Diclofop-methyl Research Articles

Diclofop‐methyl antagonism by broadleaf weed herbicides: the importance of leaf expansion rate

Summary: Avena saliva cv. Amuri and A. fatua were sprayed with diclofop methyl (1.0 kg a.i. ha−1) alone and in combination with 2,4‐D (1.1 kg a.i. ha−1), bentazone (1.0 kg a.i. ha−1), chlorsulfuron (15 g a.i. ha−1) or dicamba (0.3 kg a.i. ha−1). Effects of the herbicides on leaf extension rate during the first 8 to 10 days after spraying and subsequent growth (dry weight) after 57–75 days were determined by comparison with unsprayed plants. Diclofop‐methyl applied alone did not cause a decrease in leaf extension rate of A. saliva or A. fatua until at least 4 days after spraying. All broadleaf weed herbicides in combination with diclofop‐methyl caused a decrease in leaf extension rate of both species within 2 days of spraying. Ten days after spraying, leaf extension rates for plants sprayed with a broadleaf weed herbicide plus diclofopmethyl (all combinations) were lower than for unsprayed plants but greater than for plants sprayed with diclofop‐methyl alone. With the exception of A. fatua sprayed with bentazone, long‐term growth of plants sprayed with a broadleaf weed herbicide plus diclofop‐methyl (all combinations) was lower than for unsprayed plants but greater than for plants sprayed with diclofop‐methyl alone. Bentazone applied with diclofop‐methyl caused a substantial decrease in leaf extension rate of A. fatua within 24 h of spraying but at harvest, dry weight of plants from this treatment was similar to or less than that for plants sprayed with diclofop‐methyl alone. Application of diclofop‐methyl with bentazone at a rate of 0.3 kg a.i. ha−1 also caused a reduction in leaf extension rate of A. fatua within one day of spraying. At this rate of bentazone, dry weight of plants at harvest was intermediate to that of unsprayed plants and those sprayed with diclofop‐methyl alone. It is proposed that decreased leaf expansion rate during the first few days afte spraying is the cause of broadleaf weed herbicide antagonism of diclofop‐methyl.

HERBICIDES FOR WEED CONTROL IN SAFFLOWER (Carthamus tinctorius)

Field studies were conducted in 1986, 1987 and 1988 at Lethbridge, Alberta and in 1987 and 1988 at Indian Head, Saskatchewan to determine herbicides suitable for selective control of weeds in safflower (Carthamus tinctorius L.). Safflower exhibited acceptable tolerance to trifluralin, ethalfluralin, sethoxydim, fluazifop-p-butyl, clethodim, diclofop methyl, difenzoquat, imazamethabenz, chlorsulfuron, thiameturon, metsulfuron and DPX-A7881 over all years and locations. These herbicides offer the grower the option of preplant incorporated or postemergent herbicide application or a combination of the two. A mixture of thiameturon plus DPX-L5300 caused severe injury to safflower, reducing yield, oil content, and seed weight. Desmedipham, phenmedipham, and mixtures of these herbicides injured safflower at Lethbridge but not at Indian Head. Weeds reduced safflower yield by 39–73% over the 3 yr of the study. Control of weeds in safflower is essential to obtain optimum yields.Key words: Crop tolerance, seed yield, oil content, seed weight, weed competition

Effect of diclofop‐methyl and 2,4‐D on transmembrane proton gradient: a mechanism for their antagonistic interaction

The site of action of the postemergence graminicide, diclofop‐methyl (DM), in susceptible plants is possibly the plasmalemma. Indole‐acetic acid (IAA)‐ and fusicoccin (FC)‐induced net proton excretion in Avena coleoptiles was inhibited by the free acid, diclofop. However, net proton excretion recovered within 2 h when 2,4‐dichlorophenoxy acid (2,4‐D) was added simultaneously with diclofop. Diclofop depolarized the membrane potential (Em) within 12 min but the Em recovered within 30 min when diclofop was removed and replaced with either IAA or 2,4‐D. The inhibition of IAA‐induced coleoptile growth by DM and the membrane effects of its acid, diclofop, were partially reversed by 2,4‐D if it was added shortly after treatment of the tissue. These results are consistent with the reversal of DM injury in whole plants with 2,4‐D.

