pigweed in soybeans

Mid-South to adopt harvest weed seed control?

Australian resistant weed expert considers weed problems in the United States. Weed seed control soon to hit Mid-South?

Will Mid-South producers soon adopt widely used Australian techniques aimed to keep resistant weed seed out of fields? Steve Powles, a leading resistant weed specialist in the world, predicts that is exactly what will happen.

In his home country of Australia, “The big thing is harvest weed seed control,” says Powles, who is currently visiting the United States. “That incorporates a whole range of techniques to harvest weed seed at the time of grain harvest. The ultimate goal is to stop weed seed from entering the soil seed bank.”

The Mid-South equivalent is hand-weeding in Palmer pigweed, says Powles. “We can’t afford to do that, so we’ve developed machinery and the weed seed harvest techniques instead.

“We simply have to do it — there’s no choice for many producers. That isn’t yet the case in the United States. But you will soon watch your farmers adopt (weed seed harvest). There are U.S. researchers — including (University of Arkansas’) Jason Norsworthy — now looking at it.”

While not wanting to “pick on” anyone, Powles tells a story from a Mid-South field day he spoke at many years ago. “We were talking about Palmer pigweed, and I asked what they thought about harvest weed seed control. They said, ‘It won’t work.’ ‘Why is that?’ I asked. ‘Because it shatters before grain harvest.’ I thought, ‘What a pity.’

“Well, now work has been done that shows that perception is wrong. What do you think the percentage of Palmer pigweed seed is — present, intact on the plants — at the first opportunity for soybean harvest? It’s 99 percent! The perception was incorrect and Palmer pigweed seed is available for harvest for weed control.”

Harvest weed seed control will work in the United States, insists Powles. “Your farmers will adopt it. They won’t want to do it, but they’ll soon see the benefits of it.”

Most likely practice?

What is the most likely Australian practice Mid-South producers will adopt first?

“We do use a range. The simplest is, at the time of soybean harvest, all the straw and chaff is funneled into narrow windrows. Those windrows are then burned and the weed seeds are killed.

“Researchers here in the States have copied that system and found that it works.

“Another simple possibility is the use of carts that the chaff is funneled into. The (chaff) is sometimes used as feed for animals.

“The latest thing being used is the Harrington Seed Destructor. There are four or five of those machines coming into the United States for evaluation. (Norsworthy), who is very much on the ball, will be working with one in the Mid-South. It’ll be very interesting to see how effective they’ll be under U.S. conditions.”

What is Powles’ views on the dicamba- and 2,4-D-tolerant technologies?

“When used properly, the dicamba-tolerant crops and 2,4-D crops are another tool for farmers. The chemicals are well-known, so farmers know what they’re capable of if used improperly.

“Farmers had best use these technologies very carefully and not overuse them. They’re making use of 50-year-old chemicals that weeds have had a lot of time to get used to.”

The use of 2,4-D and dicamba sparks concerns about drift, says Powles. “There’s no doubt that Dow and Monsanto and BASF have dramatically improved their formulations to help with drift and volatilization. But farmers must carefully follow and respect the labels once the technologies are fully available. That will minimize the drift potential, which is still there. Unfortunately, 100 percent of farmers won’t respect the labels.

“Sadly, there’s not a lot of good news. New chemicals are very scarce; don’t hold your breath waiting for them. And the ones we have are seeing weeds develop resistance.”

Even so, says Powles, “farmers shouldn’t be scared of what’s happening. They should look and learn from their experience with glyphosate resistance and do whatever is necessary to keep what chemicals still work viable.

“Look at Liberty, a good herbicide. Well, we’re talking about Liberty-resistance if farmers use it the same way they did Roundup Ready crops.”

If farmers diversify, weed resistance is entirely manageable.

“They can do it! It just means not relying on one chemical, use some of the other techniques and mix it up. I always say if you’re getting great weed control with a herbicide, change it! Change it while it’s still working. It’s been the same message for 20 years.”

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