Application Of Bromoxynil Research Articles

Bromoxynil Antagonizes Johnsongrass (Sorghum halepense) Control with Graminicides

Field studies were conducted over 2 yr to evaluate rhizome johnsongrass control with tank mixtures and sequential applications of bromoxynil at 1.7 kg ai/ha and the graminicides clethodim, fluazifop-P, and quizalofop-P. When compared with the graminicide alone, bromoxynil reduced johnsongrass control 28 days after treatment (DAT) 20, 36, and 55% when applied in combination with clethodim, fluazifop-P, and quizalofop-P, respectively. Application of bromoxynil 7, 3, and 1 d before or 1, 3, and 7 d after all graminicides reduced antagonism when compared with the bromoxynil plus graminicide mixtures. Based on johnsongrass control 28 DAT, antagonism was precluded when bromoxynil was applied 3 d before clethodim and 7 d before fluazifop-P and quizalofop-P. Application of bromoxynil 3 and 7 d after quizalofop-P and 7 d after clethodim also precluded antagonism. The antagonistic tank mixtures of bromoxynil and graminicides reduced cotton yield 17% because of reduced johnsongrass control compared with graminicides alone. A 3-d or greater application interval between bromoxynil and the graminicides was necessary to maximize cotton yield.

Effect of time of application of MCPA and bromoxynil in relation to flowering on subterranean clover seed yield and quality

The importance of stage of phenological development and cultivar maturity ranking in influencing the seed yield response of subterranean clover (Trifolium subterraneum L.) to broadleaf herbicides was examined in a field study in southern New South Wales. The herbicides, bromoxynil (200 g a.i./L) at 1.4 L/ha and MCPA (500 g a.i./L) at 1.0 Wha, were applied 6 (TI) and 3 weeks (T2) before flowering, and at 5% flowering (T3) to 7 cultivars ranging from early to late flowering. The stage of phenological development at herbicide application, the maturity ranking of the cultivar and the herbicide applied, all influenced seed set. Application of bromoxynil at T1 did not reduce seed yield of any cultivar but increased seed yield of 4 cultivars by up to 30%. MCPA applied at the same time reduced seed yield in 1 cultivar by 26% and increased yields in 4 others by up to 57%. Application of bromoxynil at T3 caused reductions in seed yield in 3 of the 7 cultivars. MCPA applied at this time was more damaging than bromoxynil with all cultivars showing large seed yield reductions ranging from 22 to 64%. Despite large reductions in herbage yield as a result of some herbicide treatments, there was only a low correlation (r = 0.3, P<0.01) between herbage yield at full flower and seed yield. Our findings suggest that the reduction in herbage yield and change in canopy structure as a result of the early application of herbicides stimulated seed production. Seed number was the primary yield component responsible for the change in seed yield with a high correlation (r = 0.86, P<0.01) between these 2 parameters. Seed size was relatively insensitive to herbicide treatment but varied markedly with cultivar. Germination percentage of seed produced by swards treated with bromoxynil was unaffected, even when applied at T3, whereas MCPA lowered germination percentage of almost all cultivars if applied within 3 weeks of the commencement of flowering. The maturity ranking of the cultivars was highly negatively correlated with percentage seed yield loss (r = -0.80, P<0.01) when either herbicide was applied at T3, the seed yield of the early flowering cultivars being most depressed by the herbicides. Length of recovery period between herbicide application and flowering was shown to be very important in influencing seed yield, the effect being modified by both herbicide and cultivar maturity.

