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Weed Supplement

Monday, February 1, 2010
filed under: Weeds

A weed is defined as a misplaced plant. Historically, sunflower producers have had to deal with many misplaced plants in their fields. That was especially true a decade or more ago, when there were only two or three herbicide choices. More choices exist today, and growers are using a combination of herbicides and rotations to control troublesome weeds.

Not too long ago, sunflower growers depended on tillage for a large portion of their weed control. Since then reduced tillage has become the norm, and the crop has moved further west into drier areas where tillage isn’t as feasible. Preplant burndown and postemerge herbicides for grasses and broadleaves have dramatically changed the sunflower weed control landscape.

In this special supplement to The Sunflower, we discuss some of the most troublesome weeds, herbicide choices, some issues related to the most common products, and grower strategies for controlling weeds in today’s environment.

For the farmer, weed control is — after hybrid selection — likely the most critical production sunflower decision he makes. The National Sunflower Association has placed a great deal of emphasis on new herbicide labels by partially financing the registration costs of most of the products available today. It would be great to have more herbicide choices. Unfortunately, the number of new herbicide introductions has been minimal during the past decade — and we’re not aware of anything in the near-term pipeline that might fit sunflower.

Attaining a sunflower herbicide label is often accidental. If a new herbicide introduction doesn’t kill wild sunflower, then there is an opportunity for a potential sunflower label. Chemical companies do not generate herbicides specifically for a smaller-acreage crop like sunflower, so this industry is dependent upon some luck that a product might fit.

Roundup Ready® is not a likely reality for sunflower. This is mainly due to the regulatory hurdles related to potential pollen outcrossing to wild sunflower, a native plant in North America.

The National Sunflower Association has been conducting an intense fall field survey since 2002. Volunteers go into fields and assess production issues that may be impacting yields. Weed identification is a key category. Interestingly, the list of most troublesome weeds still finds kochia as the most common species. Grasses are much less of a problem, due largely to excellent postemergent herbicides. But other challenges — like Canada thistle and palmer amaranth — face growers today.

What has changed is the intensity of the weed populations. No longer is it common to find a field literally covered with weeds. Now, weeds are usually found in field skips or open areas, or are randomly scattered in sections of the field. The ability to control weeds has had a significant impact on sunflower yield enhancement. — Larry Kleingartner

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