PARENT SESSION
Poster Session # 16: Invasive Species.
Wednesday, August 6 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.
Rapid increase of tropical spiderwort (Commelina benghalensis L.) in herbicide-resistant crops of southeastern USA agroecosystems.
Burton, Michael*,1, Webster, Theodore 2, Prostko, Eric 3, Culpepper, A.3, York, Alan1, Sermons, Shannon1, 1 North Carolina State University, Raleigh, NC2 USDA-ARS, Tifton, GA3 University of Georgia, Tifton, GA
ABSTRACT- Tropical spiderwort (Commelina benghalensis L.) is a terrestrial invasive weed species. As a consequence of multiple herbicide tolerances, it is on the federal noxious weed list. Although previously not known to occur north of Georgia, this troublesome weed species was positively identified in North Carolina in September 2001. Affected states are now known to include California, Florida, Georgia (where it is now considered the most troublesome, although not the most common, weed species in agro-ecosystems), Louisiana, and North Carolina. This species has been observed to increase rapidly in intensively managed, frequently disturbed, cropping systems. Notably, tropical spiderwort has shown the most dramatic increase where herbicide-resistant crops are used in successive years of crop rotations. Although the National Plants Database (http://plants.usda.gov) only reports tropical spiderwort as occurring in three counties in south Georgia, preliminary results (20% of counties responding) from a statewide survey indicate that this species occurs in at least 29 counties, and is considered a moderate or greater problem in ≥17 counties. Results from growth chamber experiments demonstrate that temperature optima for plant growth are in the range of 30 to 35o C, which suggests that the climate throughout the southeast USA may be suitable for rapid growth and reproduction of tropical spiderwort. In herbicide resistant cropping systems, tropical spiderwort populations escape weed management tactics with a broad period of germination (i.e., multiple germination cohorts), rapid production of rhizomes that can both result in vegetative reproduction and production of viable seeds in cleistogamous subterranean flowers, and an ability to vegetatively regenerate from cut stem sections (provided that stems are buried less than 8-cm). Tropical spiderwort also produces aerial chasmogamous flowers that can produce viable seeds within 25-d of flowering. Population densities of other members of the Commelinacea are also reportedly increasing where herbicide-resistant crops are frequently used. Coordinated state, regional, and federal efforts/funds are needed to prevent further spread and economic injury from tropical spiderwort.
Key words: federal noxious weed, genetically modified crops, invasive weed, dayflower