Control of Triazine-Resistant Kochia (Kochia scoparia) in Conservation Tillage Corn (Zea mays)

Triazine-resistant (TR) kochia control with herbicides was evaluated in the greenhouse and in the field on ridge-till and ecofallow corn. In the greenhouse, bromoxynil, dicamba, linuron, and paraquat applied POST controlled TR kochia > 86%. Control of TR kochia with 2,4-D ester at 0.3 kg ae ha−1varied with kochia biotype. In three ridge-till fields in 1985, atrazine plus fluorochloridone at 2.2 plus 0.6 kg ai ha−1applied before planting plus a layby cultivation was the only treatment that reduced TR kochia biomass to < 750 kg ha−1. In 1986, atrazine plus dicamba at 2.2 plus 0.3 kg ha−1, atrazine plus fluorochloridone at 2.2 plus 0.3 or 0.6 kg ha−1applied EPOST; atrazine at 2.2 kg ha−1applied EPOST followed by an MPOST application of bromoxynil at 0.3 or 0.4 kg ha−1, or dicamba plus 2,4-D ester at 0.3 plus 0.3 kg ha−1; and an MPOST application of atrazine plus dicamba at 1.3 plus 0.5 kg ha−1, atrazine plus pyridate at 1.1 plus 1.0 kg ai ha−1, or pyridate plus cyanazine at 1.0 plus 1.7 kg ai ha−1followed by a layby cultivation reduced kochia biomass to < 400 kg ha−1. In ecofallow corn, the only herbicide treatment that consistently controlled TR kochia > 95% 21 to 30 d after application was pyridate plus fluorochloridone at 1.0 plus 0.6 kg ha−1. Other treatments were less effective because kochia was too large or additional kochia emerged after application. When added to atrazine plus cyanazine, paraquat at 0.3 kg ai ha−1plus dicamba was more effective than paraquat plus 2,4-D ester or paraquat alone in controlling TR kochia.

Proso Millet (Panicum miliaceum) Tolerance to Several Postemergence Herbicides

The tolerance of two proso millet cultivars to atrazine preemergence and postemergence applications of bromoxynil, clopyralid, dicamba, or metsulfuron plus amine formulations of 2,4-D was studied in the field. Proso millet grain yield, test weight, seed weight, moisture content, and plant height at harvest were not affected by any of the herbicide treatments, despite some early-season injury observed in 1990.

Bromoxynil tolerance during the seedling phase is associated with genetic grain yield improvement in maize

Genetic grain yield improvement of maize (Zea mays L.) in Ontario during the past three decades can be attributed, in part, to increased tolerance to environmental stresses. We have observed a differential response of field-grown old and new hybrids after application of the photosystem II inhibiting herbicide bromoxynil (4-hydroxy-3,5-dibromobenzonitrile). Studies were conducted to test whether tolerance to bromoxynil is associated with stress tolerance and grain yield in maize hybrids representing three decades of yield improvement in Ontario. Experiments were carried out with seedlings of eight maize hybrids grown in pots in controlled-environment growth cabinets and, in one experiment, with seedlings grown in pots outside during the months of July and August at Guelph, Ontario. Bromoxynil was applied to the youngest fully-expanded leaf of plants at the 6- to 8-leaf stage and chlorophyll fluorescence of the treated leaves was measured in the 2- to 24-h period after bomoxynil application. Results showed that the chlorophyll fluorescence ratio Fv/Fm, an indicator of photosynthetic efficiency, declined after bromoxynil application until 4 h after application and, subsequently, recovered slightly during the next 20 h. Large differences in the Fv/Fm ratio were apparent among hybrids in the response to bromoxynil. The Fv/Fm ratio was significantly higher for hybrids released in the 1980s than for hybrids released in the 1970s, and the Fv/Fm ratio of the latter group was significantly higher than that of the four oldest hybrids. Chlorophyll fluorescence ratios Fv/Fm after bromoxynil application in the seedling phase were highly correlated with grain yield of the hybrids in field experiments conducted during 1987 and 1988 (r = 0.91). Results of this study support the contention that maize genotypes that are less sensitive to bromoxynil are less susceptible to environmental stresses. Key words: Zea mays L., stress tolerance, bromoxynil, chlorophyll fluorescence, Fv/Fm ratio, detoxifying agents

