JOHNSONGRASS CONTROL USING ROUNDUP READY SOYBEAN TECHNOLOGY IN FALLOWED SUGARCANE FIELDS

Authors: VIATOR, B - LSU AG CENTER; GRIFFIN, J - LSU AG CENTER; CLAY, P - LSU AG CENTER; ELLIS, J - LSU AG CENTER; Richard Jr, Edward

Submitted to: Proceedings of Southern Weed Science Society
Publication Type: Abstract Only
Publication Acceptance Date: 1/20/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Field studies comparing single early postemergence (EPOST) and late postemergence (LPOST) Roundup applications 30 and 60 d after the late-April planting of Roundup Ready soybean on 6-ft wide fallow sugarcane beds, respectively, and sequential EPOST followed by LPOST Roundup applications to EPOST applications of Assure II, Fusilade DX, and Select and two conventional fallow weed control programs (no soybeans) were conducted in 1996 and 1997. On July 11, 1996, all herbicide treatments, with the exception of Fusilade DX, controlled johnsongrass at least 94%. The LPOST application of Roundup provided excellent control of johnsongrass, but early-season weed competition resulted in poor soybean yield (8.3 bu/A) compared with other Roundup treatments (at least 44 bu/A). Soybean yields following applications of Assure II, Fusilade DX, and Select ranged from 32.3 to 38.7 bu/A. Both the conventional fallow and soybean/Roundup treatments resulted in lower johnsongrass panicles/A and greater johnsongrass control during the initial (plant-cane crop) growing season compared with the nontreated check. Differences in cane and sugar yields were not observed at the end of the 1997 growing season, possibly due to the late planting and excellent sugarcane stands. In the second fallow study, all herbicide treatments controlled johnsongrass at least 99% on July 17, 1997, except for Roundup LPOST at 4.0 pt/A (20% control). Soybeans were not harvested due to poor seed quality associated with adverse climatic conditions.