فصلنامه مطالعات حفاظت گیاهان
سال سی و ششم شماره 3 (پاییز 1401)

 Soybean (Glycine max) is one of the major oilseeds of the Fabaceae family. Peanut mottle virus (PeMoV) is a Potyvirus that can infect not only peanuts, but also soybeans, and some other legumes. Aphids and contaminated peanut seeds transmit the virus to healthy peanut and soybean plants, causing significant damage. Soybeans infected with the virus have been found to exhibit symptoms such as mosaic, mottling, yellowing, and stunting.

 From May to October 2020, 132 leaf samples with presumptive symptoms of the virus, such as mosaic, mottling, deformation, stunting, yellowing, and wrinkling, were collected from soybean fields in Mazandaran and Golestan provinces of Iran. Total RNA was isolated using Promega SV Total RNA Isolation Kit (USA). Complementary DNA (cDNA) was synthesized using random hexamer primers and reverse transcriptase enzyme, M-MuLV thermo-resistant H (ParsTous, Iran). Subsequently, the cDNA library was amplified in the presence of Taq DNA polymerase with degenerate primers related to the genomic regions of the cylindrical inclusion (CI) and Helper component proteinase (HC-Pro) of potyviruses and the coat protein (CP)-specific primer pairs of PeMoV for Sanger sequencing. Phylogenetic analysis was performed using MEGAX (Kumar et al., 2018). Multiple alignments were performed using the MAFFT software version 7. A phylogenetic tree was constructed using the Minimum Evolution (ME) and Tamura-Nei methods with 1000 bootstraps.

 RT-PCR tests with degenerate primers for potyviruses (HC-Pro and CI) and specific primer pairs for PeMoV virus (CP), followed by Sanger sequencing, confirmed the presence of this virus in soybean samples. The RT-PCR amplified fragments of 700 and 1450 bp with degenerate primers for potyviruses and CP-specific primer pairs for PeMoV, respectively, whereas no fragment was amplified from the healthy plants. The nucleotide sequence of the coat protein region of this isolate shared 88.56-95.80% identity with the corresponding sequence of other GenBank isolates. Phylogenetic trees based on coat protein alignments of the PeMoV-soya isolate with 16 other PeMoV isolates in the GeneBank grouped these isolates into two phylogroups I and II. Group I included isolates from China, Israel, Brazil, Iran, Kenya, South Korea, Turkey, Colombia, Australia, and the USA isolated from soybean, Arachis pintoi, and peanut. Group II were consisted of two isolates from Zambia (Phaseolus vulgaris). The Iranian isolate (PeMoV-soya) was placed in Group I and formed a clade with isolates from Kenya, South Korea, and Turkey. Based on phylogenetic analysis, the results showed that isolates from different hosts with different geographical origins belonged to the same phylogenetic group and probably shared a common ancestor. It indicates that geographical distribution and host do not play a role in grouping of Iranian isolate. Accordingly, it can be assumed that the multiple transmissions from one host to another (peanuts, beans, and soybeans) or host jumping, has led to the accumulation of mutations in its coating protein gene. In the study of motifs in this region (CP), the functional DAA motif at the amino terminus of the PeMoV coat protein replaced the DAG motif which is involved in aphid transmission. All PeMoV isolates contain the DAA motif, allowing their identification. A repetitive conserved sequence (EK)3 was observed upstream of this motif. PeMoV isolates (distributed across Africa, Asia, and the United States) may be geographically widespread due to this conserved sequence. In bioassay, there was a limited host range for this isolate, which was limited to soybean (Williams 82 and Essex) and peanut.

 For effective disease management, viruses must be correctly identified. Virus detection and disease management are difficult as viruses can evolve and produce molecular and biological variations. A well-established approach that is usually used when a new virus-like disease appears is to test for known viruses. PCR is the most widely used technique for detection of plant viruses. Based on the results of this study, the presence of the peanut mottle virus was confirmed in soybean fields in the north of Iran using the RT-PCR test. Based on the CP gene, the molecular characteristics of the virus were determined. According to this, unlike mutations, recombination plays no role in the evolution of the new PeMoV. Since the Peanut mottle virus can infect peanut plants, soybeans, beans, and most legumes, avoiding cultivating soybeans, peanuts, and beans close to each other will assist in management of the disease. Using integrated cultivation and avoiding crofting will effectively reduce the creation of recombinant isolates and appearance of the resistance-breaking isolates.

