Volunteer Corn Concerns
Soybean fields took on the look of a mixed crop this past summer as volunteer corn became a leading weed control issue.
Now Purdue University entomologist Christian Krupke is concerned that volunteer corn may also be causing problems by acting as a safe harbor for Western corn rootworm larvae. Krupke says that volunteer corn often doesn't express a full dose of the Bt insecticide. "Some larvae may be exposed to a sublethal source of Bt that didn't exist before. If this occurs on a wide scale, it could be a factor in helping rootworms build up resistance,” he says.
In field tests, Krupke and Purdue weed scientist Bill Johnson found that more than half of the volunteer plants expressed some amount of Bt and, of those, some had severe rootworm damage. The concern is that rootworms could build a tolerance that, if passed to offspring, could eventually allow these pests to survive a full dose of the insecticide in commercial corn hybrids.
Be mindful. Krupke points out that Bt corn expression rates can vary within a field, and the low dose of the toxins used to target rootworms makes this a more crucial issue than merely weeds and aesthetics.
New hybrids that contain multiple modes of action may help decrease the chances of resistance developing, Krupke adds. "However, this could be offset by increased weediness of volunteer corn,” he says.
The problem is compounded in continuous corn rotation. Weed specialist Johnson suggests farmers eliminate volunteer corn as soon as possible next growing season.
Familiar Herbicide Becomes Trait
Another weapon in the war against weeds is waiting in the wings. Dow AgroSciences has submitted a new herbicide-tolerant trait technology for USDA review.
If approved, the new trait would engineer crops to tolerate broadleaf phenoxy auxin products, such as 2,4-D and grass "fop” herbicides. Tom Wiltrout, Dow AgroSciences manager for global seeds, traits and oils, says the new traits will be stacked with other traits offering tolerance to glyphosate and glufosinate.
An increasing rate of glyphosate-resistant weeds makes the product well-timed, Wiltrout says. "Growers are familiar with 2,4-D and its performance. Despite its long history, few resistant weed populations have been identified,” he says.
The new trait will allow planting immediately after application. A stewardship and education campaign will ensure farmers observe best management practices.
Watch for the new traits to appear in corn in 2012 (with commercial availability in 2013), soybeans in 2013 and cotton in 2015.
New Oil Offering
Healthy new oils continue to come gushing toward the farm gate. The latest is Plenish, the brand name for Pioneer Hi-Bred's new high-oleic soybean oil trait.
Pending regulatory approval, varieties will be available in a limited introduction for 2010 planting. Developed through the Pioneer exclusive Accelerated Yield Technology system and launched in the Y Series product line, these soybean varieties will include resistance to soybean cyst nematode, phytophthora and sudden death syndrome.
Plenish high-oleic soybean oil will provide the high stability and performance of partially hydrogenated oil without the trans fat and with lower saturated fats. There are also many bio-based industrial applications for high-oleic soy oil.
- November 2009