Application Of Bromoxynil Research Articles

Mesotrione: a new preemergence herbicide option for wild radish (Raphanus raphanistrum) control in wheat

AbstractWild radish is the most problematic broadleaf weed in Australian grain production. The propensity of wild radish to evolve resistance to herbicides has led to high frequencies of multiple herbicide–resistant populations present in these grain production regions. The objective of this study was to evaluate the potential of mesotrione to selectively control wild radish in wheat. The initial dose response pot trials determined that at the highest mesotrione rate of 50 g ha−1 applied preemergence (PRE) was 30% more effective than when applied postemergence (POST) on wild radish. This same rate of mesotrione applied POST resulted in a 30% reduction in wheat biomass compared to 0% for the PRE application. Subsequent mesotrione PRE dose response trials identified a wheat selective rate range of >100 and <300 g ai ha−1 that provided greater than 85% wild radish control with less than 15% reduction in wheat growth. Field evaluations confirmed the efficacy of mesotrione at 100 to 150 g ai ha−1 in reducing wild radish populations by greater than 85% following PRE application and incorporation by wheat planting. Additionally, these field trials demonstrated the opportunity for season-long control of wild radish when mesotrione applied PRE was followed by bromoxynil applied POST. The sequential PRE application of mesotrione, a herbicide that inhibits p-hydroxyphenylpyruvate dioxygenase, followed by POST application of bromoxynil, a herbicide that inhibits photosystem II, has the potential to provide 100% wild radish control with no effect on wheat growth.

PRE- and POST-applied herbicide options for alfalfa interseeded with corn silage

AbstractEstablishment of alfalfa by interseeding it with corn planted for silage can enhance crop productivity but weed management is a challenge to adoption of the practice. Although a simple and effective approach to weed management would be to apply a glyphosate-based herbicide, concerns about herbicide resistance and limitations in available alfalfa varieties exist. Field experiments were conducted to compare the efficacy and selectivity of PRE, POST, and PRE followed by POST herbicide programs to a glyphosate-only strategy when interseeding alfalfa with corn. Experiment 1 compared PRE applications of acetochlor, mesotrione, S-metalochlor, metribuzin, and flumetsulam. Results indicate that acetochlor and metribuzin, and S-metalochlor used at a rate of 1.1 kg ai ha−1 were the most effective and selective PRE herbicides 4 wk after treatment (WAT), but each resulted in greater overall weed cover than glyphosate by 8 WAT. Experiment 2 evaluated applications of bentazon, bromoxynil, 2,4-DB, and mesotrione at early and late POST times. Several herbicides used POST exhibited similar effectiveness and selectivity as glyphosate, including early applications of bromoxynil (0.14 kg ai ha−1) and 2,4-DB (0.84 or 1.68 kg ai ha−1), as well as late applications of bromoxynil (0.42 kg ai ha−1), 2,4-DB (0.84 kg ai ha−1), and mesotrione (0.05 or 0.11 kg ai ha−1). A third experiment compared applications of acetochlor PRE, bromoxynil POST, and a combination of acetochlor PRE with bromoxynil POST. All treatments were effective and safe for use in this interseeded system, although interseeded alfalfa provided 65% to 70% weed suppression in corn planted for silage without any herbicide. Herbicide treatments had no observable impacts on corn and alfalfa yields, so weed management was likely of limited economic importance. However, weed competitiveness can vary based on several different factors including weed species, density, and site-specific factors, and so further investigations under different environments and conditions are needed.

Application of Bromoxynil+MCPA+Metribuzin at Varied Doses for Broad-Spectrum Weed Control in Forage Maize (Zea mays L.)

