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Sustainable Agriculture

Integrating Sheep into Grain and Alfalfa Systems Knocks Back Pests

In Montana, two crop-damaging insects—the wheat stem sawfly and the alfalfa weevil—have found comfortable winter refuge in wheat and alfalfa stubble. The insects raise huge problems for crop farmers, causing grain to tip over and alfalfa yields to fall. However, introducing managed grazing of sheep on crop residues after fall harvest disrupts the insects' lifestyles, Sustainable Agriculture Research and Education (SARE)-funded research has found.

Moreover, adding sheep brings multiple benefits to crop producers. By suppressing insects, sheep save farmers the costs of control measures like burning, tillage, and insecticides. Sheep also crimp weed populations, reducing costly tillage or herbicides during fallow management. Meanwhile, sheep feed on low-cost crop residues and do their work without compacting the soil.

Pat Hatfield, a Montana State University animal scientist, found through his SARE research that grazing sheep reduced overwintering wheat stem sawfly larvae by 67 percent compared with tillage (51 percent) and burning (48 percent).

In a related study, Hatfield and Sue Blodgett, MSU integrated pest management coordinator, found that sheep grazing alfalfa re-growth in winter and spring reduced overwintering alfalfa weevil populations by 70 percent without compromising the yield or nutritional value of ensuing alfalfa harvests.

There's more than enough sawfly-infested stubble in Montana's billion-dollar grain industry to go around, and integrating sheep into grain and alfalfa production systems could add an extra income source.

Hatfield says that sheep producers, encouraged by grazing research now being conducted on commercial-size plots with economic analysis, could work alone or in groups through partnership with grain or alfalfa producers to treat insect-infested fields.

He sees ruminant grazing of crop residues—in Montana and around the world—as an economical and sustainable method of producing protein like lamb, while allowing people to enter agriculture without a large outlay of capital. However, achieving the benefits will require patience.

"Historically," says Hatfield, "farmers have been able to see immediate results from technological advances like fertilizer, pesticides, and genetically altered plant varieties. Our program, although less costly, progresses more slowly, requiring long-term commitments—but we ultimately anticipate success."


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