Peter Hall explains how the Exosex mating disruption system works. Pheromone lures and pheromone-impregnated powder are placed in dispensers on a 20-meter (66-foot) grid in the orchard. Male moths that are lured into the dispensers, which resemble wing traps, and become coated with the powder. Their pheromone receptors become overloaded so they cannot detect females. When they exit the dispensers, the males act as mobile pheromone dispensers, causing confusion among other male moths and reducing their chances of mating.
Peter Hall planted a ten-acre apple block in his U.K. orchard in 2007 to demonstrate the feasibility of growing apples organically in Britain’s soggy climate.
Hall, who manages a 300-acre farm at Marden in Kent, showed a group of International Fruit Tree Association members the organic “concept orchard,” which he planted in collaboration with the fruit marketer OrchardWorld, Ltd., and Sainsbury’s supermarket.
Most of the organic apples grown in the United Kingdom are varieties that are tolerant of diseases, such as mildew and scab, but have limited consumer appeal, Hall said. The intention of the concept orchard was to produce organic apple varieties that consumers want, while demonstrating to other growers—conventional as well as organic—how apples can be grown using organic techniques to reduce pesticide and fungicide use.
The concept orchard includes Gala, Braeburn, and the cooking apple Bramley, which are favorites in the U.K. market, along with the newer varieties Estival, Pinova, and Early Windsor.
“Our intention is to grow varieties that people want, within organic standards,” he said, “And do it using science and technology, not muck and magic.”
Hall’s Poultry Farm was established in 1894 by his great-grandfather Herbert, who sold chickens. It now has 35 acres of apples in total, of which half are produced organically. The farm also has pears, plums, wine grapes, hops, and wheat.
The concept orchard, modeled after Dutch apple-growing systems, has trees on Malling 9 rootstocks that are spaced between 2.5 and 4 feet apart, depending on the variety, with 10.5 feet between rows. It is trickle irrigated.
Hall’s production goal is 50 bins per acre at maturity in order to minimize per-unit inputs.
“One of the biggest problems with organic production traditionally is it’s rarely sustainable,” he said. “If you get eight bins per acre from a fully mature planting, you’re doing well, and much of that will end up in the juice box because of disease.”
As well as reducing per-unit costs and making growers more competitive, higher production could also increase British growers’ share of the organic apples sold in the United Kingdom, which now amounts to only 3 percent.
So far, yields for Gala, Braeburn, and Pinova in the concept orchard are exceeding those in his conventional blocks. He picked 42, 45, and 52 bins per acre, respectively in 2010, and expected even higher yields this year. “Frankly, we’re staggered by that,” he said.
The only thinning Hall does is to remove fruit damaged by codling moth or sunburn (which is rare). His apples are sold in the supermarket in 800-gram (1 pound, 12 ounce) polybags, and with smaller apples it’s easier to come close to the required weight.
“If the whole crop was 55 to 56 millimeter (2.25 inches) that would suit me down to the ground,” he said. “We can prebag them and don’t have any give-away.”
The fruit is certified by the Soil Association, which is the U.K.’s top organic certifier.
Hall said he tries to industrialize his practices as much as possible, though certifiers don’t like the idea of intensive agriculture because they associate it with battery chickens and crated veal. In fact, organic apples fare better in intensive systems, he said, because predatory insects can move through the crop more easily and spraying is more effective.
Scab and mildew
He uses sulfur for scab control and potassium bicarbonate (baking soda) for mildew. He has two electronic weather stations at the farm that relay weather data directly to an advisor in the Netherlands, who runs them through a RIMpro predictive model for scab. When alerted, Hall applies sulfur on alternate rows, then goes back through the other rows with the intention of finishing just before the rain begins.
Timing is critical with low-input systems, he said. “I cannot overstress that. If you miss the boat and the scab spores get on the fruit and start to germinate, you’re absolutely finished. You will not get scab out once it’s in.”
If the timing is right, crop losses can be minimal, and low-input systems are better for the environment as well as for the grower’s bottom line, he said. Costs are reduced, and the value of the crop increases.
He noted that maximum allowed residues have dropped almost to the limit of detection, so it’s important that growers use systems that minimize the risk of residues on the fruit.
Potassium bicarbonate is a good curative product for mildew control but must be applied in slow-drying conditions, he said. “It’s no good putting it on when it’s lovely and dry. You might as well stay in bed. We get a lot of that drizzly, mizzly, soggy, disgusting weather here, and that’s ideal weather to apply baking soda for mildew control.”
He applies it whenever the weather allows at a rate of 5 kilos in 500 liters of water per hectare (equivalent to around 5 pounds of potassium bicarbonate in 50 gallons per acre).
Although he makes 20 or more sulfur applications a year, as well as numerous mildew sprays, research in Wales has shown that the carbon footprint of making so many passes through the orchard is still less than if he applied conventional fungicides, he said.
“You’re never going to find the perfect system unless you’re going to have GMO [genetically modified organism] technology and your trees are going to generate their own nitrogen and harvest water from the atmosphere as well as being scab, mildew, and pest resistant,” he commented.
The two major pests he has to deal with are the blue bug aphid (rosy apple aphid) and apple sucker (Psylla mali). Both appear in the orchard early in the season.
As soon as the buds burst, he applies simple soap, preferably on a rainy day. “It’s amazingly difficult to find a mizzly day when you want one,” he remarked. “It’s easy when you don’t.”
He finds soap as effective as conventional pesticides, and it allows predators to play a role as the season progresses. Also, it’s unlikely that the pests will acquire resistance to drowning, he quipped.
For codling moth, he uses mating disruption and the codling moth granulosis virus.
Years ago, he tested a mating disruption system developed by BASF to control codling moth and tortrix (leafrollers). It worked like a dream, he said, but the company could not justify the great expense of registering the product for the relative small amount of crop it would be used on.
Since 2007, he’s been using Exosex. Fruit damage from codling moth at Hall’s orchard has ranged from 0.5 to 1.5 percent.