Chemical herbicides and fertilizers are two important inputs in cereal production systems. Tank mixing and foliar application of urea fertilizer and selective herbicides could cause reduction of inputs and costs, and increase the fertilizers use efficiency in wheat. For verifying this hypothesis, a three year trail was conducted during 1999 to 2001 at weed research station of Plant Pest and Diseases Research Institute in Karaj. The experiments were carried out in randomized completed block design (RCBD) with four replications in a factorial arrangement of treatments. Treatments included herbicide combination at nine levels and urea application in two methods: foliar application and top dressing. The results of the experiment indicated that foliar application of urea had a significant effect on yield. The urea tank mixing with herbicide had no effect on herbicides use efficiency. Among herbicide and urea combinations, Urea+ Tribenuron-methyl+Clodinafop-propargile were the best combination for controlling weeds and increasing grain and biological wheat yield. This combination could be used as a tool for increasing nitrogen use efficiency and best chemical treatment for weed management in wheat.

To evaluate the distribution of clodinafoppropargyl resistant wild oat to in south western Iran (Khuzestan province), 50 fields which were sprayed with aryloxyphenoxypropionate herbicides were sampled. Those fields at which wild oat had been controlled efficiently by these herbicides were selected for the experiment. Populations (50 suspicious to resistance and 1 susceptible) were studied in a randomized complete block design with four replications in 2005. Populations of wild oat were sprayed during two- to four- leaves stage using the recommended dose of herbicide. Shoot biomass, survived plant and EWRC visual rating, were recorded four weeks after herbicides application. Longitude and latitude of different sampling locations were registered using GPS.Grouping populations using cluster analysis showed that 52% of populations were resistant, 28% were suspicious to resistance and only 18% of populations were susceptible and semi susceptible. Furthermore resistant populations were detected in all of parts of khouzestan province.

In order to evaluate the resistance of wild oat (Avena ludoviciana Durieu.) to clodinafop-propargil of aryloxyphenoxypropionate herbicides, green house studies and seed bioassay experiments were conducted in 2002-2004. Greenhouse experiments included screening tests and dose response experiments whereas, seed bioassay experiment included ID50 determination and dose response experiments. The experiments were conducted on the wild oat biotypes collected from Fars, Markazi and Khuzestan provinces, using clodinafoppropargyl herbicide. Greenhouse experiments were conducted as a randomized complete block design with four replications. In green house screening experiments; biotypes of wild oat treated during 2-4 leaves stage using the recommended dose of herbicide. Shoot biomass, survived plant and EWRC visual rating, were performed four weeks after herbicides application. Furthermore, response of all biotypes to 0.1-16 times of recommended dose was measured and their R/S ratio calculated. Seed bioassay experiments were conducted using a completely randomized design with four replications. In these experiments the percentage of coleoptiles length versus control were measured 7 days after herbicide application. In order to determine the ID50 values, a herbicide dose range was applied to susceptible biotype (MS). Furthermore, the response of all biotypes to ID50 of susceptible biotypes was measured. R/S ratios of biotypes were also calculated. The results of both experiments showed that KR1, KR2, KR3 were resistant to clodinafop-propargyl.

In order to evaluate chemical control of yellow foxtail (Setaria glauca (L.) Beauv.) and common dandelion (Taraxacum syriacum boiss.) in tall fescue turf, an experiment was conducted during 2006 in Tehran using randomized complete block design with 4 replications and 11 treatments. Treatments for yellow foxtail control were diclofop methyl (Illoxan36% EC) at 2.5 and 3 l ha-1, fenoxaprop-P-ethyl + mefenpyr- diethyl (PumaSuper7.5% EW) at 0.8 and 1 l ha-1, clodinafop propargyl (Topic8% EC) at 0.6 and 0.8 l ha-1, tralkoxydim (Grasp25% SC) at 1 and 1.2 l ha-1, sulfusulfuron (Apyros75% DF) at 27 and 35 g ha-1 and untreated control. Treatments for dandelion control were 2, 4-D + MCPA (U46 Combifloied72% SL) at 1.5 and 2 l ha-1, dichlrprop-p + mecoprop-p + MCPP (Duplosan super60% SL) at 2 and 2.5 l ha-1, bromoxynil + MCPA (Bromicide10% SL) at 1.5 and 2 l ha-1, mesosulfuron-methyl + iodosulfuron-methyl-Na (Chevalier6% WG) at 350 and 400 g ha-1, metribuzine (Sencor70% WP) at 750 and 1000 g ha-1 and untreated control.All treatments were repeated 3 times during the growing period of yellow foxtail (29/6/2006, 14/7/2006, 1/8/2006, respectively) and dandelion (20/5/2006, 3/6/2006, 17/6/2006, respecrively). The results showed that, despite low efficacy, Illoxan at 2.5 l ha-1, Pumasuper + mefenpyr- diethyl at 0.8 l ha-1 and Topic at 0.6 l ha-1 (without significant differences between both doses and damage under 20 percent to turf), could be recommended for yellow foxtail control in tall fescue turf. Also, one application of Duplosan super at 2 l ha-1 or 2/4-D + MCPA at 1.5 l ha-1 can control dandelion in turf.

