and still have good quality.
With Rainier cherries, again, the most consistent effect was advanced maturity with the full-season application.
In commercial blocks, the number of picks was reduced from four to two where Extenday was applied, and 66 percent of the fruit was harvested in the first pick versus only 10 percent in a block where Mylar was applied a few weeks before harvest, Whiting reported.
He sees a role for Extenday as a management tool that large growers could use. By treating half of an orchard, they could extend the harvest and possibly pick the crop with fewer people.
Whiting warned against putting the fabric down before or during bloom because heat can be reradiated from the ground, leaving the trees more vulnerable to frost damage.
“I think the best time is post-frost risk,” he said.