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1.
In a survey conducted during October 1995, single-lesion isolates of the sugar beet leaf-spot fungus, Cercospora beticola , were tested for sensitivity to the sterol demethylation inhibiting fungicides (DMIs) flutriafol and bitertanol. The isolates were collected from fields in three different areas of northern Greece. Fields at Serres and Imathia had been sprayed with DMIs for about 15 years to control sugar beet leaf-spot. At the third site, Amyndeon, DMI fungicides had not been used. From each area 150 isolates were tested. ED50 values were calculated for individual isolates by regressing the relative inhibition of colony growth against the natural logarithm of the fungicide concentration. The mean ED50 values for flutriafol for the Serres, Imathia and Amyndeon populations were 1·07, 0·73 and 0·5 µg mL−1, respectively (significantly different at P  = 0·05). For bitertanol the mean ED50 values for the Serres and Imathia populations were 0·72 and 0·81 µg mL−1, respectively, which were not significantly different at P  = 0·05. The mean ED50 value of the Amyndeon population was 0·48 µg mL−1, which was significantly lower than those of the other two populations ( P  < 0·05). A cross-resistance relationship was found to exist between the two triazole fungicides tested when log transformed ED50 values of 60 isolates were subjected to a linear regression analysis ( r  = 0·81).  相似文献   

2.
The level of tolerance of various market classes of dry bean to cloransulam-methyl is not known. Three field studies were conducted in Ontario, Canada during 2007 and 2008 to determine the level of tolerance of black, cranberry, kidney, and white bean to the pre-emergence (PRE) and postemergence (POST) application of cloransulam-methyl at 17.5, 35, and 70 g ai ha−1. Cloransulam-methyl applied at 17.5, 35, and 70 g ha−1 caused between 13 and 23% injury in black, cranberry, kidney, and white bean, respectively. Cloransulam-methyl applied at 17.5, 35, and 70 g ha−1 reduced the shoot dry weight by between 16 and 28% compared to the untreated control. Cloransulam-methyl applied PRE reduced the height of black bean by 27% and the height of cranberry bean by 25% at 70 g ha−1 and reduced the height of white bean by 19% at 35 g ha−1 and by 37% at 70 g ha−1. Cloransulam-methyl applied PRE reduced the yield of black bean by 29% at 35 g ha−1 and by 43% at 70 g ha−1, reduced the yield of cranberry bean by 43% at 70 g ha−1, and reduced the yield of white bean by 36% at 35 g ha−1 and by 54% at 70 g ha−1. Based on these results, there is not an adequate margin of crop safety for the PRE and POST application of cloransulam-methyl in black, cranberry, kidney, and white bean at the rates evaluated.  相似文献   

3.
Pot and field tests were conducted to evaluate the efficacy of pyribenzoxim for winter weeds in wheat. In the pot tests, pyribenzoxim, at 50 g ha−1, controlled certain biotypes of blackgrass, including a fenoxaprop-P-ethyl-resistant biotype (the "Notts" biotype). A chlorotoluron-resistant blackgrass (the "Peldon" biotype) was not controlled. Cleaver, at the three-to-four-leaf stage, was completely controlled by pyribenzoxim at 30 g ha−1. In the field, the application in December gave good control of common chickweed, but did not control other weeds. No damage to wheat was observed with this rate of pyribenzoxim in December. The application in March gave complete control of blackgrass , hairy chess, and soft brome at 70 g ha−1, and cleaver at 140 g ha−1. The partial control of corn poppy and field violet was achieved. The March application scorched the wheat at 50–70 g ha−1, with prolonged stunting at 100–140 g ha−1. In conclusion, it was shown that pyribenzoxim had potential as a wheat herbicide, but needed further fine-tuning to find an optimum dosage.  相似文献   

