فصلنامه مطالعات حفاظت گیاهان
سال سی و سوم شماره 2 (تابستان 1398)

Varamin is one of the major producer regions of cantaloupes which is located in southern Tehran. Cucumber mosaic virus (CMV) is the type species of viral genus Cucumovirus in the family Bromoviridae and is causal agent of economically important losses in cucurbits. The CMV virions are isometric in shape and the genome is composed of three single-stranded positive sense RNAs. Each of the genomic RNAs 1 and 2 encodes a single large ORF and RNA-2 harbors an additional smaller ORF, 2b, involved in cell-to-cell movement and post-transcriptional gene silencing. The RNA-3 has two ORFs, 3a and 3b, encoding a movement protein and coat protein, respectively. Each of genomic RNAs has a Cap-like and tRNA-like structures at its 5ʹ and 3' ends, respectively. The virus is transmitted by different species of aphids in a non-persistent manner and is easily transmissible to the indicator hosts by mechanical inoculation. CMV is reported from several cucurbitaceae plants in Iran. Isolates of CMV are classified in different groups or subgroups based on different methods especially serology, RT-PCR-RFLP, nucleotide sequencing and phylogeny which are useful data for decision making or choosing the strategy during the development of CMV-resistant varieties and producing transgenic plants by RNA silencing strategy.

During 2014-2016, a total number of 132 leaf samples were collected from cantaloupes showing viral symptoms such as mosaic, mottling, leaf deformation and plant stunting. These samples were subjected to double antibody sandwich enzyme linked immunosorbent assay (DAS-ELISA) with specific antibodies (DSMZ, Germany) to detect CMV based on the manufactures’ instructions. Total RNA was extracted from ELISA positive samples as explained elsewhere. Two microliters of total RNA used as template in RT-PCR to amplify a 870 base pair (bp) fragment of partial CMV genomic RNA3 including the coat protein gene and its flanking regions using specific primers CMVCPf (5'-GCTTCTCCGCGAG-3') and CMVCPr (5'-GCCGTAAGCTGGATGGAC-3') corresponded to 1149–1161 nts and 1998–2015 of CMV strain Q, respectively. In order to address the subgroups of CMV isolates, RT-PCR products were digested by MspI (HpaII) restriction enzyme and electrophoresis was done on 1.5% agarose gel. We expected the presence of the bands with 335 and 537 bp in size for the sub-group I and 393 and 559 bp for sub-group II isolates of CMV. Then, based on the geographical distance of collected CMV isolates, the CP gene from four isolates were ligated into pTG19-T, an A\T cloning vector, and the recombinant plasmids were introduced in Escherichia coli. The selected plasmids were extracted via alkaline lyses method and selected recombinant plasmids were sequenced by Macrogen, South Korea. The sequencing data were aligned with those of previously reported CMV isolates. The alignment and pairwise sequencing to estimate similarity between nucleotide sequences were done with BioEdit software. The Phylogeny Inference package (Phylip) version 3.65 was used to draw phylogeny trees.

59 out of 132 samples (%44.69) positively reacted with CMV specific antibodies in DAS-ELISA. Expected DNA fragments of about 870 bp were successfully amplified via RT-PCR from the ELISA positive samples. in RT-PCR-RFLP for addressing the CMV subgroups, all MspI digested RT-PCR products from the tested samples produced two DNA bands of 537 and 335 bp and it was concluded that these isolates belong to the CMV subgroup I. Sequencing data of selected CMV CP clones showed 99-100% and 100% similarity between tested isolates at the nucleotide and amino acid levels, respectively. These isolates shared 93-100% and 97-100% similarity with previously reported CMV isolates from Iran at nucleic acid and amino acid levels, respectively. The reconstructed phylogenetic tree, re-confirmed the results of RT-PCR-RFLP, and Varamin isolates were placed with few other Iranian CMV isolates including E12, Cues, D13, F13, Sh44, Csu and Cud which were collected from non-melon hosts. Isolate LOR-F, the only CMV isolate previously reported from melons, belongs to the IB subgroup of CMV. This is the first report of CMV subgroup I isolates from melons. 

