Horticulture
NORTH CENTRAL REGION
| | | | |
 |  |
| Eric Carlson placed sticky traps around the orchard's perimeter to help snare apple maggot flies without insecticides. Photo by Ken Schneider. |
 | |
Agricultural pests and diseases ranging from apple scab to maggot flies pose major problems for apple growers who want to reduce or eliminate pesticides.
For Eric Carlson, who is trying to cut back his use of synthetic chemicals to create a more sustainable orchard ecosystem, tackling those tough pests in his Wisconsin orchard with alternative means became his top priority.
"I want to grow apples as sustainably as possible," says Carlson, who also raises blueberries, raspberries and fresh-cut and everlasting flowers on his 10 cultivated acres. "I can usually get good quality fruit with just one or two sprays. With some growers one or two dozen sprays isn't unheard of." Many of those applications are tank mixes of two or more insecticides and fungicides, he adds.
With the help of a SARE producer grant, Carlson found that some of the popular organic fungus control practices didn't work on disease-prone varieties in his orchard. But his research has led him to integrated pest management (IPM) practices that provide acceptable control of insect damage with a minimum of spray.
Carlson tested scab remedies in a planting of Cortland apples he had managed organically for two years and under a reduced spray program for two years before that. Cortlands are very susceptible to scab, a fungal disease that plagues growers particularly in the Midwest and Northeast. The fungus leaves dark blotches or lesions on leaves and fruit, making them unfit for fresh market sales.
When Carlson applied elemental sulfur to the trees at regular intervals or after rain, he saw very little scab. But disease pressure was admittedly light because of dry conditions during the season of the study.
While sulfur applications are standard practice for many organic orchardists, they concern Carlson.
"Applying sulfur may be considered organic, but I don't think it's sustainable," he says. "Every time you spray, that's 6 pounds of sulfur per acre that ends up in the soil, lowers the pH and affects the soil microorganisms."
Hoping for an even gentler way to tame scab, Carlson also tested a treatment that has little or no effect on the soil. He sprayed dilute hydrogen peroxide to sterilize plant surfaces shortly after scab infection periods began. Unfortunately, those concentrations damaged the fruit and still did not completely control the scab -- even with low disease pressure.
With both disease control remedies proving either ineffective or unsustainable, Carlson decided to try varieties that are naturally resistant to the disease.
He planted 1,000 scab-resistant trees using varieties such as 'Priscilla,' 'Liberty' and 'Sweet 16' that he expects will produce good quality fruit with little or no fungicide in most years.
For those scab-prone varieties already in the orchard when he moved there in 1989, Carlson now uses carefully timed applications of synthetic fungicides. By tracking air temperature and leaf surface moisture, Carlson is able to predict when scab infections are likely to occur and reduce his sprays by at least 30 percent compared with conventional operations.
Carlson also found that placing sticky traps around the orchard's perimeter helps snare apple maggot flies, one of the most pernicious insect pests. He spaces the round red traps 15 feet apart. Females heading for Carlson's trees mistake the traps for apples, and after landing on them, permanently adhere to the surface.
"We don't get 100-percent control," observes Carlson, adding that his maggot damage is usually between 3 and 5 percent, compared to about 1 percent for most conventional operations. "But by using the traps to control maggots, there's no reason to use insecticides after June, while conventional operations will have to keep spraying all summer."
Reducing the number of sprays may encourage populations of beneficial insects that prey on pests.
Codling moths, however, still plague Carlson. As part of his study, he placed lures throughout the orchard that emit very small amounts of chemicals -- called pheromones -- that females use to attract males for mating. The lures confuse the males, making it difficult for them to find females, and result in fewer matings.
Carlson then charted growing degree days to carefully time a spray of ryania, a botanical insecticide, to hit the next generation of moths when they were most vulnerable.
But it didn't work. Carlson still registered 30- to 50-percent fruit damage.
"At $200 per acre for the pheromone lures, I just couldn't justify it," he says, speculating that part of the problem might have been female moths flocking to Carlson's trees from a nearby neglected orchard that has since been destroyed.
"But with all the wild apples growing around here, I might never be able to control migrating codling moths without some insecticide," he says.
For now, Carlson has settled for using one or two applications of Imidan, a relatively short-lived organo- phosphate insecticide that has curtailed his codling moths quite successfully. As with the ryania sprays he tried before, he times the applications based on when the pest is most vulnerable.
"Soon my new scab-resistant varieties will start producing," Carlson says. "I've managed them organically so far. I'll have to wait and see what kind of quality fruit I can get from them before I decide if I need to spray them."
As a part of the project, Carlson has held field days and developed posters and information packets to share his findings with other growers and the public.