EFFECT OF HERBICIDES FOR THE CONTROL OF WEEDY GRASSES ON SEED PRODUCTION OF BROMEGRASS, CRESTED WHEATGRASS AND TIMOTHY

Herbicides for the control of annual grass weeds were applied to established seed-producing stands of bromegrass (Bromus inermis Leyss.) and crested wheatgrass (Agropyron cristatum (L.) Gaertn.) in spring each year 1979 through 1981 and to timothy (Phleum pratense L.) in 1980 and 1981. Flamprop methyl reduced seed yields in 2 years in bromegrass and in 1 year in crested wheatgrass and timothy. Diclofop methyl and difenzoquat reduced timothy and bromegrass yields, but not yields of crested wheat-grass. Diclofop methyl and flamprop methyl stunted timothy, reduced the number of seed heads formed, and delayed their maturation. Propanil reduced timothy seed yield 1 year, but did not reduce bromegrass yields. Dichlobenil had no deleterious effects.Key words: Bromus inermis, Agropyron cristatum, Phleum pratense, seed production, herbicides

EFFECT OF FREEZING TEMPERATURE ON THE EFFICACY OF WILD OAT HERBICIDES

In controlled environment experiments diclofop methyl, difenzoquat, flamprop methyl, fluazifop-P and seythoxydim were applied to wild oat at the three-leaf stage at recommended rates 10 h before or after a single night of freezing (−4 °C) temperature. Herbicide efficacy, as determined by the change in post-treatment dry weight accumulation of treated wild oats during the ensuing 3 wk period, was unaffected by the freezing temperature. The dry matter accumulation of wild oat exposed to the −4 °C temperature was reduced by 10–20% compared to plants which were grown under a constant 15/5 °C day/night regime.Key words: Oat (wild), frost, diclofop methyl, flamprop methyl, difenzoquat, fluazifop-P, sethoxydim

EFFECT OF SOIL MOISTURE ON THE EFFICACY OF FOLIAR-APPLIED WILD OAT HERBICIDES

In controlled environment experiments, the efficacy of diclofop methyl applied to wild oat was reduced more than the efficacy of difenzoquat or flamprop methyl when the soil water content (SWC) was cycled between −0.24 and −2.18 MPa (low SWC) compared to when it was cycled between −0.03 and −0.06 MPa (high SWC). Similarly, at low SWC diclofop methyl was much less effective than either fluazifop-p-butyl or sethoxydim in reducing the post-treatment dry weight accumulation of the weed.Key words: Oat (wild), soil moisture, diclofop methyl, flamprop methyl, difenzoquat, fluazifop-p-butyl

TOLERANCE OF LENTIL (Lens culinaris Medik.) TO HERBICIDES

Lentil (Lens culinaris Medik.) was tolerant to trifluralin, ethalfluralin, triallate, metolachlor and metribuzin applied preplant soil incorporated at rates of 1.1, 1.1, 1.7, 2.6 and 0.28 kg (a.i.)/ha, respectively. Chloramben and EPTC applied in a similar manner at rates of 2.0 and 3.0 kg (a.i.)/ha, respectively, injured lentils. Diclofop methyl, sethoxydim, fluazifop butyl, haloxyfop methyl and several experimental grass-specific herbicides were tolerated by lentil but propanil and flam-prop methyl were phytotoxic to this crop. Lentil was also tolerant to tank mixtures of trifluralin and triallate, trifluralin and metribuzin, metolachlor and metribuzin, and sequential treatments of dinitroaniline-type herbicides applied preplant incorporated followed by a post-emergence application of metribuzin or dinoseb. Lentil seed density was reduced by triallate in 1983 and seed size was reduced by flamprop methyl in 1982 and by trifluralin, triallate, metolachlor, EPTC, chloramben, metribuzin and trifluralin + metribuzin mixtures in 1983.Key words: Herbicides, lentil, preplant incorporated, postemergence, seed quality, sequential treatments

CONTROL OF WILD OATS IN WHEAT WITH BARBAN, DICLOFOP METHYL, FLAMPROP METHYL AND DIFENZOQUAT

The efficacy of diclofop methyl, flamprop methyl, difenzoquat, and barban on wild oats (Avena fatua L.) in wheat (Triticum aestivum L.) was tested in the field at Scott and Lacombe from 1978 to 1982. The four herbicides were applied at recommended rates and growth stages. Diclofop methyl consistently caused the greatest reduction in wild oat culms and plant weights and resulted in the largest wheat yield increases. Diclofop methyl, flamprop methyl and difenzoquat consistently produced yield increases over the untreated control.Key words: Wild oats, wheat, barban, diclofop methyl, flamprop methyl, difenzoquat

Control of Avena fatua L. and Cirsium arvense (L.) Scop. with mixtures of 3,6‐dichloropicolinic acid and four herbicides for control of A. fatua