The RT-PCR-RFLP and sequencing data confirmed the presence of subgroup IA of CMV isolates in Varamin, Pishva and Pakdasht cantaloupe fields whose express severe symptoms in melons. However, the change in Zucchini yellow mosaic virus has been reported from these area, the same isolate of CMV were distributed in the entire region. Unlike Zucchini yellow mosaic virus populations which has been changed in the Varamin, Pakdasht and Pishva regions, it seems that there is just one dominant CMV isolate widespread in these regions.

Squash mosaic virus (SqMV) is a member of the genus Comovirus in the family Comoviridae. It is a seedborne and beetle-transmitted virus infecting most plants in the genera Cucurbita and Cucumis. Like other comoviruses, SqMV has a bipartite positive-strand RNA genome consisting of RNA1 and RNA2, which are separately encapsidated in isometric particles of 28 nm in diameter. The genomes contain a poly (A) tail at the 3'-terminus and the genome-linked viral protein (VPg) attached to the 5'-end. It has been frequently reported in North and South America and Japan. Isolates from different regions have been extensively characterized and based on agar double-diffusion serological tests and host reactions, those isolates had been classified into different serogroups and biotypes. SqMV, which causes a serious disease of cucurbits, is transmitted by beetles and plant-plant contact and is readily seedborne in cucurbits. Fifteen species including, Cowpea mosaic virus (CPMV; type member), Andean potato mottle virus (APMoV), Bean pod mottle virus (BPMV), Cowpea severe mosaic virus (CPSMV), and Red clover mottle virus (RCMV) are distinguished in the genus Comovirus. SqMV has been reported frequently from North and South America, and less often from Australia, Israel, and Japan. Nelson and Knuhtsen have extensively characterized SqMV isolates from the United States and Puerto Rico biologically and serologically. They reported that SqMV isolates in the western hemisphere could be classified into six biotypes based on host reactions, but only into two serotypes (group I and II) by agar double-diffusion serological tests.

Plant material and virus isolates
In order to verify the presence of this virus in Southern Khorasan (Tabas) province of Iran and characterize some molecular aspects of it, 62 symptomatic leaf samples showing mosaic, vein clearing and distortion were collected from melon fields in growing season of 2015. RT-PCR reactions were used as a molecular method for the virus detection. The symptomatic leaves samples were used for RNA extraction using Rneasy mini Kit (Qiagen) and the extracted RNA were used directly or stored at minus 70 oC.

RT-PCR and sequencing

An amplification of the expected size of 1900bp for SqMV coat protein gene was obtained followed by specific primers for complete genome sequencing of RNA2. The SqMV total RNA2 was sequenced.

In spring and summer 2015, a survey was carried out in southern Khorasan province of Iran which were under the cultivation of melon (Tabas) in order to assess the current situation of SqMV. The 62 gathered samples were tested for the presence of SqMV. The symptoms were mostly mosaic, vein clearing and distortion. RT-PCR was developed using three pairs of specific primers targeting SqMV total poly protein and RNA2. The detection method was validated with melon plants sampled in fields known to be infested by this virus. The RT-PCR method also allowed SqMV to be detected in fruit and leaf samples. The RNA2 of Tabas isolate was 3271 nt in length, excluding the 3'terminal poly (A) tail. This sequence encoded a single ORF starting at AUG121 and terminating at UAG3148. This isolate translates a polyprotein containing 1009 amino acids with 110.99 KDa. The results showed that Iranian isolate RNA2 poly protein shared the highest nucleotide (88.45%) and amino acid (90.59%) identity with an Australia isolate (MF166754) and the lowest identity with a Japan isolate (NC_003800) 86.82% and Spanish isolate (KP223324) 86.36% in amino acid and nucleotide level, respectively.