4.
A study was conducted to evaluate the combined activity of a tank mixture of triclopyr plus metsulfuron with non-ionic surfactant (NIS), crop oil concentrate (COC), and organosilicon (OS) adjuvants on the control of Hedyotis verticillata under glasshouse and field conditions. The results of both the glasshouse and field experiments showed that 160 g ai ha−1 triclopyr plus 0.2 g ai ha−1 metsulfuron and 320 g ai ha−1 triclopyr plus 0.4 g ai ha−1 metsulfuron, with the addition of 0.25% NIS, 0.05% COC, or 0.05% OS, were effective in controlling H. verticillata . A comparison of the cost revealed that the most cost-effective combination for controlling H. verticillata is 160 g ai ha−1 triclopyr plus 0.2 g ai ha−1 metsulfuron combined with 0.25% NIS.  相似文献   

5.
Ontario otebo bean growers have few herbicide options available for weed management. Six field trials were conducted in Ontario, Canada, over a 2 year period (2003 and 2004) to evaluate the tolerance of otebo bean to the postemergence (POST) application of bentazon at 1080 and 2160 g ai ha−1, fomesafen at 240 and 480 g ai ha−1, sethoxydim at 500 and 1000 g ai ha−1, quizalofop-p-ethyl at 72 and 144 g ai ha−1, imazamox plus fomesafen at 25 + 200 and 50 + 400 g ai ha−1, and imazamox plus bentazon at 25 + 600 and 50 + 1200 g ai ha−1. All treatments, including the untreated control, were maintained weed-free during the growing season. The POST application of bentazon, imazamox plus fomesafen, and imazamox plus bentazon caused as much as 9% visual injury and reduced the plant height ≤ 12%, reduced the shoot dry weight ≤ 32%, and delayed maturity but had no adverse effect on the yield of otebo bean. Fomesafen, sethoxydim, and quizalofop-p-ethyl applied POST caused as much as 8% visual injury but this was transient and had no adverse effect on the plant height, shoot dry weight, seed moisture content, and yield of otebo bean, except for quizalofop-p-ethyl, which reduced the shoot dry weight as much as 18%. Based on these results, bentazon, fomesafen, sethoxydim, quizalofop-p-ethyl, imazamox plus fomesafen, and imazamox plus bentazon applied POST have an adequate margin of crop safety for weed management in otebo bean production in Ontario. However, care must be taken to avoid spray overlaps to prevent injury from bentazon, imazamox plus fomesafen, and imazamox plus bentazon.  相似文献   

6.
A study on the efficacy of tank-mix combinations on the growth of Leptochloa chinensis (L.) Nees and Scirpus grossus (L.) f. at the 3–4-leaf stage was conducted under glasshouse conditions. Sethoxydim plus cyhalofop-butyl at 8 + 25, 16 + 25, 32 + 25, 32 + 12.5, and 32 + 6.25 g ai ha−1 provided good control of L. chinensis , ranging from 89–95%. However, a comparison of the costs of herbicide mixtures revealed that sethoxydim at 32 g ai ha−1 plus cyhalofop-butyl at 6.25 g ai ha−1 were the most cost-effective among the combinations. For Scirpus grossus , bensulfuron plus 2,4-D dimethylamine at 2.5 + 18, 5.0 + 18, 1.25 + 36, 2.5 + 36, and 5.0 + 36 g ai ha−1 gave good control that ranged from 88–93%. Tank-mixing bensulfuron with 2,4-D at 1.25 + 36 g ai ha−1 was, however, the most cost-effective mixture compared to the other mixtures. None of the tank mixtures tested in this study caused injury to the rice seedlings. However, further field studies need to be undertaken to verify these findings.  相似文献   

7.
Field and greenhouse experiments were conducted in 2004 and 2005 to study weed control and the response of winter wheat to tank mixtures of 2,4-D plus MCPA with clodinafop propargyl. The field experiments were conducted at Yazd and Oroumieh, Iran, with factorial combinations of 2,4-D plus MCPA at 0, 975, and 1300 g ai ha−1 and with clodinafop propargyl at 0, 64, 80, 96, and 112 g ai ha−1 in four replications. The greenhouse experiments further evaluated the effect of these tank mixtures on weed control, where each herbicide mixture was considered as one treatment and the experiment was established in a randomized complete block design with four replications. In the field experiments, the herbicides were applied at wheat tillering, while in the greenhouse experiments they were applied at the beginning of the tillering stage and at the four-leaf stage of the grass and broadleaf weeds, respectively. The results indicated antagonistic effects between 2,4-D plus MCPA and clodinafop propargyl. The best tank mixture with regard to weed control efficacy was 2,4-D plus MCPA at 975 g ai ha−1 with clodinafop propargyl at 96 g ai ha−1. The wheat grain yield was also increased by the tank mixture of clodinafop propargyl with 2,4-D plus MCPA. Generally, to inhibit clodinafop propargyl efficacy reduction due to tank-mixing with 2,4-D plus MCPA, it is recommended that the application dose of 64 g ai ha−1 should be increased to 96 g ai ha−1.  相似文献   

