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A field study was conducted in 2017 and 2018 at the Louisiana State University Agricultural Center H. Rouse Caffey Rice Research Station near Crowley, LA, to evaluate the impact of reduced rates of halosulfuron on quizalofop activity in Louisiana rice production. Halosulfuron and a prepackaged mixture of halosulfuron plus thifensulfuron were evaluated at 0, 17, 35, or 53 g ai ha−1 and 34 or 53 g ai ha−1, respectively, in a mixture with quizalofop at 120 g ai ha−1. Control of barnyardgrass, red rice, and two non-acetyl-CoA carboxylase resistant rice lines, CL-111 and CLXL-745, were recorded at 14 and 28 d after treatment (DAT). The red rice, CL-111, and CLXL-745 represented a weedy rice population. Across all species evaluated at 14 DAT, all mixtures containing halosulfuron and halosulfuron plus thifensulfuron resulted in antagonism with an observed control of 79% to 90%, compared with an expected control of 96% to 99%. At 28 DAT, all mixtures containing halosulfuron resulted in neutral interactions for barnyardgrass control. Quizalofop mixed with halosulfuron plus thifensulfuron at the lower rate of 34 g ha−1 was able to overcome the antagonism compared with the higher rate of 53 g ha−1 for barnyardgrass control at 28 DAT. Both the high and the low rate of halosulfuron plus thifensulfuron resulted in antagonistic interaction for red rice, CL-111, and CLXL-745 control at 28 DAT. This research suggests that mixing quizalofop with halosulfuron plus thifensulfuron should be avoided, especially at the higher rate of 53 g ha−1.

A study was conducted at the Louisiana State University Agricultural Center’s H. Rouse Caffey Rice Research Station in 2017 and 2018 to evaluate the interaction between a prepackage mixture of clomazone plus pendimethalin applied at 0, 760, 1,145, or 1,540 g ai ha−1 mixed with propanil at 0, 1,120, 2,240, or 4,485 g ai ha−1. A synergistic response occurred when barnyardgrass was treated with all rates of clomazone plus pendimethalin mixed with either rate of propanil evaluated at 56 d after treatment (DAT). Unlike barnyardgrass, an antagonistic response occurred in yellow nutsedge used as a control when treated with 760 and 1,540 g ha−1 of clomazone plus pendimethalin mixed with 1,120 or 22,40 g ha−1 of propanil at 28 DAT; however, 1,145 g ha−1 of clomazone plus pendimethalin mixed with 4,485 g ha−1 of propanil resulted in a neutral interaction. At 28 DAT, rice flatsedge treated with all herbicide mixtures resulted in neutral interactions. The synergism of clomazone plus pendimethalin applied at 1,540 g ha−1 mixed with propanil applied at 2,240 or 4,485 g ha−1 to control barnyardgrass resulted in an increased rough rice yield compared with 760 or 1,145 g ha−1 of clomazone plus pendimethalin mixed with propanil applied at 1,120 or 2,240 g ha−1. These results indicate that if barnyardgrass and rice flatsedge are present in a rice field the prepackage mixture of clomazone plus pendimethalin mixed with propanil can be an option for growers. However, if yellow nutsedge infest the area other herbicides may be needed.

A major concern of sweetpotato producers is the potential negative effects from herbicide drift or sprayer contamination events when dicamba is applied to nearby dicamba-resistant crops. A field study was initiated in 2014 and repeated in 2015 to assess the effects of reduced rates of N,N-Bis-(3-aminopropyl)methylamine (BAPMA) or diglycloamine (DGA) salt of dicamba, glyphosate, or a combination of these individually in separate trials with glyphosate on sweetpotato. Reduced rates of 1/10, 1/100, 1/250, 1/500, 1/750, and 1/1,000 of the 1× use rate of each dicamba formulation at 0.56 kg ha−1, glyphosate at 1.12 kg ha−1, and a combination of the two at aforementioned rates were applied to ‘Beauregard’ sweetpotato at storage root formation (10 d after transplanting) in one trial and storage root development (30 d after transplanting) in a separate trial. Injury with each salt of dicamba (BAPMA or DGA) applied alone or with glyphosate was generally equal to or greater than glyphosate applied alone at equivalent rates, indicating that injury is most attributable to the dicamba in the combination. There was a quadratic increase in crop injury and a quadratic decrease in crop yield (with respect to most yield grades) observed with an increased herbicide rate of dicamba applied alone or in combination with glyphosate applied at storage root development. However, with a few exceptions, neither this relationship nor the significance of herbicide rate was observed on crop injury or sweetpotato yield when herbicide application occurred at the storage root formation stage. In general, crop injury and yield reduction were greatest at the highest rate (1/10×) of either salt of dicamba applied alone or in combination with glyphosate, although injury observed at lower rates would be cause for concern after initial observation by sweetpotato producers. However, in some cases yield reduction of No.1 and marketable grades was observed following 1/250×, 1/100×, or 1/10× application rates of dicamba alone or with glyphosate when applied at storage root development.

A field study was conducted in 2015 and 2016 at the H. Rouse Caffey Rice Research Station near Crowley, Louisiana, to evaluate the interactions of quizalofop and a mixture of propanil plus thiobencarb applied sequentially or mixed to control weedy rice and barnyardgrass. Visual weed control evaluations occurred at 14, 28, and 42 d after treatment (DAT). Quizalofop was applied at 120 g ai ha–1 at 7, 3, and 1 d before and after propanil plus thiobencarb were each applied at 3,360 g ai ha–1. In addition, quizalofop was applied alone and in a mixture with propanil plus thiobencarb at day 0. Control of red rice ‘CL-111' and ‘CLXL-745' was greater than 91% when quizalofop was applied alone at day 0, similar to control for quizalofop applied 7, 3, and 1 d prior to propanil plus thiobencarb at all evaluation dates. Control of the same weeds treated with quizalofop plus propanil plus thiobencarb applied in a mixture at day 0 was 70% to 76% at each evaluation date, similar to quizalofop applied 1 or 3 d after propanil plus thiobencarb. A similar trend in control of barnyardgrass by 88% to 97% occurred when quizalofop was applied alone and by 48% to 53% at 14, 28, and 42 DAT when the mixture was used. ‘PVL01’ rough rice yield was 4,060 kg ha–1 when treated with quizalofop alone; however, yield was reduced to 3,180 kg ha–1 when it was treated with quizalofop mixed with propanil plus thiobencarb at day 0, similar to PVL01 rice treated with quizalofop 1 or 3 d following the propanil plus thiobencarb application.Nomenclature: quizalofop; propanil; thiobencarb; barnyardgrass; Echinochloa crus-galli (L.) P. Beauv; weedy rice, Oryza sativa L; rice, Oryza sativa L

A field study was conducted during the 2016 and 2017 crop seasons at the LSU AgCenter H. Rouse Caffey Rice Research Station to evaluate weed control and rice yield after quizalofop-p-ethyl applications in water-seeded coenzyme A carboxylase (ACCase)–resistant ‘PVLO1’ long-grain rice production utilizing different flood systems, application timings, and quizalofop rates. The initial application of quizalofop was applied at five timings beginning when ‘PVLO1’ rice was at the coleoptile stage (PEG) through the one- to two-tiller stage. A total quizalofop rate of 240 g ai ha–1 was split into two applications: 97 followed by 143 g ha–1 or 120 followed by 120 g ai ha–1 in both pinpoint and delayed flood water-seeded management systems. A second quizalofop application was applied 14 d after initial treatment (DAIT). At 14 DAIT, a reduction in control of barnyardgrass and red rice was observed by delaying the initial quizalofop application to the two- to four-tiller stage compared with rice treated at earlier growth stages. At 42 DAIT, control of barnyardgrass was 94% to 96%, and red rice was 98% following the second application of quizalofop, regardless of initial application timing. Rice treated with quizalofop at the PEG and two- and three-leaf stage resulted in a rice height of 104 cm at harvest compared with 96 to 100 cm when the initial application of quizalofop was delayed to later growth stages. Applying the initial application of quizalofop to rice at the PEG timing in the pinpoint or the delayed flood system resulted in a total gross value per hectare of $450 and $590, respectively. Within each flood system, delaying the initial application of quizalofop to the one- to two-tiller stage resulted in a gross per-hectare value reduction of $100 ha-1 in the pinpoint flood and $110 ha-1 in the delayed flood.

