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Trainings | Field Days

Apple Happy
By Paul Bransky

This article was first printed in the November - December 2003 issue of the Organic Broadcaster, published by the Midwest Organic and Sustainable Education Service.

Since the mid-1970s, Perry-O and David Sliwa of Decorah, Iowa and Keith Kozub of River Falls, Wisconsin have searched for organic ways to protect their apples from pests. The three fruit growers shared some of their hard-won knowledge at a field day last summer on the Sliwa farm, including successful strategies to prevent apple maggot and plum curculio damage, and creative approaches to orchard design.

For market the Sliwas grow apples, pears, plums, berries, grapes, vegetables, cut flowers and honey on a forty-acre homestead next to the Upper Iowa River. Most of our visit took place in their two-acre north orchard, enclosed by deer fence, where the Sliwas and friends were experimenting with a variety of crops and ground covers. One of the primary objectives of the field day was to highlight the interplanting of a young orchard with market crops and habitat for beneficials to fully utilize the site and provide income during the years of orchard establishment. This project was supported by a SARE (Sustainable Agriculture Research and Education) grant. We saw strawberries, cole crops, and flowering perennials thriving in mulch beside the trees, and grape vines growing on the fence. These plants had plenty of sun because the Sliwas planted their orchard on twenty-foot spacing. The open pattern provides extra air drainage and light to reduce fungal problems.

The Sliwas try to grow enough flowers near their fruit trees to provide habitat for beneficial predatory insects as well as pollen for their honey bees. David said that flowers around the perimeter would not help the orchard because beneficials stay very close to their chosen plants. Besides market flowers and strawberries, the Sliwas have tried buckwheat and white dutch clover. "White dutch clover is a high quality nectar source," David said. He felt that buckwheat grew too tall for good air movement, and he would probably not use it again.

They roto-till right around the trees to prepare for their other crops. "We try to avoid tilling too close to the trees, but we are not too concerned if any surface roots are damaged because it would likely make a deeper anchored tree," David said.

"Surround" the apples
To avoid too much damage from insect pests, the Sliwas spray "Surround," a specially milled kaolin clay, on the fruit and set out traps. Surround has especially helped with discouraging plum curculios, David said, because there is no easy way to trap them. "Researchers have only recently developed a plum curculio attractant," he said, though they have trapped apple maggot adults and codling moths for many years. Until they began spraying Surround two years ago, the Sliwas could choose to go out every day for three or four weeks to tap trees and catch curculios which fall onto a bed sheet. Now they spray Surround when needed. "I watch the apples," David said, "and won't spray if I feel there is enough coating, or don't see much damage." After it dries on the fruit, Surround acts as a barrier to an insect's normal behavior. "When the plum curculio crawls on an apple, apparently the clay particles are attracted to it like a magnet attracts iron filings, so the insects are repelled," David said. He said that Surround's specially formulated shape and size cause this effect, whereas regular kaolin clogs sprayers, does not adhere to foliage, and does not discourage the insects. Apple maggots and the first flight of codling moths were also suppressed by Surround.

David begins spraying around the start of fruit set, when plum curculio egg-laying begins. "You need to keep monitoring with traps and just keep walking through the orchard," he said. He tries to minimize spraying to save work, cut expenses (the spray mixture requires a lot of material; 1/2 pound per gallon), and to mitigate any potential damaging effects Surround may have to beneficials. Surround can last on an apple for more than three weeks. "If you stop your spray right after the early season, you'll have minimal cleaning of residue at harvest time."

David put together a simple sprayer using a 55-gallon barrel on a trailer, a 60 psi 12 volt pump, a 50-foot hose and a sprayer wand. Hand spraying with a wand controls expense because he can aim just for the fruit. "When you see a white drip (on the bottom of the apple) it's done," he said. The Surround mixes in easily by hand using a long wooden paddle.

