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WeedOUT Weeds

The 6-foot, 7-inch New York Yankee outfielder Aaron Judge is akin to Palmer amaranth in that both crush everything in their paths. Judge batters baseballs, while Palmer amaranth pummels herbicides. So far, Palmer amaranth has resisted eight herbicide sites of action in the United States. 

Like every baseball hitter, though, Palmer amaranth has a weakness. Its seed is thought to remain viable for just three to five years depending on soil moisture and climate, according to NRCS data. 

“A four- or five-year concerted effort can get rid of it,” says Mike Owen, a retired Iowa State University Extension weed specialist. 

Enter WeedOUT. Scientists for this Israeli firm hit Palmer amaranth where it starts – its pollen.

“We wanted to bring a biological solution to tackle the herbicide-resistance problem,” says Efrat Lidor Nili, cofounder and co-CEO of WeedOUT. “We use the reproduction system of the weed against itself.”

WeedOUT developed a process that uses innovative pollen produced by male Palmer amaranth plants that’s irradiated to successfully compete with natural pollen. WeedOUT pollen forms a nonviable seed when it fertilizes a female Palmer amaranth plant’s ovule. 

“Another point is that it’s resistant to resistance,” says Lidor Nili. “Because we are using a natural reproduction system, it will be almost impossible for the plant [Palmer amaranth] to develop resistance. This is because pollination is such a basic process in plant reproduction.”

How It Works

WeedOUT uses equipment that collects pollen from male Palmer plants in its facilities. 

“The pollen we use undergoes an irradiation step,” says Lidor Nili. “It allows the pollen to successfully fertilize the female plant’s ovule, but it also wounds the genetic material.” The resulting nonviable seeds cannot produce weeds the next year. 

“We compete against the natural pollen that is found in the field,” she adds. “The advantage we have is that we can apply the quantity we want with the timing we want with the right machinery.” 

The directed artificial pollination also helps create a massive pollination event that spurs Palmer amaranth to shift resources from plant growth to seed development. 

“Every seed that is formed following pollination by our pollen is aborted, “says Orly Noivirt-Brik, cofounder and co-CEO of WeedOUT.

Still, control isn’t complete. When all seed is included – including plants pollinated with natural pollen – total seed production is reduced by an average 50%. 

That’s why the company has positioned it as a tool that farmers can use in combination with other management tools, says Owen, who advises WeedOUT. “It fits nicely with herbicides and harvest weed seed control,” he says. 

“It is still under development, but results are very encouraging,” says Noivirt-Brik. “We aim to optimize it even further.” 

This is a head-turning technology compared with herbicide use, as it doesn’t kill the existing plant, says Owen. The technology targets those Palmer amaranth weeds that emerge later in the season and have escaped controls like herbicides.

“Plants grow at a slower rate, but will still be there in the field,” says Owen. “The impact of the technology will not be seen in the current year. It will take several years to eliminate the [Palmer amaranth] seed bank in a normal field.”


WeedOUT technology will require farmer investment. However, Owen points out that in some cases, herbicide application costs run $90 to $100 per acre annually to control Palmer in soybeans. 

“With some new chemical-based solutions, weeds are developing resistance in just a few years,” he adds.  

Pollen viability and production is another challenge. Noivirt-Brik says WeedOUT pollen now has 15-month activity, and work is being done to extend this. WeedOUT also plans to boost production of pollen needed for large-scale use.

The technology will follow a shorter regulatory path than herbicides have. The Environmental Protection Agency indicates it will classify the technology as a biological pesticide. Its estimated regulatory path is 18 months, compared with a multiyear regulatory path for herbicides. 

Pending regulatory approval, WeedOUT expects a 2023 U.S. commercial launch. 

The technology has attracted the interest of the agricultural investment community. Syngenta Ventures was its lead investor in the latest investment round. WeedOUT also won the 2019 Radicle Challenge Israel, a contest that recognizes problem-solving entrepreneurs in the agricultural and food industries. 

WeedOUT officials are in discussions with several agricultural chemical firms to implement their solution. 

“Their products are becoming less effective due to resistance,” says Lidor Nili. “If we block resistance, it enables [herbicide] products that are available today to continue in the market. We think it will work hand in hand with chemicals applied to genetically modified crops.”

WeedOUT Application

Photo credit: WeedOUT
Palmer amaranth does not simultaneously germinate. “It has lots of flushes at different times,” says Mike Owen, a retired Iowa State University weed scientist who serves on WeedOUT’s advisory board. Thus, properly timing pollen application to meet these flushes is required. 

“Currently, our estimation is that we will need three applications during the [growing] season,” says Orly Noivirt-Brik, WeedOUT cofounder and co-CEO. “We are developing an application tool that will mount on the booms of a sprayer and enable the farmer to use existing machinery to apply the pollen.” WeedOUT scientists are also evaluating a drone application to apply the manufactured pollen.

The amount of pollen applied to fields is low: an estimated 120 grams (4.233 ounces) per acre per season. This could lead to pollen application challenges on windy days.  

“Similar to any other application, the farmer will need to choose a time to apply the pollen when it’s less windy,” says Efrat Lidor Nili, WeedOUT cofounder and co-CEO. 

Still, off-target movement consequences are negligible compared with herbicides, says Lidor Nili.  

“Our Palmer pollen will not affect the crop in any way,” she says.

The WeedOUT technology is optimal for other dioecious weeds (those with both male and female plants) like waterhemp, say Lidor Nili and Noivirt-Brik. Use in self- and cross-pollinating weeds would be more challenging, although potential exists with the right pollen dose and timing, they add. 

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