Acetyl co-enzyme A carboxylase (ACCase)-resistant rice allows quizlaofop-p-ethyl to be applied as a POST control of troublesome grass weeds. A field study was conducted in 2017 and 2018 at the H. Rouse Caffey Rice Research Station near Crowley, LA, to evaluate the influence of a crop oil concentrate (COC), a silicon-based surfactant plus a nitrogen source (SNS), or a high-concentrate COC (HCOC) in overcoming the grass weed control antagonism of quizalofop-p-ethyl when mixed with bispyribac-Na. Quizalofop-p-ethyl was applied at 120 g ai ha−1, bispyribac-Na was applied at 34 g ai ha−1, and all adjuvants were applied at 1% vol/vol. Antagonistic interactions were observed at 14 d after treatment (DAT) when quizalofop-p-ethyl was mixed with bispyribac-Na with no adjuvant for control of barnyardgrass, the non–ACCase-tolerant rice cultivars ‘CL-111’ and ‘CLXL-745’, and red rice. At 14 DAT, antagonism of quizalofop-p-ethyl for control of barnyardgrass was observed when mixed with bispyribac-Na plus COC, SNS, or HCOC, with an observed control of 43%, 63%, and 86%, respectively, compared with an expected control of 95% for quizalofop-p-ethyl alone. However, the antagonism of quizalofop-p-ethyl when mixed with bispyribac-Na plus HCOC for barnyardgrass control at 14 DAT was overcome by 28 DAT, with an observed control of 91%, compared with an expected control of 97%. Synergistic or neutral interactions were observed at 14 and 28 DAT when COC, SNS, or HCOC was added to a mixture of quizalofop-p-ethyl plus bispyribac-Na for CL-111, CLXL-745, and red rice control. According to the results of this study, HCOC is the most effective adjuvant for quizalofop-p-ethyl and bispyribac-Na mixtures for control of weedy rice and barnyardgrass.

A study was conducted at the Louisiana State University Agricultural Center's H. Rouse Caffey Rice Research Station in 2017 and 2018 to evaluate a prepackaged mixture of clomazone plus pendimethalin applied delayed preemergence (DPRE) or POST within an herbicide residual overlay with saflufenacil, clomazone, or quinclorac. POST applications included penoxsulam or halosulfuron in combination with the second residual application. No differences were observed in barnyardgrass control (92% to 98%) at 14 days after treatment (DAT). At 42 DAT, barnyardgrass treated with clomazone plus pendimethalin in combination with either clomazone or quinclorac at either timing was controlled 95% to 96%. However, when saflufenacil was applied PRE, regardless of the POST herbicide or when saflufenacil was applied POST with halosulfuron, barnyardgrass control was reduced to 78% to 81%, compared with 95% to 96% with the control with all other residual combinations. Yellow nutsedge and rice flatsedge control increased when treated with halosulfuron compared with penoxsulam across all evaluation dates. At 28 and 42 DAT, texasweed treated with saflufenacil PRE, regardless of POST applications, was controlled 83% and 87%, respectively, and this was greater control than provided by clomazone or quinclorac applied PRE regardless of POST herbicide program.Nomenclature: clomazone; halosulfuron; pendimethalin; penoxsulam; quinclorac; saflufenacil; barnyardgrass; Echinochloa crus-galli (L.) Beauv.; rice, Orzya sativa (L.); rice flatsedge, Cyperus iria (L.); texasweed, Caperonia palustris (L.) St.-Hil; yellow nutsedge, Cyperus esculentus (L.)

A glasshouse study was conducted on the Louisiana State University campus in Baton Rouge, LA, to evaluate the control of brook crowngrass, rice cutgrass, southern watergrass, and water paspalum. Florpyrauxifen-benzyl was applied at 30 g ai ha−1 to each grass species at the 3- to 4-leaf or 1- to 2-stolon stage of growth. Brook crowngrass treated with florpyrauxifen was controlled 71% at 21 d after treatment. Southern watergrass and water paspalum control did not exceed 56% and 36%, respectively, across all evaluations. Rice cutgrass treated with florpyrauxifen did not reach 15% control. Plants treated with florpyrauxifen, except rice cutgrass, displayed reduction in leaf number, stolon number, plant height, and plant fresh weight. These results indicate florpyrauxifen-benzyl can help manage a brook crowngrass infestation and suppress southern watergrass. However, florpyrauxifen-benzyl has little to no activity on water paspalum and rice cutgrass, and other management options should be employed if these weeds are present.

All herbicides will move off-target to sensitive crops when not applied correctly. Therefore, low-dose applications of flumioxazin and metribuzin were evaluated in soybean at the unifoliate, V2, and V4 growth stages. Rates evaluated were 12.5%, 25%, and 50% of the labeled use rates of 72 and 316 g ai ha−1 of flumioxazin and metribuzin, respectively. Flumioxazin injury was characterized by necrosis and visible height and width reduction. Injury increased with rate 3 d after treatment (DAT), with unifoliate, V2, and V4 soybean injured 15% to 30%, 18% to 27%, and 5% to 8%, respectively. Unifoliate and V4 soybean were injured more than V4 soybean 3 to 14 DAT, but injury decreased to −1 and a revenue loss of 71 to 141 US$ ha−1. Metribuzin injury was primarily chlorosis with necrosis and a visible reduction in soybean height and width. Soybean at the V2 growth stage was injured 14% more than V4 soybean 3 DAT, regardless of metribuzin rate. Injury to V2 and V4 soybean was similar 14 DAT, with injury of 21% to 40% across rates. Soybean injury when treated at the V2 and V4 growth stages was 6% to 29% 42 DAT compared to unifoliate soybean at 0 to 17%. Soybean yields in the metribuzin study yields were 96% to 98% of the nontreated. However, a 2% to 4% reduction equates to a loss of 90 to 180 kg ha−1 and a revenue loss of 32 to 65 US$ ha−1. Unifoliate and V2 soybean are more sensitive to a low dose of flumioxazin POST, and V2 and V4 soybean are more sensitive to a low dose of metribuzin POST. Injury and the impact on soybean growth could potentially cause economic loss for a soybean producer.

Henbit is a winter annual weed that is not effectively controlled by spring-applied herbicide applications. Research was conducted to determine henbit's emergence pattern and whether fall-applied residual herbicides would be effective for henbit control in the spring. Henbit emerges in Louisiana from late October through March, but emergence predominantly occurs in the last week of October through the first week of December. Applying paraquat plus flumioxazin, oxyfluorfen, or rimsulfuron:thifensulfuron November 1 through December 15 provided better than 90% henbit control in March. Applying paraquat plus S-metolachlor on November 15 or December 1 provided 92% henbit control, which was similar to flumioxazin, oxyfluorfen, and rimsulfuron:thifensulfuron. The addition of flumioxazin, oxyfluorfen, or rimsulfuron:thifensulfuron to paraquat reduced the height of henbit plants by 4% to 22% of nontreated plants when applied November 1 through December 15. These studies indicate that crop producers can achieve control of henbit in March following November 1 through December 15 applications of paraquat plus flumioxazin or rimsulfuron:thifensulfuron; however, paraquat plus oxyfluorfen can be applied October 15 through December 15 to achieve similar control.Nomenclature: Flumioxazin; oxyfluorfen; paraquat; rimsulfuron:thifensulfuron; S-metolachlor; henbit, Lamium amplexicaule L. LAMAM

A glasshouse study was established at Louisiana State University campus in Baton Rouge, LA, to evaluate the control of fall panicum and Nealley's sprangletop treated with florpyrauxifen-benzyl. Florpyrauxifen was applied at 30 g ai ha-1 to each grass species at the three- to four-leaf and oneto two-tiller stages of growth. At 21 d after treatment (DAT), fall panicum control was 91% when treated with florpyrauxifen at the three- to four-leaf stage, and Nealley's sprangletop control was 78% to 82%, regardless of application timing 21 DAT. Leaf number, tiller number, plant height, and plant fresh weight were reduced when fall panicum and Nealley's sprangletop were treated with florpyrauxifen. This information can be useful for developing weed management strategies with this herbicide for rice production, and it provides an additional mode of action to help manage and/or delay the development of herbicide-resistant weeds.Nomenclature: Florpyrauxifen-benzyl [benzyl-4-amino-3- chloro-6-(4-chloro-2-fluoro-3-methoxyphenyl)- 5-fluoropyridine-2-carboxylate]; fall panicum, Panicum dichotomiflorum Michx.; Nealley's sprangletop, Leptochloa nealleyi Vasey; rice, Oryza sativa L.