8.
Field experiments were conducted at five locations in the major wheat production regions of Iran to evaluate the efficacy of sulfosulfuron in controlling weed barley species (including Hordeum spontaneum , Hordeum murinum , Hordeum distichon , and Hordeum vulgare ) in the 2004–2005 and 2005–2006 growing seasons. Sulfosulfuron was applied either postemergence (POST) or preplant-incorporated (PPI) at 0, 20.25, 30.75, 40.5, 51.0, 60.75 or 71.25 g ai ha−1 to plots arranged in a randomized complete block design with four replications. Sulfosulfuron at the recommended rate (20.25 g ai ha−1) failed to provide acceptable control of the weed barley species. However, the level of control increased with the application rate, particularly at rates >51.0 g ai ha−1. Generally, PPI-applied sulfosulfuron resulted in markedly greater control levels than those of a POST application and complete control of H. murinum and H. vulgare was achieved with PPI-applied sulfosulfuron at all rates >20.25 and 30.75 g ai ha−1, respectively. In most cases, the wheat yield increased with the application rate without any crop injury. The highest yield increase (186%) was obtained with a PPI application of 71.25 g ai ha−1.  相似文献   

9.
Bispyribac-sodium {sodium 2,6-bis[(4,6-dimethoxy-2-pyrimidinyl)oxy] benzoate} has recently been introduced to California where it effectively controls Echinochloa spp. in rice ( Oryza sativa L.). However, biotypes of early watergrass ( Echinochloa oryzoides (Ard.) Fritsch) and late watergrass ( E. phyllopogon (Stapf ) Koss.) have evolved resistance to this herbicide. In 2001 and 2002, greenhouse and field experiments evaluated interactions between thiobencarb { S -[(4-chlorophenyl) methyl] diethylcarbamothioate} and bispyribac-sodium on resistant (R) and susceptible (S) late watergrass in California rice. Synergism was assessed using Colby's test and regression analysis. In the greenhouse, thiobencarb at 4480 and 5333 g ai ha−1 synergistically reduced bispyribac-sodium GR50 values on the R and S biotypes by 50–70% without increasing toxicity to rice. Synergism was also observed on S late watergrass in the field when 10 g ai ha−1 bispyribac-sodium was mixed with 1120–2240 g ai ha−1 thiobencarb. These effects could be related to interactions between thiocarbamates and enzymes in Phase I reactions of herbicide metabolism. This synergism results in better control at lower rates allowing a reduction in weed control costs, the herbicide load on the environment and a lower selection pressure towards resistant weed biotypes.  相似文献   

10.
Dry bean producers in Ontario, Canada, have few herbicide options available for annual broad-leaved weed management and there is little information on the tolerance of dry bean to linuron. The tolerance of black, cranberry, kidney, and white bean to the pre-emergence (PRE) application of linuron at the rates of 0, 500, 1000, 1500, 2000, and 2500 g ai ha−1 was evaluated in field studies conducted in 2005 and 2006 at Exeter and in 2006 at Ridgetown, Ontario. The four market classes differed in their response to linuron. Cranberry and kidney bean were more tolerant to the PRE application of linuron than black and white bean. Linuron applied PRE caused as much as 12% injury in cranberry and kidney bean, 47% injury in black bean, and 56% injury in white bean. Linuron applied PRE at 500–2500 g ai ha−1 had no effect on the height of cranberry and kidney bean but decreased the height by 7, 8, and 15% in black bean and by 10, 13, and 23% in white bean at 1500, 2000, and 2500 g ai ha−1, respectively. Linuron applied PRE at the rates evaluated did not cause any adverse affect on the yield of cranberry, kidney, and white bean but black bean yield was reduced by 16% at 2500 g ai ha−1. Based on these results, there is not an adequate margin of crop safety for the PRE application of linuron in black and white bean at rates >1000 g ai ha−1. However, there is a potential for the use of linuron PRE for weed management in cranberry and kidney bean at the rates evaluated.  相似文献   

