Todd A. Baughman

Effect of Imazapic Application Timing on Texas Peanut (Arachis hypogaea)1

Abstract: Field experiments conducted in Texas at six locations from 1996 to 1998 evaluated peanut tolerance to imazapic applied postemergence. Imazapic at 71 g ai/ha was applied weekly from ground cracking to 56 d after ground cracking (DAGC). Visible injury 70 DAGC ranged from 0 to 40%. No reduction in canopy height, canopy width, yield, or grade was observed at harvest following any imazapic treatment. Nomenclature: Imazapic; peanut, Arachis hypogaea L., ‘AT 120’, ‘GK 7’, ‘NC 7’, ‘Tamspan 90’. Additional index words: Herbicide injury, ground cracking, groundnut, herbicide timings, peanut injury, postemergence, yield. Abbreviations: DAGC, days after ground cracking; DAP, days after planting; POST, postemergence; PPI, preplant incorporated.

Effect of Cotton (Gossypium hirsutum) Tillage Systems on Off-Site Movement of Fluometuron, Norflurazon, and Sediment in Runoff1

Abstract: Research was conducted to determine the effects of tillage on fluometuron and norflurazon loss in runoff when applied preemergence in cotton. Cumulative water loss and norflurazon and fluometuron concentrations in runoff were not affected by tillage systems. In 1992, the no-till system had less sediment loss in runoff than the conventional tillage system. Tillage systems did not affect sediment loss in 1993. The highest amount of total fluometuron loss occurred with the conventional tillage system in 1992, whereas the reduced tillage system had the lowest amount in 1993. There were no differences in cumulative norflurazon loss between tillage systems in 1992, and as with fluometuron loss, norflurazon loss in runoff was less with the reduced tillage system in 1993. This research indicates that, while conservation tillage may reduce sediment loss, it may not necessarily be the best management tool for decreasing the loss of herbicides in runoff. Nomenclature: Cotton, Gossypium hirsutum L. ‘DES 119’. Additional index words: Conventional tillage, no-till, rainfall simulation, reduced tillage, stale seedbed, surface runoff. Abbreviations: CT, conventional tillage; DAT, days after herbicide treatment; GC, gas chromatography; HPLC, high-performance liquid chromatography; Koc, soil organic carbon sorption coefficient; NT, no-till; RT, reduced tillage.

Influence of Cultivation Timing on Pyrithiobac Performance in Cotton (Gossypium hirsutum) 1

Abstract: Pitted morningglory control with norflurazon or fluometuron preemergence (PRE), each at 1.12 kg/ha, was 72% or less 14 d after a postemergence (POST) application of pyrithiobac in 1993 and 1994. Pyrithiobac POST at 70 g/ha following fluometuron or norflurazon PRE cultivated at any timing controlled pitted morningglory at least 76%. Pyrithiobac POST controlled common cocklebur equal to the weed-free in 1993 at 14 d after the POST application. In 1994, when rated 28 d after pyrithiobac POST, cultivation 3 d before a single application of pyrithiobac controlled less common cocklebur than any other herbicide treatment containing pyrithiobac. At 28 d after pyrithiobac POST, no treatment controlled common cocklebur as well as the weed-free. In 1993 and 1994, seed cotton yield was equal to the weed-free when pyrithiobac followed fluometuron PRE cultivated at any timing or a single application of pyrithiobac cultivated prior to 7 d after POST application. Nomenclature: Fluometuron, N,N′-dimethyl-N′-[3-(trifluoromethyl)phenyl]urea; norflurazon, 4-chloro-5-(methylamino)-2-(3-(trifluoromethyl)phenyl)-3(2H)-pyridazinone; pyrithiobac, 2-chloro-6-[(4,6-dimethoxy-2-pyrimidinyl)thio] benzoic acid, sodium salt; common cocklebur, Xanthium strumarium L. #3 XANST; pitted morningglory, Ipomoea lacunosa L. # IPOLA; cotton, Gossypium hirsutum L. ‘DES-119’. Additional index words: Fluometuron, norflurazon, Ipomoea lacunosa, Xanthium strumarium, IPOLA, XANST. Abbreviations: ALS, acetolactate synthase (EC 4.1.3.18); DAPA, days after POST application; DBPA, days before POST application; DREC, Delta Research and Extension Center; fb, followed by; IAPA, immediately after POST application; POST, postemergence; PRE, preemergence; PSRC, Plant Science Research Center; SWSRU, Southern Weed Science Research Unit Farm.

