Reduce Herbicide Resistance, Rootworm Risk With Rotation

Reduce Herbicide Resistance, Rootworm Risk With Rotation

Volunteer corn, weed resistance to herbicides and problems controlling corn rootworm can be handled with rotation.

Volunteer corn, weed resistance and corn rootworms are just a few topics that are top of mind for farmers right now, as they plan for the 2013 cropping season. There is no simple solution to these problems, but rotation is one common management practice that can certainly help.

Mark Grundmeier, product manager at Latham Hi-Tech Seeds at Alexander, Iowa offers the following observations and recommendations. 

RE-THINK ROOTWORM CONTROL: Management of corn rootworm has become an increasingly difficult challenge for more Iowa growers the last few years. Many growers are planting the same Bt-rootworm traits in the corn hybrids they choose in the same field for three or more years consecutively. If you plant continuous corn, don't plant hybrids that have the same corn rootworm trait year after year. You can rotate use of different traits; or rotate corn with soybeans to control rootworm.

* Herbicide-resistant weeds. Resistance to glyphosate-based herbicides (such as  Roundup and other glyphosate products) is due to using these herbicides as the only source of weed management. Weed resistance can be significantly slowed down or even averted altogether with careful planning of crop rotations and herbicide product selection and use. Bringing LibertyLink or conventional soybeans into your rotation can help. Likewise, when it comes time to plant corn, planting conventional hybrids or straight LibertyLink hybrids is also recommended instead of using glyphosate resistant hybrids and applying glyphosate herbicide continuously year-after-year. Choosing and using herbicides that have different modes of action is critical.

* Control volunteer corn. With careful crop planning and herbicide use, volunteer corn can be controlled in both corn and soybeans. Several herbicides (such as Select, Fusion, Poast Plus, etc.) will take care of volunteer corn in soybean fields, but persistence is the key as more than one application may be needed.

What about corn on corn? How can you control volunteer corn in those fields? Volunteer corn in continuous corn situations can be managed by understanding the herbicide tolerances of the traits involved. For example, most Monsanto-traited hybrids contain only the glyphosate-resistant trait for herbicide use. If you plant corn following one of those corn hybrids, choose a hybrid that incorporates the LibertyLink trait. If you plan to have many years of continuous corn in the same field, stay away from hybrids that contain both the LibertyLink and the glyphosate gene for herbicide resistance. Rotating to soybeans or alfalfa also can help break that cycle.

* Corn rootworm. Continued use of the same rootworm resistant (Bt) trait in corn hybrids, coupled with the lack of required refuge acres, has caused rootworm resistance to become an issue. Rotation is the key—either rotating corn with soybeans or if you must plant continuous corn, then rotate corn hybrids that have different corn rootworm traits. Rotate traits between Monsanto, Agrisure and Dow products.

Some farmers with continuous corn who are having serious problems controlling rootworms may need to rotate to other crops (like soybean or alfalfa) if rootworms cannot be managed by rotating traits. Additionally, the use of hybrids with more than one rootworm trait (such as SmartStax) may need to be used.

Remember, refuge acres must be planted, and Refuge-In-the-Bag (RIB) hybrids make compliance simple. "Follow the rules as outlined in "Respect the refuge" and that management practice will greatly increase our likelihood of keeping rootworm traits viable in corn hybrids for years to come," says Grundmeier.

TAGS: Soybean Weeds
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