IRANIAN JOURNAL OF WEED SCIENCE
Year:2019 | Volume:14 | Issue:2 |Papers Count:10

To evaluate the efficacy of some herbicides in the control of yellow nutsedge (Cyperus esculenthus L. ) in Bermudagrass, an experiment was conducted in green zone of Ahwaz in 2014. Experiment was conducted in a randomized complete block design with 6 treatments and 4 replications. The treatments consisted of application of metsulfuron-methyl+sulfusulfuron (Total), oxadiazon (Ronstar), clethodim (Select Super), cycloxydim (Focus), nicosulfuron+rimsulfuron (Ultima) and untreated check. Herbicides were applied at the beginning of weed emergence and repeated two more times with one month intervals. The results showed that weed treatments had significant effects on the density and dry weight of yellow nutsedge. Ronstar, Focus, and Select Super, with the mean of 95. 4%, 93. 42% and 90. 9% weed control compared to control treatment, respectively, were the best treatments. Application of Total, Ultima and Ronstar herbicides caused 22. 23%, 19. 56% and 13. 58% damage to yellow nutsedge, respectively. Other herbicides had less adverse effects on Bermudagrass. Total and Focus were the most suitable herbicides because of its proper control on yellow nutsedge and its low level of adverse effects on African grass (Bermudagrass) than other herbicides and therefore, it is recommended.

The knowledge of weed seedling emergence with optimization of the time of control could enhance the efficiency of weed control. Therefore, to develop a seedling emergence model based on thermaltime to predict the emergence of weed seedling, a field experiment was conducted in different levels of nitrogen (control, 50 and 100 kg ha-1) in Pisum sativum. Weed seedling emergence was monitored from mid-December until early May. Percentage of cumulative emergence values was compared with thermal-time using the Goumpertz function. The results showed that, regardless of the nitrogen levels, the Veronica persica L., Galium aparine L., and Polygonum aviculare L., needed 92, 164, and 170 units of thermal-time for 10% of emergence, respectively. But, the Setaria viridis L. seedlings started their emergence later. In general, V. persica L., G. aparine, P. aviculare, and the S. viridis L., needed 486, 274, 731, 422 units of thermal-time for 90% of emergence respectively. The results also showed that the weed seedling emergence pattern affected by nitrogen application. Except for S. viridis, the "m" parameter, which indicates the required thermal time for 50% of seedling emergence, significantly changed with the application of nitrogen in all studied species. Overall, the use of nitrogen reduced the time of the seedling emergence in V. persica, but increased this period in G. aparine and P. aviculare when compared with control. Therefore, depending on the dominant weed species, nitrogen application can alter the cost of weed control by increasing or decreasing the weed control period.

To investigate the effects of summer cultivation of crops on weeds densities and biomass as well as yield and performance of following planted wheat, field studies were carried out in Shavoor Research Station (Ahvaz, Khuzestan) over 3 years (2013-2016) using 5 treatments in a randomized complete block design. Treatments included rice-wheat, corn-wheat, sesame-wheat, mung beanwheat and fallow-wheat rotations. The crops and weed densities and types had been observed during the year before the experiment, and no herbicides were used in all experiments to understand the pure effects of treatments. The main crop (wheat) was planted after autumn harvesting of above-mentioned crops. Densities and types of weeds were recorded 15 and 30 days after wheat primary tillering stage, and weed dry weights and grain yield were measured at the end of experiment. Results of this study indicated that considering the indices of weeds number and biomass (55-90%) as well as wheat yield (80-220%), wheat might not require to any herbicides after rice cultivation. Moreover, in the grain or forage corn planted fields, herbicide application is declined significantly, due to several and irrigations and frequent tillage. The whole three-years outcome of the experiments demonstrated that summer cultivation of crops might lead to sharp decline in the seed banks of important weeds such as wild oat (Avena ludoviciana), wild barley (Hordeum spantaneum) and some main broad leaf weed.