Weed control is one of the crucial factors to achieve higher yield of good quality forage maize. A field trial was conducted during summer 2013 to investigate the effect of bromoxynil+MCPA+metribuzin (Valent 470 EW pre mixed formulation) application at varied doses to control weeds in forage maize (Zea mays L.) at Agronomy Research Area, University of Agriculture, Faisalabad, Pakistan. Application of bromoxynil+MCPA+metribuzin @ 470, 528.75 and 587.50 g a.i/ha was made after emergence of weedsand crop. A check with no application and hand hoeing was included for comparison. The experiment was conducted with four replications under randomized complete block design. The data regarding the weed parameters, yield and yield components of maize were recorded. The results revealed that among the herbicide treatments minimum weed density (three weeks after sowing 35.75 m2 and at harvest 12.25/m2) and dry biomass (20.80 g/m2) was observed with the application of bromoxynil+MCPA+metribuzin @ 587.50 g a.i./ha. Same herbicidal treatment caused significant increase in plant height (248.75 cm), stem diameter (1.45 cm), fresh weight (467.25g) and forage yield (31.47%) of maize. Therefore, use ofbromoxynil+MCPA+metribuzin @ 587.50 g a.i./ha is the best option to manage broad leaved as well as grassy weeds in forage maize to get higher yield of forage .

Oilseed cuphea tolerates bromoxynil

Weed management is a critical feature of all crop production, but especially for new and alternative crops with which most growers have little experience. Oilseed cuphea is a new annual crop for temperate regions and, at present, it is known to tolerate only a narrow spectrum of herbicides. Additional herbicides would be useful to encourage growers to examine this crop on their farms. Of particular importance are herbicides with broad activity against dicotyledonous weeds. Accordingly, cuphea tolerance to bromoxynil was tested in both greenhouse and field settings. Oilseed cuphea tolerated postemergence applications of bromoxynil up to 210gaeha−1, which is a common label rate for this herbicide for traditional crops, but only if the plants had reached the 4- to 5-leaf stage of development at the time of application. Earlier applications, or applications at higher rates, could damage plants or reduce stands. Thus, postemergence applications of bromoxynil at or beyond the 5-leaf stage appear safe for cuphea. This result broadens the spectrum of potentially competing weed species that can be managed effectively if they co-occur with oilseed cuphea.

Characteristics and control of dicamba‐resistant common lambsquarters (Chenopodium album)

The expansion of atrazine‐resistant Chenopodium album (common lambsquarters) since the 1980s has forced New Zealand's maize‐growers to use an additional postemergence herbicide application. The frequent use of dicamba for this has selected for a common lambsquarters population with reduced sensitivity to dicamba. Initial greenhouse experiments with seeds that had been collected from the plants that survived field applications of dicamba showed that these plants could tolerate ≤1.2 kg ha−1, fourfold the recommended rate. These dicamba‐resistant plants were morphologically distinct from the susceptible population. The leaves of the resistant plants were less dentate and a lighter shade of green. The resistant plants were shorter, had a lower biomass and growth rate and flowered ≤19 days earlier than the susceptible plants. When grown together in various density ratios, the average biomass of both the susceptible and the resistant plants increased as the number of susceptible plants decreased in the mixture. The field experiments demonstrated that the resistant population tolerated dicamba at ≤2.4 kg ha−1, eightfold the recommended rate. Postemergence applications of bromoxynil, pyridate, nicosulfuron and mesotrione effectively controlled both populations. Nicosulfuron and mesotrione provided long‐term residual control, with nicosulfuron being more effective on the grass weeds. High rates of dicamba damaged the maize plants, resulting in an increased weed cover and reduced grain yield. The number of viable common lambsquarters seeds in the soil seed bank at the end of the growing season declined in the treatments in which common lambsquarters was controlled effectively.