A Bayfield County, Wis., agent who attended one of Carlson's field days praised the grower for working so diligently to identify more sustainable strategies to manage pests. Says John Markus: "We as an industry need to look at disease and insect resistant plants to decrease our reliance on chemical use."
Carlson hopes the work will pay off in more farmer acceptance of alternative strategies.
"The really good growers can take this information and use it to save considerable amounts of money," he says. "But they have to be willing to take the time to learn about the life cycles of the insects, and go out and walk around their orchards and see what's going on. They can't expect to just do it on the weekend."-- Craig Cramer
| | | | |
|  |
| While Western New York's climate is excellent for grape-growing, black rot and powdery mildew remain constant disease threats. USDA photo. |
| |
Grape grower James Mohart knew he had better things to spend money on than spraying his crop. Time and expense dictated a new system.
"The sprayer is one piece of equipment that costs me $300 every time I pull it out," he says. "I'd rather put that money in my pocket."
Trying to improve his bottom line, Mohart, a part-time Irving, N.Y., farmer, undertook a SARE-funded producer project to test whether a weather station in his vineyard, combined with a computer modeling program, could predict when the grapes are most susceptible to two major diseases. After three years, he found the $1,200 weather station and accompanying modeling saved him between $31 and $36 per acre a year in the cost of spraying fungicides.
Mohart grows 16 acres of grapes in a vineyard first planted by his father in 1971. The grape-growing region of western New York, which stretches from Niagara County south to Pennsylvania along Lake Erie, encompasses 30,000 acres. The lake moderates the climate, delaying bud break in the spring, protecting the buds from freezing and postponing the fall's first frost.
Most growers raise Concord grapes for juice; some of the largest U.S. grape juice processors, such as Welch's Growers' Cooperative and Mogen David Wine Co., have processing plants here.
While the region's climate is excellent for growing grapes, black rot and powdery mildew remain the two most devastating diseases of Concord grapes. Black rot can destroy an entire crop and powdery mildew can reduce sugar levels, rendering grapes fit only for vinegar.
Grape growers usually protect their vineyards from those diseases by applying fungicides at regular intervals throughout the season, usually spraying three or four times. Encouraging growers to use weather data and computer-generated predictions to cut down on the number of fungicide sprays, and to spray only during the critical post-bloom period would mean big financial savings for the farmers and much fewer pesticides being dumped into the environment.
It seemed like a winning situation to Tim Weigle, integrated pest management specialist for Cornell Cooperative Extension, who collaborated with Mohart on the project. Weigle reviewed research on pest biology and work he had done using computer models to predict disease infection periods.
With Mohart, Weigle wanted to monitor for climatic conditions most conducive to the disease spores of black rot and powdery mildew using a weather station. Then, he wanted to test spraying only when it would be most effective.
Ideal conditions for infection by powdery mildew spores, for example, exist when the temperature reaches 50 degrees F and one-tenth inch of rain falls. "By monitoring, you spray only when you need it," Weigle says.
The weather station in Mohart's vineyard registered such data as precipitation, temperature and leaf wetness. Plugging that information into a computer model told him when it was an ideal time to spray. "Instead of spraying every 14 days, the weather station tells you that you may be able to put it off for three or four days," Mohart says.
Concord grapes are susceptible to disease in the crucial weeks before verasion, or the point at which the sugar content of the grapes is about 5 percent and the berries change from green to purple. After that, the fruit becomes immune from the diseases.
"As soon as you hit verasion, you're home free," Mohart says. "If you can get away with just two sprays before that, you're golden."
The system still has some limitations. For instance, once the ideal weather conditions are reached, a grower has just 72 hours to get the fungicide on the grapes.
"I can spray my 16 acres in one day, but if you're a larger operation, you may not have the manpower to do it all," Mohart says. "But if it keeps raining or your equipment breaks down, you're in trouble."
Weigle is developing computer models that can use data from the weather stations to predict the best time to spray for harmful insects like grape berry moth and Eastern grape leafhopper, as well as diseases. He is putting together an extensive network of stations throughout the grape-growing regions so that not every grower would have to have a station in his or her vineyard. Instead, they could tap into relevant weather data through computers.
For now, Mohart says, the results of the project are encouraging some neighboring growers to purchase weather stations for their own vineyards. It illustrates what Weigle knows is the surest way for an innovative practice to catch on -- the success of a grower like Mohart.
Says Weigle: "We've found that if growers do it and go to the coffee shop and talk about it, it gets implemented much more quickly." -- Susan Harlow
| | | | |
|  |
| Planting a mix of rye and hairy vetch as a windbreak attracted beneficial ladybugs to Kenny Haines' Belvidere, N.C. farm. Photo by Andy Clark. |
| |
If you grow vegetables, as Kenny Haines does on 90 acres near Belvidere, N.C., aphids are your enemy. If you're an aphid, ladybugs are your enemy.
