Pest Management
NORTH CENTRAL REGION
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| Researchers Dora Carmona and Doug Landis count ground beetles in a vegetative refuge strip planted to attract insect predators. Photo by Bob Neumann. |
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When a natural disturbance occurs -- from an event as large as a landslide to as small as a tree falling in a forest -- it can wreak havoc on the animal, plant and insect populations in that ecosystem.
Agricultural landscapes, disturbed regularly by tilling, planting, cultivating and harvesting, can throw the insect world into disarray. Often, such activities kill off beneficial insects that prey on crop pests. The beneficials usually do not rebound as quickly as pests adapted to agricultural disturbances.
"When farmers disturb the habitat of the crop field, it resets the succession of ecological processes, so a series of animal and plants invade, some of which are weeds and insect pests," says Doug Landis, a Michigan State University researcher who, along with colleagues Karen Renner and Paul Marino, received a SARE grant to study ways of attracting beneficial insects into agricultural landscapes. "Natural enemies have to wait for the pest populations to come back, so they are always one step behind.
"Where we're farming road to road without leaving any undisturbed habitat, it's harder for natural enemies to move back."
Landis, other Michigan State researchers and cooperating farmers are working to better understand just how intensive agriculture affects the insect world. By minimizing the disastrous impacts crop farming can have on beneficial insect populations, the researchers hope to identify ways for growers to reduce their use of synthetic pesticides.
More specifically, they are studying whether retaining or creating undisturbed areas on farms may harbor beneficial insects that will help keep pest populations in check.
In one study, Landis worked with farmers who have created filter strips along field edges to catch runoff. Promoted by the Natural Resources Conservation Service (NRCS), which will share the cost of installing the vegetative buffers, filter strips can improve water quality off farm. Landis theorized that the filter strips, with a mix of native vegetation undisturbed by the plow, would harbor beneficial insects.
Robert Burns, who raises corn, wheat and soybeans on 250 acres near Midland, Mich., installed filter strips of either legumes and grass or switchgrass in 1995 to minimize his farm's runoff into nearby Bluff Creek. Water flowing into the creek, after emptying into two Michigan rivers, eventually empties into Saginaw Bay and Lake Huron.
"In the spring, or any time you get high water, the runoff takes fertilizers and whatever else in it to the creek," Burns says. "This way, it has to go through this grassy-type alfalfa stand, and it filters the water. Before, you'd have a lot of muddy water and dirt. Now it's more clear."
Landis worked with Burns to test which of the farmer's two 100-feet-wide strips would shelter more beneficial insects. He looked in particular for ground beetles, which not only prey on insect pests, but ingest many types of weed seeds as well.
"Ground beetles are ubiquitous in all terrestrial ecosystems in North America and probably the world," he says. "In a very conventional farming system, you would still have ground beetles present, but there would be fewer species and probably a lower abundance because you're disturbing that habitat frequently."
Landis found the switchgrass -- a native, warm-season grass with tall, stiff stems -- contained 38 ground beetle species. By contrast, the alfalfa mixture turned up 29 ground beetle species and the adjacent soybean field just 25.
When he tested the beetles' proclivity to eat weed seeds, Landis found they destroyed 84 percent of foxtail, a pervasive weed, in one week alone in the switchgrass strips versus only 17 percent in the soybean field far away. Encouraged, Landis hopes to study how well the beetles migrate from the filter strips into the crop field.
"Farmers are already creating these habitats to catch runoff," he says. "For biological control, their potential has been largely unrealized."
Landis also studied whether refuge strips comprised of cover crops and perennial plants would similarly attract ground beetles. On several Michigan farms, he created 10-feet-wide strips of clover, grass and perennials, offering a mix he hoped would prove attractive habitat. The refuge strips were placed in plots opposite fields without the refuge vegetation to test which areas the beetles would prefer.
Refuge strips comprised of orchard grass, clovers and perennial flowering plants sheltered greater numbers of beetles than the control area. Adding red clover, frost-seeded into oats, increased beetle abundance in some periods.