11.
Pot experiments were conducted to evaluate the level of imazamox tolerance in five red rice ( Oryza sativa L.) and four barnyardgrass (three Echinochloa crus-galli (L.) Beauv. and one Echinochloa oryzoides (Ard.) Fritch) morphologically distinct biotypes collected from rice fields in northern Greece. The susceptibility of barnyardgrass biotypes to propanil was also studied. Red rice biotypes were not controlled by imazamox applied at 40 g ha−1. In contrast, 80 g imazamox ha−1 provided 56–84% red rice control (averaged across shoot number and fresh weight reduction). Not all barnyardgrass biotypes were susceptible to imazamox applied postemergence. However, propanil applied at 2.6 kg ha −1 controlled the E. crus-galli biotypes well, but propanil applied at rates of 2.6 and 5.2 kg ha −1 was not effective in reducing the shoot number and fresh weight of the E. oryzoides biotype. Propanil applied at 10.4 kg ha −1 reduced the shoot number and fresh weight of this biotype by 78 and 85%, respectively. In most cases, a linear equation ( y  = % of control, x  = g ha−1) provided the best fit for regressions between red rice or barnyardgrass shoot number or fresh weight and imazamox rates. The results of this study suggest that postemergence application of imazamox is not effective against all red rice and barnyardgrass biotypes found in the rice fields of Greece and that significant variability regarding herbicide efficacy among biotypes might exist.  相似文献   

12.
The sensitivity of 22 major crops, pastures and weeds from the north-east grain region of Australia to atrazine and chlorsulfuron residues was determined in a glasshouse using a soil-free bioassay system. A logistic equation was fitted to the seedling fresh weights as a function of the logarithm of herbicide concentration by non-linear regression and used to calculate the doses for 10%, 30% and 50% inhibition of seedling growth (ID10, ID30 and ID50). The ID50 for atrazine ranged from 0.03 to 0.04 mg a.i. L–1 for Salvia reflexa Hornem. and barley to 1.47 mg a.i. L–1 for sorghum. The ID50 for chlorsulfuron ranged from 0.19 to 0.21 μg a.i. L–1 for lucerne and snail medic to 102 μg a.i. L–1 for wheat. Based on ID50 values measured, the predicted responses of each species to a range of concentrations of atrazine and chlorsulfuron were classified into four categories ranging from no damage to severe damage. These sensitivity data will assist in planning cropping sequences in soils previously treated with atrazine or chlorsulfuron.  相似文献   

13.
Field experiments were conducted from 1994 to 1997 at two locations to study the effectiveness of chlorsulfuron and triasulfuron applied through different irrigation methods (chemigation) for control of Orobanche aegyptiaca Pers. in tomato ( Lycopersicon esculentum Mill). Three split applications of chlorsulfuron at 2.5 g a.i. ha−1 and of triasulfuron at 7.5 g a.i. ha−1, through conventional sprinkler irrigation systems, 10–14 days apart followed immediately by sprinkling with water, controlled O. aegyptiaca by about 90% and 80% and increased crop yield 25–47% and 30%, respectively, without any crop injury symptoms. Repeated applications of the same herbicides at half rates resulted in slightly higher O. aegyptiaca control and crop yield than only one herbicide application at double rate. Chemigation by the sprinkler systems (microsprinklers, 60 m3 ha−1) slightly increased the herbicide efficiency as compared with the high volume spray (800 m3 ha−1). O. aegyptiaca control from sulfonylureas applied by drip chemigation was poor, as this probably requires very accurate timing and the herbicide distribution in the soil was not uniform.  相似文献   

