Tropical Spiderwort Already Present in Georgia Cotton Fields
Over the past few seasons, tropical spiderwort has regained its status as a major pest for many Georgia cotton farmers. To control this weed, one must understand the importance of placing residual herbicides strategically throughout the growing season beginning at planting.
However, the most important herbicide application may be the last one where an effective residual product must be applied in a manner where it contacts the soil. Yes, the best approach by far is to use a layby rig or hooded sprayer to apply the herbicide where it needs to go – which is not over the top of the crop.
Remember, this weed can grow in the dark, so the approach of shading it out with the cotton crop is not as effective as it is on many other weeds.
Activity of the more commonly used cotton herbicides on spiderwort is discussed below. Contact your local county Extension agent for a season-long program approach depending on your choice of technology being grown.
Consider the following when building a program:
- Residual activity from Warrant and Dual Magnum are critical to success. Limited data suggests Outlook is also effective.
- Gramoxone and 2,4-D are very effective controlling emerged plants with timely applications.
- Dicamba is not overly effective. But when mixed with glyphosate and applied sequentially, control of emerged plants is often acceptable depending on the weed’s size when the first application is made. Following sequential dicamba applications with a directed layby application – including an effective residual herbicide – will be important for long-term success with this system.
- Roundup + Staple remains quite effective on emerged plants if they are small.
- Liberty is not very effective.
- Layby materials such as diuron + MSMA, glyphosate + diuron, or any mixture with Aim can be quite effective. Remember to include a residual herbicide with the layby application and follow all application requirements.
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