By JOHN O'CONNELL
ABERDEEN, Idaho -- Growers of light-skinned potato varieties in Idaho and Washington have taken advantage of a new tool they believe addresses a glaring need for their chemical programs.
Prior to spud planting this spring, the Phoenix-based chemical company NovaSource succeeded in getting special local needs labels approved by the states' agriculture departments allowing for pre-emergence use of a herbicide they're marketing under the name Linex.
The chemical, formally sold as Lorox by DuPont, has been prohibited west of the Rocky Mountains since the 1970s. NovaSource officials aren't certain about the initial reason for the product's discontinuation in the West but acknowledge trials show it can burn crop foliage when applied post-emergence.
Linex, which contains the active ingredient linuron, a photosynthetic inhibitor, offers a new mode of action for potato growers concerned about the development of herbicide-resistant weeds. It's similar to metribuzin, another photosynthetic inhibitor that targets a different site. Metribuzin, however, causes damage to light-skinned spuds including Shepody and reds.
Pam Hutchinson, a weed scientist at University of Idaho's Aberdeen Research and Extension Center, has conducted trials that provided data to justify the special local needs labels.
"In my research, we've seen good crop safety with use of the product. I have not seen any damage from pre-emergence applications as labeled," Hutchinson said, adding post-emergence Linex applications in her trials led to burning and stunting, and it should never be labeled for use after plant growth occurs.
Hutchinson and growers who used Linex this season have found it's effective on lambsquarters, nightshade, pigweed and kochia, though the company concedes it's weak on Russian thistle. Hutchinson believes Linex makes a good tank mix partner with herbicides that control harry nightshade but tend to miss lambsquarters. Some lambsquarters plants are also naturally tolerant to glyphosate herbicide.
"I'm worried we might have a weed shift to where common lambsquarters may be dominating weed population in potato fields," Hutchinson said.
Her trials this season will seek to determine proper plant-back intervals for crops following Linex use on spuds.
Jason Cook, a field man with Moss Farms in Rupert, Idaho, said his farm had no good herbicide options for fields planted in the light-skinned McCain spud variety Innovator prior to using Linex this season. Cook avoided metribuzin due to Innovator's sensitivity, and he said plant-back restrictions prevent growing sugar beets after the next-best option, Matrix, which can also miss lambsquarters.
"(Linex) opens the door for some other management tools we've needed and have been desperate to find," Cook said. "You've got different options as far as managing crop rotation and doing a good job of cleaning up weeds without any stress on the crop."
Kyle Coleman, with NovaSource, said a dozen large farms in Idaho and Washington tried Linex on spuds this season. The company intends to continue the special local needs labels next season before pushing for a full label the following year for the Pacific Northwest.
"A lot of these chemistries have been used for a long time now, and resistance is creeping in. The need for new chemistry and modes of action is really important," Coleman said.