What is in this article?:

Surveys conducted by the University of Georgia reveal that monumental changes have occurred in a relatively short amount of time as it relates to cotton weed control practices in response to glyphosate-resistant Palmer amaranth pigweed.

During this same time, the cost of weed control in cotton production has roughly doubled.

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A UNIVERSITY OF Georgia grower and county Extension agent survey reveals substantial changes in weed control practices in response to the development of glyphosate-resistant Palmer amaranth pigweed.

Comprehensive survey

A written survey was developed and administered in order to characterize Georgia cotton growers’ production practices before and after the development of glyphosate-resistant Palmer amaranth.

The survey specifically asked growers and Extension agents from across the state to describe the chemical, cultural and mechanical weed control practices that were used on their farms prior to and then following 2005.

Additional questions queried farmers about the costs associated with weed control and about the most significant weeds occurring in cotton.

The surveys looked at the commodities being grown, herbicide use, additional weed management practices, and weed pressure, both before glyphosate-resistant Palmer amaranth — the years 2000 to 2005 — and afterwards, from 2006 through 2010.

Respondents included 65 growers in 16 counties in Georgia and 10 county Extension agents. It encompassed the major row and forage crop areas in the state.

The responding growers were responsible for 13 percent of the state’s cotton, and the total acreage from the county agents responses represented 24 percent of Georgia’s cotton.

Growers produced cotton, peanuts, soybeans and corn, with some livestock, forage and vegetables.

Prior to the development of glyphosate-resistant Palmer amaranth, morningglory was listed as the most troublesome weed pest in row-crop farming.

The growers in the survey said about 78 percent of their acres were infested with glyphosate-resistant pigweed, and the county agents’ number was close to 90 percent of total acreage.

Looking at herbicide use patterns relative to cotton planting and emergence and growth, the survey questioned respondents about the herbicides applied pre-plant and at planting, postemergence over-the-top, and postemergence layby and directed applications.

As expected, with preplant, burndown and at-plant herbicides applied, there was a significant decrease in the acres treated with glyphosate. The use of 2,4-D stayed relatively the same, but there were significant increases in the use of paraquat for controlling Palmer amaranth. The agents saw a significant increase in the use of 2,4-D.

There were significant increases in the amount of diuron, flumioxazin and fomesafen being used, and agents and growers also saw an increase in the amount of pendemetholon being applied in Georgia.

In postemergence treatments, there was a decrease in the amount of glyphosate being applied with respect to the treated acres.