Sexy weapon thwarts bugs: Codling moths find frustration at end of pheromone trail
by Lisa JonesThe war between Washington state's apple growers and their primary pest, the codling moth, has raged for nearly a century. The larval moth's passion for burrowing into the flesh of the fruit has brought the apple industry to its knees more than once. Orchardists have fought back with a battery of deadly weapons, ranging from lead arsenate - which was held responsible for the deaths of horses that worked in the orchards early this century - to DDT, best known for driving the bald eagle to the brink of extinction.
Then, in 1991, scientists unveiled a much more sophisticated weapon: sex.
In an increasing number of Washington apple orchards, growers are flooding their land with synthetic pheromones. These impostors mimic the female moth's natural pheromones, which act as a trail the males use to locate them. The synthetic pheromones confuse the males. They can't find a mate and die childless. The result: Codling moth larvae don't nibble into the billion-dollar earnings of Washington's premier crop. Pheromones have virtually no environmental impacts. By the turn of the century, they could be used on half of the state's apple orchards. This would reduce the use of Guthion by about 260,000 pounds per year; this potent neurotoxin has been the favored pesticide used against the codling moth since the 1960s.
Why is the apple industry pursuing this? First, the codling moth is starting to build immunity to Guthion. Second, the federal government is cutting down on the pool of insecticides that farmers can use. "We're seeing the beginning of the end of an era of the use of broad-spectrum insecticides," says Jay Brunner, a Washington State University entomologist researching pheromonal control of codling moths, as well as "soft program" controls for other pests. "It's the only alternative we have. The pesticides we're using will be gone to regulation or resistance."
Observers consider "soft-path" pest control a perfect example of what land-grant researchers should be doing: helping growers stay in business, and reducing the environmental impacts of farming.
The development of new pesticides is hampered by the time and money it takes to develop and register them with the Environmental Protection Agency. While pesticide companies invest in new chemicals for "major" crops like wheat, "minor" crops like apples may not be worth the effort. Although Washington's 3,500 apple growers produce up to a billion dollars a year, apples only generate about one-tenth of what wheat does nationwide. And 1988 amendments to the national pesticide law have mandated that all pesticides currently in use be re-registered. That can cost millions of dollars per pesticide with no guarantee the substance will pass muster, either environmentally or in terms of its effects on human health. Re-registration has taken a heavy toll. In 1988 there were 45,000 commercially available pesticides; now there are 19,000.
There are other, less quantifiable reasons for the fruit industry's eagerness to change. In February 1989, public concern skyrocketed over Alar, which preserved firmness as well as enhancing the color of Red Delicious apples. Alar's allegedly carcinogenic qualities made headlines and were mulled over on talk shows. The state apple commission was flooded with phone calls from panic-stricken consumers, asking such questions as, "Is it safe to pour apple juice down the drain?"
The apple industry went ballistic.
"Hundreds of growers were coming from eastern Washington to learn about organic growing," says Miles McEvoy, the organic program manager for the Washington State Department of Agriculture. "From their perspective, they were all going to have to become organic growers." There were 11 organic apple growers in Washington in 1988. By 1990 there were about 100.
They flooded the organic market, and as a result less than half of Washington's organically raised apples in 1990 were sold at the premium price commanded by organic fruit. Growers flowed out of organic farming as fast as they had flowed in, and it was not until last year that all of the organic apples raised in Washington were sold as organic.
The Alar scare left apple growers painfully aware of the mercurial nature of public opinion. "The public thinks we're out here taking advantage of workers, raping the land," says Rick Kamphaus, an orchard manager near Chelan, Washington. "They said, "You guys are bad guys." And by God, we're not bad guys."
Many growers are taking on the challenge of using "soft program" pest control. Pheromones were used to control the codling moth on 1,500 acres of orchard in 1991. Now they are used on 20,000 acres - about one-ninth of the state's total apple acreage. Ray Fuller, who uses pheromones to control codling moths in his organic orchard outside Chelan, says, "Mating disruption has made me a better horticulturist."
But pheromones don't appeal only to organic farmers.
"I don't like spraying, and I wish the people I had working with me didn't have to work with spray," says Doyle Fleming, who grows 180 acres of non-organic fruit and eight acres of organic on his Orondo orchard. "You just keep on pushing, trying to gain as much knowledge as you can to hopefully eliminate as much as possible."
Still, many growers aren't ready to jump into an exclusively "soft-path" regime because the new technologies aren't fine-tuned yet. For instance, synthetic pheromones mimic the scent emitted by the female codling moth to guide her mate to her. When there are relatively few codling moths, the pheromones flood the orchard, confuse the male moth, and disrupt mating. But when the orchard is packed with the insects, the pheromone isn't as effective because the moths can meet and mate randomly. Soft path controls are also expensive: While prices are expected to drop when pheromone use expands, it currently costs three times as much as Guthion.