A field experiment was conducted at plant pest and disease research Institute in Karaj, Iran in 2005-2006 to determine the effect of low herbicide dose of Clodinafop-propargyl on percentage of wild oat control, yield and economic return of wheat. The experiment included 2 Wheat varieties (Rooshan and Niknejad (less and more competitiveness cultivar, respectively, 4 Wild oat densities (0, 25, 50 and 75 plant m-2) and 4 herbicide doses (0, 25, 50 and 75 (recommended rate) lit ha-1 (100%, 66%, 33% and 0% reduce herbicide dose respectively)) in factorial trial based on randomized block design with 4 replications. The highest wild oat control was obtain in recommended rate and reduce dose to 33 and 66% decreased wild oat control to 0.8 and 38.39% ,respectively. Yields generally increased as rates increased recommended dose. There is no different between 33% reduce on the recommended dose and recommended dose, but 66% reduce on recommended dose couldn’t produce pleasure yield. In two cultivars economic returns increased exponentially as rates increased recommended dose, the maximum economic return was observed at the recommended herbicide dose but hadn’t different with 33% decrease in dose of herbicide. Results of this study indicate reduction to 33% from the full recommended dosage is possible when wheat was grown in optimal density in weedy condition.

In order to evaluate resistance of Phalaris minor biotypes, sampled from wheat fields of Fars and Golestan provinces, to ACCase inhibiting herbicides, a dose-response study was conducted under controlled conditions in greenhouse of Ferdwosi University of Mashhad. The results indicated that AR, SR3, MR4, FR2, FR4, and FR8 populations of Fars and GR2-1 biotype from Golestan have been resistant to diclofop-methlyl. Different levels of resistance maybe are because of involving different mechanisms in studied populations. AR, SR3, and MR4 showed a cross-resistance to the applied herbicides. These biotypes indicated a 5- to 11-fold and a 7- to 8-fold increase in resistance to diclofop-methlyl and clodinafop-propargyl, respectively compared with the susceptible biotype. Among these biotypes, SR3 showed the highest resistance to both herbicides.

In order to determine efficacy of some registered graminicides in control of resistant and susceptible ryegrass biotypes, two greenhouse trials were conducted at weed research department of Iranian plant protection research institute during 2007. Experimental design was completely randomized design with eight replications. The susceptible and resistant biotypes were treated by 19 herbicides included 10 acetyl-CoA carboxylase inhibiting herbicides, 6 acetolactate synthase inhibiting herbicides and 3 herbicides with different mode of action. Ryegrass biotypes were treated in 4 leaves stage by recommended dose of herbicide. Number of survived plant per pot, fresh and dry weight (30 days after herbicide application) and EWRC visual rating (15 and 30 days after herbicide application) was measured.  Results showed that clodinofop-propargil cycloxidim, pinoxadon (at 450 and 600 ml.ha-1), iodosolforon + mesosolforon (chovalieh), iodosolforon + mesosolforon (Atlantis) and isoprotron + diflofnikan had very good to optimum control of susceptible biotype. Results also indicated that cytoxidim, iodosolforon + mesosolforon (Atlantis), pinoxadon at 600 ml.ha-1 and isoprotron + diflofnikan had very good to optimum control of resistant biotype. Diclofopmethyl, cytoxidim and clorosolforon had less optimum control of susceptible biotype. Finally, iodosolforon + mesosolforon (Atlantis), isoprotron + diflofnikan and pinoxadon at 600 ml/ha were advised to control resistant biotype to acetyl-CoA carboxylase inhibiting herbicides in wheat fields. It is also recommended to consider crop rotation as well as herbicide rotation to use these herbicides continuously.