Spectral and time-resolved fluorescence signature of four weed species as affected by selected herbicides

In the present study we show for the first time the suitability of the laser-induced fluorescence technique to evaluate in vivo herbicide-induced damages as revealed by changes of fluorescence spectra and lifetime. Four herbicides of different modes of action (glyphosate, bromoxynil, mesotrione, and amitrole) were selected and applied to four weed species ( Stellaria media, Setaria viridis, Chenopodium album, and Viola arvensis). Modifications of the fluorescence signature depended on the agrochemical – plant species interaction as well as on the time after application. Measurements in the red and far-red spectral region reveal disturbances in the functionality of the photosynthetic apparatus and chlorophyll concentration, e.g. after application of bromoxynil or mesotrione. Recordings in the blue and green spectral regions indicate changes of both amount and composition of specific fluorophores, i.e. after application of glyphosate and amitrole. In all spectral measurements, the position of peak maxima was not affected by herbicide application. The fluorescence lifetime, expressed as LT mean or as lifetime 1 (LT1, short-duration) and LT2 (long-duration) fractions, provided additional information to the spectrally resolved data. Thereby, significant alterations of the lifetime duration and fractional characteristics were observed at specific wavelengths, e.g. after application of bromoxynil, mesotrione, or amitrole.

Multiple Applications of Reduced-Rate Herbicides for Weed Control in Onion

Field experiments were conducted at Oakes, Absaraka, and Tappen, ND, in 2006 and repeated at Oakes and Absaraka, ND, in 2007 to evaluate early season weed control of common lambsquarters and redroot pigweed in onion with POST herbicides applied at multiple reduced rates (microrates) and to determine whether microrate herbicide treatments effectively reduced early season broadleaf weed competition, caused crop injury, or affected yield. Application rates of bromoxynil, oxyfluorfen, metribuzin, and acifluorfen were reduced to 0.25, 0.13, and 0.06× of their lowest labeled rate and applied in sequential applications (every 7 d) either two or three times. The 0.25× rate of bromoxynil (70.1 g ae/ha) provided the greatest control of common lambsquarters (95%). The 0.25× rates of bromoxynil and oxyfluorfen (70.1 g ai/ha) provided the greatest control of redroot pigweed (93 and 85%, respectively). Microrate applications of metribuzin or acifluorfen did not effectively control common lambsquarters or redroot pigweed. In 2006, no onion injury was observed. However, in 2007, applications of oxyfluorfen resulted in approximately 15% injury, regardless of the herbicide rate or the number of applications. Plants outgrew symptoms by 4 wk after treatment and were similar to the untreated plants. Onion treated with oxyfluorfen had the greatest total yield, followed by onion treated with bromoxynil. Onion treated with acifluorfen had a greater total marketable bulb yield than onion treated with metribuzin, but yield was considered poor compared to the other herbicide treatments. Three microrate applications provided greater weed control and increased yield compared with two applications across herbicides and rates. Results suggest that microrate applications of bromoxynil and oxyfluorfen will provide early season broadleaf weed control in onion.

The degradation of the herbicide bromoxynil and its impact on bacterial diversity in a top soil

To study how repeated applications of an herbicide bromoxynil to a soil, mimicking the regime used in the field, affected the degradation of the compound and whether such affects were reflected by changes in the indigenous bacterial community present. Bromoxynil degradation was monitored in soil microcosms using HPLC. Its impact on the bacterial community was determined using denaturing gradient gel electrophoresis (DGGE) and quantitative PCR of five bacterial taxa (Pseudomonads, Actinobacteria, alpha-Proteobacteria, Acidobacteria and nitrifying bacteria). Three applications of 10 mg kg(-1) of bromoxynil at 28-day intervals resulted in rapid degradation, the time for removal of 50% of the compound decreasing from 6.4 days on the first application to 4.9 days by the third. Bacterial population profiles showed significant similarity throughout the experiment. With the addition of 50 mg kg(-1) bromoxynil to soil, the degradation was preceded by a lag phase and the time for 50% of the compound to be degraded increased from 7 days to 28 days by the third application. The bacterial population showed significant differences 7 days after the final application of bromoxynil that correlated with an inhibition of degradation during the same period. These analyses highlighted that the addition of bromoxynil gave rise to significant shifts in the community diversity and its structure as measured by four abundant taxa, when compared with the control microcosm. These changes persisted even after bromoxynil had been degraded. Here we show that bromoxynil can exert an inhibitory effect on the bacterial population that results in decreased rates of degradation and increased persistence of the compound. In addition, we demonstrate that molecular approaches can identify statistically significant changes in microbial communities that occur in conjunction with changes in the rate of degradation of the compound in the soil.

