Shocking Research: Electric Weed Control Fruitful in Various Berry Crops

Weed management is one of the most persistent challenges in organic fruit and berry production. Effective control relies heavily on expensive manual labor, while approved bioherbicides are often limited and less effective than synthetic options. Researchers in New York and the Pacific Northwest are currently exploring an innovation promising to reduce weed pressure in organic fruit orchards. Electric weed control (EWC) entails application of electrical current to harvest-damaging invaders, right down to the root system. Heat generated by electrical resistance vaporizes cellular water, leading to cell membrane rupture and plant death.

Although not a novel technology, limited information exists regarding EWC’s optimal application. Researchers at Oregon State University, UC Davis, and Cornell University are addressing this knowledge gap through field trials in regional organic blueberry and orchard systems.

Participating scientists shared their findings during a recent webinar. Long-term goals include optimization of EWC as an effective, economical production practice in tree and berry cultivation. This approach can also diversify weed management practices, reducing overreliance on soil tillage and plastic weed mats, researchers said.

While sawdust, pine bark mulch, and synthetic mats can suppress weeds, they also present sizable drawbacks, noted Luisa Baccin, a PhD student in the Oregon State University Department of Horticulture.

“Mulches need to be reapplied every two or three years to guarantee they have good effectiveness for weed suppression,” said Baccin, whose research evaluates EWC in organic blueberry production along with control of certain weed types. “For plastic mats, weeds can find ways to pop through once the plastic gets older and ripped apart.”

Baccin’s work focused on two perennial weeds — Canada thistle and yellow nutsedge — at a research farm in Corvallis, OR. Electric weed control reduced weed populations in Duke highbush blueberries, including a decrease in troublesome weed species.

“What we can see is EWC performed better for total weed control and the reduction of a number of those species,” Baccin said. “Meaning that when we treat with EWC, we have fewer species of weeds in this plot.”

Though no clear indicator of plant growth was observed with EWC, combining this practice with mulch applications resulted in larger canopy and shoot sizes. Meanwhile, Baccin warned about the hazards of using electric weed control in drier conditions.

“When there are dry weeds in the field during mid-to-late summer, sparks from EWC can start fires, so it’s important to have a water source nearby,” said Baccin. “There’s also the risk of melting plastic mulch. To avoid that, we should have (EWC) applications on the side of the plastic, instead of running on top of it.”

PROVIDING CRUCIAL CONTROL

Almonds are a top-three agricultural commodity in California, making weed control crucial for maintaining the viability of this important crop. Beginning in 2023, University of California Davis researchers used a tractor-mounted Zasso electric weed control unit to evaluate the technology’s efficacy in almond and blueberry crops.

Participants, including Department of Plant Sciences PhD candidate Tong Zhen, tested different combinations of speed and power, with the goal of controlling total current flowing underground. Zhen and the team implemented EWC at speeds from 0.7 mph to 1.4 mph, adjusting power settings from high to low.

All treatments showed promising outcomes, Zhen said. For example, the highest-power EWC application kept an almond crop weed free from 35 to 40 days. In the blueberry experiment, researchers applied sawdust and plastic mulch, resulting in lowered weed pressure throughout the season.

“You can see some weed escape with lower energy input, which obviously is not as effective as treatments with the highest energy input,” Zhen said during the webinar. “We also measured tree height, trunk diameter, and blueberry plant canopy volume, finding no significant differences in plant growth across treatments for either crop.”

Last year UC Davis scientists continued monitoring crop growth while collecting soil samples for analysis. Zhen reported no significant negative impact on soil microbes after two weeks of EWC treatment.

A TREATMENT FOR THE FUTURE

On the other side of the country, Cornell University horticulture PhD student Aleah Butler-Jones examined electric weeding’s impact on weed and soil biological communities. Herbicide-resistant weeds make electric weeding a unique opportunity to control plant pests while increasing crop vigor and productivity.

Butler-Jones studied the effect of EWC compared to current organic management practices on weed cover and biomass in apple production. Field trials compared monthly applications of electric weeding to traditional cultivation and organic herbicide treatments over the same timeframe.

“We found that EWC significantly reduced weed cover compared to cultivation and organic herbicide use in established orchard systems,” Butler-Jones said in the webinar. “When averaged over the season, we see these reductions in the percent of weed cover (with EWC), followed by cultivation, with highest percentage of weed cover with our organic herbicide treatment.”

Traditional organic weed control requires frequent soil disturbance, hand labor, high rates of organic herbicides, or the application of large amounts of organic or synthetic mulches. Although electric weed control may not eliminate those treatments completely, the practice is an effective means of reducing weed populations, adds Butler-Jones.

“The main takeaway is that EWC reduces weed cover and biomass and may be more effective when combined with other tactics such as cultivation,” Butler-Jones said.