"A lot of ground beetles overwinter in the strips," Landis said. "Refuge strips have a lot of dead plant material and they are insulated with snow. In the spring, the beetles move into the crop to seek food."
There, he found, the beetles removed more than 40 weed seeds per square foot per day.
On Burns' field, where they tested existing filter strips, the farmer has noticed fewer insects since he planted the strips. In fact, he stopped spraying insecticides in his field after planting the strips, saving him $6 to $10 per acre.
"You're going to have bugs, but the strips give the beneficials a good place to harbor because it's dense and you don't work it up, so it has a chance to build up," he says. "However we can get away from sprays and weed killers and figure out ways to make nature help us instead of work against us is a step in the right direction." -- Valerie Berton
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| Apple researchers found high rates of fungicide can kill some of the beneficial insects-such as this lady beetle larvae- that prey on fruit-damaging pests. Photo courtesy of Northeast Region SARE. |
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The Northeast Region is prime apple-growing territory. In 1995, the nation's most popular fruit brought about $222 million to the Northeast apple industry.
Apples are good to the region: The fruit often is grown on hilly land that might not otherwise be farmed, the apple industry provides steady jobs, and orchards contribute to a working farm landscape prized by tourists, especially in the autumn.
But apples are tough to grow without synthetic pesticides. Not native to North America, apples are beset by a rash of diseases and insects that can destroy or blight them, causing today's consumers to pass them up.
Apple scab, for instance, remains a serious disease for apple growers. In Vermont alone, it costs growers about $1 million a year in pesticides and other controls.
The devastating fungus was one impetus for a group of Northeast researchers from Vermont to Pennsylvania to collaborate in Northeast Region SARE's longest-running, most comprehensive project. Their goal: to identify more sustainable ways of growing apples.
Researchers hoped to develop a sustainable production system that focuses on apple varieties naturally resistant to some of the tree's most plaguing pests and diseases. They conducted detailed economic analyses to determine whether replacing expensive synthetic treatments with integrated pest management (IPM) strategies would benefit farmers' pocketbooks, while evaluating the impact of fewer chemicals on soil, water and wildlife around the orchard ecosystem.
The project -- first led by Lorraine Berkett, plant and soil scientist at the University of Vermont, then Terry Schettini, formerly of Rodale Institute -- planted, grew and evaluated more than 30 cultivars, or types, on 5,000 trees over the eight years of the project. Collaborators at Pennsylvania's Rodale Institute, Cornell University, Rutgers University, the University of Massachusetts and growers in four states all contributed to the research effort, the first effort of its kind on such a large scale.
"Our group was really the first to take a look at how scab-resistant cultivars fit into commercial enterprises," says David Rosenberger, associate professor of plant pathology at Cornell's Hudson Valley Laboratory.
Project results, in many ways, were encouraging.
The methods project participants used to assess cultivars with immunities to apple scab so impressed experts in the field that a national evaluation process based on their work is being established that includes 22 cultivars in 18 states.
Berkett and her colleagues found that fungicide usage can be reduced by 50 to 100 percent with scab-resistant cultivars. By using other IPM methods, a savings of $200 per acre in direct pesticide costs can be achieved. IPM involves a variety of insect and disease controls, such as encouraging the presence of beneficial insects or bacteria that prey on unwanted pests, scouting before spraying and weighing the value of using a pesticide against potential crop loss.
Apple producers have responded. Over the course of the project, more than 15 growers have established plantings of cultivars recommended by the research team. Many more commercial growers adopted IPM techniques; 75 percent of the apple acreage in Massachusetts alone now is managed under IPM.
Grower Jim Gallot of New Haven, Vt., planted several experimental varieties in his 30-acre West Meadows Orchard as part of the project. Gallot is confident the project will help lead to better cultivars because of the way the project has influenced the industry and other apple scientists.