It stands to reason then, that Haines would want to do anything he could to get the two insects together, especially since he's determined to hold on to the organic certification he was granted in 1989. For organic producers, synthetic pesticides aren't an option.
Haines had heard about businesses, most located in California, that specialize in the rearing and delivery of beneficial insects like ladybugs, but he'd also heard the frequent complaint that applications of bugs were temporary solutions at best. The bugs tended to clean a crop of its pests, then fly away in search of more. The next time a pest invasion took place, more bugs had to be ordered, and the process would begin anew.
In 1994, Haines discovered another alternative, almost by accident, that, nonetheless, is helping advance the science of integrated pest management (IPM) in North Carolina. He planted rye and vetch as a cover crop and windbreak, but soon realized an unexpected benefit.
"The following spring, I had a cover crop with a few aphids but massive amounts of ladybugs," he recalls. He mowed most of the covers to plant his vegetable cash crop, then found the ladybugs had migrated to the vegetables to eat aphids.
The ladybugs nested in the windbreak, which Haines had not yet mowed. "I'm not an entomologist, but it seemed to me those ladybugs then started mating, and gestating, and before long there were even more ladybugs," Haines says. "They stayed there all through the winter, too."
And that made them available, in much larger numbers, for pest control in Haines' 1995 crops.
By then, Haines -- spurred by the excited urgings of entomologists from North Carolina State University -- had applied for and received a producer grant from SARE to expand his use of cover crops and windbreaks. He wanted to see what kinds of insects various grain and leguminous cover crops would attract. He also wanted to experiment with retaining strips of cover crop within his fields of broccoli, cabbage, squash and cucumbers.
Haines' interest in a cover crop seeding operation isn't proprietary. Eventually, he hopes his efforts will lead to the establishment of an operation that can supply seeds for cover crop mixes based on the types of beneficial insects a farmer wants, to help further sustainable agriculture in North Carolina and beyond.
"I'm still learning every day about this," he says. "But what I think I've learned is that so many of us, so many times, have blinders on. For years, the entomologists only looked at bugs, while the plant biologist only looked at the plants and the soil engineers only looked at the condition of the soil.
"This kind of project helps emphasize how all of it works together and how important balance is."
And that's something he said he hadn't thought of in quite the same terms before, even though he's farmed for more than 20 years.
"The sad fact is that you're not encouraged to by the so-called 'experts.' More often than not, you get Extension people telling you how things can't be done that way."
Haines said it takes "crazy people like me, who don't know any better," to shake things up every now and then to prove the experts wrong. And that's why he believes SARE grants are important. "
It gives people a chance to try out an idea. Then I can start telling people about what I've learned, and after a while someone from the university comes around and takes notice, and they say, 'Hey, this just may work.'"
That, Haines adds, is when things really start happening. He says he intends to continue his own on-farm experiments, showing his results to as many people as possible. His latest challenge is figuring out the attractive powers of flowering plants.
One of the cooperators in Haines' project is Michael Sligh, with the Rural Advancement Foundation. He believes the potential impact of Haines' work is "enormous." Sligh said that experimentation in California already had established a fair amount of data about what types of cover crops encourage beneficials, and how flowering and mowing patterns can encourage an influx of beneficials at just the right times to combat and control pests in that state's agricultural areas.
"What Kenny's doing is forming the seed of knowledge and experience necessary for making the same determinations about what will work for farmers in the coastal plains region," he says. "It's vital stuff. Once we learn it, it can lead to successful farming that doesn't use any chemical pesticides."
Sligh said he expects Haines to assemble a base of knowledge that experts can then augment. That base likely will better define the mixes of flowering, leguminous and grain crops that attract and retain beneficial bug populations sufficient to control pests not only on vegetables, but cotton, peanuts and other crops grown in the South.
"We've really just touched the tip of the iceberg with this kind of thing," adds Haines, who looks forward to the day when more integrated field work experimentation takes place between entomology and agriculture professionals. He hopes those professionals will view him as a resource.
Sligh says that attitude underscores for him the wisdom of SARE's decision to fund the project. "SARE is unique in the way it supports on-farm, farmer-led experimentation," he says. "Growers like Kenny Haines show how that can work to benefit all of us.
"If we had to wait for the official experts to look into these things," he adds, "we wouldn't know nearly what we know now." -- David Mudd
| | | | |
|  |
| Strip-till, which works a narrow band of soil in-between strips of residue, attracts beneficial insects. Photo by John Luna. |
| |
Oregon's normally lush Willamette Valley used to turn brown between fall's vegetable harvest and spring planting, a result of "clean" farming practices that left soil bare. Today, a drive through the agriculturally productive region in winter offers a much greener look.
Top