ISSUE 11   July 19, 2007


DuPont has completed regulatory submissions for its Optimum GAT trait in corn to the U.S. Food & Drug Administration and the U.S. Department of Agriculture. The company also announced it is on track to complete its submission to the EPA later this year.

After completing U.S. regulatory submissions for the trait in soybeans in 2006, they are now meeting our regulatory milestones for the trait in corn. Dupont plans commercial introduction of the Optimum GAT trait in soybeans in 2009 and in corn in 2010.



Poast herbicide has received supplemental labeling for use in borage, buckwheat, dill, okra and certain root vegetables. All applicable directions, restrictions and precautions on the EPA-registered label are to be followed.

The preharvest interval (PHI) for borage and buckwheat is 23 days, the maximum rate per acre per application for both crops is 2.5 pts, the maximum rate per acre per season for both crops is 5 pints, and the livestock grazing and feeding for both crops is non applicable. Aerial application is permitted for all labeled crops.



Research from the University of Missouri shows that early emerging weeds compete with corn in its developmental stages for available nitrogen and usually win.

Grasses allowed to grow to 12 inches tall accumulated 16 to 50 pounds of N per acre. When additional N was applied to corn at sidedress before weeds were controlled as a replacement for lost N, the weeds accumulated an additional 10 to 16 pounds of N per acre.

N loss to uncontrolled weeds that are not controlled early adds up to a cost of 33 cents per pound, and 15 to 25 pounds of N used by grass instead of corn results in a loss of $5 to $8 per acre of N.

N loss to weeds lowers yields by 10 to 15 bushels of corn could cause an additional loss of $35 to $52.50 of net income for corn prices at $3.50/bu.



Milestone and ForeFront herbicides are registered for use to control broadleaf weeds in areas with established grasses.

When can post emergence applications of aminopyralid- containing products be applied to minimize injury to newly seeded perennial grass stands?

Do not apply until seeded grasses have an established secondary (adventitious) root system. A secondary root system is usually sufficiently developed by the time the grass seedling produces a second tiller. Depending on environmental conditions and grass species planted, a secondary root system usually develops by 45 to 60 days after planting. Over 20 species of warm- and cool-season grasses have been tested for tolerance to aminopyralid. Established grass stands have excellent tolerance at the maximum use rates.

What do we know about the effect of preplant and preemergence applications of aminopyralidcontaining products on grass seedings?

Do not apply aminopyralid-containing products at the same time as planting grass seed.

What about ryegrass and timing of applications of aminopyralid containing products?

Established ryegrass appears to be tolerant when applied at labeled rates. Ryegrass can be safely planted in the fall after a spring application.

What are symptoms of aminopyralid-containing products injury to established grasses?

Postemergence applications may cause stunting and "splaying" of leaves of a few susceptible grass species, such as brome, consistent with other materials in the same herbicide class or mode of action. The plants rapidly out-grow symptoms under good environmental growing conditions. Leaves of established smooth brome may appear slightly discolored (chlorotic or purple) after application. Injury is most pronounced with ForeFront R&P. With good environmental growing conditions, the plants rapidly out-grow the symptoms.

What are my rotational crop restrictions after using Milestone when coming out of CRP?

Grasses can be planted the fall after a spring treatment. Further research is being conducted to evaluate different intervals between application and planting.

12 months after application = Corn can be planted only after spring treatment.

2 YAR (years after treatment) = Canola

3 YAT = Alfalfa. A bioassay should be conducted but it is likely that alfalfa can be planted.

For other sensitive crops such as potatoes, lentils, soybeans, and peas, a soil bioassay should be conducted before planting (see label for directions). Depending on environmental conditions, 3 YAT may be adequate for most crops.

Richard Zollinger
NDSU Extension Weed Specialist

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