A study was established to evaluate herbicides registered for barnyardgrass control in rice for activity on creeping rivergrass. Treatments included 208 g ai/ha cyhalofop early POST (EPOST) followed by (fb) 315 g/ha cyhalofop late POST (LPOST), 22 g ai/ha bispyribac EPOST fb 22 g/ha bispyribac LPOST, 66 g ai/ha fenoxaprop EPOST fb 86 g/ha fenoxaprop LPOST, 70 g ai/ha imazethapyr EPOST fb 70 g/ha imazethapyr LPOST and 50 g ai/ha penoxsulam mid-POST (MPOST). Each POST program was evaluated with and without 448 g ai/ha clomazone PRE. Barnyardgrass control, averaged over days after treatment (DAT), was 88 to 92% with the addition of clomazone PRE. Clomazone applied PRE followed by two applications of cyhalofop controlled creeping rivergrass at 91%. Creeping rivergrass control was less than 75% at 35 to 49 DAT. This response indicates only suppression of creeping rivergrass is achieved with the herbicide programs evaluated in this study.
Rice was planted at 78 kg/ha with different densities of creeping rivergrass. Creeping rivergrass at stand densities (SD) of 10,000 to 70,000 stolon segments/ha produced 5.4 to 6 stolons per introduced segment; however, 130,000 through 520,000 SD produced 1.4 to 2.1 stolons per segment. Stolon production was 60,000 plants/ha and increased to 760,000 stolons/ha at planting densities of 10,000 to 520,000/ha, respectively. The 260,000 and 520,000 SD produced similar stolon lengths of 217 and 318 km/ha; however, stolon length was less at lower SD. Total node production was 290,000 nodes per ha with an average of 29 nodes per segment in the 10,000 SD and 5.4 to 9.8 nodes per segment with 70,000 or greater SD. Total biomass increased as SD increased. Creeping rivergrass shoot emergence from soil was 31, 63, 44, and 25% for segments planted at 0, 1.3, 2.5, and 5 cm deep, respectively. In a greenhouse study, glyphosate at 1,260 g ai/ha controlled creeping rivergrass 91% and biomass production was 19% of the nontreated creeping rivergrass. Bispyribac, cyhalofop, fenoxaprop/s, fenoxaprop/s plus fenoxaprop, glufosinate, imazethapyr, penoxsulam, propanil, and quinclorac were less effective than glyphosate.
A study was conducted in 2004 and 2005 near Crowley, LA to evaluate soil‐applied herbicides labeled for barnyardgrass control in rice for activity on Echinochloa polystachya. The study included: clomazone applied preemergence (PRE), clomazone plus quinclorac applied PRE, pendimethalin plus quinclorac applied delayed PRE, imazethapyr applied PRE, and mesotrione applied PRE. Each soil applied herbicide program was followed by cyhalofop applied postemergence (POST). Averaged over 7 to 49 DAT, all of the herbicide programs controlled barnyardgrass at least 87%. Averaged over herbicide program, barnyardgrass control was 91 to 93% from 28 to 42 DAT; however, control at all evaluations was at least 85%. The herbicide programs with a single application of clomazone or imazethapyr applied PRE, or pendimethalin plus quinclorac applied delayed PRE controlled E. polystachya 78 to 81%. Control was 72% for programs containing mesotrione or clomazone plus quinclorac applied PRE. The combination of clomazone and quinclorac PRE followed by (fb) cyhalofop POST controlled E. polystachya 72% while clomazone PRE fb cyhalofop POST controlled the weed 80%.
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