 Beneficial soil microorganisms such as plant growth-promoting rhizobacteria (PGPR), mycorrhiza fungi, endophytic fungi and plant growth-promoting fungi can increase plant growth and their defense against some plant diseases and insect pests. Some species of Trichoderma spp. known as plant growth stimulants are found in many soils where crops are grown, especially around the rhizosphere. These species increase growth rate, nutrient uptake, plant efficiency and defense ability against herbivorous insects. In this regard, a very important approach is the use of microorganisms that enhance plant growth, which achieves optimal plant performance and reduces pest damage and environmental pollution.

 In this study, the seeds of Falat cultivar were inoculated with spores of T. harizianum strainT22 (30 mg of 5 mg suspension of fungal spores were inoculated next to the plant), which they were cultivated under greenhouse conditions (25 ±5 °C, 55±5% RH 16: 8 h, L: D). First to fourth instar larvae of Helicoverpa armigera were placed on the leaf and fourth to sixth instar larvae were placed on the fruit of treated or untreated plants (as control). Then the relative growth rate of larvae, larval developmental time, percentage of larval mortality and total fecundity and fertility of adult female were recorded. Also, some growth and biochemical parameters of the experimental plants were measured.

 The results showed that the larval developmental time and percentage of larval mortality were significantly higher than these parameters in insects raised on control plants and in contrast to, the relative larval growth rate and total fecundity and fertility of female insects in treated plants was significantly less than these indicators in insects fed to control plants. Amounts of some micro- and macro- elements, number of leaves, root volume, fruit weight per plant (yield), the amount activities of polyphenol oxidase and catalase enzymes as well as amounts of proline and hydrogen peroxide in plants treated with fungi were significantly more than these parameters on control plants. Stimulation of the plant's defense system by the use of this fungi, which has resulted in the production of more plant defense products, proline and hydrogen peroxide. This fungus stimulates the plants defense system in the direction of different metabolic pathways of different defense materials. Since the production of proline and hydrogen peroxide is the same in the metabolic pathway, the production of these two defense molecules in treated plants has increased significantly. Comparing the amounts of these two molecules in plants that have not been fed by larvae is also quite clear that the presence of this fungus has stimulated the plant's defense system. In plants fed on pest larvae, these values have increased significantly due to damage to the fruit tissue of the tomato plant. The production of proline and hydrogen peroxide are in the same metabolic pathway, the production of these two defense molecules in treated plants has increased significantly. Comparing the amounts of these two molecules in plants that have not been fed by the larvae of the pest is also quite clear that the presence of this fungus has stimulated the plant's defense system. In plants fed on pest larvae, these values have increased significantly due to damage to the fruit tissue of the tomato plant

 This study is the first evidence that indicated positively affected by T. harizianum strain T22 on the strength of tomato plant response in both aspects of higher nutrient uptake and increase its vegetative and reproductive growth, as well as increasing the function of the plants defense system in response to feeding of fruits of tomato. From the results of this study, it is inferred that the use of biological product of T. harizianum T22 helped to absorb more nutrients to the plant and stimulated and strengthened the plant's defense system against the attack of tomato fruit worm. The results of this study show that the use of beneficial soil microorganisms to strengthen plant defenses in terms of crop protection is a promising strategy to control an important group of pests such as vegetarians to reduce the use of pesticides. Finally, the results of this study proved that inductive resistance can be used as an important tool for pest management to reduce the use of chemical insecticides.

