The response of peanut to low rates of MSMA under weed-free conditions was studied in 1992 and 1994 near Tifton, GA. MSMA was applied 40, 70, 100, or 130 days after emergence (DAE). At each application timing, MSMA was applied at 0, 90, 168, and 336 g ai ha−1. MSMA application timing did not affect peanut yield. Increasing rates of MSMA caused minor reduction in peanut yield. Analysis using atomic absorption spectroscopy showed elemental arsenic accumulation of ≤ 0.7 ppm in peanut kernels from MSMA applied 70 and 100 DAE. This approximates the time interval of peanut pod and kernel formation. MSMA applied 40 and 130 DAE resulted in little detectable arsenic in kernels. Low rates of MSMA, originating as drift from aerial applications to cotton or illegal and unsound applications to peanut for Florida beggarweed control, are not likely to reduce peanut yields. The greatest hazard from peanut exposure to MSMA is accumulation of arsenic in kernels, which would adversely affect peanut marketability and consumer demand.

Field experiments were conducted at one location in Georgia (1994) and at two locations in Alabama (1994 and 1995) to evaluate the effects of MSMA or DSMA plus pyrithiobac applied postemergence (POST) in cotton. Pyrithiobac at 0.07 kg ai/ha was applied POST alone or in combination with MSMA at 1.1 kg ai/ha or DSMA at 1.7 kg ai/ha at the pinhead square stage of cotton growth. Cotton was tolerant to the POST applications of pyrithiobac. Adding MSMA or DSMA to pyrithiobac injured cotton similar to MSMA or DSMA applied alone. Plant mapping data indicated that all treatments had no effect on height : node ratio, reproductive or vegetative node production, or square retention at the first or second fruiting position. Cotton maturity response to MSMA and DSMA ranged from no effect to delayed maturity. Adding DSMA to pyrithiobac increased Florida beggarweed and common cocklebur control over pyrithiobac applied alone in 1995 but did not increase control in 1994. Adding DSMA to pyrithiobac increased sicklepod control over pyrithiobac applied alone in the three site years it was rated in the Alabama tests. Where sicklepod is present, the addition of an arsenical herbicide to pyrithiobac will generally increase control but has the potential to delay maturity and decrease cotton yield equal to the arsenical herbicide applied alone.

Field experiments were conducted in 1997 and 1998 at the Prattville Experiment Field in Prattville, AL and the Wiregrass Substation in Headland, AL to determine if ammonium thiosulfate (ATS) additions to monosodium methanearsonate (MSMA) affects weed control, reduces MSMA-induced cotton injury, lessens the fruiting and maturity delay on cotton caused by MSMA, and lessens MSMA-induced yield reductions in cotton. Treatments were applied before cotton was at the pinhead square stage and the weeds were 5 cm tall. Weeds evaluated were sicklepod, morningglory species, yellow nutsedge, and Texas panicum. ATS additions to MSMA occasionally enhanced control of all weeds 5 to 20%. However, the addition of ATS did not reduce crop injury caused by MSMA, the effects of MSMA on cotton maturity, or yield reductions caused by MSMA.

Field studies were conducted to evaluate foramsulfuron for postemergence control of goosegrass in bermudagrass turf as a possible replacement for MSMA. In field trials on a golf course and sports fields planted to bermudagrass, mature goosegrass was controlled effectively (>85% goosegrass dead on the basis of canopy area) with two applications of foramsulfuron plus metribuzin. The herbicide rates that were effective varied among studies, e.g., foramsulfuron at 0.029 or 0.044 kg ai/ha mixed with metribuzin at 0.105 to 0.210 kg ai/ha. Goosegrass was often controlled with MSMA at 2.24 kg ai/ha plus metribuzin at 0.105 to 0.210 kg/ha, but foramsulfuron was always as effective, or more effective, than MSMA, in controlling mature goosegrass, at the same rate of metribuzin. Bermudagrass phytotoxicity of foramsulfuron plus metribuzin was temporary and not different from MSMA plus metribuzin. In one location there was noticeable phytotoxicity 4 wk after initial treatment.

New weed management tools and growth regulators make production of ultra narrow row (UNR) cotton possible. Weed control, cotton yield, fiber quality, and net returns were compared in UNR bromoxynil-resistant, glyphosate-resistant, and nontransgenic cotton. Weeds included broadleaf signalgrass, carpetweed, common cocklebur, common lambsquarters, common ragweed, goosegrass, jimsonweed, large crabgrass, Palmer amaranth, pitted morningglory, prickly sida, sicklepod, smooth pigweed, and tall morningglory. Pendimethalin preplant incorporated (PPI) in conventional-tillage or preemergence (PRE) in no-till systems plus fluometuron PRE did not adequately control many of these weeds. Pyrithiobac plus MSMA early postemergence (POST) often was more effective than pyrithiobac alone. Pendimethalin plus fluometuron at planting followed by pyrithiobac plus MSMA early POST controlled sicklepod 82%, goosegrass 89%, Palmer amaranth 92%, and the other species at least 95% late season. Pyrithiobac at mid-POST did not improve control. Bromoxynil plus MSMA early POST was more effective than bromoxynil alone only on sicklepod. Pendimethalin plus fluometuron at planting followed by bromoxynil plus MSMA early POST controlled sicklepod 62%, Palmer amaranth 81%, goosegrass 83%, and all other species at least 95%. Glyphosate early POST did not adequately control many species due to sustained weed emergence. Glyphosate early POST followed by glyphosate late POST (after last effective bloom date) controlled all species except pitted morningglory and tall morningglory at least 93%. Pendimethalin plus fluometuron followed by glyphosate early POST was the most effective glyphosate system overall, and it controlled sicklepod 88%, pitted morningglory 90%, and other species at least 93%. Glyphosate late POST did not increase control in systems with pendimethalin plus fluometuron at planting followed by glyphosate early POST. Yields and net returns were similar with all herbicide/cultivar systems at two of five locations. At other locations, yields and net returns were similar with systems of pendimethalin plus fluometuron at planting followed by pyrithiobac plus MSMA early POST, pendimethalin plus fluometuron followed by bromoxynil plus MSMA early POST, and glyphosate early POST. Greatest yields and net returns were obtained with pendimethalin plus fluometuron at planting followed by glyphosate early POST. Herbicide systems did not affect fiber quality.