SummaryControl of Avena fatua (L.) (wild oat) with diclofop methyl applied at 0·7 kg ha−1 at the two‐leaf stage and difenzoquat at 0·84 kg ha−1 at the four‐leaf stage in wheat (Triticum aestivum L.) under field conditions was good and not affected when either of these herbicides was mixed with 3,6‐dichloropicolinic acid as the monoethanolamine salt at 0·14, 0·20 or 0·30 kg ha−1. In the glasshouse, mixtures containing 3,6‐dichloropicolinic acid at rates as high as 0·6 kg ha−1 also did not affect control of A. fatua. When barban at 0·35 kg ha−1, or flamprop methyl at 0·56 kg ha−1 was mixed with similar rates of 3,6‐dichloropicolinic acid and applied at the two‐leaf and four‐leaf stage of A. fatua respectively, a reduction in control of A. fatua (antagonism) occurred under both field and glasshouse conditions. The herbicides for control of A. fatua did not influence the fresh weight suppression of C. arvense shoots obtained in the glasshouse with 3,6‐dichloropico‐colinic acid at 0·3 kg ha−1. Early tolerance of wheat (cv. Neepawa) was acceptable with all mixtures. Wheat yields with diclofop methyl or difenzoquat alone or in mixture with 3,6‐dichloropicolinic acid were increased over the yields from the A. fatua‐infested control.

CROP COMPETITION AIDS EFFICACY OF WILD OAT HERBICIDES

Field experiments were conducted over a 2-yr period to evaluate the need for competition by crop plants along with the application of postemergence herbicides for wild oat (Avena fatua L.) control in barley and wheat. Barban, difenzoquat, and barban plus difenzoquat were used in barley and barban, benzoylprop ethyl, diclofop methyl, flamprop methyl, and barban plus benzoylprop ethyl were used in wheat, at the two-leaf stage and the four-leaf stage of wild oats seeded alone or in a crop. Barban and diclofop methyl were effective for wild oat control at both the two-leaf and four-leaf stage of wild oats. Benzoylprop ethyl, difenzoquat and flamprop methyl alone or in combination with barban were more effective at the four-leaf than at the two-leaf stage of wild oats. Herbicide treatments increased barley yield up to 84% and wheat yield up to 177%. In the absence of herbicide treatments, crop competition from barley or wheat reduced the wild oat dry weight by about 50%. Competition by crop plants was essential for effective wild oat control with all foliage-applied wild oat herbicides included in this study.Key words: Competition, crop, wild oat, herbicides, wheat, barley

Control of the nematode associated with annual ryegrass toxicity

To control the nematode Anguina funesta (considered by some to be A. agrostis), the vector in annual ryegrass toxicity, pasture management treatments were applied before and after gall initiation. Before gall initiation, the herbicides paraquat and diclofop methyl were used to remove ryegrass. These treatments gave good control of the nematode, but reduced pasture production in winter when feed is generally scarce. Diclofop methyl had no detrimental effect on legume growth, and was more effective on actively growing ryegrass than was paraquat, which severely retarded subterranean clover. Desiccating the ryegrass heads, with mechanical topping or the desiccant herbicide paraquat, after gall initiation, but before hatching of the second-stage juveniles ( J2s ) , gave good control of the nematode population. The main limitations with mechanical topping are that the ryegrass heads must be tall enough to cut before the J2s hatch and not all paddocks are suitable for topping. With paraquat, the main limitations are that treated material was susceptible to weathering and there was less regrowth to set seed. Oxamyl, a systemic nematicide applied after gall initiation, had no effect on the nematode, nor had spraying pasture with the nematode parasitic fungus Verticillium sp.

The antagonism of IAA‐induced hydrogen ion extrusion and coleoptile growth by diclofop‐methyl

Diclofop‐methyl (DM) (ester) was readily absorbed by peeled and unpeeled coleoptiles of wheat, Triticum aestivum L. cv. Waldron, and oat, Avena sativa L. cv. Garry. Substantial absorption of diclofop (acid) occurred only in peeled coleoptiles of the two species. IAA‐induced acidification in peeled coleoptiles of both species was inhibited by 100 μM DM or diclofop (acid) during a 3 to 4 h period. There was no recovery of acidification after DM or diclofop inhibition in oat coleoptiles; however, acidification in wheat coleoptiles recovered from inhibition by DM but not from diclofop. The recovery from DM inhibition may be due to a reduction in the diclofop pool derived from DM by efflux and metabolism (detoxification) in peeled wheat coleoptiles. Diclofop was not detoxified in oat coleoptiles. IAA‐induced elongation of unpeeled oat coleoptiles was inhibited totally by 100 μM DM but not by 100 μM diclofop after 3.3 h of treatment. Wheat coleoptile elongation was relatively unaffected by either DM or diclofop. Basal elongation (no IAA) of both wheat and oat coleoptiles was inhibited by DM and diclofop. The inhibition by DM appeared to be irreversible, whereas the inhibition by diclofop was overcome by the addition of 10 μM IAA.

