Research Triangle Park, North Carolina, USA
December 20, 2017
Fall and winter are the perfect times to evaluate weed management programs in corn. During harvest, the elevation of the cab provides a better vantage point to see between rows to areas growers couldn't scout earlier in the year. Dirt between the rows or remnants of dead weeds are telltale signs of how a herbicide program worked.
After harvest, growers can overlay those observations with yield monitor results to further hone next year's herbicide program. After all, uncontrolled weeds can have a staggering effect on corn yields. You can compound the loss when you factor in the fact that driver weeds, such as Palmer amaranth and waterhemp, can develop resistance to some herbicides.
Mark Waddington, selective corn herbicides product development manager for Bayer, explained that a long-term weed management program should focus on controlling the seed bank.
"Controlling the seed bank is a numbers game," said Waddington. "The fewer weed seeds, the less chance of emergence and competition, and the lower the risk of resistance development. A long-term weed management program manages the things that affect yield and, at the end of the day, production. It all comes down to how much competition exists in a field."
As the challenge of resistant weeds continues, many growers have begun to take a closer look at their weed control approach.
"Growers have always known weed control is critical. However, they are now realizing that some of their practices need to evolve to stay ahead of the weed threat," added Frank Rittemann, selective corn herbicides product manager for Bayer.
Rittemann and Waddington recommend that while planning for 2018 growers ask themselves six questions to determine the best weed control program for their operation.
1) What is the history of the field? Understand the current and past weed pressure in a field, including the specific weed species and resistance issues. It's also important to understand the herbicide history of the field.
2) What is the weed pressure in the region? Consider not just weed pressure in the surrounding fields, but also throughout the local geography.
3) What type of weather does the field typically experience? Mother Nature plays a significant role in herbicide program effectiveness. Waddington says that environmental factors, such as rain and temperature may affect how herbicides work.
4) How does the soil hold the herbicide? Heartier soils can absorb and hold on to a herbicide for longer periods of time, whereas sandy soils and lighter soils are at risk of having the herbicide flushed away with rain.
5) What is the economic approach on my operation? In planning a weed control program, growers should consider yield goals, the type of crop they plan to grow and the current market conditions, among other crop-management decisions.
6) How do weed escapes affect my season-long plan through harvest? Weed escapes compete with nutrients. If left in fields, they can chip away at crop potential.
Once growers have answered these six questions, Rittemann and Waddington recommend determining if a one-pass or two-pass approach works best for their operation, and then choose products that work with their selected approach. Recommended products include:
- Pre-emergence
- Corvus® herbicide, tankmixed with atrazine, for burndown, residual and reactivation. Corvus is the most reputable pre-emergence herbicide of the last decade amongst growers.
- Balance® Flexx works well on all soil types and offers a flexible application window and tankmix partners.
- Early post-emergence
- Capreno® features a wide application window and powerful post-emergence control of grass, broadleaf and resistant weeds.
- Mid-to-late post-emergence
- DiFlexx® DUO is tough on problem weeds, including glyphosate-resistant Palmer amaranth, waterhemp, ragweed and marestail. It also has built-in resistance management with two effective sites of action.
- Rittemann recommends partnering Capreno and DiFlexx DUO with a non-selective herbicide like Liberty®, the only working non-selective herbicide that is effective on tough-to-control grasses and broadleaf weeds.
Bayer is committed to bringing new technology and solutions for agriculture and non-agricultural uses. For questions concerning the availability and use of products, contact a local Bayer representative, or visit Crop Science, a division of Bayer, online at www.cropscience.bayer.us.
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