Submitted to: Proceedings Washington State Potato Conference
Publication Type: Proceedings
Publication Acceptance Date: 2/1/2001
Publication Date: 3/1/2001
Citation: BOYDSTON, R.A., HUTCHINSON, P., RANSON, C.V. NEW HERBICIDES FOR WEED CONTROL IN PACIFIC NORTHWEST POTATO PRODUCTION. PROCEEDINGS OF THE 40TH WASHINGTON STATE POTATO CONFERENCE, MOSES LAKE, P. 17-20. 2001.
Interpretive Summary: Weeds cause tremendous losses in potato production and more potato acres in the United State are treated with the herbicide metribuzin than any other pesticide. The annual value of metribuzin to U.S. potato growers is estimated to be $81 million. Although metribuzin is still the main weed control tool used in potato production, several weed species are not consistently controlled by metribuzin and weeds resistant to metribuzin have increased. In addition, several potato varieties are sensitive to metrubuzin, limiting its use to tolerant varieties. Several new herbicides with modes of action different than metrubuzin are being tested for weed control in potato production. Sulfentrazone (Spartan) and flumixazin (Valor) are new herbicides that inhibit an enzyme in plants important in the synthesis of chlorophyll. Both herbicides control hairy and black nightshade which are currently difficult to control in potatoes. Since the mode of action is different than herbicides currently labeled in potatoes, these herbicides may provide growers with new management tools for resistant weeds. Results of field trials in Idaho, Oregon, and Washington are summarized.
Technical Abstract: Several new herbicides with modes of action different than metribuzin are being tested for weed control in potato production. Sulfentrazone (Spartan), flumioxazin (Valor), and azafenidin (Milestone) control hairy and black nightshade and since the mode of action is different than herbicides currently labeled in potatoes, may provide growers with new herbicide resistance management tools. Sulfentrazone and flumioxazin were tested in Russet Burbank potatoes for crop tolerance and weed control at three locations in 2000 representing major potato growing regions in Idaho, Oregon, and Washington State. Trials were conducted under sprinkler irrigation at Ontario, OR, and near Paterson, WA. In all three trials herbicides were applied after the final hilling and prior to potato and weed emergence. Flumioxazin applied at 0.05 to 0.13 lb/a controlled hairy nightshade and common lambsquarters well, but redroot pigweed control was marginal in Idaho and Oregon. Redroot pigweed control improved as flumioxazin rate increased in Oregon. Flumioxazin did not control tame oats, barnyardgrass, or large crabgrass. Little or no potato injury was observed when treating with flumioxazin in Idaho and Oregon, but flumioxazin slightly injured potatoes when applied at 0.13 lb/a in Washington. Sulfentrazone applied at 0.06 to 0.25 lb/a controlled common lambsquarters, redroot pigweed, and hairy nightshade greater than 90% at all locations. Sulfentrazone controlled barnyardgrass greater than 90% at 0.19 and 0.25 lb/a in Oregon. Tame oats and large crabgrass were not controlled by sulfentrazone. Sulfentrazone visually injured potatoes at 0.19 lb/a or more in Oregon and Washington, but potato tuber yield was not reduced compared to potatoes treated with herbicide standards.