14.
In 2002, the Malaysian government had banned the use of the hazardous herbicide, paraquat. Most growers perceive that paraquat is the most effective herbicide and provides the fastest mode of action to control weeds. An experiment was conducted at MAB Agriculture-Horticulture, Sepang, Selangor, Malaysia, from February 2004 to February 2005 to evaluate the efficacy and ability of the less hazardous herbicides, glufosinate ammonium and glyphosate, as an alternative to the hazardous herbicide, paraquat, in controlling weeds in immature oil palm (<3 years old). The results showed that paraquat needed high rates, 600 and 800 g ha−1, to control weeds effectively. However, lower rates of glufosinate ammonium (200 g ha−1) and glyphosate (400 g ha−1) gave excellent weed control. The results showed that the efficacy of glufosinate ammonium and glyphosate were much better than paraquat. The results also showed that, with no direct contact with the plants, paraquat, glufosinate ammonium, and glyphosate had no adverse effect on the vegetative and generative growth of oil palm in this study. These results proved that the less hazardous herbicides, glufosinate ammonium and glyphosate, could be used as an alternative to paraquat to control weeds in immature oil palm.  相似文献   

15.
A new compound 3-(3-bromothiophen-2-yl)-5-(2,6-difluorobenzyl)oxymethyl-5-methyl-4,5-dihydroisoxazole was synthesized and the herbicidal activity was assessed under glasshouse and flooded paddy field conditions. This compound demonstrated good rice selectivity and potent herbicidal activity against annual weeds at 125 g ai ha−1 under greenhouse conditions. Soil application of this compound showed the complete control of barnyardgrass to the 4th leaf stage at 250 g ai ha−1. Field trials indicated that this compound, combined with pyrazosulfuron-ethyl, controlled annual and perennial weeds rapidly with good tolerance by transplanted rice seedlings from postemergence and soil application. This compound showed a low mammalian and environmental toxicity in various toxicological tests.  相似文献   

16.
Fenpropimorph-resistant mutants of Ustilago maydis were obtained at high frequency (30 × 10−6) after UV-irradiation followed by selection on media containing fenpropimorph (50 μ g mL−1). Genetic analysis of 30 such mutants resulted in the identification of two unlinked chromosomal loci, the U/fpm -1 locus with two allelic genes ( U/fpm- 1A and U/fpm -1B) and the U/fpm -2 locus. The mutant genes U/fpm- 1A and U/fpm -2 are responsible for high resistance levels (Rf: 75–100 or 257–286 based on MICs or ED50s, respectively), while the U/fpm -1B mutation gives only a small reduction (approximately 7–10-fold) in fenpropimorph sensitivity. Cross-resistance studies with other SBIs showed that the major gene ( U/fpm- 1A and U/fpm -2) mutants were cross-resistant to the related compound fenpropidin (Rf: 15–20 or 53–66 based on MICs or ED50s values, respectively) and to tridemorph (Rf: 5 or 7.1–9.5 based on MICs or ED50s values, respectively), but not to the inhibitors of steps of ergosterol biosynthesis preceding the Δ14-reductase. The minor gene ( U/fpm -1B) mutants also had low-level resistance (approximately 5-fold) to tridemorph and to fenpropidin, but in contrast with the major gene mutants they were 2–10 times more sensitive to the triazoles studied (triadimefon, triadimenol, propiconazole and flusilazole) and to the pyridine, pyrifenox.
Studies of the fitness of U. maydis mutants showed that in major gene mutants, resistance was not associated with changes in growth rate in liquid culture or pathogenicity on young maize plants. The minor gene mutation reduced significantly the growth rate in liquid culture and the pathogenicity, either in homozygous or heterozygous condition in dikaryotic mycelium.  相似文献   

17.
There is a limited number of registered herbicides in white beans. Field trials were conducted at two Ontario, Canada, locations (Exeter and Ridgetown) in 2001 and 2002 to evaluate tolerance of two white bean cultivars, AC Compass and OAC Thunder, to preplant-incorporated applications of S -metolachlor plus imazethapyr (1600 + 75 and 3200 + 150 g ai ha−1, respectively), flumetsulam plus S -metolachlor ( premixed at 1443 and 2886 g ai ha−1) and cloransulam-methyl (35 and 70 g ai ha−1). There were no differences between the two cultivars in their responses to the herbicide treatments. S -metolachlor plus imazethapyr caused as much as 5% visual crop injury and decreased plant height up to 20%, shoot dry weight up to 39% and yield as much as 21%. Flumetsulam plus S -metolachlor caused as much as 7% visual crop injury and reduced plant height by up to 25%, shoot dry weight by up to 46% and yield as much as 24%. Cloransulam-methyl caused as much as 10% visual crop injury and decreased plant height up to 35%, shoot dry weight up to 55% and yield as much as 44%. There were no differences in seed moisture content among any of the herbicide treatments. This research suggests that the margin of safety of white bean is inadequate to support the preplant-incorporated registration of S -metolachlor plus imazethapyr, flumetsulam plus S -metolachlor and cloransulam-methyl in Ontario.  相似文献   