Two field studies were conducted in Louisiana to determine the impact of Nealley’s sprangletop on rough rice yield under multiple environments in 2014, 2015, and 2016. The first study evaluated optimal timings of Nealley’s sprangletop removal for optimizing rough rice yields. The second study evaluated the impact of Nealley’s sprangletop densities on rough rice yield. Nealley’s sprangletop was removed with applications of fenoxaprop at 122 g ai ha–1at 7, 14, 21, 28, 35, and 42 d after emergence (DAE). Nealley’s sprangletop removal at 7 and 14 DAE resulted in higher rough rice yields of 7,880 and 6,960 kg ha–1, respectively, when compared with the rice from the season-long Nealley’s sprangletop competition with a 6,040 kg ha-1yield. Delaying herbicide application from 7 DAE to 42 DAE resulted in a yield loss of 1,740 kg ha–1. Over the 35-d delay in application, rough rice yield loss from Nealley’s sprangletop interference was equivalent to 50 kg ha–1d–1. Nealley’s sprangletop densities were established at 1, 3, 7, 13, and 26 plants m–2by transplanting Nealley’s sprangletop when rice reached the one- to two-leaf stage. At Nealley’s sprangletop densities of 1 to 26 plants m–2, rough rice yields were reduced 10 to 270 kg ha–1, compared with the rice from weed-free plots. Based on regression analysis, Nealley’s sprangletop densities of 1, 35, 70, and 450 plants m–2reduced rough rice yield 0.14%, 5%, 10%, and 50%, respectively.

A field study was conducted in 2015 and 2016 at the H. Rouse Caffey Rice Research Station (RRS) to evaluate antagonistic, synergistic, or neutral interactions of quizalofop when mixed with ALS-inhibiting herbicides labeled in rice production. Quizalofop was applied at 120 g ai ha−1. Mixture herbicides included penoxsulam at 40 g ai ha−1, penoxsulam+triclopyr at 352 g ai ha−1, halosulfuron at 53 g ai ha−1, bispyribac at 34 g ai ha−1, orthosulfamuron+halosulfuron at 94 g ai ha−1, orthosulfamuron+quinclorac at 491 g ai ha−1, imazosulfuron at 211 g ai ha−1, and bensulfuron at 43 g ai ha−1. All ALS herbicides mixed with quizalofop indicated antagonistic responses for red rice, CL-111, CLXL 745, or barnyardgrass control at either 14 or 28 days after treatment (DAT). At 28 DAT, quizalofop mixed with penoxsulam or bispyribac controlled barnyardgrass 34 to 38%, compared with an expected control of 97%. In addition, these same mixtures controlled red rice, CL-111, and CLXL-745 61 to 67% at 28 DAT compared with an expected control of 96 to 97%. A second application of quizalofop at 120 g ha−1was applied at 28 DAT. At 42 DAT, neutral responses were indicated for all mixtures except with quizalofop mixed with penoxsulam containing products.

A study was conducted at three locations in Louisiana to evaluate the response of common Louisiana rice weed species to different rates of application of benzobicyclon herbicide. Benzobicyclon was applied at 31, 62, 123, 185, 246, 493, 739, 986, and 1,232 g ai ha-1 into flooded field conditions when ducksalad was at the first elongated-leaf stage. Barnyardgrass, false pimpernel, and yellow nutsedge control never exceeded 50% from any rate of benzobicyclon applied, averaged across evaluation timing. Ducksalad control, averaged across evaluation timing, was 83% when treated with 493 g ha-1 and did not increase when treated with higher rates of benzobicyclon. At 42 d after treatment (DAT), purple ammannia and Indian toothcup treated with 185 and 246 g ha-1 of benzobicyclon were controlled 58% and 81%, respectively, and did not differ in control compared with higher rates of benzobicyclon. All weeds were hand-harvested from each plot and separated by species at the conclusion of the study. No differences in fresh-weight biomass were observed for barnyardgrass, false pimpernel, purple ammannia, or yellow nutsedge. Treatment with benzobicyclon at ≥62 g ha-1 resulted in reduced ducksalad fresh weight 42 DAT compared with the nontreated sample. Indian toothcup fresh weight was reduced 77% to 96% compared with the nontreated sample when treated with benzobicyclon at 246 to 1,232 g ha-1.Nomenclature: Benzobicyclon; barnyardgrass, Echinochloa crus-galli (L.) Beauv.; ducksalad, Heteranthera limosa (Sw.) Willd.; false pimpernel, Lindernia dubia (L.) Pennell var. dubia; Indian toothcup, Rotala indica (Willd.) Koehne; purple ammannia, Ammannia coccinea Rottb.; yellow nutsedge, Cyperus esculentus L.

A study was conducted in three locations in Louisiana to evaluate interactions of imazethapyr at 0 and 70 g ai ha-1 mixed with propanil at 0, 1,120, 2,240, 3,360, and 4,480 g ha-1 for the control of red rice, barnyardgrass, and hemp sesbania. According to Blouin's modified Colby's, a synergistic response occurred for red rice treated with imazethapyr mixed with propanil at 4,480 g ha-1 for all evaluations. Observed control was 93% to 95% compared with expected control of 81% to 87%. An antagonistic response occurred for barnyardgrass control with imazethapyr mixed with propanil at 1,120 g ha-1 at 35 and 49 d after treatment (DAT), with control of 75% and 64%, respectively, compared with expected control of 89% and 78%. However, a neutral response occurred for barnyardgrass control when treated with all other imazethapyr plus propanil combinations. An antagonistic interaction occurred for hemp sesbania when treated with imazethapyr plus propanil at 3,360 and 4,480 g ha-1 at 21 DAT with an observed control of 89% compared with an expected control of 96%; however, a neutral response occurred at all other evaluation dates. An increase in rice yield was observed with an imazethapyr plus propanil at 4,480 g ha-1 mixture compared with a single application of imazethapyr or propanil at any rate evaluated.Nomenclature: Imazethapyr; propanil; barnyardgrass, Echinochloa crus-galli (L.) Beauv.; hemp sesbania, Sesbania herbacea (P. Mill.) McVaugh; red rice/rice, Oryza sativa L.

Weed-free field experiments were conducted to evaluate soybean injury, growth, and yield following PRE or POST pyroxasulfone application. Soybean was injured 1 and 15% following pyroxasulfone PRE and POST application, respectively, 7 d after treatment (DAT). Injury following PRE and POST application was observed as delayed emergence and leaf necrosis and crinkling, respectively. Injury ranged from 0 to 6% following both application timings 14 and 28 DAT. Soybean was injured 5% or less following 60, 120, 180, 240, and 300 g ha-1 of pyroxasulfone. Soybean plant population, height, and yield were not affected by pyroxasulfone application timing. Only 300 g ha-1 of pyroxasulfone reduced soybean plant population to 90% of the nontreated 30 d after PRE. Pyroxasulfone rate did not influence soybean heights and yield. Data indicates that pyroxasulfone can safely be applied to soybean without a detrimental effect on plant growth or yield. Nomenclature: Glyphosate; pyroxasulfone; soybean, Glycine max (L.) Merr.

