Herbicide-resistant weeds remain one of the top concerns for growers across the country, according to a recently completed survey.

BASF Corp., Research Triangle Park, N.C., recently polled growers about their views on herbicide-resistant weeds and the effects they had on their operations, according to a news release.

When asked if they had plans to alter weed-control programs this season because of herbicide resistance, 80 percent of respondants said they were.

More than 50 percent acknowledged the existance of glyphosate-resistant weeds in their field, with many saying the weeds were affecting yields.

In 2010, BASF asked farmers if resistant weeds affected yields, and 23 percent said "yes."

The 2011 survey posed the same question, and 73 percent said resistant weeds had at least some effect on yields.

Even farmers who said they didn't believe they had glyphosate resistance said they planned to change their weed-control program this year.

More than 80 percent of respondants said they were willing to spend more to control resistasnce weeds.

And nearly one-third said they planned to use multiple modes of action this year.

Using multiple modes of action is one of the pillars of resistance management, according to the Weed Science Society of America and the Herbicide Resistance Action Committee.

The Weed Science Socity has confirmed 13 different herbicide-resistant weed species in 28 states.

Although most of the resistance problems are in field crops, such as corn, soybeans and cotton, resistant weeds have been confirmed in permanent crops and vegetable fields.

But not every grower responding to the survey said they believed weed resistance was a problem.

Sixteen percent said they would not spend any more to control resistant weeds, and one-third said they didn't believe resistant weeds affected their return on investment.