"We've learned quite a bit from the research," Gallot says. "Instead of just asking, 'What can we do with Macintosh?' we're thinking about apple-growing in a new way. It's very important to keep pushing the limits and trying things."
Fungicide research revealed such important data as the minimum amount of fungicide farmers actually need. Synthetic fungicides can impact the orchard system environment in complex ways -- researchers found high rates killed some of the beneficial insects that preyed on apple mites.
"In dropping some fungicides, we learned things we didn't even suspect before, like some were having a negative effect on mite predators," Gallot says. "Fungicides aren't as benign on the insect and predatory ecology as we thought. They affect other things, too, in ways we never imagined."
The research spanned a range of climates and growing conditions from the mid-Atlantic to northern New England. Project participants also learned more about optimum apple marketing strategies, from retailing at roadside stands to wholesaling to large processors.
The breadth of the work aided in the completeness of the project, Berkett says.
"It's almost a new way of doing business, with people from many disciplines and different states working together," she says. "Within the region, we have different production systems, different climates and different cultivars."
One of the project's findings on a regional scale proved disappointing: Many of the scab-resistant varieties the researchers recommend face serious obstacles. Some cultivars attract other insect pests or diseases; others do not store well or may have trouble catching consumers' eyes in the marketplace.
Despite the potential negatives, most of the project findings have been well received by apple and IPM specialists throughout the region. New information quickly spread to state apple IPM programs.
In Massachusetts, data from the study was included in a project to develop IPM strategies for combatting sooty blotch and flyspeck, a serious disease in southern New England.
In New York, researchers discovered that fungicide applications could be delayed from two to three weeks and still control flyspeck.
And in Vermont, studies on the use of T. pyri, a predatory insect that can help control the damaging spider mite, continues.
Project participants produced a comprehensive reference, "The Management Guide for Low-Input Sustainable Apple Production," in 1990. They also developed a newsletter -- the only publication in the Northeast devoted to alternative apple production -- and a World Wide Web site called "The Virtual Orchard." -- Susan Harlow
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| Planting crimson clover and reducing tillage allows cotton grower Benny Johnston to reduce seasonal pesticide use from five applications to two. Photo by Gwen Roland. |
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For years, the desired standard for cotton farming has been a kind of tidiness bordering on sterility: nothing but clean-tilled ground between rows and along field edges before and after each crop.
With no extra vegetation, insect pests had no place to hide.
It went against deeply held beliefs, then, when entomologist Joe Lewis and horticulturist Sharad Phatak suggested in 1993 that cotton farmers may be better off using cover crops and vegetative refugia strips, thereby encouraging all kinds of insects to take up residence in and around their crops.
The two had a hard time convincing any of the south central Georgia growers they had worked with over the years to even experiment with their new system, but Benny Johnston finally told them he'd give it a shot.
The willingness of Johnston and his son, who raise about 900 acres of cotton near Tifton, about 60 miles north of the Florida line, to go along with Lewis and Phatak's ideas surprised both scientists.
"Benny Johnston's a real good, by-the-book kind of farmer," Lewis said. "I didn't think he'd be comfortable having any other vegetation growing in his fields when it came time to plant cotton."
But like a lot of other cotton growers, no matter how conventional, Johnston was looking for ways to reduce his use of chemical pesticides, for some very compelling reasons: The cost of inputs keeps rising while the market for chemically treated cotton shrinks.
As Lewis explains it, U.S. cotton production already has weathered three historic boom and bust cycles. The first major blow to the industry coincided with the collapse of the southern economy in the wake of the Civil War. The next plummet rode in on the hard-shell back of the boll weevil during the early 1920s followed by the hardscrabble days of the Depression.
The boom started with a chemical input-fueled bang after World War II. And it was during those hard-driving days that Johnston began farming. His yields increased initially, but so did his need for applications of increasingly expensive synthetic fertilizers, herbicides and pesticides. Then the chemical inputs grew less and less effective, and his yields began dropping despite increased applications.
