Protecting growers from hail
Hail damage to a young orchard can be financially devastating.
When board members of the Batlow Fruit Cooperative in New South Wales, Australia, held a strategic planning process to figure out how to sustain their growers, they wondered why growers were leaving the industry. The answer turned out to be hail.
Every year, growers were losing some of their crop to hail, and it was taking a heavier toll on them than in the past, Ron Gordon, the cooperative's field services manager, related at the International Fruit Tree Association's annual conference in Tasmania.
Gordon cited several reasons why he believes that hail damage is more devastating to tree fruit crops than it used to be:
• Consumers demand unblemished fruit. There is no market for number-two grade fruit.
• The capital cost of establishing an intensive apple orchard is so high that growers cannot afford to lose their crop in year three or four, when they're banking on early income from the planting. If they're hailed on two years in a row, they might lose the orchard.
• Buyers want reliable fruit supplies. Without hail protection, a grower might not be able to guarantee that.
Producers who want to survive in the business and get contracts with major buyers must consider installing hail protection over their orchards, Gordon said. A hail protection system can provide a number of secondary benefits to the grower, such as:
• Protection from birds.
• Sunburn protection for sensitive apple varieties, such as Fuji, Jonagold, and Cameo.
• Less wind, allowing the orchard to be sprayed in a wider range of conditions.
• Moderated temperature.
The drawback is that a hail net can be expensive, Gordon said. Hail structures are usually tall and designed to carry thousands of tons of ice. The cables need a lot of tension put on them with sophisticated equipment. "They usually require very specialized and expensive labor and equipment to install," he said, estimating the typical cost at Aus.$35,000 to $50,000 per hectare (U.S. $11,000 to $16,000 per acre).
The Batlow Fruit Cooperative set out a couple of years ago to design a system that would be less costly and could be installed by the growers themselves, he related. It hired engineers to develop a system using steel posts, instead of hardwood. The system devised uses a three- or four-wire trellis structure to support both the fruit trees and the hail net, whereas most of the existing net structures don't incorporate tree support.
The net can be flat or peaked and is held in place with bungee straps. It is "designed to fail," meaning that when the ice load reaches a certain point, the bungee straps stretch, allowing the ice to fall to the ground between the tree rows, so that the net doesn't have to bear such a heavy load.
Gordon said the company has been checking into what color of net works best.
"We can't get any firm information that colored nets do anything except interfere with the light levels," he said. "It's been claimed they change the color of the fruit."
He thinks the new system will cost about half the price of a standard hail net. It could be used with any number of wires on the trellis. Batlow Fruit Cooperative planned to have a few hectares of netting put over one of the company's existing orchard by late May of this year and hoped to have 50 hectares (20 acres) of netted orchard by the end of the year.
Dr. Simon Middleton, horticulturist with the Queensland Department of Primary Industries, said a hail net will cut the light level in the orchard by 13 to 24 percent. Fruit set will be reduced, but the need for hand thinning may also be less. A gap must be maintained between the tops of the trees and the netting to allow movement of bees during pollination. Some growers have been reluctant to use chemical thinning under netting, for fear of overthinning.
There is a lot of scattering and reflection of light under a white net, he said, which usually has a positive effect on fruit color, provided that tree vigor is under control.
The netting reduces wind speed, allowing growers to apply sprays in a timelier manner. It also reduces the tree's water use by 25 to 30 percent. Evaporation is reduced, and the soil does not dry out as fast.
In Middleton's studies, there was less damage to the hail structure by heavy hail when a weaker fabric was used because it tore when the ice load became too great. With stronger netting, the weight of the ice on the netting pulled down the supporting poles. "It may not be a bad thing to lose your net to the hail," he said. "It's better than losing the whole structure."
An economic analysis of Fuji under netting in Australia showed that even without a hailstorm, the netting would pay for itself within seven years just because of improved packouts. With Red Delicious, however, the cost would not be recouped unless there were several hailstorms.