A major hindrance to establishment of successful complementary forage systems that include warm-season perennial grasses and clovers is tolerance of the latter to herbicides available for weed control. Field experiments were conducted in 2013 at two locations in northeast Louisiana to evaluate simulated residual rate effects of fluroxypyr plus triclopyr and 2,4-D plus picloram applied at 0, 0.25, 0.38, and 0.5× use rates immediately after fall planting of ball, white, crimson, and red clover. For all clovers, when averaged across herbicide rates, plant population 161/171 d after planting (DAP), ground cover, and height 184/196 DAP were equivalent for fluroxypyr plus triclopyr and the nontreated control and greater than 2,4-D plus picloram. Averaged across clovers, plant height after all rates of fluroxypyr plus triclopyr was equivalent to the nontreated control (14.2 to 14.3 vs. 15.3 cm) and greater than 2,4-D plus picloram. Compared with the nontreated control, 2,4-D plus picloram at 25, 38, and 50% of the normal use rates reduced height 58, 76, and 85%, respectively. When averaged across clover species, yield for fluroxypyr plus triclopyr at all rates was equivalent to the nontreated control (2,624 to 2,840 vs. 2,812 kg ha−1). Compared with the nontreated control, 2,4-D plus picloram at the 0.25, 0.38, and 0.50× use rates reduced yield 65, 89, and 99%, respectively.

A study was established to evaluate interactions between imazamox at 0 and 44 g ai ha−1mixed with propanil at 0, 1,120, 2,240, 3,360, and 4,480 g ai ha−1for the control of red rice and barnyardgrass. Blouin's Modified Colby's procedure was used to test for interactions. At 7 d after treatment (DAT), a synergistic response occurred for red rice treated with imazamox at 44 g ha−1mixed with propanil at 3,360 and 4,480 g ha−1by increasing expected control of 62% to an observed control of 67 and 75%, respectively, and the synergistic response continued across all evaluations through 49 DAT. No antagonism occurred for any imazamox plus propanil mixture for red rice control. An antagonistic response was shown for barnyardgrass control with imazamox at 44 g ha−1mixed with any rate of propanil, at 7 DAT. However, imazamox plus propanil at 4,480 g ha−1resulted in a neutral response at 14 through 49 DAT. Rice treated with imazamox plus propanil at 4,480 g ha−1plus imazamox resulted in a yield of 6,640 kg ha−1. The synergistic response observed for red rice control with a mixture of imazamox plus propanil can benefit producers by increasing control of red rice, and this mixture contains two different modes of action that can be part of an overall resistance management strategy.

A study was conducted near Crowley, Louisiana, to evaluate the efficacy of quizalofop-p-ethyl mixed with different synthetic auxin and ACCase-inhibiting herbicides for barnyardgrass and weedy rice control in rice production systems. Quizalofop was applied at 0 or 120 g ai·ha−1 mixed with 2,4-D at 1336 g ai·ha−1, triclopyr at 282 g ai·ha−1, quinclorac at 420 g ai·ha−1, cyhalofop-butyl at 314 g ai·ha−1, or fenoxaprop-p-ethyl at 122 g ai·ha−1. Cyhalofop, fenoxaprop, 2,4-D, quinclorac, and triclopyr antagonized quizalofop for barnyardgrass control at 14 days after treatment (DAT). At 28 DAT, an antagonistic response persisted for barnyardgrass control, except when cyhalofop was mixed with quizalofop, which indicated a neutral response. Red rice, CLXL-745, and CL-111 control decreased due to antagonism of quizalofop when mixed with 2,4-D. However, quinclorac, triclopyr, cyhalofop, or fenoxaprop mixed with quizalofop resulted in a neutral response for red rice, CLXL-745, and CL-111 control at 28 DAT.

Field studies were conducted near Crowley, LA to evaluate the effects of simulated herbicide drift on ‘Cocodrie' rice. Each treatment was made with the spray volume varying proportionally to herbicide dosage based on a spray volume of 234 L ha−1and a glufosinate rate of 493 g ai ha−1. The 6.3%, 31 g ha−1, herbicide rate was applied at a spray volume of 15 L ha−1and the 12.5%, 62 g ha−1, herbicide rate was applied at a spray volume of 29 L ha−1. Glufosinate applied at one-tiller, panicle differentiation (PD) growth stage, and boot resulted in crop injury at 7 and 14 d after treatment. At 21 and 28 d after treatment, crop injury was still evident but was less than 10%. Glufosinate applied at one-tiller resulted in plant height reductions of 4 to 6%; however, at harvest, height reductions were 1% or less. Glufosinate applied to rice in the boot stage had lower rice yield in the primary crop, but no difference was observed in the ratoon crop. Harvested seed from the primary crop germinated 7 to 11% less than the nontreated when rice was treated with 31 and 62 g ha−1of glufosinate. Seedling vigor was reduced when treated with 31 and 62 g ha−1of glufosinate.

The sugarcane borer, Diatraea saccharalis (Fabricius) (Lepidoptera: Crambidae), is a major agronomic pest in the southeastern USA. This study was conducted to investigate the performance of D. saccharalis on eight rice cultivars widely grown in Louisiana and to assess the relationship between oviposition preference and offspring performance. In a previous study, oviposition preference of sugarcane borers was found to vary on the same eight rice cultivars. In this study, variation in larval performance on the eight cultivars was observed. The overall performance of larvae in terms of relative growth rate and boring success of larvae was highest on Priscilla and Cocodrie. Larval performance was lower on the hybrid XL723, the Clearfield (herbicide-resistant) variety CL161, and the medium grain Bengal. Also, larvae took more time to enter into the stem of the hybrid XL723 compared with Cocodrie. Significant positive correlations were observed among relative growth rate and boring success and between larval performance and oviposition preference. Significant positive correlations among measures of larval performance and oviposition preference suggest the operation of a common resistance mechanism. Results in laboratory and greenhouse extended into the field, where Cocodrie and Cheniere were the most damaged cultivars, whereas CL161 and the medium grain Jupiter were least injured in terms of average number of stem borer entry/exit holes per plant. Results from this study could contribute to the use of resistant cultivars in an integrated management program for stem borers and the resistant cultivars identified in this study could be used as sources of resistance in breeding programs for resistance against stem borers.

Field studies were conducted near Crowley, LA in 2005 through 2007 to evaluate the effects of simulated herbicide drift on ‘Cocodrie' rice. Each application was made with the spray volume varying proportionally to herbicide dosage based on a constant spray volume of 234 L ha−1 and a glyphosate rate of 863 g ae ha−1. The 6.3%, 54–g ha−1, herbicide rate was applied at a spray volume of 15 L ha−1, and the 12.5%, 108–g ha−1, herbicide rate was applied at a spray volume of 29 L ha−1. Compared with the nontreated, glyphosate applied at one tiller, panicle differentiation (PD), and boot resulted in increased crop injury. The greatest injury was observed on rice treated at the one-tiller timing. Applications of glyphosate at one tiller, PD, and boot reduced plant height at harvest and primary and total crop yield. Rice treated at primary crop maturity was not affected by glyphosate applications.

Studies were conducted to evaluate growth and reproductive capabilities of creeping rivergrass in response to rice herbicide programs. Creeping rivergrass grown from single-node stolon segments, multiple-node stolon segments, and rhizomes was treated with various herbicides to evaluate activity on subsequent growth and viability of nodes produced from treated plants. Comparison with the nontreated, cyhalofop, glyphosate, and imazethapyr reduced creeping rivergrass fresh weight by more than 84 to 96%. Glyphosate reduced sprouting of nodes from treated plants 93% compared with nontreated plants. Activity from these herbicides may decrease when applied to plants grown from rhizomes versus rhizome clusters. Plants treated with cyhalofop, glyphosate, and imazethapyr had reduced fresh weight of 36 to 46% when plants were grown from a rhizome cluster, and 69 to 90% when plants were grown from a single rhizome segment, compared with nontreated. Cyhalofop and glyphosate reduced node sprouting by 81 to 98% of nontreated, regardless of parent structure.

