Search

The level of resistance and patterns of cross-resistance to clodinafop, sethoxydim, and pinoxaden were examined in 12 putative resistant and one susceptible populations of winter wild oat ( Avena ludoviciana) collected from Fars Province, in the southwest of Iran. The responses of biomass and length of coleoptiles to the increasing dosages of the three herbicides were determined in both whole-plant and seed bioassays. In the whole-plant bioassay, all 12 putative resistant populations were found to be resistant to clodinafop with resistance ratios (R/S) ranging from 1.76 to >47.04. Most clodinafop-resistant populations exhibited low levels of cross-resistance to sethoxydim. Three highly sethoxydim-resistant populations, F2, S2, and ES4, were slightly resistant to clodinafop. Six populations (M1, M2, F2, S2, S4, and ES4) showed high cross-resistance to pinoxaden with R/S values as large as 10.73 to 40.29. A highly clodinafop-resistant population, M2, was more sensitive to pinoxaden than the susceptible population. The results of the seed bioassay resembled those obtained from the whole-plant experiment suggesting seed bioassay as an inexpensive, rapid method for screening-resistant genotypes. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Surfactants can improve postemergence herbicide efficacy and reduce the amount of herbicide required to obtain weed control. The effect of surfactants on the efficacy of herbicides is complicated and depends on the interaction among the plant, surfactant, and herbicide. The effects of surfactants on the efficacy of clodinafop-propargyl and/or tribenuron-methyl on wild oat ( Avena ludoviciana) and wild mustard ( Sinapis arvensis) under greenhouse conditions were investigated. In addition, the surface tension of aqueous solutions of the surfactants and surfactants + herbicides was determined. Significantly lower surface tension values were obtained with the aqueous solutions of citofrigate (Citogate plus Frigate) alone and with the herbicides used in this study. The citofrigate surfactant lead to the greatest enhancement of clodinafop-propargyl and/or tribenuron-methyl efficacy and the effect was species-dependent. The efficacy of clodinafop-propargyl and/or tribenuron-methyl in the presence of surfactants in controlling wild oat was higher than for wild mustard. The foliar activity of the tested herbicides rose with increasing surfactant concentrations. The tank mixture of clodinafop-propargyl and tribenuron-methyl showed a synergistic effect in controlling wild oat and wild mustard. The synergistic effect in controlling wild mustard was greater than for wild oat. [ABSTRACT FROM AUTHOR]

The photodecomposition of post emergence herbicides on leaf surface can be affected via adding vegetable oils to spray tank. Nine vegetable oils were compared to assess the photodecomposition of sethoxydim on wild oat leaf surface under simulated light conditions. The experiment was conducted as completely randomized factorial design with three replications at the College of Agriculture, Ferdowsi University of Mashhad, Iran, in 2013. Each herbicidal solution (with and without vegetable oil) was exposed to simulated light at 0, 5, 10, 20, 30, 60, 120 and 240 MAS (min after spray), for 30 min. The performance of sethoxydim in the presence of turnip, olive, soybean, corn, sunflower, canola, sesame, castor and cotton seed oils, compared to non-vegetable oil solution, increased up to 4.02-, 3.44-, 3.22-, 3.08-, 2.86-, 2.09-, 1.96-, 1.77- and 1.25- fold. All vegetable oils significantly improved the resistance of sethoxydim to light treatment. The effect of vegetable oils on the resistance to photodecomposition of sethoxydim was significant different at less than 60 MAS, while no significant differences were noted among vegetable oils when light treatment occurred at 120 and 240 MAS. Data from the light treatments have confirmed that when vegetable oils were added to sethoxydim, light adverse effect was lower, which is presumably due to disturbance of the cuticule and the rapid absorption of sethoxydim by wild oat leaves. Vegetable oils fatty acids composition effect the resistance to photodecomposition of sethoxydim, as with increasing the unsaturated fatty acid values, the resistance to photodecomposition was improved. [ABSTRACT FROM AUTHOR]

Sethoxydim is an acetyl-coenzyme A carboxylase (ACCase) inhibitor that changed the shape of the chlorophyll fluorescence curve (kautsky curve) in wild oat (Avena ludoviciana Durieu.) in greenhouse experiment. This experiment was conducted as completely randomized factorial design with three replications at the College of Agriculture, Ferdowsi University of Mashhad, Iran, during 2012. Results of this study revealed that sethoxydim only and plus emulsifiable turnip oil changed the shape of the chlorophyll fluorescence curve (kautsky curve) 7 days after spraying. Sethoxydim plus emulsifiable turnip oil changed the shape of the kautsky curve more than for sethoxydim only. We found that in our study the fv/fm (maximum quantum efficiency) was closely linked to the fresh and dry weight dose-response. Sethoxydim plus emulsifiable turnip oil proved more rapidly effect on fv/fm in comparison with sethoxydim only. The fresh and dry weight dose-response relationship with fv/fm showed a similar behavior. This study revealed a good relation between fresh and dry weight according with values of 28 DAS and fv/fm 7 DAS. In general, the findings of this study revealed that Fv/Fm is a good parameter for evaluating effect of sethoxydim little time after spraying. Also, this research showed that 4 folds more time for classical screening methods comparing to chlorophyll fluorescence method. Thereupon, classical screening methods may be replaced by chlorophyll fluorescence method in future. [ABSTRACT FROM AUTHOR]