Altai wild ryegrass yield response to herbicides applied during establishment

The effects on productivity of Altai wild ryegrass (Leymus angustus (Trin.) Pilger) of 14 herbicide treatments applied during establishment were investigated in two field experiments at Melfort, Saskatchewan. Weed control achieved with metsulfuron, chlorsulfuron, thifensulfuron and tank-mixed applications of bromoxynil with diclofop or fenoxaprop during the establishment year ensured satisfactory forage establishment which in turn caused a "residual effect" for 1–3 yr increasing individual cut as well as cummulative forage dry matter yields significantly. When established with a heavy broadleaf weed infestation (138 m−2) dominated by stinkweed (Thlaspi arvense L.) in 1985, bromoxynil plus diclofop increased yield 359% over a 3-yr period. Sulfonylurea herbicides increased yield 221–346%. Bentazon and MCPA/mecoprop/dicamba increased yields 85%. With a moderate weed infestation (40 m−2) dominated by lamb's-quarters (Chenopodium album L.) in 1986, sulfonylurea herbicides and bromoxynil plus the graminicides increased cummulative yields only 37–59%. Sethoxydim and fenoxaprop, tested alone, caused significant crop injury in both experiments. Key words: Altai wild ryegrass, Leymus angustus (Trin.) Pilger, herbicide, weed control, forage yield

Environment and Bromoxynil Phytotoxicity

Experiments in controlled-environment chambers indicated that high temperature, 30 C, increased the phytotoxicity of bromoxynil (3,5-dibromo-4-hydroxybenzonitrile) to wild mustard (Sinapis arvensisL. # SINAR) and redroot pigweed (Amaranthus retroflexusL. # AMARE) compared to low temperature, 10 C, during and after treatment. Bromoxynil phytotoxicity generally was higher at relative humidities of 90 to 95% compared to 40 to 60%, but relative humidity had less influence on bromoxynil phytotoxicity than did temperature. A simulated rain immediately after bromoxynil treatment reduced control of both species, but the reduction was of no practical importance for wild mustard. The data indicate that wild mustard and redroot pigweed control would be reduced by bromoxynil application during a period of low temperatures or to plants in advanced growth stages.

CONTROL OF BROADLEAVED WEEDS IN CREEPING RED FESCUE GROWN FOR SEED

Field studies were conducted from 1977 to 1981 on the control of dandelions (Taraxacum officinale L.) and other broadleaved weeds in creeping red fescue (Festuca rubra var. geniuna L.). Creeping red fescue was established either alone or with a companion crop of barley (Hordeum vulgare L.) or rapeseed (Brassica campestris L.). The barley was harvested in early August for fodder or in early September for grain. Several herbicide treatments were applied to each crop situation. Bromoxynil plus MCPA applied at 0.28 + 0.28 kg a.i./ha when the creeping red fescue was in the three-leaf stage (and 1–2 mo old) controlled 75% or more of the annual weeds during the year of seeding. This herbicide combination also provided substantial control of dandelions and other weeds during the year following seeding. A second herbicide treatment of dicamba plus 2,4-D at 0.28 + 0.56 kg a.i./ha in May of the year following seeding provided an improvement in the control of dandelions and other weeds over the single application of bromoxynil plus MCPA in some but not all seedings. The use of rapeseed as a companion crop without any herbicide treatments did not provide consistent weed control. Seed yields during the second production year were increased by 25% or more from the use of herbicide treatments when creeping red fescue was seeded alone or with barley harvested for fodder. First production year seed yields were not increased by any of the herbicide treatments. Similarily, first and second production year seed yields were not increased by any of the herbicide treatments when creeping red fescue was seeded with barley harvested for grain. Harvesting barley as fodder rather than grain produced marginally higher first production year creeping red fescue seed yields but had no effect on second production year seed yields.Key words: Creeping red fescue, dandelion, companion crop, 2,4-D plus dicamba, MCPA plus bromoxynil