Field studies were conducted in 2008 and 2009 near Crowley, Louisiana, to evaluate the addition of different propanil formulations in mixture with a standard imazethapyr program of 70 g ai ha−1 early postemergence followed by (fb) 70 g ha−1 late postemergence. Weeds evaluated included red rice, barnyardgrass, Texasweed, and alligatorweed. Control of all species with treatments, including a propanil formulation applied at 3,400 g ai ha−1, was equivalent to, or greater than, the standard imazethapyr program. Rough rice yield and economic returns were maximized when the propanil formulations of Propanil 1 or Propanil 3 were mixed with imazethapyr in the early postemergence applications. The addition of propanil to imazethapyr increased rough rice yield and economic returns because of improved weed control. Nomenclature: Imazethapyr; propanil; alligatorweed, Althernanthera philoxeroides (Mart.) Griseb.; barnyardgrass, Echinochloa crus-galli (L.) Beauv; red rice, Oryza sativa L.; Texasweed, Caperonia ...

Twelve thousand to 16,000 ha of Louisiana sugarcane (Saccharum spp.) fields were flooded by saltwater from the Hurricane Rita storm surge in September 2005. A four treatment, 12-replication study comparing storm surge flooded and nonflooded plant and ratoon sugarcane fields was conducted during summer 2006 to assess sugarcane borer, Diatraea saccharalis (F.), pest severity, pest control actions, and soil-associated arthropod abundance and diversity. Even with a significant 2.4-fold increase in the average number of insecticide applications used for D. saccharalis management in flooded fields, growers still incurred higher injury. A significant 2.8-fold reduction in the predaceous red imported fire ant, Solenopsis invicta Buren, was associated with the storm surge, whereas no reduction in abundance of other soil-associated arthropods was recorded. Arthropod diversity measured by the Shannon diversity index significantly increased by a factor of 1.3 in sugarcane fields flooded by the storm surge. Increase in D. saccharalis pest severity associated with the storm surge caused an estimated loss in revenue between $1.9 and $2.6 million to the Louisiana sugarcane industry for the 2006 production season.

Steers and heifers were generated from Angus (A) and Belgian Blue (BB) sires mated to Brahman x Hereford (B x H) F(1) cows to characterize their growth, carcass traits, and LM shear force. A total of 120 B x H cows purchased from 2 herds and 35 bulls (14 A and 21 BB) produced calves during the 5-yr project. After the stocker phase, a representative sample of A- and BB-sired heifers and steers were transported to the Iberia Research Station to be fed a high-concentrate diet. The remaining cattle were transported to a commercial feedlot facility. Each pen of cattle from the commercial feedlot was slaughtered when it was estimated that heifers and steers had 10 mm of fat or greater. The BB-sired calves were heavier at birth (P < 0.01) than the A-sired calves. During the feedlot phase, the A-sired calves gained more BW (P < 0.05) than the BB-sired calves. The BB-sired calves had heavier (P < 0.01) carcass weights than the A-sired calves. This was due to a combination of a heavier final BW and greater dressing percent. Because of their greater muscling and reduced (P < 0.01) fat, carcasses from BB-sired calves had greater yield (P < 0.01) compared with carcasses from A-sired calves. Carcasses from A-sired calves had a greater (P < 0.01) marbling score and greater (P < 0.01) USDA quality grade than carcasses from BB-sired calves. Tenderness, as measured by shear force of the steaks aged for 7 d, was similar for A- and BB-sired calves. However, steaks aged for 14 d from the A-sired calves had a reduced shear force (P < 0.01) compared with steaks from the BB-sired calves. Steer calves were heavier (P < 0.01) at birth and weaning, and had more total BW gain in the feedlot, which resulted in a heavier final BW and HCW compared with the heifers. Steer carcasses also had greater marbling scores and quality grades, whereas the heifer carcasses had larger LM area per 100 kg of carcass weight. In conclusion, the BB-sired calves had heavier carcass weights and greater cutability, whereas the A-sired calves had a greater degree of marbling and greater quality grade, and steaks from carcasses of A-sired calves were more tender as measured by shear force at 14 d.

Field trials were conducted during 2006 and 2007 and a container study was performed twice in 2007 at the Dean Lee Research and Extension Center in Alexandria, LA to evaluate the interaction of glyphosate and zinc coapplied to selected weeds. Across all experiments, no differences in either visible weed control or weed fresh weight were detected among glyphosate formulations. In the field studies, weed control was greatest when glyphosate was applied alone, in which case control of barnyardgrass, browntop millet, and Palmer amaranth ranged between 93 and 95%. When glyphosate was coapplied with formulations of zinc, control of the aforementioned weed species was reduced to 39, 39, and 45%, respectively. Visual estimates of weed control in the container studies showed glyphosate performance to be the highest (82 to 98%) in the absence of zinc for control of barnyardgrass, browntop millet, johnsongrass, ivyleaf morningglory, and redroot pigweed. Across all weed species, control was reduced 43 to 59% when zinc was coapplied with glyphosate. Similar results were noted in reduction of weed fresh weights. Results indicate that glyphosate-based weed control is reduced when coapplied with the zinc products at their current use rates. Producers should be aware of this antagonism and these coapplications should not be recommended.

Populations of the bollworm, Helicoverpa zea (Boddie), and the tobacco budworm, Heliothis virescens (F.), were monitored with pheromone-baited wire cone traps on the Red River Research Station from 1986 to 2005. Data are presented on population variation and changes observed during the sampling period for the months of May through August. Bollworm moths made up 87.8, 79.0, 82.7, and 63.5% of the total number of male moths captured in May through August, respectively. Overall, 76.3% of the male moths captured from May though August were bollworms. The abundance of bollworms in pheromone traps indicated considerable variation on a yearly and monthly basis. The number of bollworms captured in traps and an analysis of variance provided no evidence that the introduction of Bt cotton in 1996 had any significant effect on bollworm abundance at this location. However, abundance of tobacco budworm has been decreasing since approximately 1993–1994. Analysis of variance confirmed that abundance of male tobacco budwo...

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 nontr...

A study was conducted to test the effect of water clarity, as related to water seeding system, on herbicide efficacy in water-seeded imidazolinone-resistant rice production. Red rice control was 88 to 89% when 140 g/ha imazethapyr was applied in a single application immediately prior to permanent flood in the clear-water seeding system. All herbicide applications in either clear- and muddy-water systems controlled red rice 90 to 95%. The benefits of reducing soil erosion and surface water contamination from muddy-water discharge at seedling establishment can be obtained in a clear-water system without experiencing a decrease in weed control or rice yield. Nomenclature: Imazethapyr, red rice, Oryza punctata Kotchy ex. Steud., rice, Oryza sativa L

Field studies were conducted 2004 and 2005 to evaluate weed control following POST applications of glyphosate in combination with eitherS-metolachlor (premix formulation), pyrithiobac, or trifloxysulfuron in conjunction with glyphosate in second-generation glyphosate-resistant cotton (Roundup Ready Flex). These herbicides were applied in combination with glyphosate in a two-application program at the 2-leaf (LF) (followed by glyphosate alone at the 10-LF growth stage), 6-LF (following glyphosate alone at the 2-LF growth stage), or 10-LF (following glyphosate alone at the 2-LF growth stage) cotton growth stages. No differences in weed control between residual herbicide were observed for goosegrass, hemp sesbania, Johnsongrass, Palmer amaranth, redroot pigweed, sicklepod, or smellmelon. Optimum control of barnyardgrass and browntop millet was achieved with glyphosate plusS-metolachlor. No differences were observed among application timings for control of goosegrass, hemp sesbania, Johnsongrass, pitted morningglory, and smellmelon. Control of barnyardgrass, browntop millet, Palmer amaranth, redroot pigweed, and sicklepod was optimized with residual herbicide application at the 2- or 10-LF timing. No yield differences were observed between residual herbicides, and seed cotton yield averaged 2,800 kg/ha. Yield was maximized when residual herbicide was applied at the 2- or 10-LF growth stage (2,960 to 2,730 kg/ha). Analysis based on numerical yield at particular residual-herbicide application timings and calculated yield for each timing based on the percentage of a standard three-application glyphosate program indicated the most consistent residual-herbicide timing for optimizing yield in a reduced-input Roundup Ready Flex weed-control program occurred at the two-leaf growth stage. All reduced-input programs, however, resulted in cotton yield of at least 93% of that obtained with the standard program.