The results illustrated that Iranian isolate RNA2 poly protein shared the highest nucleotide (88.45%) and amino acid (90.59%) identity with an Australia isolate (MF166754) and the lowest identity with a Japan isolate (NC_003800) 86.82% and Spanish isolate (KP223324) 86.36% in amino acid and nucleotide level, respectively. Phylogenetic analysis of SqMV RNA2 nucleotide sequences showed that Khorasan isolate was clustered with China (EU421060), Arizona (AF059532) and Spanish isolate in one subgroup.
This is consistent with the observation of Nelson &Knuhtsen (1973) for six biotypes, on the basis of symptoms and host range, but only two serological groups, one of which (group I) contained all the variability in host range and symptomatology. Hu et al. (1993) reported typing H-SqMV as a member of SqMV serogroup I on the basis of biological rather than serological comparisons, and L-SqMV was typed to serogroup I by Alvarez & Campbell (1978). Given that other stdies have encountered difficulties in reproducing the expected phenotypes on watermelon, the latter explanations are most likely. In comoviruses, RNA-2 encodes the two CPs and the MP. Thus, amino acid sequence differences found in the putative polyprotein of our RNA-2 clones may be expected to result in possible variations in serological response. However, both RNAs may function in determining host range and symptomatology and a precise correlation of our hybridization groups with the serological groupings has not yet been established.

Nematodes are an abundant and very diverse group among the living organisms of soils. They are few information about them as animals which can live in all habitats including fresh waters, marines, soil of farms, gardens, forests and pastures. In addition to plant parasitic nematodes, which have parasitic relationship with different plants in agricultural soils, nematodes belonging to other trophic groups also have indirect impacts on the growth of plants in the agroecosystems and nature. They are used as biological indicators of soil health. The knowledge on their abundance, presence or absence of different groups of nematodes in the soils are considered important in various biological sciences.

In order to study the diversity of dorylaimid nematodes in Arasbaran forests, 65 soil samples were collected during 2015-2016 from different plant rhizosphere. The soil samples were transferred to the Nematology laboratory- University of Tabriz and kept at four degree centigrade until extraction time. They processed and the nematodes extracted, killed, fixed and transferred to anhydrous glycerin using common nematology methods. After preparing permanent microscopic slides, their morphometric and morphological characteristics were studied under optical microscope and identification was done using related valid literature. The morphometric data of nematode and microscopic images prepared using Motik optical microscope connected to scaled lens and future wine camera, respectively. All figures were prepared by Corel draw® 12 software.

As a result 20 dorylaim species (Crassolabium saccatum, C. himalum, C. ettersbargense, Syncheilaxonchium nairi, Paravulvus hartingii, Eudorylaimus spaulli, Epidorylaimus lugdunensis, Nygolaimus brachyuris, Paraxonchium carmenae, Metaxonchium persicum, Aulolaimus oxycephalus, A. nanocephalus, Discolaimus mariae, Longidorella soadi, Sectonema demani, Xiphinema macroacanthum, X. vuittenezi, X. uthahense, Longidorus africanus, Tylencholaimus constricus, T. tahatikus, Xiphinemella globilabiata, Enchodelus macrodorus which are belonging to 16 genera and ten different families. The family Qudsianematidae had more number of genera (five) and two genera, Crassolabium (three species) and Xiphinema (three species) were found having the most number of species compared to the other genera. Six species namely Discolaimus mariae, Crassolabium saccatum, C. himalum, C. ettersbargense, Xiphinema uthahense and Tylencholaimus tahatikus that are new records for Iran nematode fauna described here in.

mariae has been reported for the first time around the roots of olive trees in Spain by Pen-santiago. In this study, the nematode was collected and identified in Arasbaran forests -Shirin Bolagh. Comparing the present population of D. mariae with its main description there were not much differences. The only difference was in the c index (80-95 vs. 88-73).