EVALUATION OF THE INTEGRATED WEED MANAGEMENT IN SEED ALFALFA (MEDICAGO SATIVA L.)

This experiment was conducted for three consecutive years from 2000 to 2002 to evaluate the effects of integrated weed management on weeds of alfalfa at the Safi Abad Agricultural Research Farm of Dezful. The experimental design was a randomized complete block with strip-split plot arrangement of treatments. Herbicide treatment was as horizontal factor at five levels which in 2000, consisted of application of bromoxynil at 0.45 kg ai /ha at the 2 - leaf stage of alfalfa + metribuzin at 0.35 kg ai /ha after the cutting for seed, application of bentazon at 0.96 kg ai/ha at the 6 - leaf stage of alfalfa + metribuzin at 0.52 kg ai/ha after the cutting for seed, application of bentazon at 0.96 kg ai /ha at the 6 - leaf stage of alfalfa + bentazon at 1.44 kg ai /ha after the cutting for seed, weed free and weedy checks. Cultivation was as vertical factor at three levels which in 2000, consisted of reciprocal application of shovel cultivator and rolling + shovel cultivator when alfalfa was 30 cm tall and after the cutting for seed and noncultivated plot. In 2001 and 2002, treatments were applied after the cutting for seed and were as follows: application of metribuzin at 0.35 and 0.52 kg ai/ha, bentazon at 1.44 kg ai /ha, weed free and weedy checks, and cultivation treatments were as abovementioned treatments. In 2000, total number of broadleaved weeds were reduced by application of bromoxynil + metribuzin, bentazon + metribuzin and bentazon + bentazon by 77, 81 and 56%, respectively, and on average, by cultivation by 59%. In 2001, total number of broadleaved weeds were reduced by application of metribuzin at 0.35 and 0.52 kg ai/ha and bentazon by 83, 95 and 83%, respectively, and in 2002, by 68, 87 and 65%, respectively, by the aforementioned herbicide treatments. Compared to the weedy check, alfalfa seed yield increase in application of metribuzin at 0.35 and 0.52 kg ai/ha, bentazon and weed free check treatmensts was 51, 11, 83 and 37%, respectively.

Weed control and wheat ( Triticum aestivum L.) yield under application of 2,4-D plus carfentrazone-ethyl and florasulam plus flumetsulam: Evaluation of the efficacy

Three field experiments were conducted at the research fields of Plant Protection Research Institute, Iran, at different locations in 2004–2005 to study the efficacy of different broadleaved herbicides to control weeds in wheat. Treatments were the full-season hand weeded and weed-infested controls, and post-emergence applications of florasulam plus flumetsulam at 8.75, 10.50, and 12.25 g a.i./ha, 2,4-D plus carfentrazone-ethyl at 210, 245, 280, and 490 g a.i./ha, bromoxynil plus MCPA at 75, 100, and 150 g a.i./ha, 2,4-D at 560, 720, and 1120 g a.i./ha, tribenuron methyl, and 2,4-D plus MCPA. Herbicides were applied at wheat tillering stage. Naturally occurring broadleaved weed populations were used in experiments. Results indicated that bromoxynil plus MCPA at 150 g a.i./ha, 2,4-D plus MCPA, and 2,4-D plus carfentrazone-ethyl at 490 g a.i./ha were the best options to control weeds. Bromoxynil plus MCPA at 150 g a.i./ha and 2,4-D plus MCPA also resulted in the highest wheat yield. Overall, it could be concluded that rotational application of bromoxynil plus MCPA at 150 g a.i./ha, 2,4-D plus MCPA, and 2,4-D plus carfentrazone-ethyl at 490 g a.i./ha would be the best option to achieve satisfactory weed control, high grain yield and prevention of evolution of herbicide-resistant weeds.