David mentioned that Surround also helps keep plant temperatures cool resulting in continued photosynthesis on hot days. Sunburn damage on coated fruit is also reduced. He said some conventional orchards in Washington State use Surround just for this purpose.

Insect traps
Although they are pleased with the effectiveness of Surround, the Sliwas would rather trap than spray, if possible. They have experimented with a variety of trap designs and attractants. At the field day they displayed free-standing "kill" and pyramid traps, and branch-mounted funnel traps. David cited research at Michigan State University which found trap effectiveness improved 1 1/2 times with a sex pheromone and doubled with a kairomone (plant scent). The Sliwas place traps beside a nearby woods (where insects overwinter), at the orchard perimeter, and in the orchard. David said that each plum curculio female lays an average of about 200 eggs in its lifetime, "so I feel every one caught is valuable in reducing damage immediately, and reducing future populations."

On his four-acre organic orchard near River Falls, Keith Kozub has pursued the apple maggot for fifteen years, having lost a lot of apples from the brown inside tracks they make. "They can become a major problem," he said. He tried pyrethrins, but found it hard on beneficials. "My orchard got way out of balance, so I switched to a different way," he said. He now uses tangle foot traps to monitor the populations and provide some control.

Keith has found that a commercial apple painted with tangletrap makes an excellent trap for apple maggots. He buys the apples by the case and pierces each one with 17 gauge wire, curved to hang on a branch. He recommended using "paintable" tangletrap and disposable dairyman's gloves for the application. Using real apples rather than plastic red balls, Keith does not have to buy apple scent. However, because of the petroleum-based tanglefoot coating, unpeeled apples require landfill disposable. Ketih also likes how their density keeps real apples in the tree during a storm. "In a storm the plastic balls blow off, or into leaves, and leaves get stuck on them," he said.

"One trap on a big standard tree is enough,"he said. "You kind of get an idea where hot spots are. Maybe they are arriving through a very narrow area. I might put three or four on the corner when they come in from strawberry patch." He has also found much more insects trapped on the south side of his orchard than the north. "I rarely hang traps on the Connell Reds" he said. "I think apple maggot and plum curculio don't like waxy skin. Soft skin is I think more attractive."

Keith prefers to hang the traps on the south or southwest side of a tree approximately head high. "Put it out where a fly can see it-you want it to stick out," he said. "If you have a lot of apples, I sometimes hang all around the perimeter of a tree."

After a week Keith scrapes off and counts the apple maggots. "A couple is not much concern to me; four or more is. Ten or fifteen is enough to cause major damage," he said. He once caught 98 on one trap, but said it is rare for him to catch more than eight.

Orchard maintenance
Keith emphasized the importance of through orchard maintenance. "Generally I think most apple maggots come from right nearby," he said, from apples left to lay under untended trees. The larvae crawl out of apples and into the ground to overwinter as pupae. Most adults emerge the following year over a several week period, depending on the weather. Some pupae overwinter a second winter. "That adds to its unpredictability," Keith said. "Keep apples off the ground and pick wormy apples," he said. "Every five days you have to police the windfalls." In his 150 + trees he can keep up with windfalls by gathering them for a couple hours twice a week.

Keith grinds the windfalls and mixes them with other materials to compost in a stock tank. "Plum curculio and apple maggot can't handle the heat of apples in a stock tank," he said. For growers who do not have a grinder, he recommended "put the apples in a garbage bag and let the sun cook them. Or leave them in a bucket for a few days."

After planting trees Keith uses hay mulch around them for two years, then lets the sod take over. Over the years he has just mowed and left the clippings there to build top soil. He wondered if this system made too much nitrogen; he had two feet of new shoot growth last year with some fire blight. He mows to inhibit meadow voles. "You don't want to leave them habitat in the fall." he said. " I lost 100 trees one year from meadow voles." Late in the season he also sprays humates on the fallen leaves to encourage decay.

Paul Bransky is a Wisconsin organic vegetable grower, and the former editor of the Organic Broadcaster.