A researcher in New Mexico State University's College of Agricultural, Consumer and Environmental Sciences is leading the efforts in understanding the biology of what's happening inside weeds and trees as electricity is being used to safely and effectively kill them.
Erik Lehnhoff, assistant professor of weed ecology in the Department of Entomology, Plant Pathology and Weed Science and his team, which includes Paul Neher, a local inventor and hobby farmer; Donovan Bailey, a professor of biology; Wayne Van Voorhies, a molecular biologist and Leslie Beck, an extension weed specialist, received a competitive grant of $45,115 from the College of ACES to collect background data and write a proposal on the safe and effective way electricity can be used to control weeds.
Researchers are working on two different systems, a tree killing operation and a weed killing operation. Both operations work on the same principal of running an electric current through the plants and into the ground through a continuous loop.
"It's a very low current, less than an electric fence so you can get shocked a little. It's not pleasant but it won't harm or kill you," Lehnhoff said. "For trees we put a screw into the tree near the root crown and attach the lead to it and it runs electricity through the tree and down to the roots. Over the course of a couple of days, it will end up killing the tree. It does depend on the diameter of the tree so; bigger ones will take longer."
This operation has been tested on nuisance trees like Siberian Elm or Mulberry that are growing though someone's landscape and where they don?t want them. Cutting them off at the surface often doesn't kill these invaders because they regrow from the roots. If they are dug out, a mess will be made and other desirable plants can be ruined. If herbicides are used, one runs the risk of accidentally killing plants in the surrounding areas.
When it comes to killing herbaceous weeds, a quarter inch screen mesh is placed on the ground to allow an electric current to run through it.
"The screen almost acts like a preemergent herbicide. When weeds contact the screen there will be a low current of electricity going through them and preventing them from growing," Lehnhoff said. "This will be a great application for a landscape where you have a few ornamental plants and don't want anything anywhere else. We'd cut out a hole for the size of plant you want to keep and have the electric mesh everywhere else."
This operation has been used to kill Bermuda grass, which spreads through stems above and below ground and proves to be very difficult to remove. The mesh screen is laid on the desired spot of grass for removal and hooked up the electricity. Over several days the grass will be killed. Researchers believe the current is going down to the roots, causing something that inhibits plant growth. Plants that haven't yet contacted the screen eventually emerge, connect with the screen, and are ultimately killed as well.
Lehnhoff explained that there have been other similar systems in the past, but they used very high voltage that ended up boiling the plant. It is not safe and does not always kill trees targeted for removal.
"In terms of how it works, we still don't really know," Lehnhoff said. "There are a lot of electro chemical processes going on within plants at the cellular level and with transports of solutes through the plants. So it could be something as simple as disrupting water and nutrient uptake in to the plant or it could affect photosynthesis and the movement of ions across cell walls. Those are the types of things we are still working on and we have a lot of experiments going on."
Neher developed this idea in an effort to kill the weeds at his house and his few acres of pecan trees without using herbicides. As an electrical engineer, Neher began experimenting with electricity.
"He started playing around with this idea of electricity and ended up discovering a certain signal that could be used to kill weeds," Lehnhoff said.
Lehnhoff said the current method has a use mostly for landscaping. There is still research that needs to be done to see how to apply these methods to larger scale farming because irrigation presents a problem when trying to use electricity to manage weeds.
"This could be a tool that replaces some herbicide use because a lot of people don't want to use herbicide anymore. Also, this method would be great for someone with an organic garden," Lehnhoff said. "It can also replace the plastic weed barrier that is placed under landscapes to minimize weeds from coming up."
Lehnhoff and his team are currently running tests in the lab to understand what's going on within the plants as electricity runs through them. They are setting up sample plants that will have different levels of exposure to electricity. Plant tissues will be collected and gene expression w analyzed in an attempt to determine which plant pathways are being affected.