 Herbicide safeners are chemical compounds used in combination with herbicides to make them "safer" that is, to reduce the effect of the herbicide on crop plants, and to improve selectivity between crop plants versus weed species being targeted by the herbicide. Herbicide safeners can be used to pretreat crop seeds prior to planting, or they can be sprayed on plants as a mixture with the herbicide. Salicylic acid (SA) and other salicylates are known to affect various physiological and biochemical activities of plants and may play a key role in regulating their growth and productivity. This hormone is synthesized by many plants and is accumulated in the plant tissues as the impact of unfavorable abiotic factors, contributing to the increase of plants resistance to stress. The aim of this study was to evaluate the efficacy of salicylic acid as a safener in corn tolerance to non-selective herbicide; sethoxydim, and the response of two weed species of johnsongrass (Sorghum halepense (L.) Pers.) and junglerice (Echinochloa colona (L.) Link) to it.
 The effect of sethoxydim (0.5, 22.5, 45, 94, 187 and 375 grams of active ingredient per hectare), and salicylic acid (in concentrations of 0, 1 and 2 mM) as factorial experiment in a completely randomized design were investigated to evaluate the response of fresh weight of corn, johnsongrass and junglerice. Salicylic acid treatment was used in seed priming form also. Pre-treatment of salicylic acid was done three days before herbicide spraying. Spraying different doses of sethoxydim herbicide in a complete five-leaf stage, was done using a mobile rail sprayer (Matabi, Spain) equipped with a flat-fan nozzle (8002), a delivery of 220 L ha-1 and a spray pressure of 200 kPa. To investigate the changes in photosynthesis in the treated plants, chlorophyll fluorescence of the leaves was evaluated on the sixth day after application of herbicides by PEA model fluorometer. Three weeks after spraying the herbicide, the shoots of the plants were removed from the surface of the pot and their fresh weight was measured.  Analysis of variance was performed using generalized linear models (GLM) in SAS 9.2 software environment. Before performing analysis of variance to determine the normality of the data from Anderson-Darling test in Minitab ver. 17 were used, and in cases of non-normal data, Box-cox two-way power transformation was used in the same software. Analysis of variance, was performed as a factorial experiment for each plant to investigate the effect of the herbicide dose of sethoxydim and the concentration of salicylic acid and their interaction. The trend of wet weight changes of different species under the influence of different amounts of herbicide sethoxydim was investigated using the four parameters log-logistic equation.
 Dose-response curves of fresh weight of the treated plants showed that weeds were significantly affected by sethoxydim compared to corn. In all species, by increasing the concentration of salicylic acid, the ED50 increased. For all three levels of salicylic acid treatment, this parameter was the greatest in salicylic acid treatment as seed priming than others, and the lowest values of this parameter were observed for jungle rice. The highest amount of ED50 was 210 gram of active ingredient per hectare for corn sown with 2 mM / L salicylic acid treatment, and the lowest value was 31.5 gram of active ingredient per hectare for non-salicylic acid treatment in jungle rice. Kutsky’s curves for corn and weeds showed that Fluorescence chlorophyll was increased with the use of steroids herbicide, but salicylic acid treatment could reduce the rate of chlorophyll fluorescence, so that weed and corn after weeding the control without grass was observed at the lowest salicylic acid treatment (2 mM / L).
 In general, the results of this experiment showed that under the influence of sethoxydim, all three species of maize, johnsongrass and junglerice showed a positive response to salicylic acid foliar application. Therefore, in order to use salicylic acid as a safener, its seed treatment in corn should be used. Overall, the results showed that salicylic acid can be used as a stress reducer due to the use of sethoxydim in narrow-leaved plants. But as a safener we cannot use it universally and foliar spraying, because there is no differentiation in the response of crops and weeds. Therefore, in the use of salicylic acid as an immunizer for the sethoxydim, its seed treatment will give better results.

