For Calvin Penkauskas, pigs are the secret weapon in a battle against a farmer’s enemy: filbertworms. The porkers’ chorus of delighted grunts cancel out their stealth. But they work fast—and they’re nothing if not dedicated to the cause.
Penkauskas is witnessing just how persistent hogs can be when unleashed on a foe hiding inside delicious hazelnuts.
The University of Oregon junior is conducting research in a collaboration between assistant biology professor Lauren Hallett’s lab and Taylor Larson of My Brothers’ Farm in Creswell, Oregon. Larson teamed with the UO research group to test his idea to use pigs to control filbertworms in the hazelnut orchards of his 320-acre organic farm.
Hazelnuts, also called filberts, are important for Oregon farmers, who produce more than 99 percent of the nation’s supply, landing on tables and in salads and chocolaty spreads.
But Larson’s farm is also home to about 1,000 white oaks. The trees are critical to the ecosystem but colonization drastically reduced their numbers and in the Willamette Valley they now occupy just 5 percent of their historical range.
White oaks and hazelnut trees are worrisome neighbors because the filbertworm can infest acorns in the former and then spread to the latter.
“Their little eggs will hatch out, and the worm will crawl into a soft nut before the shell hardens,” Larson says. “When you process the nut, you crack it open and there’s a bunch of worm poop.”
Filbertworm larvae in white oak acorn, fall 2018
The inside of a hazelnut after the filbertworm larvae has left
But Larson wouldn’t dream of removing the white oaks—his environmental and social values drive him to find sustainable solutions.
Larson thought up the pig project and a multipronged question: can you reduce filbertworms that threaten hazelnuts while conserving endangered white oaks?
Penkauskas, a major in biology and environmental science, is testing whether the farm’s pigs can interrupt the cycle during which filbertworms spread from the white oak groves to the hazelnut orchards.
Mentored by graduate student Alejandro Brambila, Penkauskas hypothesized that giving the pigs the run of the oak forest floor would enable them to eat acorns infested with filbertworm larvae, preempting the pest’s maturation into winged adults that attack hazelnut trees. Releasing the pigs into the hazelnut orchard would allow them to eat infested hazelnuts, too, further reducing the filbertworm population, he reasoned.
The idea hasn’t been applied to the oak-hazelnut-filbertworm conundrum, according to Penkauskas, but it has a basis in history.
“It’s a common permaculture practice to have chickens or pigs glean fallen infested fruits,” he says. “For hundreds of years, especially on the East Coast and back in Europe, livestock used to eat the rotten fruits from the orchard floor. And Spain has been using pigs to eat acorns specifically (to produce) the most expensive ham in the world.”
First, Penkauskas, Brambila, and their teammates painstakingly measured the filbertworm population, setting traps so they could track and collect data.
Next, they determined the best time to turn the pigs loose on the forest floor: October, when the first acorns fall—infested acorns fall a bit earlier than healthy ones—and the filbertworms are most vulnerable. Using electric fencing, the researchers cordoned off two-acre swaths of the oak grove last fall. Working one patch at a time, the research team and farmers released the pigs into the designated area, where they stayed for a few days before moving to another patch.
Each time the hogs set hooves on a new section of the forest, Penkauskas says, they went wild with excited squealing. A group of pigs is called a “sounder,” and the name fits, he says, because once the pigs were let loose, researchers heard the hogs rooting for treasure more than they saw them.
“It’s like the world’s most competitive Easter egg hunt,” Larson says. “The first four to five hours that they’re in an oak grove, I don’t think they stop moving. They go crazy—it’s a race to get all the nuts.”
A trailer parked in the area provided the pigs with shelter, and water was set out for them. At night, the pigs slept near the trailer, Penkauskas says, but in the daytime they meandered and foraged, getting bolder with each passing day. “The last two days, they definitely venture out farther,” he says. “They know where they want to go—they have a nose for it.”
After the pigs covered the ground beneath the oaks, they took a turn through the hazelnut orchards, after harvesting.
The initial results of the project showed significant reduction in infested acorns, a preliminary success. There’s more work to be done to determine whether fewer infested acorns will lead to fewer filbertworms in the hazelnut orchard.
Penkauskas plans to continue and expand the project, mentoring incoming undergraduate researchers in the process. But he’s pleased with the direction of the endeavor, to date.
“It’s looking promising,” he says. “It’s pointing toward ‘the pigs did their thing,’ and in the hazelnuts it looks like less pest pressure at the moment.”
Emily E. Smith, BA ’10 (women’s and gender studies, journalism: news-editorial), is a freelance writer and editor in Bozeman, Montana.
Photos by Dustin Whitaker, University Communications; filbertworm larva image by Calvin Penkauskas