BARC researchers wage battle against weeds
By LAURIE SAVAGE
BELTSVILLE, Md. (Nov. 14, 2017) — Researchers across the country are using a toolbox of control methods, mixing, matching and making strides in the war against weeds.
Local scientists hosted an Integrated Weed Management Field Day Thursday, Nov. 2, at the USDA’s Beltsville Agricultural Research Center.
According to a Penn State Extension handout, IWM is a “diversified approach to agricultural weed management that aims to more effectively target problem weeds by incorporating multiple strategies together.”
There is a need to diversify selection pressure through a multi-tactic approach using tools such as herbicides, crop rotation, cover crops and precision nutrient management, said Dr. Steven Mirsky, a researcher in BARC’s Sustainable Agricultural Systems Laboratory who headed up the event.
The event included demonstration of harvest weed seed control methods, including the Australian-born Harrington Weed Destructor.
Used in trials at BARC, the facility’s HSD is a pull-behind trailer, but the future of the piece is integrated into the combine, Mirsky said.
Trailers pulled behind combines may work in Australia’s large fields but not in some areas of the United States. Combines must be newer and more powerful to handle the integrated version. The HSD uses a conveyor belt to deliver the lighter chaff back to the field while capturing the weed seeds to prevent their return to the field.
“The combine is going to do a great job spreading weed seeds,” said Michael Flessner, Extension weed specialist at Virginia Tech. “We have the opportunity to take the combine and turn it into a seed predator.”
Seeds must be on the plant at harvest time for the technology to work, Flessner said. “The combine is not a vacuum.”
Mirsky said the HSD is being tested in wheat in Australia, but researchers here believe it will work well in soybeans. The technology does not work well in corn, they said.
Another cheaper method of harvest seed control is narrow windrow burning, which uses a chute to deliver the chaff into a more narrow row for burning. Producers may not have time to wait for optimal burning conditions if another crop will be planted behind the first, Flessner said.
Research is looking at how these tools perform individually, together and in rotation.
IWM has become more important in recent years because of an increase in herbicide-resistant weeds. Effective, affordable herbicides and crop genetics can no longer be used alone to combat weeds, particularly stubborn varieties.
Producers can tailor an IWM program for their own operations by mixing prevention, mechanical, chemical, cultural and biological approaches, according to the handout.
BARC researchers are working with a team across the United States. The focus of the area-wide effort is to bring together a large number of people to address the issue of weeds and resistance, Mirsky said.
He showed the workshop attendees BARC’s cover crop systems project, a long-term experiment located within the facility’s 7,000 acres.
At BARC, there are four conventional systems involving corn, soybeans, wheat and double-crop soybeans, as well as several organic systems. The long-term research projects are particularly focused on whether cover crops are efficient at controlling weeds.
“The easy answer is sometimes they do, sometimes they don’t,” said Dr. Bill Curran, professor in Penn State University’s Department of Plant Science who also spoke at the event.
The researchers are also looking at how older technology, such as a high residue cultivator, can fit into the weed control regimen. Curran said he believes this technology will make a comeback.
The BARC researchers made modifications to their planter, adding a tool bar on the tongue with coulters sandwiched with depth wheels.
A collection of cutting and trash wheels help with residue left from a cover crop planting. Trash wheels move some residue out of the way.
“For our growers in this area, cover crops are a no-brainer,” said Dr. Mark VanGessel, professor and Extension weed specialist, at the University of Delaware, due to the incentives farmers receive to plant. “We are in a unique area compared to the rest of the U.S.”
Terminating a cover crop improves weed management and serves as a physical barrier to summer weeds. Cover crops especially help control weeds with smaller seeds.
Mirsky said small-seeded summer annuals are controlled well with cover crops, which is why they are a good complement to a weed control system.
Grant money has allowed for more research at BARC on legumes, such as winter pea and crimson clover. Brassicas, such as turnips, are also growing in the facility’s test plots.
Seeding a fine fescue and then planting legumes into the fescue has worked well there, Mirsky said.
Brassicas are in the early stages of crop improvements, unlike other commodity crops such as corn, he said. Planted in mid-September, brassicas provide value in preventing marestail from becoming established.
“The above-ground material is not a major player. All the action is in the soil with the roots,” he said.
The researchers are also looking at these plants’ allelopathic properties, Mirsky said. Plants produce chemicals and continue to produce them when they die. Some of these chemicals are toxic to other plants, and this toxicity can be used in a weed suppression program. Small-seeded weeds, such as pigweed, are especially affected.
For more information on IWM, visit www.integratedweedmanagement.org.
Easton, MD 21601-8925