 Plant development is defined as a series of phenological events that are controlled by external factors and determine changes in the shape or function of some organs. Temperature and photoperiod are two of the most important environmental factors affecting phenological development. Papaver rhoeas L. and Papaver dubium L., from the Papaveraceae family, are common annual winter weeds in northern Iran. The life cycle of these species is closely related to winter crops such as wheat (Triticum aestivum L.) and other winter cereals that compete severely with them. The Papaver species are capable of producing a huge amount of small-sized seeds that remain dormant at maturity. The timing of emergence, growth and sexual reproduction is highly important for the success of invasive weeds. Checking the phonological behavior of these plant species along with their seed production would be useful for decision-support systems helping managers select the best management strategies and, thereby, improving P. rhoeas and P. dubium control. Also, the phenology data would allow predicting these species invasibility of new areas. The present study was aimed to quantify the phonological behavior of these weeds.
 In the present study, the phenology of P. rhoeas and P. dubium were studied in the research field at Agricultural Sciences and Natural Resources University of Sari, Iran, with an annual rainfall of 851 mm per year. Seeds of these species were collected from a wheat field located in Mazandaran province, north of Iran during spring 2018. These species seeds were cultivated on 12 November 2018. The phenological stages were recorded from emergence to the end of the seeding stage. The phenology was studied based on the growing degree day. At the end of the experiment, the period of each phenological stage was calculated based on the day and the growing degree day. In order to determine the morphological traits of the plant, eight sampling steps were performed. Morphological traits such as plant height, number of leaves, number of flowers, number of capsules, and dry matter were measured.
 The results showed that P. rhoeas and P. dubium grow from 0 to 1723.56 and 1759.06 growth degrees day, respectively. During this period, seven phenological stages were recorded for these two species. These stages were included emergence, rosette (7-8 leaves), stem elongation and branching, blooming, flowering, fruiting, and seed maturity. The flowering stage period in both species was long, 48 days in P. dubium and 46 days in P. rhoeas. The results showed that the shortest and longest stages of development of these two weeds were emergence and stem elongation, respectively. In this study, the growth period of P. rhoeas and P. dubium took about eight months. It has some variation with regard to height, the number of flower, number of capsule and dry matter between both species under the same environmental conditions but both plants started their developmental stages at the same time and finished at almost the same rate. The trend of changes in height, number of leaves, number of flowers, number of capsules, and dry matter were similar in both species. The life cycle of these two species begins with germination in autumn and ends with seed production in late June. The longest period of growth stage in both species was in spring and this trend decreases in late spring. The flowering stage begins in late March and ends in mid-June. The maturity period of these two species was from mid-June to the end of the first decade of July. One of the characteristics of these two species is high seed production. In P. rhoeas, at the end of the fruiting stage, each plant produced an average of 13 capsules and each plant produced an average of 5000 seeds. Also, in P. dubium, each plant produced an average of 14 capsules, and each plant of this species produces an average of 5922 seeds.
 Based on knowledge of the different phenological stages of the two species, it is possible to plan for proper management. From a managerial point of view, these two species should be controlled before the blooming stage; so that their seeds do not enter the seed bank, because their seeds are considered as causes of contamination in the field.

 Brassica napus L. is one of the most important crops in the world and Iran which accounts for about 20% of the world total oil production. The area under cultivation of this crop is 13,000 hectares in Fars province. Weed interference is also one of the most important limiting factors which decrease crop yields. Weed can decrease crop yield by competing for resources such as water, light and nutrients and production of allelopathic compounds. Weed competition reduced average onion yield by 50% compared with the weed-free control. The most important broad leaf weeds of rapeseed in Fars province are including Carthamus oxyacanthus M.B., Capsella bursa-pastoris, Centaurea solstitialis L., Polygonum aviculare L., Mavla neglecta wallr, Descurainia Sophia (L.) Webb&Berth, Veronica persica L., Sinapis arvensis L. Application of herbicides is the most prevalent method of weed control in Rapeseed fields. Herbicides are recommended for control of broad leaf weeds in rapeseed included of trifluralin, clopyralid and butizanstar. Clipfort is a new herbicide of broadleaf weeds product from Barzegar Barjesteh containing 720 g kg-1 Clopyralid, formulated as a soluble granule (SG). This experiment was conducted to evaluate the efficacy of Clipfort herbicide with some preplant, preemergence and postemergence registered herbicides on weed control and rapeseed yield.