The closest species to C. saccatum is C. circuliferum which distinguished from that by non-sclerotized vulval region in C. saccatum. C. diversum as another related species to C. saccatum is characterized by a complete offset head (vs. relatively offset head) and posterior position of vulva (V= 52.9-57 vs. V = 49-50).
This population of C. ettersbargense can be compared to the morphometric characteristics of previous reports that has shorter body length (0.5-0.6 mm vs. 0.6-1 mm). In members of Crassolabium having equal to less than one millimeter body length is characteristic of C. ettersbergense, C. medianum, C. pumilum, C. goaens and C. pumilum. C. medianum species has bubble-like organs in the tail (vs. absence of them in C. ettersbergense). C. pumilum has no pars refringense, and the expanded part of the esophagus is one third of length of the esophagus (vs. absencs pars refringense in C. ettersbergense, and the above ratio is 50-60% of the esophagus). C. goaens distinguished from C. ettersbergense with longer Odontostyle (15-17 vs. 11-12 µm). The head in C. parvulum, is different in comparing C. ettersbergense (continues vs. offset).
Crassolabium himalum comparing the main description has slightly longer tail (25-27 vs. 21-24 μm. C. himalum is comparable for morphological traits with C. neohimalum and C. porosum. The C. neohimalum is characterized by a shorter body length (1.07-1.35 mm vs. 1.32 to 1.47 mm) and the asymmetrical lips (vs. symmetrical). The C. himalum is also distinguished from C. porosum by having offset head- (vs. countinouse) and a relatively tall tail (25-27 μm versus 21).
Xiphinema uthahense is member of Xiphinema americanum - group and compared to the main description and previous reports, there was no significant difference between the morphological traits and the morphology. The species X. taylori, due to the lower coefficient b (5.6-7.5 vs. 8-8.5), has a lower coefficient (39.3 -51 vs. 61-6605) and the coefficient c 'less (0.75 - 1 vs. 1.2-1.7) can be distinguished from X. utahense species. X. pacificum is relatively longer (5.8-7.8 vs. 8-8.5).
Tylencholaimus tahatikus in morphological characteristics has similarity to T. mongolicus and T. innebus. Compared to T. mongolicus it has a longer odontostyle (10.6 - 15 μm vs. 7-6 μm), longer tail (19-22 μm vs. 14-8 μm), greater c (44-50 vs. 24-30) and c 'is less (0 / 9-7 / 0 vs 1/2 - 1). In T. innebus, V is greater (V =62-64 vs. V= 57-53) and shorter body length (0.54-0.68 mm vs. 0.95 -0.90 mm).

Population growth and the high food demand have led to more efforts to increase agricultural production. With making chemical pesticides, farmers were encouraged to use much chemicals, but their destructive effects on the environment, human and other organisms have been later revealed. Parasitoids are important natural enemies of crop pests. Most of them belong to order hymenoptera and superfamily Ichneumonoidea. The Braconidae is a family of parasitoid wasps and one of the richest families of insects. Nowadays, parasitoid wasp, Habrobracon hebetor Say has been widely used against lepidopteran larvae. Habrobracon hebetor is a well-known gregarious, idiobiont, ectoparasitoid of the larvae of a wide range of economically important moths infesting stored grains, nuts, and fruits as well as field crops worldwide. Due to overuse of chemical pesticides for larvae controlling, determining the side effects of insecticides on the biocontrol agents such as parasitoids is required.

In the present study, we investigated the side effects of three insecticides on H. hebetor by direct (contact) and indirect (poisonous-host) methods. After rearing this parasitoid on the laboratory host, Ephestia kuhniella Zeller (Lep.; Pyralidae), the lethal and sub-lethal concentrations of insecticides were evaluated. Bioassay experiments were carried out under laboratory condition (25±2°C, 60±5% RH, 16L: 8D photoperiods) in five replicates and each replication included 30 parasitoids in contact method and 15 flour moth larvae in poisonous-host method. The lethal concentrations of these insecticides in contact method on the parasitoid were determined to be 1.38, 0.037 and 6.621 ml/L and on flour moth larvae were 0.490, 2.155 and 0.138 ml/L, respectively. For contact method, different concentrations of insecticides were applied on all inner sides of transparent plastic cup (4.5×8 cm) and air-dried. 15 pairs of 24-hours old parasitoids were introduced inside each cup. After 24 hours, one pair of alive parasitoids was introduced into cup with four last instar host larvae to oviposit. The host larvae were replaced daily. The parasitoid characteristics such as longevity and survival rate of different stages, TPOP and Ovi-day, the number of deposited eggs and sex ratio were then recorded. As to poisonous-host method, whole wheat flour (10 g) was mixed with 3.5 ml of each tested concentration of insecticides per each experimental set. After 72 hours, alive larvae were transferred in a plastic cup with one pair of H. hebetor wasp for 24 hours. Then, each larva was transferred separately in a petri dish with untreated flour. Different growth factors of parasitoids such as longevity and survival rate, TPOP and Ovi-day, the number of deposited eggs and sex ratio were recorded. Estimated LC30 and LC50 were considered as sub-lethal and lethal concentrations in all experiments, respectively.

