Hasta la Vista, Weeds

Technology - Hasta la Vista, Weeds

Matt Wilde
By  Matthew Wilde , Progressive Farmer Crops Editor
University of Missouri senior research associates Delbert Knerr (left) and Brian Dintelmann collect samples of weed seeds and crop residue crushed by the Seed Terminator. (Progressive Farmer image by Gregg Hillyer)

It was judgment day in the fall of 2019 for weed seeds on Paul Garrett's farm, near Columbia, Missouri. Most of the weed seeds were terminated.

The Seed Terminator, a weed seed destructor attached to a Case IH 8250 combine, was merciless on waterhemp that stood among soybeans being harvested as part of a research study by University of Missouri graduate student Travis Winans on nonchemical weed-control options. The terminator's dual hammer mills pulverized plants, which included weed seeds, after the threshing process.

Last spring and summer told more about escapees from this project designed to explore the efficacy of machines crushing seeds of some of the toughest-to-control weeds. Seed destruction has been a popular weed-control tactic in Australia but not widely used in the United States.

Unlike Arnold Schwarzenegger's character in "The Terminator," who is virtually indestructible, weed seeds are not. Test results indicate 98.7% of the waterhemp seeds that entered and got spit out the back of the combine in the 40-acre test plot were destroyed or damaged to the point they likely didn't germinate last spring.

"We found out as it warmed up [and weeds germinated] how good it really did," Garrett says. "I believe this product will work. I think in three years of use, you would likely notice a drastic reduction [in weed pressure]."

Initial results indicate the Seed Terminator could be an effective tool to combat herbicide-resistant weeds, explains Kevin Bradley, University of Missouri weed scientist.

The terminator was tested in the fall of 2019 on four waterhemp-infested fields, ranging from 40 to 60 acres, in central Missouri. Besides Garrett's Boone County farm, results are in from one other location in Montgomery County. The waterhemp seed damage rate was 98.6%. Seed destruction is also being evaluated for velvetleaf, morningglories and foxtails.

"If you get something that keeps nearly 99% of weed seeds that enter a combine from going back in the soil and consistently works well, it will be very useful," Bradley says.


More than 250 weed species have developed resistance to herbicides, according to the Weed Science Society of America (WSSA). Weeds slash yields by competing with row crops for water, nutrients and sunlight.

Waterhemp is among the toughest, having shown the ability to outwit seven herbicide sites of action. It is also a prolific seed producer. Although seed-destruction tactics appear to be very effective, Bradley notes that not every weed seed makes it into the combine. There's also the risk that overreliance on mechanical tools could eventually cause weeds to change behavior and become resistant to mechanical control.

It will take a combination of chemical and mechanical tools to reduce weed seed banks and make weed control more cost-effective and manageable again, Bradley says.

Another Australian-developed seed-destruction tool called the Integrated Harrington Seed Destructor (iHSD) is being tested at the University of Arkansas. Like the Seed Terminator, it is designed to pulverize weed seeds before they hit the ground.

Tom Barber, a University of Arkansas weed scientist, reports seed-destruction percentages with the iHSD to be similar to those found in Missouri tests on a variety of weeds, including Palmer amaranth.

"We're running out of weed-control tools, and our answers in the next few years won't come out of a jug," he says. "It will take a systems approach going forward."

In soybeans alone, WSSA estimates uncontrolled weeds could cut yields in half and cost U.S. farmers $16 billion a year. Farmers have seen weed-control costs grow dramatically in recent years as herbicide tools have become less effective.

Garrett went from spending $15 per acre to control weeds in soybeans when glyphosate was effective to more than $50 per acre, and he still has weed issues. "What we have isn't working," Garrett admits. "I see this as another alternative to control weeds (and cost) in the future."


Chaff is funneled into one or two fast-spinning, usually 2,500 revolutions per minute or more, hammer mills or rolling cage mills in weed seed destructors that are surrounded by up to three different sizes of removable screens. Plant material is degraded until it can fit through the screens and spread out the back of the combine. When that occurs, most weeds seeds are crushed or damaged to the point that they aren't viable.

Clogging has been a problem for the Seed Terminator and iHSD in the Missouri and Arkansas tests.

"The machines are mostly used in wheat to destroy ryegrass seed in Australia and in very dry conditions," Bradley says. "We're testing on pigweed species in soybeans in the Midwest and Mid-South, which is a whole different situation with the amount of green plant material and moisture."

Some reengineering to increase airflow, increasing mill speed and finding the right screen combination did the trick on the Seed Terminator, Bradley says. Still, more work is needed to make the machine work efficiently in high-moisture areas that don't always have the benefit of a drying, killing frost before harvest. "We'll continue to work on it," he adds.

Similar reengineering and changes helped lessen clogging issues in the Harrington, Barber states. But, more work is needed, including studying how the use of desiccants can help by promoting leaf drop and reducing material moving through the machine at harvest.


Nick Berry, co-founder and CEO of Seed Terminator, is optimistic sales will eventually take off in the U.S.

There are 200 Seed Terminators in action worldwide, according to the company. Three are currently operating in the U.S. -- two on farms and the University of Missouri's test unit.

"Herbicide resistance and the threat of herbicides being taken off the market is real (worldwide)," Berry says. "It was apparent to many Australian farmers they needed to use other measures to control weeds. My vision for the U.S. is no different," he continues. "To me, it makes no sense to let viable weed seeds leave the back of the combine."

The terminator unit is designed to fit on any combine and costs about $77,000 installed in the U.S., Berry explains. The price will fluctuate with the exchange rate.

Despite tough economic conditions for farmers, Berry is confident the terminator will eventually pay for itself in lower herbicide use and higher yields.

Bradley's 2019 research of the Seed Terminator shows an increase in combine engine load of approximately 15 to 30% when engaged. Fuel consumption can increase by as much as 4 to 8 gallons per hour. Combine speed was marginally affected, if at all.

Garrett, who farms 2,500 acres, would like to buy the University of Missouri terminator provided by the company when testing is done. His only issue with it is the noise. "It sounds like a high-pitched turbine."

He surmises saving $20 per acre on herbicides would pay for the implement in a few years.

"Even at 70 years old, I'm interested," Garrett says. "That's how positive I am this product will work.

- Emily Unglesbee, DTN Staff Reporter, contributed to this story.

> Follow Matthew Wilde on Twitter @progressivwilde.


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