OREGON STATE UNIVERSITY

Weather can interfere with control of sugar beet weeds

08/06/1997

KLAMATH FALLS - To control weeds in sugar beets, farmers should consider using pre-emergence herbicides. Those chemicals give the grower more weed control options later in the season.

Growers can use an all-post-emergence program, but then they're playing Russian roulette with the weatherman, say Oregon State University scientists.

"If growers can start with banded pre-emergence herbicides and the weed population isn't too heavy, they can pick up weeds between rows with cultivations," said Kerry Locke, a row crop specialist in OSU's Klamath County Extension Service office. "Then they can apply Eptam during the last cultivation to provide weed control later in the season.

"You can use only post-emergence herbicides, but then you need to get these on weeds early and often," he added. "That's the problem. Sometimes weather screws you up."

Locke said the use of a pre-emergence herbicide gives the grower more flexibility in eliminating or reducing the number of post-emergence applications. It also allows growers to select products with different chemistry, reducing the risk of developing herbicide-resistant weeds.

In Klamath Experiment Station trials, Locke and OSU Agricultural Experiment Station researchers Randy Dovel and Ken Rykbost compared nine herbicide programs to see which produced the highest yields and most profit per acre.

They said several combinations worked well, but they had the highest yield on plots where they used Upbeet, Stinger and Nortron combined. That produced a yield of 27.2 tons and a gross return per acre of $1,400.

Betamix Progress alone yielded 25.6 tons and gave a $1,345 return per acre. Close behind were pre-emergence herbicides Nortron followed by Upbeet plus Betamix, with a gross return of $1,362 per acre; and Pyramin followed by Eptam, with $1,360 per acre. Untreated plots yielded only $790 per acre.

"Lack of adequate weed control continues to be the most limiting factor for profitable sugar beet production in the intermountain region," Locke said. "Selecting the best treatment is important because the cost of chemical and mechanical weed control represents 20 percent of the variable costs of sugar beet production."