In contact method, the highest survival rate of pre-adult stages and adult female were observed in Sirinol treatment at lethal concentration, after control. In poisonous-host method, the highest survival ratio of the pre-adult stages belongs to Sirinol and in adult female the highest survival ratio was observed in lethal concentration of Sirinol. The lethal concentration of Proteus reduced pre-adult longevity of the parasitoid significantly, followed by lethal and sub-lethal concentration of Sirinol. Lethal and sub-lethal concentrations of Proteus also exhibited a significant reduction of total longevity. In poisonous-host method, all concentrations of all insecticides generally induced highly significant differences for ovi-day compared with that of control (17.91 days), as the shortest value was recorded for sub-lethal dose of Abamection (7.46 days) and the longest period was found for sub-lethal dose of Sirinol (13.2 days). In poisonous-host method, the longest TPOP was observed in sub-lethal concentration of Sirinol (16.02 days), followed by sub-lethal concentration of Abamection (14.63 days), and the shortest period was recorded in sub-lethal concentration of Proteus (12.3 days), after control (12.19 days). On the other hand, in contact method, the longest ovi-day and TPOP were observed in sub-lethal concentration of Sirinol (18.19 days) and lethal concentration of Abamection (13.26 days), respectively. The shortest adult female longevity was observed in lethal concentration of Proteus (27.55 days) in contact method and lethal concentration of Sirinol (22.85 days) in poisonous-host method. In all treatments, the number of deposited eggs was significantly reduced compared with control. The largest reduction in egg deposition was recorded for sub-lethal concentration of Proteus (71.05 eggs) in contact method and sub- lethal concentration of Abamection (36.14 eggs) in poisonous-host method, compared with control (227.47 eggs). It seems that Sirinol is suited to be used as a component of IPM alongside with H. hebetor.

The common pistachio psylla, Agonoscena pistaciae (Hemiptera: Aph alaridae), is a key pest of pistachio trees. Nymphs and adults suck sap from leaves resulting in defoliating, falling flower buds, stopping tree growth and finally yield loss. The population dynamics of insects is influenced by several physical and biological factors such as temperature and natural enemies. Identifying the key factor in population dynamics is difficult due to the potential interactions between biological and environmental factors. Non-linear analysis methods such as artificial neural networks (ANNs) are suited to be applied in the ecosystem with non-linear and complex ecological data. These methods have been widely used as a robust information-processing instrument in many research fields, especially in predicting pest occurrence. For example, a neural model is used to predict bionomic variables related to the nutritional dynamics of blowflies.
In the present investigation, the seasonal abundance of A. pistaciae in a pistachio orchard was evaluated for two years. This study aimed to assess the performance of ANN in representing nonlinear dynamic data for common pistachio psyllid populations. To this end, back propagation ANN was implemented to evaluate the relationship between the pest occurrence and influential factors.
 

The population density of ‎psyllids was monitored weekly by the yellow sticky trap for the adult and direct counting for ‎the nymph. After collecting the related data, the curves of the seasonal dynamic population of adults and nymphs were drawn. Then, the number of generations and duration activity of psyllid in each generation were determined. Multi-layer perceptron neural network ‎‎(MLP), genetic algorithm (GA) and multi-linear regression (MLR) were used to determine the relative significance of biotic (natural enemies) and ‎abiotic (weather variables) factors for predicting A. pistaciae density. An ANN model was designed by using the inputs (average temperature, average rainfall, average relative humidity, wind speed and direction,  and population of natural enemies), hidden layer (the number of neurons in the hidden layers determined by trial and error), and one neuron in the output layer (the occurrence amount for predicting the population). The Levenberg–Marquardt algorithm was used as the learning algorithm. The root mean square error (RMSE) and coefficient of determination (R2) were statistics, calculated for both the training and testing set for each iteration.