The monomeric hemoglobin of the nemertean worm Cerebratulus lacteus functions as an oxygen storage protein to maintain neural activity under hypoxic conditions. It shares a large, apolar matrix tunnel with other small hemoglobins, which has been implicated as a potential ligand migration pathway. Here we explore ligand migration and binding within the distal heme pocket, to which the tunnel provides access to ligands from the outside. FTIR/TDS experiments performed at cryogenic temperatures reveal the presence of three transient ligand docking sites within the distal pocket, the primary docking site B on top of pyrrole C and secondary sites C and D. Site C is assigned to a cavity adjacent to the distal portion of the heme pocket, surrounded by the B and E helices. It has an opening to the apolar tunnel and is expected to be on the pathway for ligand entry and exit, whereas site D, circumscribed by TyrB10, GlnE7, and the CD corner, most likely is located on a side pathway of ligand migration. Flash photolysis experiments at ambient temperatures indicate that the rate-limiting step for ligand binding to CerHb is migration through the apolar channel to site C. Movement from C to B and iron-ligand bond formation involve low energy barriers and thus are very rapid processes in the wt protein.

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%.

Generalized mixed linear, threshold, and logistic sire models and Markov chain, Monte Carlo simulation procedures were used to estimate genetic parameters for calving rate and calf survival in a multibreed beef cattle population. Data were obtained from a 5-generation rotational crossbreeding study involving Angus, Brahman, Charolais, and Hereford (1969 to 1995). Gelbvieh and Simmental bulls sired terminal-cross calves from a sample of generation 5 cows. A total of 1,458 cows sired by 158 bulls had a mean calving rate of 78% based on 4,808 calving records. Ninety-one percent of 5,015 calves sired by 260 bulls survived to weaning. Mean heritability estimates and standard deviations for daughter calving rate from posterior distributions were 0.063 +/- 0.024, 0.150 +/- 0.049, and 0.130 +/- 0.047 for linear, threshold, and logistic models, respectively. For calf survival, mean heritability estimates and standard deviations from posterior distributions were 0.049 +/- 0.022, 0.160 +/- 0.058, and 0.190 +/- 0.078 from linear, threshold, and logistic models, respectively. When transformed to an underlying normal scale, linear sire, mixed model, heritability estimates were similar to threshold and logistic sire mixed model estimates. Posterior density distributions of estimated heritabilities from all models were normal. Spearman rank correlations between sire EPD across statistical models were greater than 0.97 for daughter calving rate and for calf survival. Sire EPD had similar ranges across statistical models for daughter calving rate and for calf survival.

A study was conducted to evaluate weed control with imazethapyr applied at different timings or a combination of timings with or without an early POST application of bensulfuron, bentazon plus aciflurofen, bispyribac, carfentrazone, halosulfuron, propanil plus molinate, or triclopyr in drill-seeded imidazolinone-resistant rice. Control of barnyardgrass, red rice, and alligatorweed was insufficient with imazethapyr at 87 g/ha PRE or at 53 g/ha late POST alone. Imazethapyr at 87 g/ha PRE followed by imazethapyr at 53 g/ha late POST controlled red rice 86% or greater but did not control hemp sesbania. The imazethapyr PRE followed by late POST combination was also weak on barnyardgrass and alligatorweed early in the season. The addition of an early POST application of the other herbicides to the imazethapyr combination improved overall weed control, especially hemp sesbania control. Among the early POST herbicides, bispyribac, carfentrazone, or propanil plus molinate were more effective in helping improve the overall weed control, resulting in better rice grain yield.

The heme-binding proteins Shp and HtsA are part of the heme acquisition machinery found in Streptococcus pyogenes. The hexacoordinate heme (Fe(II)-protoporphyrin IX) or hemochrome form of holoShp (hemoShp) is stable in air in Tris-HCl buffer, pH 8.0, binds to apoHtsA with a K(d) of 120 +/- 18 microm, and transfers its heme to apoHtsA with a rate constant of 28 +/- 6s(-1) at 25 degrees C, pH 8.0. The hemoHtsA product then autoxidizes to the hexacoordinate hemin (Fe(III)-protoporphyrin IX) or hemichrome form (hemiHtsA) with an apparent rate constant of 0.017 +/- 0.002 s(-1). HemiShp also rapidly transfers hemin to apoHtsA through a hemiShp.apoHtsA complex (K(d) = 48 +/- 7 microM) at a rate approximately 40,000 times greater than the rate of simple hemin dissociation from hemiShp into solvent (k(transfer) = 43 +/- 3s(-1) versus k(-hemin) = 0.0003 +/- 0.00006 s(-1)). The rate constants for hemin binding to and dissociation from HtsA (k'(hemin) approximately 80 microm(-1) s(-1), k(-hemin) = 0.0026 +/- 0.0002 s(-1)) are 50- and 10-fold greater than the corresponding rate constants for Shp (k(hemin) approximately 1.6 microM(-1) s(-1), k(-hemin) = 0.0003 s(-1)), which implies that HtsA has a more accessible active site. However, the affinity of apoHtsA for hemin (k(hemin) approximately 31,000 microm(-1)) is roughly 5-fold greater than that of apoShp (k(hemin) approximately 5,300 microM(-1)), accounting for the net transfer from Shp to HstA. These results support a direct, rapid, and affinity-driven mechanism of heme and hemin transfer from the cell surface receptor Shp to the ATP-binding cassette transporter system.

Systematic performance trials have been conducted in several states for more than 20 yr to evaluate agronomic performance of annual ryegrass (Lolium multiflorum Lam.). Despite development and testing of many annual ryegrass cultivars, the first improved cultivar, Gulf, has remained one of 10 to 12 cultivars recommended for planting in the southeastern USA. Our objectives were to evaluate cultivar yield performance across 12 yr at five locations, to assess cultivar yield distribution within growing seasons, and to estimate cultivar yield stability (consistency of relative performance environments). Efficacy measures were early-season yield (total before 1 March), late-season yield (total after 1 March), and total annual yield. Overall means for all cultivars and individual cultivar performance (for common years) were compared with Gulf or Marshall. Neither location effects nor cultivar X location interactions were found. Cultivar and year effects, plus cultivar × year interactions were detected (P < 0.05) for all three yield responses. Mean early season yields ranged from 2.3 to 4.6 Mg ha -1 , with mean late-season yields ranging from 5.1 to 7.4 Mg ha -1 . No trend existed for mean total yield relative to Gulf or Marshall to increase over time in association with availability of newer cultivars. Given large yearly fluctuation in yields, it is apparent that unpredictable environmental factors, including climate and perhaps pests, are the primary determinants of annual ryegrass performance rather than differences in yield potential among cultivars. Thus, yield stability may be an appropriate selection factor to include among the criteria for development of improved annual. ryegrass cultivars.

The response of rice and barnyardgrass to clomazone rates (0.22, 0.45, 0.67, 0.9, and 1.12 kg ai/ha) and application timings of preplant incorporated, preemergence (PRE), and delayed PRE (DPRE) were evaluated from 1997 to 1999. Rice bleaching at 14 d after planting (DAP) increased from 5 to 35% as the clomazone rate increased. At 14 and 49 DAP, barnyardgrass control decreased with clomazone at 0.22 kg/ha compared with control at higher rates. Clomazone at 0.22 kg/ha resulted in lower grain yield. Clomazone PRE caused less rice bleaching and lower grain yield compared with DPRE timings. These results indicate that initial bleaching by high clomazone rates may not translate into yield loss. Higher clomazone rates may increase rice yield by improving weed control. Nomenclature: Clomazone; barnyardgrass, Echinochloa crus-galli (L.) Beauv. #3 ECHCG; rice, Oryza sativa L., ‘Lemont’, ‘Cypress’. Additional index words: Application timing, herbicide rate response. Abbreviations: DAP, days after planting; DPRE, del...

