With the increase in GT cotton acres, Georgia growers have seen a dramatic increase in tropical spiderwort, a noxious weed. In just the past couple years, tropical spiderwort has emerged as a serious weed in south Georgia cotton fields:
- Present in U.S. for more than 70 years
- Became an isolated weed problem in 1999
- Identified as the most troublesome weed in Georgia cotton in 2003
- Found in 41 counties
- Classified as a moderate or severe pest in 17 counties
- Researchers attribute population increase to:
- Tropical spiderwort’s natural tolerance to glyphosate, the primary herbicide applied to fields
- Decrease in tillage for weed control
This weed shift brings a significant economic impact for growers, according to University of Georgia (UGA) research. - Increases weed control costs an estimated $1 million per year
- Decreases cotton yields from 5% to 45%, depending on the duration of competition
- Later cotton plantings are more susceptible to yield loss
Tropical spiderwort management solutions: - Adding residual control
- Early post program: Sequence or glyphosate and Dual MAGNUM®
- Late post-directed program: MSMA and Valor®
- Most effective control program evaluated by an UGA study
Average costs are $37 to $43 per acre for early post and late post-directed applications
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