 In order to study the effect of herbicides to control broad leaf weeds of rapeseed fields, an experiment was conducted during 2020- 2021 at Fars Agricultural and Natural Resources Research and Education Center, Darab, Iran. Plots were located on a clay loam soil with pH 7.9. This experiment was carried out in randomized complete block design with 9 treatments and 3 replications. The treatments included post emergence application of Clipfort (Clopyralid, SG 72%) at dose rates of 150, 167,184, 201 g/ha or 108, 120, 132 and 144 a.i. ha-1, post emergence application of Lontrel (Clopyralid, SL 30%) at dose rate of 800 mm/ha or 240 a.i. ha-1, post emergence application of Watch (Clopyralid, SL 30%) at dose rate of 800 mL ha-1 or 240 a.i. ha-1, preemergence application of butisanstar (quinmerac+ metazachlor, SC 41.6%) at dose rate of 205 mL ha-1 or 1040 a.i. ha-1, preplant soil application Treflan (trifluralin , EC 48%) at dose rate of 2000 mm/ha, or 960 a.i. ha-1 and ) and weed free. The narrow leaf weeds were control by Gallant-super (haloxyfop-r-methyl ester 10.8% EC) at dose rate of 1000 mL ha-1 in the 3–4 leaf weeds. The herbicides were applied using a Matabi sprayer equipped with an 8002 flat fan nozzle tip delivering 300 L ha-1 at 200 kP bar spray pressure. Weed numbers and dry weights were determined in random 0.50-m2 quadrates per plot. The grain yield and biological yield were recorded for a 2 m2 and 0.30 m2 from each plot, respectively. Traits were recorded including density, biomass of weed and control percentage of weed, and grain yield and biological yield. Statistical analyses of data were done with SAS var 9 software and comparison of mean was tested using the LSD test at 5% level.

 Broad-leaf weeds infestations included Hirschfeldia incana L., Decurania sophia L., Carthamus oxyacanthus L., Centaurea pallescens L., Veronica persica L., Malva neglecta L. The highest and lowest relative density was V. persica and H. incana 52 and 7 percent respectively. The highest and lowest relative weight was C. oxyacanthus and V. persica 31 and 11 percent respectively. The statistical analysis of the data on the weed density and biomass revealed that herbicides were applied significantly decreased the weed density and biomass. Visual observation confirmed that these weeds were effectively controlled using the Clipfort herbicide. Results showed that applications of Clipfort herbicide at dose rates of 201 g ha-1 provided excellent control of the mention weeds. Thise treatment decreased weed density of H. incana (90 %), D. sophia (98 %), C. oxyacanthus (98 %), C. pallescens (100%), V. persica (66 %), M. neglecta (80 %) and total weed (88%) compared to weed infested control. Also, this treatment decreased weed biomass of H. incana (95%), D. sophia (98%), C. oxyacanthus (99%), C. pallescens (100%), V. persica (68%), M. neglecta (82%) and total weed (91%) compared to weed infested control. However, butizan-star herbicide had the highest control of V. persica. This herbicide decreased density and weed biomass of V. persica by 94 and 97 percent comported to infested control. The grain yield and biological yield were 2.2 and 7.6-ton ha-1 respectively when applied Clipfort herbicide at dose rates of 201 g ha-1. This treatment also increased grain yield and biological yield by 36 and 30 percent, respectively.

 Results showed that the best results achieved from applications of Clipfort herbicide at dose rates of 201 g ha-1. This treatment decreased density and biomass weeds, and increased rapeseed yield. Therefore, the application of Clipfort herbicide (201 g ha-1) is recommended for canola fields.

Plant Protection Organization (PPO) has registered 22 commercial herbicides formulations for weed control of wheat, barley and triticale in Iran. Among these herbicides, sixtheen herbicides introduced act as two proposed or only for broadleaved weeds. Their active ingredients including acetolactate synthase (ALS) enzyme inhibiting groups, synthetic-auxin groups,a photosynthetic inhibitor of photosystem II, and pigment synthesis inhibitor groups (Tomlin, 2009). Previous studies show that existing weed species do not similarly respond to herbicides and therefore the percentage control of some of the weed species is lower than the other species (Ohadi, 2010). These hard-to-control weeds are naturally tolerant to herbicides or may be developing resistant to one mode of action. Thus, we need new herbicides to suppress such weeds. The aim of this work was to find the best chemical treatments against weeds in wheat production based on using the new herbicide fluroxypyr and comparing their efficacy with commonly registered herbicides in the major wheat growing areas of Iran.

