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Learning more about weed control in IP soybeans

When it comes to meeting the challenge of controlling weeds in identity preserved (IP) soybeans, the key piece of advice is having the right plan to deal with the specific weeds in each field. With the resurgence of IP soybeans in Ontario and Quebec, farmers may face the additional challenge of making those plans early to ensure they get the herbicides they want.

Although the IP sector is here to stay, the challenges of weed control continue to hamper growers, says Dr. Peter Sikkema.

In the wake of a June 2009 Statistics Canada estimate that calls for a record 2.4 million acres of soybean, reports surfaced about spot shortages of herbicide products.

Of the 2.4 million acres, 50 percent was not genetically modified (GM). By contrast, the 2008 acreage was 2.1 million acres, of which approximately 43 percent (900,000 acres) was non-GM. “For 2009, it was a very hectic market. It was a great year to launch a product because demand was strong,” says Regina Rieckenberg, sales and marketing manager for Valent Canada, referring to Valtera herbicide. “We sold out immediately and could have sold a lot more if we had it, and I think a lot of the other manufacturers were in the same position.”

Valtera, a new herbicide for Canada, can be used in both GM and IP soybean programs. For IP soybeans, Rieckenberg says it is used as an “add-on” in programs with other residual herbicides, providing control of small-seeded broadleaf weeds such as pigweed, lamb’s-quarters and eastern black nightshade.

“I don’t think it should be a concern, although I would say it is good for the grower to work with their retailer to help them understand what their product needs are going to be,” says Dave Kloppenburg, row crops project leader with DuPont Canada, commenting on the possibility of herbicide shortages.

The rise of the glyphosate-tolerant market, particularly in the United States, which dwarfs the Canadian IP market in
comparison, has led to speculation that the supply of conventional soybean herbicides will be short-changed. Kloppenburg, however, is noticing a different trend. “Our conventional soybean herbicides have had a real resurgence in both the United States and Canada, and the United States, is mostly a glyphosate-tolerant market. Conventional chemistry is being used in conjunction with glyphosate on GM soybeans on a pretty wide scale,” says Kloppenburg, noting that conventional herbicides are being added to control weeds that are not addressed by glyphosate or to provide alternative modes of action to delay glyphosate resistance.

Trevor Kraus, supervisor of research and commercial development in Eastern Canada for BASF, echoes Kloppenburg’s comments, saying his company responded to the surging Canadian IP market by acquiring more product than in previous years. “I think we were in pretty good shape for what transpired in the market. The whole industry has done a good job positioning itself in the global marketplace and global buyers really trust our IP system. I think we have a pretty vibrant market and I don’t see it disappearing,” says Kraus.

The weeds that rob yield, may actually set seed in the growing season before IP soybeans are planted.

Same message, different fields
If the IP soybean market is here to stay, then it would appear as though the difficulties of weed control will also be around for a long time. “You can use the exact same herbicide program two years in a row: one year you get exceptionally good results and the following year it can be quite disappointing,” says Dr. Peter Sikkema, professor of field crop weed management, University of Guelph, Ridgetown Campus, commenting on the inconsistency of controlling weeds in IP soybeans. “When I started, I wanted to develop simple rules of thumb that everyone can use. What I have learned is I’ll never get there.”

Sikkema stresses that weed management in an IP system will always be field specific, and producers should adjust their weed management program to each field. “I think it’s important that you start with a broad-spectrum soil-applied herbicide program and then be prepared to walk the field to address the weed escapes,” says Sikkema, noting that producers will also have to be wary of weeds resistant to Group 2 and Group 5 herbicides.

“Where people fall down on weed control is that they spray and they expect it to be perfect,” says Kloppenburg, echoing Sikkema’s recommendation. “If you have a plan, and you do have some weed escapes, then you’re ready, but it requires more management.”

Management strategies to consider
Based on several years of field experiments, Sikkema found that this option is more consistent than relying on a post-emergent program alone.

Trevor Kraus suggests growers can take the pressure off their soybean herbicide program by effectively controlling weeds in the previous crop. “Too many times I see a field that is in corn, maybe it’s a Roundup Ready corn, and they put on a timely glyphosate. But they have late-season weeds emerging that are setting seed, increasing the weed seed bank,” says Kraus.
“Those same fields, if they are getting rotated into IP soybeans, are going to have much bigger weed control challenges.”

In addition to knowing the weed spectrum and matching the products to address those weeds, Sikkema says growers should also realize that soil texture and soil pH will affect herbicide performance. For example, a product like Sencor can result in more injury on sandy soils and high pH soils. Another important consideration when choosing an IP soybean herbicide is crop rotation. Certain herbicides should not be used in IP soybeans, if producers plan to grow vegetable or sugar beet crops the following year.

Timing is also key; Sikkema says that it is critical to apply post-emerge herbicides when the weeds are small. Producers are also reminded to rotate their herbicides to reduce the risk of  resistant weeds. This ensures that the products available for IP soybean production remain effective and give growers one less challenge to contend with, in their weed control program.