A study was conducted in 2000 and 2001 to evaluate interaction of fenoxaprop with other herbicides for barnyardgrass control in rice. Changes in herbicide interaction over time were also evaluated, and herbicide combinations were ranked on the basis of compatibility. Fenoxaprop at 0.075 kg/ha plus bentazon or propanil plus molinate resulted in an additive response for barnyardgrass control at 10, 20, and 30 d after treatment (DAT); however, when the rate of fenoxaprop increased to 0.089 kg/ha, an antagonistic effect was found. Carfentrazone and halosulfuron consistently antagonized the activity of fenoxaprop at both rates on barnyardgrass. Bensulfuron at 10 and 20 DAT and triclopyr at 20 DAT were antagonistic to fenoxaprop. An increase in interaction over time was detected when fenoxaprop at 0.089 kg/ha was applied in mixture with carfentrazone at 0.04 kg/ha or halosulfuron at 0.05 kg/ha. These results indicate that propanil plus molinate and bentazon are more compatible with fenoxaprop at 0.075 kg/ha for barnyardgrass control, whereas bensulfuron, carfentrazone, halosulfuron, and triclopyr can antagonize fenoxaprop activity on barnyardgrass.

The efficacy of imazethapyr in drill-seeded imidazolinone-resistant rice was evaluated in Louisiana in 2000 and 2001. Imazethapyr was applied preemergence (PRE), or no PRE, followed by a postemergence (POST) application of imazethapyr alone, or in a mixture with bensulfuron, bentazon plus aciflurofen, carfentrazone, halosulfuron, propanil plus molinate, triclopyr, or V-10029. Imazethapyr applied PRE followed by a POST application of imazethapyr controlled barnyardgrass equivalent to or higher than other treatments evaluated. Red rice control at 35 days after postemergence treatment (DAT) was 66 to 81% with imazethapyr applied PRE followed by any POST application, but a reduction in control was observed with a POST application of imazethapyr. Although alligatorweed control increased with POST applications, these treatments suggested only suppression. Hemp sesbania control never exceeded 10% with imazethapyr-only treatments and at 35 DAT, all POST applications, except bensulfuron, increased control above 84%. Rice yield increased with treatments receiving a PRE application of imazethapyr compared with no imazethapyr applied PRE.

Tolerance of nine rice varieties to clomazone at 1.12 kg ai/ha was evaluated from 2000 to 2002. Rice injury was 27 to 51% at 14 d after treatment (DAT) and reduced to 5 to 30% at 42 DAT with long-grain ‘Drew’ having less injury compared with all medium-grain varieties. Medium- grain ‘Earl’ and ‘LL-401’ were injured most compared with all other varieties at 42 DAT. Plant height was reduced by clomazone with all varieties except Drew at 34 DAT. Clomazone also reduced plant population of Earl, LL-401, and ‘Wells’, but other varieties were not affected at 34 DAT. However, rice grain yield reduction was only observed with LL-401. These results indicate that differential tolerance to clomazone exists among rice varieties. Nomenclature: Clomazone; rice, Oryza sativa L. ‘Bengal’, ‘Cocodrie’, ‘Cypress’, ‘Drew’, ‘Earl’, ‘CL-141’, ‘LL-401’, ‘LL-601’, ‘Wells’. Additional index words: Herbicide tolerance. Abbreviations: DAT, days after treatment; DPRE, delayed preemergence; PPI, preplant incorporated; PRE, preemergence.

Imazethapyr-based weed control treatments were evaluated in water-seeded imidazolinone-resistant (IR) rice in Louisiana in 2000 and 2001. Treatments included imazethapyr applied to soil before seedling flood (surface [SURF] applied) or no soil application (no SURF), followed by imazethapyr applied postemergence (POST). Averaged over SURF application treatments (SURF, no SURF), all imazethapyr mixtures increased control of barnyardgrass at 14 and 42 d after POST treatment (DAT) compared with imazethapyr alone. Treatments containing imazethapyr-applied SURF followed by POST treatments controlled red rice 90 to 96% at 21 DAT. Alligatorweed and hemp sesbania control increased with POST mixtures compared with imazethapyr-only treatments at 35 DAT. Rice yield increased with imazethapyr applied SURF compared with no SURF application, averaged over POST applications. Other herbicides will be required to control troublesome weeds such as hemp sesbania and alligatorweed in an IR rice production system. Nomenclature...

Feeding by insect herbivores activates plant signaling pathways, resulting in the enhanced production of secondary metabolites and other resistance-related traits by injured plants. These traits can reduce insect fitness, deter feeding, and attract beneficial insects. Organic and inorganic chemicals applied as a foliar spray, seed treatment, or soil drench can activate these plant responses. Azelaic acid (AA), benzothiadiazole (BTH), gibberellic acid (GA), harpin, and jasmonic acid (JA) are thought to directly mediate plant responses to pathogens and herbivores or to mimic compounds that do. The effects of these potential elicitors on the induction of plant defenses were determined by measuring the weight gains of fall armyworm, Spodoptera frugiperda (J. E. Smith) (FAW) (Lepidoptera: Noctuidae) larvae on four crop plants, cotton, corn, rice, and soybean, treated with the compounds under greenhouse conditions. Treatment with JA consistently reduced growth of FAW reared on treated cotton and soybean. In contrast, FAW fed BTH- and harpin-treated cotton and soybean tissue gained more weight than those fed control leaf tissue, consistent with negative crosstalk between the salicylic acid and JA signaling pathways. No induction or inconsistent induction of resistance was observed in corn and rice. Follow-up experiments showed that the co-application of adjuvants with JA failed to increase the effectiveness of induction by JA and that soybean looper [Chrysodeixis includens (Walker)], a relative specialist on legumes, was less affected by JA-induced responses in soybean than was the polyphagous FAW. Overall, the results of these experiments demonstrate that the effectiveness of elicitors as a management tactic will depend strongly on the identities of the crop, the pest, and the elicitor involved.

A study was conducted to compare Brangus, Beefmaster, Gelbray, and Simbrah breed influences for economically important traits. Brangus (9), Beefmaster (12), Gelbray (10), and Simbrah (7) sires were used in purebred and crossbred (Brahman x Hereford F1 cows) matings to generate calves (326) in eight breed groups. Beefmaster cows were of similar size (448 kg), Brangus and Gelbray cows were 11% heavier (501 and 503 kg), and Simbrah cows were 21% heavier (548 kg) compared to Brahman x Hereford F1 cows (452 kg). Calves sired by Brangus and Beefmaster bulls had lower birth weights (35 vs 38 kg; P < 0.05), preweaning growth rates (0.87 vs 0.91 kg x d(-1); P < 0.01), and weaning weights (206 vs 219 kg; P < 0.01) than Gelbray- and Simbrah-sired calves. Birth weights, preweaning ADG, and weaning weight and hip heights were similar between Brangus- and Beefmaster-sired calves. Simbrah-sired calves had greater preweaning growth rates (0.94 vs 0.88 kg x d(-1); P < 0.05), weaning weights (227 vs 211 kg; P < 0.01), and adjusted 205-d hip heights (126 vs 122 cm; P < 0.05) than Gelbray-sired calves. Straightbred Angus steers were introduced in the postweaning portion of the study. Steer calves were placed on feed at an average age of 14.5 mo. Steers were removed from the feedlot upon attaining a targeted 10 mm of backfat. Feedlot ADG did not differ among sire breeds. Brahman-derivative sired steers required an additional 54 d on feed (P < 0.01) and were 86 kg heavier (P < 0.01) at harvest than Angus steers. Continental-Brahman steers spent an additional 25 d on feed (P < 0.05) and were 35 kg heavier (P < 0.01) at harvest than British-Brahman steers. Simbrah-sired steers were 52 kg heavier (P < 0.01) at harvest than Gelbray-sired steers when fed for a similar number of days (211 vs 203 d). However, straightbred Simbrah steers required an additional 12 d on feed (P < 0.01) and weighed 47 kg more (P < 0.01) than Simbrah-sired crossbred steers. The economic value of the heavier calf weaning weights may be offset by the attendant larger cow size of the Continental-Brahman compared to the British-Brahman breeds. Similarly, the heavier weights of Continental-Brahman compared to British-Brahman steers, when harvested at a prescribed level of fatness may be viewed as a benefit, but the increased number of requisite days in the feedlot is a disadvantage.