"Farming is a business," says Kamphaus. He uses pheromone traps to monitor the codling moth population in his orchard, but controls outbreaks with Guthion. This year's apple crop is Washington's biggest in history, and growers fear prices will be flat. "With the prices we're going to get for fruit this year we're really going to have to cut costs. It sounds like pheromones work real well, but the expense exceeds the expense of Guthion." Kamphaus knows a lot about profit margins. He put 200 acres under an organic regime following the Alar scare. The orchard lost $250,000 that year, an experience Kamphaus sums up as "the shits."
Yet Kamphaus says he's on a soft path. He applies Guthion at half the registered dose to preserve the predator insects. Toward the same end he uses Dipel, a bacterial insecticide, against leafroller. "It's organic and expensive, and I use it to target one bug," he says. "I want to keep the good bugs in the field. But if I could get a synthetic chemical that'd be as specific and cheaper, I'd use it."
It is precisely the fact that soft path pest control leaves the predatory bugs in the field that makes it a good economic bet for the farmer, points out Andy Kahn, an entomologist and consultant based in Wenatchee. Predators spared by "soft path" methods will kill pests like aphids and leafminers, which destroy the leaves of the apple trees, making them less productive.
"On one hand we may be spending more to control codling moth and leafroller, but we potentially will be spending less on controlling aphids and leafminer," says Kahn.
Whatever the cost of the materials, there is unanimous agreement on the fact that soft path pest control is much more management-intensive than its traditional counterpart. "If you put on a broad-spectrum insecticide you can get into a little bit of trouble, but not a lot," says Larry Gut, a post-doctoral entomologist at WSU. "If you use the pheromone and do it just maybe slightly less effectively - if you don't put it on right, if you don't monitor correctly, if you don't correct it - you're in a lot of trouble."
The slack in pest-management information is being filled in part by private consultants, who are signing on with growers who are willing to do the careful monitoring demanded by the soft pest control.
"There's a lot more going on on an acre of land, and a lot more opportunity for things to screw up," says Kahn, who has worked in the Wenatchee Valley for four years. "One reason I've been welcomed here by people who might otherwise consider me competition is that everything in the business has gotten more complicated."
Indeed, the other historical pest-management advisors - fieldmen from chemical companies and fruit packing houses - are often busy with changes in other areas of orchard management: Growers are planting "high density" orchards, where closely planted trees barely larger than saplings bear fruit. Irrigation and fertilization systems are becoming more complicated.
Even though some growers are hesitant about soft path pest control, the fruit industry as a whole has accepted the need for it. The Washington Tree Fruit Research Commission, which raises money from growers for fruit research, will cover the losses suffered by growers who participate in an on-farm soft path research project next year. The project will compare conventional pest management with a regimen that uses pheromones, bacteria and pathogens against pests. At each of six sites, 10 acres will be treated with soft pesticides. It will be funded by the federal government as well as by the research commission.
The test growers haven't been picked yet, but Jay Brunner, the project's principal investigator, knows who he wants. "We're going after industry leaders, good adapters, good spokespersons for the industry," he says. "Down the road we'd like (growers) to be talking to their peers."
Meanwhile, a group of researchers from Washington State University and elsewhere is investigating whether consumers are willing to pay more for "sustainably raised" produce - a study which could go a long way toward making orchardists more willing to try new, more costly technologies like pheromonal control of codling moth.
"Sustainably raised" doesn't mean organic. It means that wherever practical the grower avoids chemical treatments, cuts down on water use and controls erosion.
"Mating disruption in apples costs about $100 more per acre than conventional pesticides," says David Granatstein, coordinator of Washington State's Center for Sustaining Agriculture and Natural Resources, one of the participants in the project. "So if we take that and translate it into cents per pound, it's maybe two cents a pound more to produce apples. That's not much. It shouldn't be a big deal. It's a heck of a lot less than the 30 to 40 percent premium for organic food. Are people willing to pay for that? Can they relate to that? Can the retail system relate to that? ... In marketing you don't have the luxury of explaining. It's black or white. So that's going to be a real challenge; what's going to be the hook?"
The group - called the Marketing and Production Alliance for Sustainable Agriculture - will start its four-year study in this year with funding from the Kellogg Foundation. Its participants come from industry and environmental groups in the Northwest, as well as Oregon State University. The group wants to avoid the certification approach, and instead use a "process-oriented" approach that would assign points for different practices, like water, soil practices and pesticide use, says Granatstein. "We felt if we could get 50 percent of the growers to go this way, we'd do a lot more environmental good than just have .5 percent of them going organic." n
For more information on WSU's Center for Sustaining Agriculture and Natural Resources and its programs, contact David Granatstein, Center for Sustaining Agriculture and Natural Resources, WSU, 1100 Western Ave. N., Wenatchee, WA 98801 (509/ 663-8181, ext. 222).
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