A field study was conducted in four regions of Iran, including Karaj, Shahryar, Ahwaz, Shiraz, and Gonbad during 2017-2018 growing season. The statistical layout was a completely randomized block design with four replicates. Ten herbicides in 12 treatments were 2,4-D+MCPA (U46-Cambi fluid® 67.5%SL, 1.5 1 L ha-1), Mecoprop-p + Dichloprop-p + MCPA (Duplosan super® 60% SL , 1 L ha-1), Bromoxynil + MCPA (Bromicide® 40% EC, 1.5 L ha-1), Tribenuron-methyl (Granstar® 75% DF, 20 gr ha-1), Mesosulfuron-methyl + Iodosulfuron-methyl sodium+ Diflufenican+Mefenpyre-diethyl (Othello® 75% WG, 1.6 L ha-1), 2,4-D + Dicamba (Dialant super® 46.4 SL, 0.8 L ha-1), Triasulfuron + Dicamba (Lintur® 70% WG, 165 gr ha-1), Bromoxynil + 2,4-D (Buctrile Univeral® 56% EC 1.5 L ha-1), Dichloprop+bentazone (Basagran DP 56.6% SL, 2 L ha-1) and the new herbicide Fluroxypyr with th recommended doses (Kavin Flurox® 20% EC 1.5, 2 and 2.5 L ha-1). An unweeded treatment served as controls. Weed density and weed dry weight for each plot were measured four weeks after the last application the herbicides.  Wheat was harvested from six m2 of each plot after removing border plots. Wheat grain yield was determined after adjusting the moisture level of grain to 14 %. Data from each region were subjected to statistical analysis using SAS/STAT® statistical software and the means were separated by Duncan (α=5%).

The results showed a diverse spectrum of weeds (14 species) at the experimental locations. Descuriania Sophia was dominant in two tested locations Karaj and Shiraz. The next dominant weed species were Galium aparine L., Conringia orientali and Centaurea depressa M.B. were present dominantly in Shiraz. Polygonum aviculare, Fumaria vailantii and Veronica persica were present in Karaj. Lepyrodiclis holosteoides as a noxious weeds, were dominant only in Shahryar. Malva neglecta and Scorpiurus muricatus were in Ahwaz and Bifora testiculata was dominat in Gnbad. Across the experimental locations, fluroxypyr was efficient at 2-2.5 L ha-1 concentrations for weed control (85.77 to 90.68%). However, when applied at dosage of 1.5 L ha-1, total weed control efficiency was lower (80.75%). Bromoxynil + 2,4-D (85.43%) , Dichloprop-p + Bentazon (83.98%) were the most efficient after fluroxypyr. Mecoprop-p + Dichloprop-p + MCPA and Bromoxynil + MCPA with 80% average efficiency controled weeds in all the locations. Triasulfuron + Dicamba and 2,4-D + Dicamba were inefficient in weed control (67.75 and 68.22% , respectively) across all locations. These findings were in agreement with the results of some previous studies (Minbashi and Saeedi, 2019, Minbashi et al. 2020). Lepyrodiclis holosteoides with average control of 63.68% and CV= 23.98% was the most difficult-to-control weed in this experiment. Other weeds beside that were Scorpiurus muricatus, Polygonum aviculare, Malva neglecta and Bifora testiculata identified as difficult-to-control weeds. None of herbicides showed visual injury symptoms on wheat.

According to these experiments, we found that the Fluroxypyr (2-2.5 L ha-1) as new candidate herbicide showed good to excellent (85%-100%) weed control efficiency averaged in the all experimental locations and it could be recommended to be used in wheat field after registration process. Due to environmental concern, it should be applied at lower doses for non-difficult-to-control weeds. We found that Bromoxynil + 2,4-D was the most efficient next herbicide after fluroxypyr and Triasulfuron + Dicamba as an unefficient herbicide overall. L. holosteoides as the most hard-to-control weed was controlled only by upper dose (2.5 L ha-1) of new herbicide. Other difficult-to-control weed species were Scorpiurus muricatus, Polygonum aviculare, Malva neglecta and Bifora testiculata.