Similar results already had begun to drive other cotton farmers out of production, and once again, in the 1970s and early '80s, the southern cotton industry fell on hard times.
Johnston stuck with cotton, but he was looking for a better way and was willing to believe Lewis and Phatak might have found it. After receiving a SARE producer grant in 1994, he lent a 20-acre plot to the cover crop and refugia strip experiment, using the grant to lease the conservation-tillage equipment he'd never needed before.
The plan was to attract and retain sufficient populations of the kind of insects that feed on and control cotton pests. The results have been more than encouraging.
Lewis, a research entomologist with the USDA's Agricultural Research Service, says it seems clear that the use of a leguminous cover crop -- crimson clover in Johnston's case -- along with conservation-tillage or no-till, leads to fewer crop-destroying pests. Johnston's conventional crop received five applications of pesticide per season during the trials, while the cover-cropped and refugia-stripped fields needed only two.
Lewis sees these results -- along with the virtual eradication of the boll weevil in North America -- as the genesis of the newest boom in American cotton production, a boom he's hoping will be much more sustainable than those preceding it.
"We licked the boll weevil in certain parts of the Cotton Belt with a tough eradication program in the 1980s," Lewis says. "And now we're finding we can encourage the kinds of beneficials, including ants and spiders, that help control all the other cotton pests."
As it turns out, fire ants and other Central American interlopers like the boll weevil appear to be desirable predators in a cotton field given the right circumstances. Lewis isn't certain whether they are encouraged by the choice of a cover crop -- crimson clover, in Johnson's case -- or the fact that their nests are left relatively undisturbed when clear-tilling is foregone.
Whatever the case, Benny Johnston appears to have proven that a sufficient population of fire ants, along with a mix of native spiders and a variety of other beneficials, can hold infestations of common cotton pests such as aphids, bollworms, armyworms, budworms and stinkbugs to manageable levels.
And that's making more than chemical-weary cotton farmers happy. Patagonia, a manufacturer of sport clothing, recently announced its intent to purchase only organic cotton. Other upscale manufacturers are expected to follow suit.
If the innovative practices begun on Benny Johnston's farm take hold across the Cotton Belt, these companies shouldn't have to look far for the product they want. And farmers may be able to pull in premium prices for their cotton.
As for Lewis and Phatak, further experiments are convincing them that cover crops alone may be the better approach to sustained yields and sustained beneficial bug populations.
"At first," Lewis says, "we thought you had to have a pretty high concentration of refugia strips worked into the crop to keep the insect density high enough to be effective, and that's going to limit the room you have for planting your crop. But now we're thinking you can achieve the same effect or better with the use of cover across the entire field. When it comes time to sow cotton, you keep the cover on and just drill narrow bands through it for planting."
Farmers benefit from reduced erosion, more organic residue after the cover matures and dies, less nutrient leaching, a natural weed suppressant and a great place to attract and grow the bugs that will eat unwanted pests.
Lewis says his attempts to change the way cotton farmers feel about insects and cover is driven by a belief that a truly balanced ecosystem -- which isn't possible under the "chemical umbrella" cotton farming's existed under for 40 years -- will provide long-lasting benefits for both growers and the environment. -- David Mudd
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| Winter wheat growers fighting jointed goatgrass weeds with soil bacteria could reduce tillage costs and herbicide use. USDA photo. |
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Western winter wheat growers have a deep desire to uproot an invasive, persistent weed called jointed goatgrass. They plow it under, burn it off, mow it down and change crop rotations.
Despite their best efforts, jointed goatgrass infests at least 5 million acres in wheat-growing areas from Washington to Texas and causes more than $145 million in losses each year. As farmers' frustrations grow, so does the jointed goatgrass, which has gained ground rapidly over the past 20 years.
"It is such a tremendously fast-spreading weed, it can take over a field and ruin the quality of your wheat crop," says Eddie Johnson, a small grain producer from Wilbur, Wash. "Some of the fields in the Palouse region have 20- to 30-percent goatgrass infestations."