To evaluate the effect of different weed management methods and corn densities on weed and yield of corn, an experiment was conducted in 2009 at Azad University of Takestan. The experiment was a factorial based on complete block design with four replications. Treatments were corn density in three levels (recommended density, 16 Plant. m-2); 25% and 50% more than recommended density) and weed management in five levels (hand weeding, without weeding, nicosulfuron herbicide in two and four leave stages of corn life cycle, once and two times cultivator). The results showed that the corn densities had significant effects on density and dry matter of prostrate pigweed (Amaranthus blitoides), corn biomass and total weed densities and biomass. Different weed management methods had significant effects on all weed species, but no significant effects on corn. The interaction effect between corn densities and different weed management methods on prostrate pigweed density was significant. Finally, the best corn density for weed controlling and achieving the higher biological yield in corn is 50% above the recommended density (39155 kg. ha-1). Also, among different weed management methods, one-time cultivation is the most suitable treatment compared to twice cultivations and hand weeding.

To evaluate the comparative phenology of wheat and Lepyrodiclis (Lepyrodiclis holosteoidesFenzl. ) growth stages and to determine the best phenological stage for some recommended post-emergence herbicide applications as well as their efficacy on Lepyrodiclis controll, this study was conducted during 2014 – 2015 in the fields of Animal Science Research Institute, Karaj. In the first experiment, comparative phenology between wheat and Lepyrodiclis was determined based on growing degreedays. Results showed that Lepyrodiclis completed its life cycle, from the seedling stage to the end of ripening, during 202 days, by achieving 2673 GDD and its developmental stages were fully adapted to the developmental stages of wheat. The second study was a split plot experiment carried out in randomized complete block design. Treatments were herbicide application time (two different wheat phenological stages; 2nd and 5th stages of Feekes scale) as main plot and application recommended doses of some broadleaved and dual purpose herbicides for wheat farms as sub plot Results showed that application of bromoxynil suppressed Lepyrodiclis effectively and reduced more than 90% of the density and biomass of the weed. Due to its decisive controlling effects, it was the best treatment between all applied herbicides. Although the use of herbicides at 5th stage of the Feekes scale increased the yield of wheat, but because of the mechanism of action of bromoxynil and according to phonological stage of Lepyrodiclis, application of bromoxynil in stage two of Feekes lead to favorable control of Lepyrodiclis in wheat fields.

Pre-harvest application of herbicides is considered as a way for decreasing seed production, vigour and germination of the weeds that have escaped from weed control methods and have the ability to increase the soil seed bank s by producing their seeds. This study conducted to investigate the effects of preharvesting spraying on properties of wheat and Glycyrrhiza glabra seeds in different growth stages of wheat. This method also may cause damages to the crop seeds. A field experiment was carried out in split-split plot design with three replications. Experiment treatments consisted of different growth stages of wheat (milk y, dough and seed ripening) as main plots, application of glyphosate (SL 41%) and paraquat (SL 20%) herbicides as sub-plots and different concentrations of herbicides (0, 1, 2 and 3 liters per hectare) as sub-sub plots. The results indicated that herbicides applied at different growth stages showed different effects on the properties of wheat and G. glabra seeds. Glyphosate and paraquat had different effects on the properties of wheat and G. glabra seeds. Given the various concentration levels of herbicides applied, different results related to different concentrations of herbicide were obtained. Application of 1 l/ha glyphosate at the seed ripening stage showed the lowest negative impact on the properties of wheat seeds and the highest negative effect on the properties of of G. glabra seeds.

To study the effect of weeds on the different characteristics of pistachio (Pistacia vera L. ), an experiment was conducted in Qom, during 2015-2016 growing season. The experiment was carried out in a randomized complete block design with three replications. Treatments were based on the competition critical period and the phenological stages of pistachio in two series. The first series consisted of weed removed until the end of the swelling of the bud, the end of flowering, the end of nutshell growth, the beginning of k ernel filling and the end of k ernel filling and then weed maintained until harvest. The second series consisted of weed maintaining until mentioned stages and then weed removed until harvest. In addition, two control treatments (weed free and weed infested for all of the growing season) were applied. In this experiment, Chenopodium album and Cynodon dactylon, with 21. 83%, had the highest frequency. The most important traits influenced by treatments, based on principal components analysis, were splitting and un-splitting percentages, size at ounce and yield. Weed-free until the beginning of kernel filling treatment, with an average yield of 3. 91 kg/tree had the highest and treatment weed interference until the end of the swelling of the bud treatment with an average yield of 2. 69 k g/tree had the lowest yields in the experiments. Totally, with regard to the results of present research, two times weed control, one time the end of sprouting and the other at the end of nutshell growth unt il the beginning of kernel filling, would be recommended.