Efficacy of four corn (Zea mays L.) herbicides when applied with flat fan and air induction nozzles

Twelve field experiments were conducted over a 4 year (2002–2005) period to determine the influence of the herbicide dose, nozzle type, spray volume, and spray pressure on herbicide efficacy in field corn (Zea mays L.). The control of Abutilon theophrasti (velvetleaf ), Ambrosia artemisiifolia (common ragweed), Chenopodium album (common lambsquarters), Amaranthus powellii (green pigweed), and Echinochloa crus‐galli (barnyard grass) was improved with the use of full herbicide doses compared to half doses of bromoxynil, glufosinate, dicamba, and nicosulfuron. The yield was increased for bromoxynil, glufosinate, and nicosulfuron when the full herbicide dose was used. When applied at the manufacturer’s recommended dose, flat fan nozzles, compared to air induction (AI) nozzles, provided better control of A. theophrasti, A. artemisiifolia, and C. album with bromoxynil, A. artemisiifolia and C. album with dicamba, and E. crus‐galli with nicosulfuron. Bromoxynil, in relation to weed control, was the only herbicide that was affected by the water carrier volume. By increasing the spray pressure with an AI nozzle, there was an improvement in the control of A. theophrasti, A. artemisiifolia, and C. album with the application of bromoxynil and E. crus‐galli with the application of nicosulfuron, with a yield increase with bromoxynil. Overall, this study concludes that the optimum nozzle type, water carrier volume, and spray pressure is herbicide‐ and weed species‐specific.

Effect of dose and spray volume on early-season broadleaved weed control in Allium using herbicides

Field studies were conducted near Oakes, Absaraka, and Carrington, North Dakota to determine if bromoxynil and oxyfluorfen applied post-emergence at reduced doses and spray volumes to one-leaf onion would provide effective early-season broadleaved weed control without significant crop injury. Oxyfluorfen generally provided more effective early-season broadleaved weed control than bromoxynil when applied at reduced spray volumes and doses. Onion injury 1 week after treatment (WAT) was more severe with oxyfluorfen than bromoxynil applied post-emergence, but was not visible 3 WAT. Large-grade and total onion yields at Absaraka, where broadleaved weed pressure was the least, were similar in all treatments except the untreated check. At Carrington and Oakes, where broadleaved weed pressure was much greater, no treatments had large-grade or total onion yields similar to the hand-weeded check. However, large-grade and total yields from onion treated with reduced doses of bromoxynil or oxyfluorfen, regardless of the spray volume, were similar to those treated with almost a four-fold increase in herbicide dose, suggesting that a reduced bromoxynil or oxyfluorfen dose at lower spray volumes to one-leaf onion may provide sufficient early-season Chenopodium album and Amaranthus retroflexus control so that post-emergence applications of bromoxynil plus oxyfluorfen to larger onion provide more effective broadleaved weed control.

The application of the herbicide bromoxynil to a model soil-derived bacterial community: impact on degradation and community structure

Bromoxynil degradation by soil micro-organisms has been shown to be co-oxidative in character. In this study, we investigate both the impact of the application of increasing bromoxynil concentrations on soil-derived bacterial communities and how these changes are reflected in the degradation of the compound. Our aim was to test the hypothesis that the addition of bromoxynil to a soil-derived bacterial community, and the availability of a readily utilizable carbon source would have an impact on bromoxynil degradation, and that would be reflected in the bacteria present in the soil community. Degradation of bromoxynil was observed in soil-derived communities containing 15 mg l(-1), but not 50 mg l(-1) of the compound, unless glucose was added. This suggests that the addition of carbon stimulates co-oxidative bromoxynil degradation by the members of the bacterial community. Measurable changes in the bacterial community indicated that the addition of bromoxynil led to deterministic selection on the bacterial population, i.e. the communities observed arise through the selection of specific micro-organisms that are best adapted to the conditions in the soil. The addition of bromoxynil was also shown to have a negative impact on the presence of alpha and gamma-proteobacteria in the soil community. Bromoxynil degradation is significantly inhibited in bacterial soil communities in the absence of readily accessible carbon. The application of bromoxynil appears to exert deterministic selection on the bacterial community. This study highlights the effects of increasing bromoxynil concentrations on a model bacterial population derived from soil. Soil communities show qualitative and quantitative differences to bromoxynil application depending on the availability of organic carbon. These findings might have implications for the persistence of bromoxynil in agricultural soils.