 Sweet corn (Zea mays L. var. saccharata) is an important crop, grown over 2,000 hectares in Iran. The consumption demand for sweet corn in its fresh form or as a processed crop has contributed to a significant increase in its cultivation in recent years. Sweet corn is susceptible to weed competition for nutrients, moisture, and light interception. Herbicides labeled for use on sweet corn are limited. Chemical control can be very important because of the low efficiency and cost effectiveness of mechanical or other methods of weed control. Hence, it is necessary to provide information about the sulfonylurea herbicides and suitable doses. Sulfonylureas such as nicosulfuron, rimsulfuron, and foramsulfuron are effective group of herbicides for annual and perennial weed control in maize. These herbicides provide a new chance for weed management in maize. Their mode of action occurs through inhibiting acetolactate synthase (ALS), thereby interfering with the production of branched-chain amino acids, leucine, isoleucine, and valine. The objectives of this experiment were to evaluate the effect of different doses of sulfonylurea herbicides on weeds control and growth and yield of sweet corn.

 In order to evaluate the effect of different doses of sulfonylurea herbicides on weeds control and growth and yield of sweet corn (KSC403su), a field study carried out during 2015 growing seasons at the Agricultural College of Shiraz University. The experiment was conducted in a randomized complete block design with 4 replications. Treatments included different doses of nicosulfuron (1.5, 2 and 2.5 l ha-1), foramsulfuron + idosulfuron (1, 1.5 and 2 l ha-1) and acetochlor (4.5, 5 and 5.5 l ha-1) herbicides and weed free and weedy control. The number and dry weight of aboveground weeds parts were harvested within three fixed 1 × 1 m quadrats in every plot, separated by species, enumerated, oven-dried at 75 °C for 48 h, and then weighed. Then, percent weed density and dry weight reductions were measured. The traits included ear length, ear diameter, ear number per plant, row number per ear, grain number per row, grain number per ear and canned grain yield. Data were analyzed using SAS v. 9.1 software (SAS Institute 2003). When significant differences were observed among treatments, mean comparisons were made using Duncan's multiple range tests (P < 0.05). Correlation coefficients between different traits were also calculated.

 Results showed that the canned grain yield, 1000 grain weight and number of grain per ear were reduced by weeds up to 73, 33 and 60%, respectively. The highest dry weights reduction obtained were of redroot pigweed (Amaranthus retroflexus) (75.8 and 59.5%), lambsquarters (Chenopodium album) (49.84 and 38.76%), barnyard grass (Echinochloa crus-galli) (58.37 and 40.85%) and bindweed (Convolvulus arvensis) (60.56 and 55.06%), so that applying of nicosulfuron )2.5 l ha-1) and foramsulfuron + idosulfuron (2 l ha-1) herbicides caused reduction in total dry weight of weeds in comparison with weedy treatment, and canned seed yield increased by nicosulfuron )2.5 l ha-1) and foramsulfuron + idosulfuron (2 l ha-1) herbicides in comparison to the acetochlor. Acetochlor was the weakest treatment in the reduction of weed density and dry weight. The highest canned grain yield (8.00 and 7.03 t ha-1), number of row per ear (12.00 and 11.50), number of grain per row (25.00 and 24.75), number of grain per ear (299.00 and 285.50) and 1000 grain weight (325.06 and 308.44 g) were obtained in nicosulfuron )2.5 l ha-1) and foramsulfuron + idosulfuron (2 l ha-1) herbicides, respectively. Positive correlation was found between canned grain yield and 1000 grain weight (r = 0.83, p<0.05) and number of grain per ear (r = 0.96, p<0.05). Applying nicosulfuron showed a high efficiency as compared to the foramsulfuron + idosulfuron and acetochlor for weed suppression.

 It can conclude that nicosulfuron at 2.5 l ha-1 showed the best performance for weed control, especially broadleaved weeds and were associated with the maximum sweet corn canned grain yield. Therefore, due to the restricted use of herbicide in sweet corn, the herbicide used in this experiment is not created serious injury in sweet corn at the recommended rate while effectively controlling weeds. Hence, utilization of this herbicide could be a favorable option in contemporary weed control programs for local or regional sweet corn growers.