Crop Tech Corner

Community Weed Control Pays Off; Scientists Search for Flood-Tolerant Beans

Emily Unglesbee
By  Emily Unglesbee , DTN Staff Reporter
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Farmers in Clay County, Arkansas, are successfully implementing a zero-tolerance community policy toward herbicide-resistant weeds to slow the spread of Palmer amaranth. (DTN photo illustration by Nick Scalise)

ST. LOUIS (DTN) -- This bi-monthly column condenses the latest news in the field of crop technology, research and products.

TACKLING WEEDS TOGETHER

It takes a village to stop herbicide-resistant weeds. According to a Weed Science Society of America press release, community cooperation has helped some Arkansas farmers control aggressive herbicide-resistant populations of Palmer amaranth far better than relying on individual efforts. With help from extension specialists, farmers on the eastern side of Clay County, Arkansas, banded together a few years ago and implemented a group policy of zero tolerance for Palmer amaranth weed escapes. In addition to pre-emergence and post-emergence herbicide passes, they committed to aggressive hand weeding and spot spraying to root out resistant weeds from their fields, ditches, and roadsides.

The initial hard work paid off within a year, according to University of Arkansas weed scientist Jason Norsworthy. By the second year, hand-weeding escapes in a 50-acre cotton field required only five hours of extra work from the farmers, compared to 110 hours the first year. One farmer found that the presence of Palmer seeds in his field dropped by 65% in the first year and was undetectable by the second year.

"We haven't beaten pigweed, but our fields are much cleaner," Andy Vangilder, Clay County Extension chair, said in the press release. "You see far less pigweed in the eastern half of the county where we have a community-based approach than you do in the western half where resistance management remains an individual effort."

For more information on zero-tolerance community weed control programs and how to implement one in your region, see the WSSA news release here: http://bit.ly/….

BRINGING FLOOD-TOLERANT SOYBEANS TO THE SURFACE

Soybeans aren't good swimmers, but new research from the University of Missouri could make them a little more flood-tolerant. According to a United Soybean Board news release, researchers at the MU Fisher Delta Research Center have zeroed in on several varieties that tolerate wet soils and ponding better than most. The scientists combed through more than 19,000 global soybean specimens and mapped genes that appeared to favor flood tolerance. The most promising candidates are now undergoing testing.

So far, some of the flood-tolerant varieties have been able to yield three times as much as conventional beans under flooded test conditions. Resistance to the root-rotting disease Phytophthora has appeared in some of these new varieties, a nice bonus since the disease prefers the warm, wet conditions of flooded fields. Commercially available flood-tolerant soybean varieties are still at least a year away, as the researchers continue to push for higher yields, the release noted.

For more information on this research, see the USB news release here: http://bit.ly/….

WHEN AN HERBICIDE OVERHEATS

If temperatures above 90 degrees Fahrenheit get you down, then you have something in common with a certain class of herbicides -- HPPD-inhibitors. According to a university press release, a new study from Kansas State University weed physiologist Mithila Jugulam shows that high temperatures can make HPPD-inhibitor herbicides significantly less effective at controlling Palmer amaranth. Jugulam and her team sprayed 8- to 12-inch-tall Palmer amaranth plants with mesotrione under three different temperature scenarios: low (high of 77 degrees, low of 59 degrees), optimum (high of 90.5 degrees, low of 72.5 degrees), and elevated (high of 104 degrees, low of 86 degrees). Under the elevated temperatures, the Palmer plants survived the herbicide instead of dying, the scientists found.

Two factors appear to be hindering the overheated herbicides. First, the enzyme that HPPD-inhibitors block in order to kill a plant actually becomes more active under high heat, making it harder for the herbicides to effectively inhibit it. Second, the high heat speeds up Palmer amaranth's metabolism of the HPPD-inhibitors, allowing the weed to process and neutralize the herbicide before it can do its work. Essentially, in high heat, HPPD-inhibitors are forced to do a more difficult job faster, and will often fail.

The study helps explain why HPPD-inhibitors work better earlier in the growing season or during cooler morning hours, Jugulam said. It may also help growers distinguish true HPPD-inhibitor-resistance in Palmer plants from this more manageable environmental failure, noted KSU weed scientist Curtis Thompson.

For more information on the study, see the KSU news release here: http://bit.ly/…, and the study itself here: http://bit.ly/….

Emily Unglesbee can be reached at emily.unglesbee@dtn.com

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(PS/AG)

Emily Unglesbee