Background Previous research indicates that bahiagrass may be successfully conserved as baleage, but nutritive value is typically low for lactating dairy cows. The purpose of this study was to determine the effect of adding modest amounts of alfalfa forage (22%), achieved by inter-seeding alfalfa into an existing bahiagrass pasture, on baleage nutritive value and lactation performance of Holstein cows. Forage treatments employed were monoculture bahiagrass baleage (MBB; negative control), bahiagrass-alfalfa mixture baleage (BAB) and conventional corn silage (CCS; positive control). Thirty six mid lactation Holstein cows [34.8 ± 5.8 kg 3.5% fat-corrected milk and 112 ± 19 d in milk (DIM)] were stratified according to milk yield and DIM and assigned randomly to 1 of 3 forage treatments. Cows were trained to Calan feeding gates and were offered a common CCS-based TMR in a 10-d covariance period followed by a 42-d treatment feeding period. Results The BAB contained more protein and less NDF than MBB (12.6 vs 10.3% CP and 71.8 vs 76.6% NDF). Diet DMI was similar for MBB and BAB (19.5 vs 21.6 kg/hd/d), but cows consumed more of the CCS diet (25.5 kg/hd/d) than either baleage-based diet. Cows offered BAB tended to produce more milk than cows offered MBB based TMR (28.4 vs 26.1 kg/hd/d), but both baleage diets generated less milk than CCS-based diets (33.1 kg/hd/d). Milk composition was similar across diets except for milk protein concentrations which were higher for CCS than either MBB or BAB diets; however, milk urea nitrogen (MUN) was lowest for cows fed CCS diets. Cow BW gain was higher for BAB than MBB implying that a portion of the higher energy contributed by the alfalfa was being used to replenish weight on these mid lactation cows. Conclusions Data from this study indicate that alfalfa inter-seeded in bahiagrass sod that produces BAB with as little as 22% alfalfa may improve nutritive value compared to monoculture bahiagrass baleage and marginally improve lactation performance of Holstein cows. However, the CCS diet was vastly superior to either MBB or BAB-based diets for milk production.

Early-season forage production of annual ryegrass (Lolium multiflorum Lam.) is reduced in the southeastern USA when established no-till rather than with conventional tillage. We hypothesized that annual warm-season grass residue interferes with seedling establishment under no-till. In a two-year study, we evaluated six strategies for managing residue from warm-season annual grass on annual ryegrass establishment, forage production, and soil moisture. Treatments were (i) no herbicide, mow, and leave residue; (ii) tillage 30 and 7 d before planting ; (iii) apply glyphosate [isopropylamine salt of N-(phosphonomethyl)glycine] 30 d before planting, mow, and leave residue; (iv) apply glyphosate 7 d before planting, mow, and leave residue; (v) apply glyphosate 7 d before planting, apply additional residue from twice the plot area (i.e., three times the other residue treatments); and (vi) apply glyphosate 7 d before planting, burn residue 1 d before planting. Better stands and more forage production at first harvest of annual ryegrass were obtained by spraying and burning residue (two-year average of 96% stand and 0.92 Mg ha -1 yield at the first harvest) or spraying 30 d before planting (92% stand. 0.92 Mg ha 1 ) than when annual ryegrass was planted into a 3 x residue (55% stand, 0.24 Mg ha '). Soil moisture at planting did not cause differences in stand establishment among treatments. We conclude that managing residue during no-till establishment by controlling warm-season annual grasses and burning or controlling warm-season annual grasses 30 d before planting can improve stands and forage production of annual ryegrass.

Frequent rainfall in south Louisiana often limits the successful harvest of annual ryegrass (Lolium multiflorum L.) as high quality hay. A 2-yr study was conducted to determine the effect of conserving ryegrass as balage on ensiling efficiency, storage losses, and feeding value. Ryegrass conservation treatments were balage (BLG), haylage (HLG, positive control), and hay (HAY, negative control). Ryegrass was cut at the boot stage and, following a 48-h wilt, was baled and wrapped with stretch film (BLG) or was chopped and stored in a bag silo (HLG), HAY (bloom stage) was harvested approximately 3 wk later when weather permitted and was stored indoors. At the conclusion of the 6-mo storage period, the nutritional value of stored forages was assessed with lactating Holstein cows (n = 21). Ryegrass pH values were lower, and lactate concentrations were slightly higher for HLG than BLG. Storage losses averaged 8.9% of dry matter (DM) for BLG compared with 3.7% for barn-stored HAY. Forage nutritive value was similar between ensiled forages; however, HAY was lower in protein and energy than other treatments. Cows fed HLG consumed 17.3% more forage DM and tended to produce more fat-corrected milk (FCM) than cows fed BLG. Feed efficiency (Ib FCM/Ib dry matter intake [DMI]) was higher for the BLG treatment than HAY. No treatment differences were observed for milk composition or cow weight/condition changes, Balage is an acceptable means of storing high quality ryegrass forage.

Tropical corn (Zea mays L.) has potential as a silage crop in double-crop systems with cool-season annual grasses in the southeastern USA. In a 3-yr study conducted in silt loam soils in southeast Louisiana, plots within stands of Pioneer hybrid X304C tropical corn planted at 89 000 plants ha -1 were thinned to achieve harvested plant densities of 44 830, 52 150, 58 130, 65 150, and 72 920, plants ha -1 to determine the effect of plant density on total forage mass, plant morphology, and forage nutritive value of tropical corn. Total forage mass was greater at higher plant densities than at lower plant densities, but forage mass was not different among plant populations that exceeded 58 130 plants ha -1 . Leaf concentration of dry matter did not differ among plant populations and averaged 300 g kg -1 . The sum of stem and grain concentrations was similar among treatments and ranged from 622 to 637 g kg -1 . Within the stem and grain components, grain concentration decreased and stem concentration increased in an almost one-to-one relationship as plant density increased. Forage nutritive value of tropical corn was similar among plant densities. In vitro true digestibility averaged 654 g kg -1 across all plant densities. Increasing forage mass, coupled with stable forage nutritive values, indicates that, until some factor limits production of high-quality tropical corn silage, high plant densities are desirable. Under the environmental conditions of this experiment, it appears that plant densities of about 58 000 plants ha -1 are optimal.

Early-season forage mass production of annual ryegrass (Lolium multiflorum Lam.) is reduced in the southeastern USA when ryegrass is established no-till rather than with conventional tillage. Two studies were conducted to evaluate forage mass distribution of annual ryegrass established under tillage vs. no-till. One evaluated the effect of sod-suppression, and the other evaluated past and current tillage practices. In the sod-suppression study, no-till plots established with herbicides produced 27% more forage mass at first harvest than did no-till plots that were mowed. However, tilled plots produced 55% more forage mass at first harvest than no-till plots established with herbicides. After January, no-till plots produced as much or more forage mass than tilled plots in both studies. In the 1994-1995 growing season, forage mass produced at first harvest was positively correlated (P = 0.01) with stand count in both the sod- suppression (r = 0.62) and the tillage history (r = 0.73) studies. After the first harvest, stand count was not correlated (P > 0.ll) with forage mass production. In the tillage history study, current seedbed preparation had a much greater impact than past seedbed preparation on early-season production of annual ryegrass. When combined over both studies, ryegrass established with tillage (4.9 tons/acre) and established no-till with herbicides (4.6 tons/acre) produced more season total forage mass than no-till ryegrass established without herbicides (4.3 tons/acre). In annual ryegrass establishment systems, tillage does more than reduce competition from warm-season grasses. However, suppression of warm-season grasses with herbicides is still important for no-till establishment of annual ryegrass.