The population fluctuations of A. pistaciae on Akbari pistachio cultivar during 2015 and 2016 indicated that the psyllid populations in the field had five apparent peaks from late March to October. Agonoscena pistaciae in Rafsanjan county had six complete and one incomplete generation in 2007 and 2008 (9). The general population trends were similar over time within two years, but population densities of adults and nymphs were higher in 2016. Statistical comparison of weather variables between two years showed no significant difference. 
Several topologies were examined and the best result was obtained with 15 and 9 neurons in the first and second hidden layer for both adult and nymph in MLP method, respectively. In genetic algorithm, a hidden layer with 14 neurons for adult and 16 neurons for nymph was employed. The R2 values of MLR, MLP and GA methods (at test phase) were 0.32, 0.61, 0.73, respectively and the RMSE values were 31.79, 0.223 and 0.083, respectively for adult. In the prediction of the population density of the nymph by MLR, MLP and GA, the R2 values were obtained to be 0.22, 0.84, 0.88, respectively, and the RMSE values were 48.03, 0.051 and 0.051, respectively.

The R2 and RMSE values showed reliable performance of ANN and GA. The ANNs also modeled the numbers of the psyllid with high accuracy. In addition, the higher R2 and lower RMSE were obtained for MLP and GA methods relative to MLR. It has been reported in the related literature that the ANN consistently outperformed the statistical models. The ANN as a nonlinear predictor exhibited a high accuracy in predicting the richness of aquatic insect species in running waters by a set of four environmental variables (21). Based on the principal components analysis and back propagation artificial neural methods to analyze historical data on the population occurrence of Scirpophaga incertulas, the new model could improve the prediction accuracy, compared with other methods (27). It is worth noting that in regression models, the weak correlation between dependent and independent variables does always not imply that these variables are not associated, as they may have a nonlinear correlation.

Tomato leafminer, Tuta absoluta (Meyrick), is considered as the most important tomato pest in the world. The pest is also devastated tomato fields and considered as a big threat for tomato production especially in greenhouses in Iran. The exceptional speed and extent of T. absoluta enforced to use several pest control methods for controlling the damages. The strategies might be applied a complex of different approaches from cultural to biological and finally chemicals control. Chemical pesticides are often used to control this pest, which not only pose a risk for environment, but also is harmful for public health (due to the fresh use of the product). Therefore, the use of other pests control methods should be considered. Mass trapping of the adults are could significantly reduce the percentage of infested leaves and fruits. Given that the adults are nocturnal, they fly towards a light source, since the night light traps are developed to capture adult. The use of light traps is one of the low-cost and low-risk methods for capturing adult’s moths, and as a consequence of reducing the pest damages.
Methods and Materials: Cylindrical transparent containers (8.5 cm diameter and 15 cm height), which were made from clear plastic (polyethylene terephthalate (PET)) were chosen as traps. For entering the attracted moths, several holes (0.5 cm in diameter) were embedded in the traps walls, except the below part (2.5 cm) that some 0.5% detergent solution were poured in there to entrap the captured moths. Then a BLB bulb was installed in each trap as light sources. The traps were installed at about 70 cm above the infested plants, with four different density (2, 4, 6 and 8 in a 1000 m2 of greenhouses) to find out the best density of traps. The comparisons were done in a completely randomized design with six replications (six days). The light of the traps were turn on from the sunset until next morning. The numbers of captured moths from each trap were recorded and were analyzed using generalized linear models.

In the greenhouse assessment in Hormozgan province, the mean numbers of moths were 27.75 in the two-trap and 14.39 in the four-trap, while for the four-trap were 11.67 compare to the six- traps 7.87, and finally for the six-trap were 112.67 compare to the eight-trap 113.33. In Qazvin province, the average numbers of moths were 10.93 in the two-trap compare to 13.61 for the four traps, while, the number of moths for the four-trap were 11.38 and for the six-trap were 11.91. In the Markazi province (Greenhouse complex of Aveh), the mean numbers of moths were 27.70 for the two-trap treatment and 18.95 for the four-trap treatment. In the second step, the mean numbers of moths were 8.25 in the four-trap compare to 9.47 for the six-traps. Mass tapping is an approach of pest control methods in several crops. This technique is non-poisonous and non-hazardous to natural enemies as a part of the integrated pest control program, and environmentally friendly. The light traps can captured not only males, but also a large number of females. Therefore, light traps are more effective than conventional pheromone-baited water traps in reducing the damage especially at low/moderate T. absoluta population density. Up to now most of the used light traps for capturing T. absoluta, were installed on the ground. However, the adult’s moths can fly very well (250 matters in two hours) and could fly from one place to another place and disperse easily and quickly. The present study demonstrates the success of mass trapping of T. absoluta by hanging up the light traps above the infested tomato plants.