18.
In late 2003, nine populations of Sclerotinia homoeocarpa in Ontario Canada (seven of which had been previously sampled in early 1994, prior to the registration of sterol demethylation-inhibiting (DMI) fungicides for turf disease control in Canada) were sampled and tested for sensitivity to propiconazole. Four of the nine populations had not been treated with DMI fungicides during the intervening years, and isolates from these locations were sensitive to propiconazole (geometric mean EC50 values of 0·005–0·012 µ g mL−1, compared with 0·005–0·008 µ g mL−1 for the original 1994 populations). Among the five populations from 2003 that had been exposed to DMI fungicides, mean EC50 values were significantly greater, ranging from 0·020 to 0·048 µ g mL−1. A significant correlation of determination was found between estimated number of fungicide applications and log EC50 ( R 2 = 0·832, P  = 0·0001), and the equation predicted that 42·3 applications of propiconazole would be needed to bring a sensitive population (EC50 < 0·01  µ g mL−1) to a resistant level (EC50 > 0·10  µ g mL−1). Fungicide sensitivity vs. duration of fungicide efficacy was also tested, and it was found that isolates with decreased sensitivity were able to more quickly overcome the inhibitory effects of fungicide application, reducing the duration of control from 3 weeks to 2 weeks.  相似文献   

19.
Galium aparine plants were treated at the two-whorl stage with technical-grade phenmedipham. The active ingredient was applied at 10 doses as an acetone:water solution, without emulsifier, alone or in mixture with an ester of oleic acid (methyl, butyl, octyl, dodecanyl, octadecanyl). The plant response was described by a log-logistic regression model. Phenmedipham applied alone did not kill the plants even at the highest dose (1621 g a.i. ha−1). In contrast, addition of any alkyl oleate to phenmedipham killed the plants at the 200–400 g a.i. ha−1 doses. The alkyl oleates differently affected activity of phenmedipham. Their effects could be ranked as follows: butyl ≥ methyl; octyl> methyl; dodecanyl ≤ methyl; octadecanyl < methyl oleate. Thus, butyl and octyl oleate promoted phenmedipham activity more than methyl oleate.  相似文献   

20.
Optimizing the herbicide dose by the addition of adjuvants is an acceptable way to reduce the risk of side-effects from herbicides. Therefore, to detect a suitable adjuvant for diclofop-methyl, cycloxydim, and clodinafop-propargyl against littleseed canarygrass ( Phalaris minor ) and wild oat ( Avena ludoviciana ), six dose–response experiments were conducted. The treatments consisted of diclofop-methyl at 0, 112, 225, 450, 675, and 900 g ai ha−1, cycloxydim at 0, 15, 30, 60, 90, and 120 g ai ha−1, and clodinafop-propargyl at 0, 8, 16, 32, 48, and 64 g ai ha−1 with and without the adjuvants of Frigate, olive oil, and castor oil at 0.2% (v/v) in order to control both littleseed canarygrass and wild oat. Tested herbicides performance was enhanced by all adjuvants against littleseed canarygrass and wild oat. The addition of Frigate and the vegetable oils had the lowest and the highest effect on the performance of all of the herbicides on both littleseed canarygrass and wild oat, respectively, which confirms the solubilizing nature of the cuticular waxes by vegetable oils. A comparison between the two vegetable oils revealed that olive oil exerted a greater control of littleseed canarygrass than did the castor oil. In contrast, castor oil exerted a greater control of wild oat than did the olive oil, which can be related to differences in the leaf surface micromorphology of the weeds.  相似文献   

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