Early Season Broadleaf Weed Control in Onion

Field studies were conducted at Absaraka, Carrington, and Oakes, N.D., in 2005 to evaluate early season broadleaf weed control and onion (Allium cepa L.) injury with herbicides applied preemergence to the crop. DCPA is a common preemergence herbicide used in onion. However, DCPA can be uneconomical in most high-weed situations, or the usage may be restricted due to possible groundwater contamination. Potential substitutes evaluated were bromoxynil, dimethenamid-P, and pendimethalin. Main broadleaf weeds were redroot pigweed (Amaranthus retroflexus L.) and common lambsquarters (Chenopodium album L.). In general, all herbicides, except bromoxynil, provided acceptable broadleaf weed control 4 weeks after treatment. The highest herbicide rate provided greater weed control compared with the lowest rate for each herbicide. However, onion height was also reduced with the highest herbicide rate. In addition, the two highest rates of dimethenamid-P reduced the onion stand compared with the untreated. A postemergence application of bromoxynil + oxyfluorfen + pendimethalin to onion at the four- to five-leaf stage controlled the few broadleaf weeds that escaped the preemergence treatments and provided residual control of mid- and late-season germinating broadleaf weeds at two of the three locations. Intense germination of redroot pigweed during July at the Oakes location reduced onion yield with all treatments compared with the hand-weeded check. In contrast, total onion yields with all herbicide treatments except the high rate of dimethenamid-P were similar to the hand-weeded check at Absaraka and Carrington.

Weed Efficacy Evaluations for Bromoxynil, Glufosinate, Glyphosate, Pyrithiobac, and Sulfosate

Thirteen field trials were conducted in 1999 and 2000 to evaluate postemergence (POST) weed control with single applications of bromoxynil at 420 or 560 g ai/ha, glufosinate at 291 or 409 g ai/ha, glyphosate at 1,120 g ai/ha, pyrithiobac at 36 or 72 g ai/ha, or sulfosate at 1,120 g ai/ha. Additional treatments evaluated included two applications with glufosinate at both rates in all possible combinations, two applications of glyphosate, and two applications of sulfosate. Weeds were 2 to 5 cm or 8 to 10 cm tall for annual grass and broadleaf weeds whereas yellow nutsedge and glyphosate-resistant corn were 8 to 10 cm tall. All herbicide treatments controlled 2- to 5-cm common cocklebur, Florida beggarweed, jimsonweed, ladysthumb smartweed, Pennsylvania smartweed, pitted morningglory, prickly sida, redroot pigweed, smooth pigweed, and velvetleaf at least 90%. All herbicide treatments except pyrithiobac at either rate controlled 2- to 5-cm common lambsquarters, common ragweed, and tall morningglory at least 90%; pyrithiobac at the lower rate was the only treatment that failed to control entireleaf and ivyleaf morningglory at least 90%. Bromoxynil and pyrithiobac at either rate controlled 2- to 5-cm sicklepod 33 to 68% whereas glufosinate, glyphosate, and sulfostate controlled ≥99%. Glyphosate and sulfosate applied once or twice controlled hemp sesbania less than 70% and volunteer peanut less than 80%. Bromoxynil and pyrithiobac were the least effective treatments for control of annual grass species and bromoxynil controlled Palmer amaranth less than 80%. Glufosinate controlled broadleaf signalgrass, fall panicum, giant foxtail, green foxtail, large crabgrass, yellow foxtail, seedling johnsongrass, Texas panicum, and glyphosate-resistant corn at least 90% but controlled goosegrass less than 60%. Glyphosate and sulfosate controlled all grass species except glyphosate-resistant corn at least 90%. In greenhouse research, goosegrass could be controlled with glufosinate POST plus a late POST-directed treatment of prometryn plus monosodium salt of methylarsonic acid.

