Voen Covers
Overnight rainstorms in Okanagan summers are often followed by the sound of helicopters heading out at dawn, an expensive way to deal with potential rain damage for cherry crops.
Rain events during the “June monsoon” and early July raise the chance of significant losses to the BC cherry crop every year.
Growers employ an aggressive regime of helicopters, wind machines, and tractor-towed blowers to dry the fruit, but despite these efforts, crop losses from weather damage can range from 20 per cent to total crop failure. To compound the problem, certain cherry varieties are more sensitive and bruising can occur with the blow drying methods. Orchard neighbours don’t like the sound of helicopters and they are certainly expensive for the growers to hire.
Growers at Coral Beach Farms in Lake Country have tested Voen rain covers over the last several years and plan to cover a second block this spring in an effort to reduce rain damage.
While the 2017 cherry season was hot and dry, that was not the case in 2016.
“In 2016, the covers were worth their value,” says Gayle Krahn, Horticulture/Vernon Manager for Coral Beach Farms. “We had as much as 70 per cent damage in uncovered blocks.”
If a rain storm soaks a cherry orchard during the last couple of weeks before harvest, there is a risk the fruit will absorb some of the water through the skin. That extra moisture, particularly combined with warmer temperatures, may contribute to expanding the fruit size. A cherry does not grow more skin, or cuticle, it simply stretches and becomes thinner. Stretch too far and the cherry splits, and cannot be sold in the fresh fruit market.
In 2010, the company planted a 14 acre block of Rainiers, Stardust, and Pollinators on Mazzard rootstock on the west side of Okanagan lake. In 2012, they installed a set of Voen covers on 10 acres.
The Climate Action Initiative had funds available to support work on local adaptation strategies. As Choral Beach had already installed and begun evaluating the orchard covers, they received funds to cover about 50 per cent of the costs to set up and take down the covers and to conduct and report on their study.
“It made sense to look at some way of protecting our blush cherries, they are our highest value cultivar,” says Krahn. Industry FOB prices can be up to $7.50lb to export markets. “They are a tender fruit that is prone to split,” she adds. Indeed, the 2016 uncovered crop of Stardust in the block was abandoned on the trees, when extensive July rains destroyed over 70 per cent of the fruit.
Voen Cover Setup
The Voen steel infrastructure is permanently installed and the covers are hung in the weeks leading up to harvest.
“The orchard remains uncovered through fruit set, and up to several weeks before harvesting,” Krahn says. “We conduct the exact same spray, fertilizer and irrigation program as we would for any other block.”
A heavy rainstorm on June 22, 2016 caught them unprepared and on June 23 they started putting up the covers and picked off the damaged fruit. “On July 8 we had a freak rain storm with high winds,” says Krahn. “The wind brought in sideways rain so we did have rain come under the covers. At the end of the season in that block we ended up with about 25 per cent splits and less than 5 per cent rot.”
Krahn says the set up costs are high, about 750 man hours to put up in the spring and 500 hours to take down, for the 10 acres. “We have been spending two and a half hours per row to install with clips,” says Krahn. “Voen has since come up with a zipper system that will cut our time down to 10 minutes per row.”
Krahn says they are not going to change the current system over to zippers, but a new 12.5 acres of covers for a block in Lavington will have the zipper system. “We were recently on a study trip down in Tasmania and they were having success with the zipper method,” says Krahn. “It’s a huge improvement”
The covers create an artificial environment that has some challenges, Krahn told the BC Cherry Association AGM in February. “We are finding increased humidity of about 25 per cent and a temperature increase of up to three degrees,” she says. “Although most people wonder about the higher humidity, we have not noticed more mildew here at Coral Beach Farms.”
“The fruit is definitely softer under the covers due to the increased humidity and temperature,” Krahn says “And it is less comfortable for the pickers. We turn on our air machines for harvest.” She adds that picking can still carry on if there is rain.
There are a variety of affects on the fruit. Depending when the covers are in place, the fruit will mature earlier. “We are getting maturity about four days earlier, but in Tasmania, where they have a cool spring and put them up much earlier. They can harvest 12 days earlier, Krahn points out.
Trees under cover need less water. “We have reduced our irrigation by 30 per cent while still maintaining the same moisture level as the rest of the orchard,” Krahn says. “Our stems are greener under the covers.”
“We find 90 per cent of our fruit under cover is 9.5 row and larger,” says Krahn. “Compared to uncovered fruit that is only 80 per cent 9.5 and larger.”
“We also found that the brix under covers is approximately 1 per cent lower and we suspect that is due to the filtered sunlight,” she adds.
The lower sunlight also affects cherry colour. “Fruit colour is an issue with Rainiers. A yellow cherry is not going to have great returns so we have done a couple of things to bring up the colour,” she says. “We use ExtendDay ground cover. It has been very beneficial, but we also do leaf pruning.” The pruning is more labour, she admits, but it has made a difference in colour.
Costs are about $25,500 per acre to install. Yearly set up and take down is about $3,000 per acre and $3,000 per acre for ExtendDay and the summer pruning. “You need to balance those costs against the price of flying a helicopter, tractor drying and the loss of damaged fruit,” Krahn points out.