Effects of Row Pattern Configurations and Reduced (1/2×) and Full Rates (1×) of Imazapic and Diclosulam for Control of Yellow Nutsedge (Cyperus Esculentus) in Peanut

Field studies were conducted from 2000 to 2002 to evaluate yellow nutsedge control and peanut yield when diclosulam and imazapic were applied at the rate recommended by the manufacturer (1×) and reduced (1/2×) rates in single and twin-row planting patterns. In 2001, both diclosulam and imazapic applied to the twin-row pattern at the full and reduced rate provided better yellow nutsedge control than herbicide applications to the single-row spacing. Because of excessive rainfall in 2002, yellow nutsedge control was considerably reduced with all treatments. Imazapic at the full rate (71 g/ha) controlled yellow nutsedge 80 to 96% in the twin-row pattern, and 79 to 86% in single-row spacings. Yellow nutsedge control was less than 65% when diclosulam and imazapic were applied at the reduced rate. The twin-row configuration yielded higher than the single-row pattern when averaged across herbicides in 1 yr. All herbicide treatments enhanced yield relative to the nontreated control, except the reduced rate of imazapic in 2002. This study revealed that to fully maximize yellow nutsedge control, the full rate of either imazapic or diclosulam should be applied to peanuts planted in a single or twin-row spacing. However, these treatments may not necessarily increase peanut yields. Nomenclature: Diclosulam; imazapic; yellow nutsedge, Cyperus esculentus L. CYPES; peanut, Arachis hypogaea L. ‘Georgia Green’

Weed Control and Bermudagrass Tolerance to Imazapic Plus 2,4-D

Field studies were conducted during the 2000 and 2001 growing seasons to evaluate imazapic plus 2,4-D for weed control and bermudagrass tolerance. Imazapic at 140 g ai/ha plus 2,4-D at 280 g ai/ha or greater controlled dallisgrass at least 82% and provided at least 90% control of field sandbur, johnsongrass, and field mint. A mixed stand of Texas panicum and large crabgrass was controlled less than 75% and bahiagrass less than 25% with all rates of imazapic plus 2,4-D. Coastal bermudagrass injury was greater than 24% at three of four locations and Tifton 85 injury was greater than 50% at 3 wk after treatment with rates of imazapic plus 2,4-D as low as 70 plus 140 g/ha. Coastal bermudagrass yield was reduced at the first cutting with imazapic plus 2,4-D at 140 plus 210 g/ha and 240 plus 420 g/ha. Imazapic plus 2,4-D at 200 plus 350 g/ha reduced Tifton 85 forage production at the first two cuttings. Nomenclature: Imazapic, 2,4-D, dallisgrass, Paspalum dilatatum Poir. PASDI, field mint, Perilla frutescens (L.) Britt. PRJFR, field sandbur, Cenchrus incertus M. A. Curtis CCHIN, johnsongrass, Sorghum halepense (L.) Pers. SORHA, Texas panicum, Panicum texanum Buckl. PANTE, large crabgrass, Digitaria sanguinalis (L.) Scop. DIGSA, bahiagrass, Paspalum notatum Fluegge PASNO, bermudagrass, Cynodon dactylon (L.) Pers. CYNDA, ‘Coastal’, ‘Tifton 85’

Effects of Fungicides, Time of Application, and Application Method on Control of Sclerotinia Blight in Peanut

Field studies were conducted from 2007 to 2010 to evaluate the response of peanut cultivars to different fungicides, application timings, and methods. Overall, fungicides reduced Sclerotinia blight incidence and increased pod yields when applied to susceptible and partially resistant cultivars. Disease suppression was greater when full fungicide rates were applied preventatively; however, yields between fungicide treated plots were similar. Lower levels of disease and higher yields were achieved with the partially resistant cultivar Tamrun OL07 compared to the susceptible cultivars Flavor Runner 458 and Tamrun OL 02. Despite possessing improved resistance Tamrun OL07 responded to all fungicide applications. While similar levels of disease control were achieved with broadcast or banded applications made during the day or at night, the yield response for the different application methods was inconsistent among years. A negative relationship (slope = −73.8; ; ) was observed between final disease incidence ratings and yield data from studies where a fungicide response was observed. These studies suggest that both boscalid and fluazinam are effective at controlling Sclerotinia blight in peanuts. Alternative management strategies such as nighttime and banded applications could allow for lower fungicide rates to be used; however, additional studies are warranted.

