Weed resistance was a big issue for many soybean producers in 2012, says Matt Hubsch, Legend Senior Agronomist with Legend Seeds.
"I was shocked by the number and species of weeds I saw in grower’s soybean fields in last growing season that could not be controlled with glyphosate," Hubsch said.
What was even more concerning to Hubsch was the number of glyphosate resistant weeds which also had multiple resistances in their background.
"A good example of these would be kochia and waterhemp. Both of these species are known to have resistance to ALS (acetolactate synthase) or amino acid synthesis inhibitors, which really complicates the issue," he said.
Because producers can no longer control these weeds with multiple chemistries – such as glyphosate or ALS chemistries – their options are fairly limited, explains Hubsch.
One option Hubsch suggests growers consider is using a post-emergence Protoporphyrinogen oxidase or PPO inhibitor.
"A PPO can work post-emergence on these weed species if spraying is done in a timely manner. These chemistries do not translocate throughout the plant like glyphosate or ALS chemistries, so coverage is crucial," he said.
Pre-emergent herbicides are key
Treatment with herbicides like Flexstar® or Cobra®, have to be done early, post-emergence, when weeds are small. Since coverage is essential Hubsch recommends heavy amounts of spray volume (between15 and 20 gallons of water).
"The use of pre-plant/pre-emergence herbicides is going to be a primary "tool" in managing glyphosate resistant or tolerant kochia or waterhemp," Hubsch said.
Products like Authority® Assist, Authority® MTZ DF, Sonic®, Authority® First, Valor® will be key residual pre-plant/pre-emergence herbicides that will help reduce the potential financial losses that may ensue from glyphosate resistant weeds.
Be proactive
"We have been hearing some real horror stories from the southeastern soybean- producing states. Stories of farmers losing their farms due to glyphosate resistant weeds such as palmer amaranth; or incredible cost accrued from hand weeding of soybean fields," Hubsch said. "Being proactive with managing weeds that may be confirmed or are showing sign of glyphosate resistance in your fields is critical."
To avoid these issues, Hubsch encourages growers to use pre-plant/pre-emergence herbicides along with a tank mix partner post-emergence.
He recommends using herbicides pre like Authority® Assist, Sonic®, or Valor®, followed by tank mixes of Flexstar®, Flexstar® GT or Cobra® post-emergence.
"This will be a strong combative tool in the fight to reduce financial losses from glyphosate resistant weeds in soybeans," he said.
Whatever herbicide program growers use in their soybean acres in the summer of 2013, Hubsch says the message is clear – we have to change.

Using multiple modes of herbicides in soybean fields can be critical in reducing the potential economic losses from glyphosate resistant weeds.

To learn more contact your local Legend Seeds Sales Agronomist, 800-854-3346.