A study was conducted from 2013 and 2014 to assess the changes of population indices of wild barley (Hordeum spontaneum Koch. ) in different wheat fields (including: Tehran, Alborz, West Azarbaijan, Isfahan, Kermanshah, Khuzestan and Fars provinces). First, the fields that had been evaluated in the past years (2003) were selected and second field selection was based on the wheat cultivated area in any city and the new fields were evaluated and selected (2013). Using the existing equations, the frequency, uniformity and mean density of this species were calculated. Finally, the map of the spatial distribution of wild barley for each province was produced using Geographic Information System (GIS). The results showed that frequency and uniformity of wild barley in wheat fields of provinces that had lower populations of this weed in the past years, greatly had been enhanced (Alborz and West Azarbaijan). But in the wheat fields of provinces that wild barley was more populated in the past years, mean density increased (Tehran, Fars and Khuzestan). Distribution of the wild barley in the wheat fields were dependent on the numerous factors including seed longevity, distribution mechanisms and competition reproductive characteristics, that all these factors have caused this species spread in different regions of Iran. Another success factors of the spread of this weed is drought. Continuous wheat cropping (monoculture) and plowing in dry soil in autumn in wheat fields due to late rains and continuous application of Accase inhibitors herbicides that does not control this weed in wheat fields, can be effective in expanding wild barley.

Field bindweed is a deep rooted prenial weed that is resistant to drought in Iran. Herbicide applications indicates the low control of this weed. However, little data are available to verify efficacy with repeated treatments in flowering stage in the orchards in Iran. These experiments were conducted in the completely randomized designe with four replications and 13 treatments in Tehran and Isfahan. Treatments were post emergence applications of glyphosate (Roundup, SL 41%) at 2%, 3% and 4% plus amonium sulphate, new glyphosate (Weedmaster, SC 35%) at 0. 75% and 1%, amitrol+ ammonium thiocyanate+ glyphosate (Illico, Sl 30. 9%) at 4%, 5% and 6%, triclopyr (Garlon, EC 60%) at 1% and 1. 5%, fluroxypyr (Starane, EC 25%) at 0. 5% and 0. 75% and control (without herbice). Treatments in Tehran reduced field bindweed growth 100%. However, 3 to 4 months after the treatments, stem regrowth was 0%. In Isfahan, fluroxypyr and triclopyr controlled field bindweed by 94-97% on visual injury estimation. Furthermore, some herbicides reduced up to 93% field bindweed stem biomass and densities at the end of second year.

Because of the importance of weed control in corn inbred lines, this study was carried out based on a randomized complete block design with 10 treatments and 4 replications in Meshkindasht, Karaj, Iran. Two lines including Mo17 (male strile, CMS) as male parent and B73 as female paraent were used. Treatments were: nicosulfuroun (SC 4%), nicosulfuroun + (bromoxynil + MCPA (EC 40 %)), rimsolforun + nicosulfuroun (DF 75%), foramsulfuron (OD 22. 5%), 7 & 8) mesotrione + Smetolachlor + terbuthylazine (SE 53. 75%), weed infest control and hand weeding control. Results showed the significance (P < 0. 01) of the effect of herbicide treatments in reducing weed density and dry weight. The results of the percentage reduction in density and weeds dry weight and herbicide performance evaluation by the European scoring (EWRC) showed that the effectiveness of herbicides was good except for mesotrione-terbuthylazine-S-metolachlor herbicides. The highest corn grain yield was obtained from (nicosulfuroun + (bromoxynil + MCPA)) 400 + 40 g ai/ha and hand weeding with 4. 26 and 4. 03 ton/ha and the lowest grain yield were obtained from mesotrione-terbuthylazine-S-metolachlor and weed infest control with 2. 30 and 1. 11 respectively. Totally, for weed management in corn inbred lines, application of (nicosulfuroun + (bromoxynil + MCPA)) 400 + 40 g ai/ha, rimsolforun + nicosulfuroun 90 g ai/ha, foramsulfuron 337 g ai/ha and nicosulfuroun 80 g ai/ha are recommended. The herbicide applications did not have an adverse effect on seed germination of corn hybrid obtained from lines fertilization.