nickkurzenko / iStock / Getty Images Plus Tropical spiderwort is now trying to regain status as a major pest again for Georgia cotton farmers. Suggested Event Jun 15, 2021 to Jun 17, 2021 Back before herbicide-resistant pigweed became enemy No. 1 for southern farmers, the exotic, invasive tropical spiderwort contended for the title. Tropical spiderwort is now trying to regain status as a major pest again for Georgia cotton farmers. Timely residuals can stop it. "To control this weed, one must understand the importance of placing residual herbicides strategically throughout the growing season beginning at planting. The most important herbicide application may be the last one where an effective residual product must be applied where it contacts the soil, says Stanley Culpepper, University of Georgia Extension weed specialist.