Growers, researchers evaluate biological weed suppression
By RENE FEATHERSTONE
For the Capital Press
CONNELL, Wash. -- Mimic hedge rows.
That's the advice of researchers focused on biological solutions to weed and pest pressures. In practical terms they're promoting "beetle banks," berms of soft soil held in place by grass roots where ground beetles can burrow, safe from the plow.
Brad Bailie of Lenwood Farms in Connell is one grower who took the advice. His beetle banks, about 100 yards total, curve along the upwind edge of circles that raise organic potatoes, onions, peas, sweet corn, mint and grain crops in rotation.
Initially, Bailie was coached in beetle bank design by Alec McErlich, who at the time was ag research manager at the Sedro-Woolley satellite facility of Small Planet Foods.
"The beetle bank concept originated in Britain," McErlich said at the Lenwood Farms field day last year. "As the traditional English landscape of hedge rows kept disappearing, because it's expensive to maintain hedge lines, scientists studied the effect this had, back in the 1980s. They found a decline in biodiversity -- flora and fauna were declining."
Ground beetles were among the impacted species, which was not good for farms because many beetles feed on substantial amounts of small weed seeds. This has been documented since the 1980s by beetle bank research in many countries, including McErlich's native New Zealand.
"Lots of farmers are doing it now," he said of beetle banking.
He quoted a Midwest study of one ground beetle species, called harpalus, that ate 90 percent of the available pig weed seed, in addition to millet, canary grass and nightshade seed.
At Oregon State University in Corvallis, Ore., Gwendolyn Ellen is involved in the Lenwood beetle bank research as manager of the OSU Farmscaping for Beneficials program. She said she works directly with nine farmers in Oregon and Washington, and her workshops serve a network of 150 growers.
Ground beetles are generalists, Ellen explained: "In addition to weed seed they eat crop prey. Pests come in from the edge, so it's nice to have physical barriers like beetle banks."
In terms of weed suppression, beetles are most effective in concert with rodents, Ellen said.
"A lot of that information actually comes from England," Ellen said. "The harvest mouse and the barn owl are threatened species over there, so the U.K. paid farmers to shelter mice. Researchers found that when rodents and ground beetles work in conjunction, weed seed predation is between 80 and 90 percent."
How those lab test results translate to efficacy in real fields is part of her study, Ellen said. "To measure the effect of beetle banks we put traps out at night along a transect across the field." Indications are that the beetles forage as far out from their bank as 60 feet.
For Bailie, who shells out a lot of money every season for weed control, much of it being manual labor, the efficacy of beetle banks is important.
"I want to see some hard numbers," he said, explaining that establishing and maintaining beetle banks adds up.
He does like the concept for its natural elegance: Before he experimented with beetle banks, he put in flower-and-forb insectaries designed as habitat for parasitoid wasps that suppress aphids effectively.
Bailie has pondered how best to arrange for weed and pest predation in a circle-farming scenario. The logical place to set up beetle banks and insectary strips is on circle corners, he said, but it's obvious that predation does not reach the whole circle that way.
One approach he tried is locating the insect habitat alongside the pivot road that leads to circle center. "But that's awkward, when tilling, weeding and harvesting you're driving across the strips," he said.
If he's willing to be convinced of beetle bank benefits, Bailie already appreciates their aesthetic value. "They look nice in the summer, next to the insectaries in bloom."