KIMBERLY, Idaho — A $57,000 specialty crop grant will fund University of Idaho field experiments designed to help Idaho dry bean growers deal with one of their biggest production challenges: the nightshade weed.
The money, which was provided to the Idaho Bean Commission through the Idaho State Department of Agriculture, will be used to conduct several different experiments in furrow- and sprinkler-irrigated beans.
Nightshade costs the Idaho dry bean industry millions of dollars a year and the commission hopes the experiments will help growers get a handle on the problem, said IBC member Don Tolmie.
"Nightshade is probably the biggest problem, by far and away, that the Idaho dry bean industry has to deal with," said Tolmie, production manager for Treasure Valley Seed Co.
Idaho bean growers listed finding ways to combat nightshade as their top research priority in surveys in 2013 and 2014. Based on the survey results, IBC officials estimate the weed costs the industry about $8 million a year.
"That's one weed we can't seem to get a handle on," said IBC member and Parma farmer Mike Goodson.
If the gelatinous fluid in nightshade seeds is crushed during harvest, it can stain beans, lowering their marketability, and the presence of even one nightshade seed in a lot of dry bean seed can result in it not being certified as disease-free.
In addition to reducing yields, nightshade stays green longer than bean plants and can clog harvesting equipment.
"It's an issue all the way through the process," said IBC member Lorell Skogsberg, large seed production manager for HM Clause.
The UI field experiments include trying 8-inch spacing between rows vs the standard 22-inch spacing, with the hope that the beans will outcompete the weeds for water and nutrients, said UI weed scientist Don Morishita, who will oversee the two-year project.
"Our hypothesis is that the beans will be more competitive against the weeds because they're closer together," he said.
Nightshade continues germinating throughout the season and the narrower spacing between rows could provide enough shade to prevent the weed from germinating, Tolmie said.
Another experiment will evaluate the application of a post-emergent herbicide, bentazon, at different times throughout the day, to analyze the effects that humidity and temperature have on weed control.
Morishita said the herbicide has worked well in the Midwest but results in this area have been inconsistent, possibly because it's less humid in Southern Idaho.
"It seems to work better under more humid conditions," he said. The research seeks to determine if the herbicide is applied early in the morning, when humidity is highest, "would that be better than applying it later in the afternoon, when humidity is lowest."
UI researchers will apply the herbicide at three-hour intervals throughout the day, beginning at 6 a.m.
Another experiment will include comparing several herbicides with and without cultivation, followed by different timings of furrow irrigation.