installing the light trap up to the height of the host plants could capture more adults and could reduce the damages. Based on the results we can say that, during the growing season, four traps light with a BLB source is sufficient for 1000 m2 of greenhouses that should be installed above the plants canopy. This technique can be used in the IPM programs in greenhouses. Where, the isolation of area will strongly raise the chances of the mass trapping methods by reducing the possibility of immigration of adult’s pests from adjacent area. Of course, combination with other pest control methods should also be considered.

Oilseeds such as sesame (Sesamum indicum L.) are one of the rich sources of energy and protein that form the second most important food resource of the world after cereals. The factors like suitable plant density and weeds control are important for maximum economical yield. This crop is highly adapted to the climatic conditions of Iran and is highly tolerated to the drought. Therefore, the objective of the present study was to investigate the effect of weed free periods and plant density of sesame on yield, yield components and agronomic traits of sesame in Birjand, Iran.

The present study was carried out in research farm of Islamic Azad University of Birjand (Long. 59°13' E., Lat. 32°52' N., Alt. 1491m.). This experiment was performed as factorial based on Randomized Complete Blocks Design with three replications in 2013. Treatments were including weed free periods at five levels (weed free until 20, 40, and 60 days after sesame emergence, perfect weed interference and perfect weed free) and plant density at three levels (7, 14, and 28 plant m-2). In this research morphological traits, yield and yield components of sesame and dry weight and number of weeds per m2 were measured. The texture of the soil in research farm was clay loam with the pH of 7.24, electrical conductivity of 4.14 mmhos cm-1 and total N, P and K content was 0.038%, 7.21 and 223.5 ppm at the depth of 0-30 cm, respectively. Data were analyzed by SAS statistical software and means were compared by Duncan's Multiple Range test at 5% probability level.

Analysis of variance showed that yield and yield components traits were significantly influenced by plant density and weed free period. In addition, plant height, stem diameter, branches number of main stem, length capsule were significantly influenced by weed free period, but plant density affected only on plant height and first capsule height from the soil. The interaction between weed free period and sesame plant density was not significant on all traits except biological yield. Means comparison showed that increasing of weed free period had positive effect on morphological traits, yield and yield components of sesame, so that capsule number per m2 increased 3.98, 2.45 and 1.1 times, respectively in perfect weed free treatment compared to the treatments of the perfect weed interference and weed free until 20 and 40 days after sesame emergence. In addition, seed number per capsule increased 155, 20.2, and 9.8%, respectively and 1000-seed weight increased 20.3, 13.6, and 8.9%, respectively. The highest of seed yield (913.62 kg ha-1) belonged to the perfect weed free treatment that in comparison with treatments of perfect weed interference and weed free until 20, 40 and 60 days after sesame emergence had superiority of 15.5, 4, 1.8 and 1.3 times, respectively. Moreover, results indicated that in the perfect weed interference, weeds number per m2 had superiority of 22.6, 3.7 and 2.4 times, and weeds dry weight per m2 had superiority of 40, 8 and 2.8 times, respectively as compared with treatments of weed free until 60, 40 and 20 days after sesame emergence. These findings can be attributed to the increase in competition between crop plant and weeds for growth resources with prolonged weed growth. However, increasing the weed free period caused lower weeds emergence and growth and hence greater resources uptake by sesame plants that finally increased yield component and seed yield of sesame. Means comparison showed that the increase in plant density from 7 to 28 plants m-2 increased capsule number per m2 and seed yield by 76.4 and 72.79%, respectively and decreased weeds number and dry weight by 26.4 and 45.39%, respectively. It is seems that higher plant density per unit area caused maximum usage of production parameters and on the other hand, suitable density (28 plant m-2) increased the ability of crop competition  with weeds.

