Tunnels are feasible for apples if the fruit can be sold for a premium.
A British Columbia, Canada, orchard is pioneering crop tunnels for apple --production.
Raymond and Sonja Barker of Silverhill Orchard in Mission, B.C., about an hour's drive east of Vancouver in the lush Fraser Valley, erected a tunnel over two rows of Alkmene trees this past spring hoping to reduce disease and boost the quality of their crop, which they sell at local farmers' markets.
"I think this system is the way of the future," Raymond Barker said, standing between rows of Alkmene apples that colored up nicely in the tunnel. The fruit ripened two weeks earlier than usual, despite cold, wet weather during the season that hurt pollination and crop development.
"They're as good as last year if not a little better, but the weather conditions we've had this year have been horrible," he said, noting that his Cox's Orange Pippin and Rubinette trees saw no pollination whatsoever.
The tunnels, which consist of a sheet of Ginegar plastic atop a structure of arched extension poles, are open on the sides. The plastic sheet can be rolled back for venting. The tunnels can be dismantled between seasons if desired.
Developed in Israel, Ginegar allows 85 percent light penetration while reducing ultraviolet exposure. The five-layer resin sheets also diffuse light, enhancing coloring of fruit while reducing sunburn.
"Under the plastic, I have absolutely zero sunburn on these apples, whereas in other parts of the orchard, it's a major, major factor," Barker said. Up to a tenth of his crop is at risk from sunburn in an average --season. Barker also credits the tunnels with reducing disease by shielding his trees from wet weather. While the rest of the orchard suffered from fireblight, trees in the tunnel were untouched.
With climate change altering precipitation patterns, Barker suspects crop tunnels will be more important than ever in the future for production of high-quality, high-value fruit.
"The major problem of growing anything in the lower mainland is rain. Keep the rain off your product, and 95 percent of your problems are solved," he explained. "I have a record of our weather for the last four years, and we're not really getting any more rain, it's just starting to move.
"Most of our rain used to be in November and February," he explained, "and trees don't really have a problem with --having wet feet when it's cold—50°F or lower. They tend to be okay.
"What we're getting is more wet weather when it's warmer. That's when you do have a problem."
The potential of crop tunnels to protect and improve Silverhill's fruit under such conditions has made them integral to a major renovation the Barkers are undertaking of their 4.5-acre orchard, which currently has about 3,000 trees producing more than 30 varieties.
The renovation will reduce Silverhill's tree count to approximately 1,500. The crop tunnels will support a shift into varieties Barker feels will fetch a premium at the farmers' markets.
In addition to boosting counts of Aurora Golden Gala, Cox's Orange Pippin, and William's Pride trees, Barker will add Honeycrisp to his offerings while cutting back on less lucrative varieties such as Belle de Boskoop, Northern Spy, and --Jonagold.
A second tunnel will have Sandra Rose and Lapins cherries as well as Harbright and Glohaven peaches, while another will be dedicated to ever-bearing strawberries. An assortment of raspberries, tomatoes, and salad greens will be grown in pots alongside and between the fruit rows.
Since buyers at local farmers' markets are willing to pay for quality, Barker believes the tunnels will be a worthwhile investment, even though the cost of a tunnel (including three rows of apple trees) will be at least Can.$15,000 (U.S.$15,400).
Economics have been the main barrier to the tunnels' adoption by apple growers in the past, said Graham Moore, technical manager with the tunnels' manufacturer, Haygrove, Ltd., of Herefordshire, England.
While the tunnels are popular with many stone fruit growers in --England and the United States, Moore doesn't know of anyone using the tunnels for apples. A big reason is the cost versus the anticipated return.
"Trees are certainly good under tunnels; the question is more about the value of the produce," Moore said. "The use of the tunnels over apples is most unusual, not because they won't work, but because the value of apples, or of the impact of the tunnels, is relatively low for most growers."
Dr. Greg Lang, a professor in the Department of Horticulture at Michigan State University in East Lansing, Michigan, who is studying cherry and apricot production in the tunnels, said the economics of apple production mean growers need to have a definite marketing strategy for their fruit.
"We're looking at niche crops where there's not a lot of competition from high-volume producers," he said.
By the same token, he was recently visited by a grower in Alaska who erected a tunnel similar to Haygrove's last spring in order to produce apples in that state's abbreviated growing season.
For the Barkers, the tunnels also complement steps to reduce their labor requirements.
Since the tunnels promise high-quality fruit commanding premium prices, Barker thinks he'll be able to afford having fewer trees, meaning less work and more time to devote to other aspects of the business.
"With the tunnels, we think we can grow fruit we couldn't normally grow successfully," Barker said. "[And] if I reduce the trees, change the cultivation system, I'll actually have more time."