When I was a teenager, my dad and uncle bought a device for weed control in soybeans called a "weed wiper." It was basically a PVC pipe full of herbicide mounted to our loader tractor with rope wick applicators on one side. You filled the pipe, drove through the field, and the applicators would wipe the weeds above the canopy with herbicide to kill them.
This was in the early 1990s. They used the weed wiper for a few years (it was significantly better than walking beans), but then Roundup Ready soybeans hit the market, and they really didn't need to use it anymore. The wiper is probably still in a shed somewhere on our farm.
I thought of this older technology as I read a news release from the University of Missouri (MU) Extension detailing new technology researchers are evaluating to control weeds that have become resistant to herbicides. This new technology is called the "Weed Zapper."
The Weed Zapper has a copper boom that attaches to the loader of a tractor, similar to the weed wiper. The device is driven by the PTO of the tractor, and it shocks weeds with 15,000 volts of electricity from a 110,000-watt generator mounted on the back of the tractor.
Metal wheels are grounded, and booms adjust to different heights. Weed kill is generally the best at lower speeds and the implement is even more effective when used at seven-day intervals in late summer, according to UM Extension weed scientist Kevin Bradley.
The new technology was demonstrated at the 2021 MU Pest Management Field Day at the Bradford Research Center in Columbia earlier this summer.
MU graduate student Haylee Schreier has studied weed electrocution in row crops for the past two years under Bradley's direction. Schreier's data shows that by the end of the season, there is almost complete control of giant ragweed, common ragweed, marestail and waterhemp. It is slightly less effective on grasses.
The growth stage of soybeans and the degree of contact that the boom makes with the foliage influence soybean injury. Soybean yield loss is possible if the boom makes constant contact with the bean canopy at growth stages R3 or later.
Electrocution also affects the viability of surviving weed seeds. The largest effect has been seen in waterhemp, where about 65% of seeds become nonviable.
Bradley said electrocution is not a new technology to weed management, as sugar beet growers in the Dakotas have been using this method since the 1950s and 1960s.
The Weed Zapper model used in the MU research was designed by two brothers in Illinois with backgrounds in farming and engineering. A different pair of brothers purchased the technology and now manufactures the implement at a plant in Sedalia, Missouri.
Models cost between $42,000 and $72,000.
The technology is of special interest to Bradley because it might be the answer to Missouri's growing waterhemp problem. A prolific producer of seeds, waterhemp is the state's No. 1 weed problem and one of 14 weeds that are herbicide-resistant.
Russ Quinn can be reached at firstname.lastname@example.org
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