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May 31, 2002

Voles don't eat like a mouse in no-till fields, warns specialist

WEST LAFAYETTE, Ind. – Thunder, lightning, rain and flooding. Eastern Corn Belt farmers have seen and heard it all this spring. Now that the atmospheric fireworks are subsiding, producers could face a new threat that's quiet as a mouse – literally.

Large vole populations are possible in the weeks ahead, as farmers complete planting and those late-planted crops emerge, said Kenneth Eck, a Purdue University conservation program specialist.

Voles feed on seeds and young plants. The rodents can chew up crops anywhere but are a bigger problem in fields with rolling terrain and heavy vegetation. No-till acres are especially at risk, Eck said.

"Meadow voles look like small mice with shortened tails," Eck said. "They thrive in higher residue systems or buffer areas, along fence rows and filter strips, and wildlife areas where there's a lot of vegetation. In those undisturbed areas they'll create colonies. A colony can feed on an area up to a quarter acre in size and cause a lot of damage to corn and soybean plants."

Voles prefer to hunt for food undetected by natural predators and man. They are attracted to no-till fields because of the built-in cover the crop residue provides, as well as the available vegetation. Untilled land also offers more suitable, undisturbed surfaces for burrowing and establishing colonies.

Although they are small, voles have enormous appetites. The rodents feed 24 hours a day, year-round. Voles dine both on seeds they've dug up and crops that are newly emerged, Eck said.

"Voles will cause the biggest problem with seeds that are in the ground – mainly corn and soybeans," he said. "As those seeds emerge, they'll eat away the succulent tips. They're looking for very fresh vegetation. They'll get on their hind legs and eat what they can reach. Once a plant gets 6-12 inches high the voles won't do much damage, because the plant tips are beyond their reach."

Most vole damage occurs within 28 days after corn and soybeans are planted, Eck said. Crop losses become costly to farmers when the vole population reaches five or more colonies per acre.

Farmers planting in no-till systems are advised to scout their fields for voles before putting seed in the ground. Should they find trails or other signs voles are present, producers should begin a control program.

Producers have three control options, Eck said. Two disrupt or divert vole feeding, while the third eradicates the rodents.

"The first thing they should consider is habitat modification, where you're trying to reduce the vegetation," Eck said.

"You can do that by mowing along the buffer areas, prescribed burning if you have warm season grasses and you can work along fence rows. Early preplant herbicide programs used 21-28 days before planting also help remove cover and succulent plants that voles eat. Voles need cover so they can go out and feed."

A second control method is providing another food source, commonly called alternative baits.

"What we're doing is giving them something to eat for the time being, until the crops gets past a stage where they can survive without significant damage from vole feeding," Eck said.

Cracked corn, soybeans, wheat and rye all are good alternative baits, he said.

Grain should be derived from a weed-free source. The bait can be spread over the soil during fertilizer applications. Vegetation should be dry during application to prevent the bait from sticking to plants. Recommended amounts per acre are four bushels for cracked corn and two bushels for soybeans, wheat and rye.

A final control option is zinc phosphide, a rodenticide.

Zinc phosphide pellets are applied in the crop rows with no-till corn. Voles eat the pellets, ingest the chemical and die. Application rates are 4-6 pounds per acre, depending on vole colony sizes. Zinc phosphide is not approved for use in soybeans, Eck said.

Soybean fields with large vole numbers may be better planted no-till by drilling than in conventional rows, Eck said.

"Drilling kills more voles by simply having additional knives in the ground," he said. "Drilling the soybeans also causes the rodents to eat on several plants at random locations instead of entire rows of plants in a row system, leaving critical gaps in plant canopy."

More information on voles and control methods are available in Eck's paper, "Rodent Control in No-Till." The paper can be downloaded online.

Writer: Steve Leer, (765) 494-8415, sleer@purdue.edu

Source: Kenneth Eck, (812) 482-1171, keck@purdue.edu

Ag Communications: (765) 494-2722; Beth Forbes, bforbes@aes.purdue.edu; http://www.agriculture.purdue.edu/AgComm/public/agnews/

Related Web site:
Purdue Soil and Water Quality Program Education and SWCD Support

Purdue News Service: (765) 494-2096; purduenews@purdue.edu


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