EFFECT OF DICLOFOP METHYL AND 2,4-D ALONE AND IN COMBINATION ON LEAF CELL MEMBRANE PERMEABILITY OF WILD OATS AND BARLEY

Diclofop methyl (2-[4-(2,4-dichlorophenoxy)Phenoxy]) propanoic acid increased leaf cell membrane permeability of wild oats at 48 h and barley at 96 h after treatment while 2,4-D did not affect leaf cell membrane permeability in either species. A combination of both herbicides had a similar effect on leaf cell membrane permeability of wild oats as diclofop methyl alone. In barley, the combination increased leaf cell membrane permeability at 24 h after treatment compared to 96 h with diclofop methyl alone.

THE INFLUENCE OF IMMERSION IN WATER ON THE EFFICACY OF POSTEMERGENCE WILD OAT HERBICIDES

Wild oat foliage was immersed in water after treatment with postemergence herbicides. The interval required between spraying and immersion to maintain herbicidal activity was: barban, 0–0.5 h; benzoylprop ethyl, 0–0.5 h; difenzoquat, 1–4 h; barban-benzoylprop ethyl, 0–0.5 h; barban-difenzoquat, 4–8 h; diclofop methyl, 8–12 h; flamprop isopropyl, 0 h; flamprop methyl, 0–0.5 h.

GERMINATION, AFTERRIPENING, EMERGENCE, PERSISTENCE AND CONTROL OF PERSIAN DARNEL

Low temperatures were conducive to germination of Persian darnel (Lolium persicum Boiss and Hohen.). Light stimulated germination at temperatures above 10 °C. Seeds exposed to 10 °C for 16 h, and 30 °C for 8 h, with and without light, showed an average increase in germination of 25% in light. Dry seeds afterripened or lost their dormancy rapidly at a constant temperature of 20 °C. Dormancy was lost slowly in seeds stored at + 1 °C or lower, but occurred more rapidly at alternating temperatures of − 3 and + 20 °C than at + 1 and + 20 °C. Seeds in moist soil afterripened faster at alternating temperatures, near 0 to + 20 °C, than at constant temperatures. There was little difference in the emergence of Persian darnel in Regina heavy clay, Asquith sandy loam or Weyburn loam from a depth of 5 cm or less. At depths below 7.5 cm, emergence was very limited or not observed. In two populations, more than 90% of the seeds on the surface or buried in the soil died within 2 yr. Seeds collected in 1973 and put out in June 1974 persisted longer on the surface than in the soil. After 3 yr not more than 2% of the seeds buried in the soil were viable. Under greenhouse conditions, diclofop methyl controlled Persian darnel at the three-leaf stage, but not the five-leaf stage. Compared to foliar or foliar and soil applications, a soil-incorporated treatment of diclofop methyl gave the most pronounced reduction in height and dry weight of Persian darnel seedlings.

EFFET DES APPLICATIONS REPETEES D’HERBICIDES ET DES DATES DE PREPARATION DU SOL SUR LES CHANGEMENTS DE POPULATIONS DES MAUVAISES HERBES

The immediate and residual effect of diclofop methyl (2(4-(2,4-dichlorophenoxy)-phenoxy propionic acid methyl ester)), diclofop methyl plus 2,4-D ((2,4-dichlorophenoxy) acetic acid), and the 2,4-D/mecoprop (2,(4-chloro-1-tolyl oxy) propionic acid)/dicamba (3,6-dichloro-o-anisic acid) mixture applied during 2 consecutive yr and for two dates of soil preparation has been evaluated on plots sown and unsown with oats (Avena sativa L.). The population changes observed during the 2 yr of herbicide applications have been related to the nature of the products and were of short duration. No difference between the herbicide treatments has been observed 1 yr after the treatment. Soil preparation in early June and the presence of oats have reduced considerably the weed populations during the 2 yr of herbicide applications. This effect has been noticeable 1 yr after the treatments. Herbicides are not solely responsible for weed population changes. From this study, it appears that cultural practices play a role as important as herbicides in controlling weed populations at least on a short-term basis.

EFFECT OF PHENOXY HERBICIDES ON COLD HARDINESS OF WINTER WHEAT

In a controlled environment experiment, five phenoxy herbicides were sprayed at two rates on 14-day-old winter wheat (Triticum aestivum L. emend Thell ’Norstar’). After 7 additional days of active growth, the plants were cold-hardened for 14 days and then subjected to a freezing test. Four of the herbicides — MCPA amine, 2,4-D ester, 2,4-DB, 2,4-D amine — significantly reduced the cold hardiness of winter wheat whereas diclofop methyl had a minor effect. The reduction in hardiness was greater at the higher rates of application than at the lower rates.