Response of non–bromoxynil-resistant cotton to reduced rates of bromoxynil

Abstract Field research was conducted for 2 yr to determine the effects of reduced rates of bromoxynil on growth and yield of non–bromoxynil-resistant cotton. Rates of 4.5, 9, 17, 35, 70, and 140 g ha−1, representing 0.008, 0.016, 0.031, 0.063, 0.125, and 0.25 fractions of the maximum labeled use rate per application (560 g ha−1), were applied to cotton at the two-, five-, or nine-node growth stage. Visual injury was reduced because application timing was delayed from two- to five-node stage in all experiments and from five- to nine-node stage in two of three experiments. Although negatively affected at all application timings, plant height reduction response decreased with increasing cotton maturity. Plant dry weight was most negatively affected after application at the two-node stage. Bromoxynil application, based on the node above white flower number, did not result in maturity delays but did promote earlier maturity when applied at 140 g ha−1 to two- and five-node stage cotton in one of the three expe...

Mixtures of CGA 362622 and Bromoxynil for Broadleaf Weed Control in Bromoxynil-Resistant Cotton (Gossypium hirsutum)1

Studies were conducted in 1999, 2000, and 2001 to evaluate broadleaf weed control in cotton with postemergence applications of bromoxynil and bromoxynil plus CGA 362622. Bromoxynil was applied at 280 and 560 g ai/ha, and CGA 362622 was applied at 0, 3.8, and 7.5 g ai/ha in a factorial treatment arrangement. Cotton injury 7 d after treatment (DAT) during the 3 yr was 11 to 35% with the herbicide mixtures, but injury did not exceed 2% 28 DAT when averaged over years. CGA 362622 plus bromoxynil controlled velvetleaf, smooth pigweed, common ragweed, and common cocklebur at least 77% 28 DAT. Control of morningglory species was at least 87% with herbicide combinations, except in 2001 when control was only 60% with 280 g/ha bromoxynil plus 3.8 g/ha CGA 362622. Bromoxynil also controlled jimsonweed, but CGA 362622 did not. Spurred anoda control pooled over years did not exceed 53% with bromoxynil or bromoxynil plus CGA 362622 mixtures. Cotton yields generally reflected the level of weed control from the herbicide...

The tolerance of three transgenic subterranean clover (Trifolium subterraneum L.) lines with the bxn gene to herbicides containing bromoxynil

A bxn gene, coding for the nitilase enzyme that catalyses the detoxification of the herbicide bromoxynil, was inserted into subterranean clover (Trifolium subterraneum L. subsp. yanninicum). The agronomic characteristics of 3 transgenic lines (BXN 5, 7, 10) and their response to herbicides containing bromoxynil, were compared with that of the non-transgenic parent, cv. Gosse, in 1 glasshouse and 2 field experiments.The application of bromoxynil at 1.5 L/ha resulted in a 50% reduction in the spring herbage yield of the non-transgenic control but no reduction in BXN 5 and 7. The level of the phyto-oestrogens, genistein and biochanin A, in the leaf tissue were low in Gosse and the 2 transgenic lines, BXN 7 and 10, but the level of genistein increased significantly (P < 0.05) from 0.85% in Gosse to 1.43% dry weight in BXN 5, and biochanin A increased from 0.35% in Gosse to 0.73% in BXN 5. The application of the herbicides bromoxynil, bromoxynil+MCPA, and Jaguar (bromoxynil+diflufenican) at the cotyledon stage in a glasshouse study significantly reduced the leaf area of the non-transgenic Gosse, but did not reduce the leaf area of the 3 transgenic lines. When applied at the 4–5 leaf stage, the leaf area of Gosse was again reduced by all the herbicides, but only the bromoxynil+MCPA treatment reduced the leaf area of the transgenic lines relative to the control. The application of bromoxynil or Jaguar at the 4–5 leaf stage depressed the herbage yield of Gosse by about 62% compared with 0–24% in the 3 transgenic lines. In the field studies, BXN 5 and 10 had similar seed yields to Gosse in the absence of herbicide application, but the seed yield of BXN 7 was significantly less than the other 2 transgenic lines. The level of hard-seed in BXN 7 was also lower at 25% compared with 55–57% in the other transgenic lines and Gosse.These findings stress the need to carefully assess the agronomic qualities of transgenic lines prior to release as although tolerance to bromoxynil may be greatly increased by the bxn gene, other important agronomic characteristics, such as seed yield, hardseededness, and isoflavone content, may change as result of the gene or transformation process.