Yellow Nutsedge (Cyperus Esculentus) Control and Peanut Tolerance to S-Metolachlor and Diclosulam Combinations

Field studies were conducted in different peanut-growing areas of Texas during the 1999 through 2001 growing seasons to evaluate yellow nutsedge control and peanut tolerance to diclosulam alone applied PRE, S-metolachlor alone applied POST, or diclosulam applied PRE followed by (fb) S-metolachlor applied POST. Yellow nutsedge control was > 80% at five of six locations when diclosulam at 0.018 or 0.026 kg/ha applied PRE was fb S-metolachlor applied POST at 0.56, 1.12, or 1.46 kg ai/ha. Peanut stunting was noted with diclosulam at the High Plains locations but not at the Rolling Plains or south Texas locations. This stunting with diclosulam was due to a combination of peanut variety and high soil pH. Peanut yield was not always increased where yellow nutsedge was controlled. Nomenclature: Diclosulam, N-(2,6-dichlorophenyl)-5-ethoxy-7-fluoro[1,2,4]triazolo[1,5-c]pyrimidine-2-sulfonamide; S-metolachlor; yellow nutsedge, Cyperus esculentus L. CYPES; peanut, Arachis hypogaea L., ‘Flavor Runner 458’, ‘Florunner’, ‘Georgia Green’

Peanut Response to Carfentrazone-ethyl and Pyraflufen-ethyl Applied Postemergence1

Abstract Field experiments were conducted at six locations in Texas in 2004 and 2005 to evaluate peanut tolerance to carfentrazone-ethyl and pyraflufen-ethyl. Carfentrazone-ethyl at 27 and 36 g ai/ha or pyraflufen-ethyl at 2.6 and 3.5 g ai/ha were applied early postemergence (EP) 28 to 51 days after planting (DAP) or late postemergence (LP) 93 to 121 DAP in weed-free plots. In the Texas High Plains, carfentrazone-ethyl and pyraflufen-ethyl applied EP resulted in 62 and 48% visual injury, respectively, when rated 14 days after treatment (DAT). With the exception of the low rate of carfentrazone-ethyl at one location, this injury was greater than the injury caused by paraquat at 210 g ai/ha plus bentazon at 280 g ai/ha. All injury declined over time, but was still apparent at harvest (up to 3%). Peanut injury from applications made late postemergence did not exceed 16%. In the Rolling Plains, peanut injury did not exceed 12% at Lockett and 25% at Rochester regardless of herbicide, rate, or timing. In south ...

Influence of Simulated Imazapic and Imazethapyr Herbicide Carryover on Cotton (Gossypium hirsutum L.)

Field studies were conducted during the 2001 and 2002 growing seasons in the Texas peanut growing regions to simulate residual concentrations of imazapic and imazethapyr in the soil and subsequent effects on cotton (Gossypium hirsutum L.). Simulated imazapic or imazethapyr rates included 0, 1/64X (1.09 g ai/ha), 1/32X (2.19 g ai/ha), 1/16X (4.38 g ai/ha), 1/8X (8.75 g ai/ha), 1/4X (17.5 g ai/ha), and 1/2X (35 g ai/ha) of the full labeled rate for peanut (Arachis hypogaea L.) and incorporated prior to cotton planting. Cotton stunting with imazapic or imazethapyr was more severe at Denver City than other locations. All rates of imazapic and imazethapyr resulted in cotton stunting at Denver City while at Munday and Yoakum the 1/8X, 1/4X, and 1/2X rates of imazapic resulted in reduced cotton growth when compared with the untreated check. At all locations imazapic caused more stunted cotton than imazethapyr. Cotton lint yield was reduced by imazapic or imazethapyr at 1/4 X and 1/2 X rates at all locations when compared with the untreated check.

Peanut Response to Pyraflufen-ethyl Applied Postemergence

Field studies were conducted in various peanut production regions of Texas and Oklahoma during the 2013 and 2014 growing seasons to determine peanut response to single and sequential postemergence applications of pyraflufen-ethyl at the labelled use rate (3.6 g ai ha-1). Pyraflufen-ethyl injured peanut in all single and two-application treatments. Injury consisted of white spots on leaves up to 14 d after treatment and became small necrotic spots on older leaf tissue. No injury was apparent on any new growth. Injury did not translate into yield loss in three of five locations; however, yield reductions (approximately 26%) were observed in two of five locations. Peanut grade was not affected by pyraflufen-ethyl applications. Nomenclature: Pyraflufen, peanut, Arachis hypogaea L.