In dryland production areas of the Pacific Northwest, where annual rainfall ranges from 8 to 24 inches, jointed goatgrass steals moisture from winter wheat, reducing yields dramatically. Just a few weeds per square foot can cut yields by 25 percent. Even losses of 50 percent are common.
At the grain elevator, wheat with jointed goatgrass seed can be downgraded from top-quality export wheat to feed grain at a loss of a dollar per bushel. "At 50 bushels per acre, it adds up quickly," says Johnson, who has battled jointed goatgrass in some of his own fields for more than five years.
To find better options, Johnson and other growers cheerfully have donated some of their weedy wheat to the innovative research of Ann Kennedy of USDA's Agricultural Research Service housed at Washington State University. A soil microbiologist, Kennedy works with bacteria that slow the growth of jointed goatgrass but leave wheat alone.
"We're taking bacteria from the soil, culturing them in the lab, applying them back on the field at higher rates and having a negative effect on weeds," she explains. The bacteria she uses, called pseudomonads, attack the roots of jointed goatgrass, inhibiting its growth, while leaving wheat unscathed.
What makes jointed goatgrass so tough to deal with is its close kinship to wheat. Both crop and grassy weed share a common set of chromosomes and similar germination and growth patterns. In the field, it's hard to tell the two apart before they mature.
No available herbicide can effectively take out jointed goatgrass without harming wheat. If farmers turn to intensive tillage to get rid of the weed, they increase erosion. If they shift to spring cropping, they limit their profits and diversification.
With the SARE grant, Kennedy tested six promising bacterial isolates, first in the greenhouse and then in the field. Compared with the dramatic effects of herbicides, her biological weed control appeared to just "nick" jointed goatgrass, she says. But some of the bacteria suppressed weed growth by 30 to 70 percent -- enough to give wheat a competitive advantage.
"The interesting thing is that you don't have to kill off a weed totally and you don't have to have a clean field to have a good crop," Kennedy says. "Any time that we can suppress jointed goatgrass growth by 40 percent or more, we generally see an increase in yields."
Kennedy's research showed wheat yield increases of up to 16 percent when weed growth was stunted by at least 40 percent. When bacteria were combined with less-than-lethal doses of herbicide, she says, the "double whammy" inhibited jointed goatgrass' growth even more.
For growers, managing jointed goatgrass with natural soil bacteria could help reduce costs, tillage and herbicide use. Using less herbicide could reduce the risk of groundwater contamination.
Using bacteria also could make conservation tillage a viable option. Applying the bacteria to fields is fairly simple and doesn't require sophisticated equipment, Kennedy says.
In the ground, the added soil bacteria survive just long enough to accomplish their weed control mission, dying off as temperatures rise.
Although bacteria must be reapplied to the soil each year, that protects the environment, Kennedy says. "Ecologically speaking, it's better not to make any permanent changes."
Another promising finding was that some bacteria reduced jointed goatgrass seed production, which could help curtail its rapid advance across the West. The joints of the annual weed shatter into seed spikelets that are carried by wind, equipment and animals. In loads of grain, the lighter-than-wheat weed seeds stay on top, where they can blow into new fields. Once established in soil, jointed goatgrass seeds can survive for years.
Within the next decade, Kennedy is hopeful that the soil will yield commercially available weed-fighting bacteria. However, she found that jointed goatgrass samples collected throughout the West varied in their responses to soil bacteria. More research will be needed to find a solution.
Another key will be educating producers to accept less than 100-percent weed control with biology and teaching them how to care for soil bacteria.
"When I work with growers, I tell them that agri-microbials like these are living organisms," Kennedy says. "You can't just leave them on the dashboard of the pickup and assume they are going to live."
Johnson thinks producers will be glad to learn more about a new ally against jointed goatgrass. "And, this is a natural, sustainable way of using our own soil." -- D'Lyn Ford
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