Weed management with pyrithiobac preemergence in bromoxynil-resistant cotton

An experiment was conducted at two locations in Georgia and one location in North Carolina during 1994 and 1995 to evaluate weed management systems utilizing pyrithiobac applied preemergence (PRE) in conventional-tillage bromoxynil-resistant cotton. Weed management systems evaluated included different combinations of pyrithiobac PRE, bromoxynil or bromoxynil plus MSMA applied early postemergence (EPOST), bromoxynil applied postemergence (POST), and cyanazine plus MSMA applied late postemergence-directed (LAYBY). Pyrithiobac PRE improved control of Florida beggarweed, pitted morningglory, prickly sida, sicklepod, and spurred anoda compared with systems that did not include pyrithiobac PRE. Averaged across locations, pyrithiobac PRE increased cotton lint yields 330 kg ha−1. Bromoxynil applied EPOST or POST increased weed control and cotton lint yield. Bromoxynil EPOST, POST, or EPOST plus POST did not control sicklepod. The addition of MSMA to bromoxynil EPOST improved sicklepod control. Two applications of bromoxynil controlled more pitted morningglory and sicklepod than one application. Control of all dicotyledonous weeds was increased by cyanazine plus MSMA LAYBY, and this treatment increased yields at all locations. Cotton was not injured by pyrithiobac PRE or by bromoxynil applied EPOST or POST, but temporary visual injury was observed with EPOST treatments of MSMA.

Interaction of Bromoxynil and Postemergence Graminicides on Large Crabgrass (Digitaria sanguinalis)

The effect of bromoxynil on large crabgrass control by clethodim, sethoxydim, fluazifop-P, fluazifop-P plus fenoxaprop-P, and quizalofop-P was evaluated in 1996 and 1997 in bromoxynil-tolerant cotton and in fallow areas. Bromoxynil at 560 g ai/ha reduced large crabgrass control 4 weeks after treatment (WAT) when mixed with labeled rates of fluazifop-P, fluazifop-P plus fenoxaprop-P, or quizalofop-P. Control 9 WAT was reduced when bromoxynil was mixed with any of the graminicides. Antagonism with the mixtures was greatest with quizalofop-P, intermediate with fluazifop-P plus fenoxaprop-P and fluazifop-P, and least with clethodim and sethoxydim. Increasing the graminicide rate 50% in mixtures with bromoxynil alleviated antagonism only for clethodim. No antagonism was noted 9 WAT when bromoxynil was applied 3 d before or 3 d after application of clethodim or sethoxydim or when bromoxynil was applied 3 d after fluazifop-P plus fenoxaprop-P. Antagonism was observed when bromoxynil was applied 3 d before fluazifop-P plus fenoxaprop-P or when applied 3 d before or 3 d after fluazifop-P and quizalofop-P. Regardless of bromoxynil application, greatest yields were obtained from cotton treated with clethodim or sethoxydim. Bromoxynil applied 3 d before or 3 d after clethodim, sethoxydim, or fluazifop-P plus fenoxaprop-P did not reduce yield. Yield was reduced when bromoxynil was applied 3 d before or 3 d after application of fluazifop-P or quizalofop-P and when bromoxynil was mixed with any graminicide.