Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: 2/16/2006
Publication Date: 5/1/2006
Citation: Webster, T.M., Grey, T.L., Burton, M.G., Flanders, J.T., Culpepper, A.S. 2006. Tropical spiderwort (Commelina benghalensis): The worst weed in cotton? In: Proceedings of the 2006 Beltwide Cotton Conference, January 3-6, 2006, San Antonio, Texas. p. 2181-2183.
Technical Abstract: Tropical spiderwort is an exotic invasive weed, listed as a Federal Noxious Weed. GA and FL list spiderwort as the most troublesome weed in cotton, and it is a pest in peanut, corn, soybean, nursery stock, and orchards. Key identifying characteristics are: 1.) leaves that are no more than three-times as long as wide; 2.) red hairs at the top of the leaf sheath; 3.) small aerial flowers with blue petals; and 4.) underground flowers–spiderwort is the only Commelina spp. in the US to flower underground. In GA, spiderwort has increased in severity since 1999 when it was identified in 5 counties. By 2005, spiderwort was confirmed in 33 GA counties. Radical changes in cropping systems in the last 10 years coincided with the domination of these systems by spiderwort. The most significant changes that have likely contributed to this phenomenon include: 1.) adoption of conservation tillage on 45% of the acres in Georgia (up from 1% in the early 1990’s); 2.) elimination of tillage as a weed control tactic. Every cotton acre had 2 to 3 cultivations per season in the early 1990’s; currently less than 15% of the acreage receives any type of cultivation; 3.) increased cotton acreage due to boll weevil eradication, resulting in a four-fold increase between 1988 and 2003, up to 1.45 million acres; 4.) widespread adoption of glyphosate-tolerant cotton cultivars; glyphosate controls spiderwort <55%; 5.) elimination of PRE herbicides with soil residual activity.