Weed fights back

Published 12:00 am Monday, February 14, 2011

VIDALIA — Concordia Parish farmers have another problem to worry about this year when planting their crops.

The LSU AgCenter has found three locations, including one in Tensas Parish, where there is a group of weeds with resistance to glyphosates, the primary herbicide used in the Round Up Ready System.

They were found in soybean and cotton fields, and are currently causing farmers in states such as Tennessee, Arkansas and Georgia some very serious problems, LSU AgCenter research coordinator Donnie Miller said.

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“They have survived multiple applications of the herbicide,” he said.

Miller said all three locations have been hit with the same weed, amaranth, a type of pig weed.

Miller said he and LSU AgCenter weed scientist Daniel Stephenson took the weed specimen from a research field in Tensas Parish and then put them in a pot to test.

“We grew them in pots and then collected the seeds from them,” he said. “We took those seeds and planted them to watch them grow and then sprayed with them the herbicide. They also showed resistance.”

Miller said weeds have to show the traits over two generations before they can be officially considered resistant to the chemicals.

“We have expected this over the past few years, but we have never been able to prove the heritability factor,” he said. “This has a major impact on farmers because the Round Up Ready system is used by the majority of farmers.”

Miller said glyphosate was a major improvement on other herbicides when it came out.

“When it came out it allowed farmers to get away from herbicides that has soil residual activity,” he said. “They did not cause any damage to the soil and the ground around it.”

Miller said any farmers experiencing problems with amaranth have a few options to help deal with these problems.

Tilling your crops can help get rid of the weeds, Miller said.

The main thing farmers can do is rotate the type of herbicide they are using so the weeds are being fought by more than one mode of action, Miller said.

“There are a number of glyphosates and they all have the same mode of action. Continuing to use them causes them to build up a resistance problem,” he said. “You have to find a herbicide that uses a different method to get rid of the plant.”

Miller said herbicides are generally placed in groups based on their mode of action, and their grouping is usually on their labels, making it easy for farmers to find another way to combat the weed.”

Applying fall-residual herbicides to your soil can also prevent the weeds from sprouting, Miller said.

If worse comes to worse, Miller said simply removing the weed by hand is always an option.

Miller said farmers need to remember if they come in contact with the weeds when using any equipment, remembering to keep the equipment clean can help prevent spreading the weeds to other crops.

“If you suspect you are going to have an issue, clean the equipment,” he said.

Early detection is the best way to make sure there are no problems with amaranth in area crops, Miller said.

“This is a problem that if do not do everything you can to mitigate the resistance, it can spread rapidly,” he said. “It is like cancer detection. If you catch it early, you have a better shot at winning the war.”