Repeated Annual Applications of Herbicides for Control of Rhizome Johnsongrass (Sorghum halepense) in Cotton (Gossypium hirsutum)

Abstract

When postemergence applications of sethoxydim {2-[1-(ethoxyimino) butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one} were compared with DSMA (disodium salt of methylarsonic acid), MSMA (monosodium salt of methylarsonic acid), and glyphosate [N-(phosphonomethyl)glycine] for control of johnsongrass [Sorghum halepense(L.) Pers. # SORHA] in cotton (Gossypium hirsutumL. ‘Acala SJ-2′), repeated annual applications of sethoxydim were more successful than other herbicides in protecting yields of cotton and reducing populations of rhizome johnsongrass over time. After the first year of treatment with sethoxydim in 1982, when an 18% yield loss of cotton occurred, populations of rhizome johnsongrass were reduced to the extent that they were no longer a threat to yields in plots treated with sethoxydim in 1983 and 1984. Although DSMA and glyphosate improved yields when compared to cultivated control plots, substantial yield losses occurred every year, and populations of johnsongrass remained unchanged after 3 yr of treatment. Averaged over 3 yr, plots treated with sethoxydim produced 94% as much cotton as weed-free plots, compared to 60 and 45% for plots treated with glyphosate and DSMA/MSMA, respectively.

Herbicide Systems for Johnsongrass (Sorghum halepense) Control in Soybeans (Glycine max)

“…trol with split applications than with single applications of selective grass herbicides (1,7,22), although single applications can be effective (17).…”

“…Glyphosate, applied with a ropewick applicator or recirculating sprayer, controls johnsongrass, although repeated applications often are required (7). A height differential between crop and weed must occur before glyphosate can be applied with a ropewick applicator without injuring crops (5,7,16). Because the height differential usually occurs late in the season, soybean yield may be reduced from early season johnsongrass competition.…”

“…Banks and Tripp (1) obtained johnsongrass control of 75% or more with sethoxydim and fluazifop, but regrowth occurred within 90 days of treatment. Sethoxydim and other selective postemergence herbicides applied repeatedly are often more effective than single applications for reducing johnsongrass populations (1,3,7,22).…”

“…Dinitroaniline herbicides have been applied in sev eral experiments in conjunction with postemergence herbicides to ensure that the postemergence herbicides were evaluated for control of rhizome, rather than seed ling, johnsongrass (3,7,8,13), but control with and without the dinitroanilines was not compared. Rogers et al (18) found that the use of fluchloralin did not significantly affect control of johnsongrass from seth oxydim or fluazifop-butyl.…”

“…The rate of fluchloralin used in these experiments probably did not control much rhizome johnsongrass. McWhorter and Anderson (13) reported that at least 1.7 kg/ha of trifluralin was needed for effective control of rhizomes; difiitroaniline herbicides at 0.6 to 1.0 kg/ha, how ever, have been used to control seedling johnsongrass (3,6,7).…”