Electric Weed Control Shows Promise
Start with a heaping helping of weeds in an orchard owned by an electrical engineer, then add in a weed scientist and a dash of Western IPM Center funding.
What you get is a promising (dare we say shocking?) new way to control weeds in certain landscapes.
It’s electric weed control, and New Mexico State University’s Paul Neher, the engineer, and Erik Lehnhoff, the weed scientist, are pioneering the technology.
“It uses a low dose of electricity over an extended period of time to kill weeds and unwanted small trees,” Lehnhoff explained. “It works extremely well.”
Test plots using the system are 100 percent weed free, and the pair have also shown it can prevent bindweed from climbing power poles.
The system is composed of wire mesh spread out over the area where weeds are unwanted. Experiments in 2020 showed that the best configuration for that mesh is between two layers of large gravel – the top layer to protect people or animals from coming into contact with the mesh, and the bottom to keep the system from shorting out due to moisture on the ground.
“We’ve been using two milliamps, which can be adjusted up or down, and running several hours at a time,” Lehnhoff said. “That’ll kill trees up to one inch in diameter and maintain weed-free areas in landscapes.”
The scientists are still studying how the low-dose current kills the plants.
“It’s a lot like when the first herbicides were developed and they didn’t know why they worked, they just knew they killed the plant,” Lehnhoff said. “We’re collecting leaf and tissue samples and our colleague Donovan Bailey in the Biology Department is conducting an analysis and doing all of the bioinformatics. He’s seeing all kinds of elevated stress responses compared to the control samples. It seems to be triggering many different defensive pathways within the plant.”
There are other things still to learn, too, and the work is ongoing. How low can the current be to be effective? What is the minimum amount of time the system must be cycled on? Does it have to be used year-round, or only during times weeds actively grow?
Lehnhoff sees potential for the technology in xeriscaped yards – designed to need little or no watering – and other desert landscapes seen throughout the Southwest and Southern California.
The costs have been calculated, and they’re low. The electric components are just about $100 plus the wire mesh, and operating the system would cost less than a dollar or two a month. A solar panel can also provide the electricity, making the weeding cost effectively free.
There are safety issues, but the researchers don’t think they’re insurmountable.
“Anything above 10 milliamps could be lethal to humans, and we’re staying well below that,” Lehnhoff said. “We’ve all touched it a few times and you notice, but it’s definitely less than an electric fence. More a tingle than a shock.”
The team have built safety features into the control panel to prevent accidental shocks, and think proper site selection and use addresses the other potential danger, which is fire.
“This isn’t something you’d use in rangeland, for instance,” Lehnhoff said. “With dry grass, it could spark a fire. But I think used in a yard to prevent weeds from growing, there’s not that danger.”
With the clean demonstration plots and from this year’s experiments and usability refinements to the system, Lehnhoff and Neher are hoping to see electric weed control go from the experimental stage into real-world use.
“We think there’s potential for this system anywhere in the Southwest where there’s gravel landscaping and a few sizeable plants,” Lehnhoff said. “It’s a replacement for weed cloth, which doesn’t work for long, and an alternative to using herbicides.”