The results of this study showed that both weed interference and plant density, are the affecting factors on yield and yield components of sesame. The lowest yield was achieved at the highest level of weed interference and the lowest density of plants per square meter. High plant density is effective in crop yield due to reduced weed interference. Also, since the plant is susceptible to weed growth in the early stages, increasing the free weed period causes rapid plant growth and increases performance. According to the obtained results in this study, the best treatment for high yield production was perfect weed free and density of 28 plant per square meter.

Increasing public awareness and concern about the impacts of herbicides on the environment, development of herbicide-resistant weeds, and high economic cost of herbicides have increased the need to reduce the application of herbicides in agriculture. The prediction of weed emergence timing would help to reduce herbicides through the optimization of the timing of weed control. Seedling emergence is probably the most important phenological stage that influences the success of an annual weed. Wild barley (Hordeum spontaneum [C. Koch]) grows in diverse habitats in the eastern Mediterranean and in south-western Asia and is widely distributed in winter fields of Iran. Based on the recent weed surveys, it is now present in more than 16 provinces in Iran and it is increasing in in winter wheat fields. Prostrate knotweed (Polygonum aviculare L.) is one of the most widespread weeds in nearly all the temperate regions of the world. It is an annual weed that colonize open, human-made habitats and able to adapt to different ecological conditions.

In order to predict the emergence of wild barley and prostrate knotweed using the temperature model, an experiment was conducted at the research field of college of agriculture and natural resources of the University of Tehran located in Karaj during 2012-13. The first objective was to determine whether accumulated heat degree-days after wheat planting can adequately predict shoot of wild barley and prostrate knotweed emergence. The other objective of this work is that how the presence or absence of wheat affects the emergence patterns and total emergence of aforementioned weeds under growing conditions in Karaj. The experimental area was infested with natural weed populations of two species. No herbicides were used during the course of the experiment to allow the greatest number of weeds to emerge. Ten quadrats 1.0 by 1.0 m were used. Four quadrats placed at the center of the field, four and two quadrats placed at outer and inner margins of field, respectively. Half of the quadrats were assigned for sampling of seed bank and the half of them for emergence recording. Three soil samples were taken from depth of 5 cm. Soil samples were initially poured sieve (9-mesh) and the residues were placed in oven at 65ºC for 24 hours. After that, they were placed in cloth bags under running water. Weed seedling emergence was recorded every week. Weed seedlings were counted by species and cut at the soil surface to minimize soil disturbance. Weather data were obtained from weather stations located next to the experimental field. Heat sums (temperature units or cumulative growing degree days) were calculated based on the base temperature (Tbase) of 5ºC for both species. The nonlinear regression model (logistic 3 parameters) emergence versus cumulative growing degree days was used.

Results showed that the emergence of prostrate knotweed occurred earlier than wild barley in the outer margin and the center of the field at fourteen weeks after planting. Also based on the results, emergence of wild barley in outer margin of the field was happened at lower mean GDD and seedlings were appeared over fourteen weeks in 35.8 GDD. Cumulative emergence of wild barely was increased after received 50 GDD in the absence of wheat (outer margin of field) but decreased at inner margin and the center of wheat field. The presence of wheat affected the emergence of wild barely. Wheat canopy was probably developed to affect light levels or soil temperature needed for weed germination and, consequently, seedling emergence. Required GDD for 50% seedling emergence of wild barely was higher than prostrate knotweed at outer and inner margin of field and center of the field. Therefore, it is expected that wild barely was emerged later than prostrate knotweed.

Integrated weed management systems require a comprehensive knowledge of weed biology. Timing of the emergence often determines whether a plant competes successfully with its neighbors, is consumed by herbivores, infected with diseases, and whether its flowers reproduce, and mature properly by the end of the growing season. The simplicity and accuracy of this model would make it an excellent tool to predict wild barley and prostrate knotweed seedling emergence in field situations, facilitating the determination of the timing of scouting in integrated weed management systems. More prostrate knotweed seedling emerged at the margin of field before 100 GDD, thus, control methods such as herbicide must done as soon as possible at early of growing season in the field infested with this species.

Cyerus rotundus is a perennial weed of the Cyperaceae family spread throughout the tropical and subtropical parts of the world. It is a C4 and fast-growing plant that replicates rapidly through the extensive underground system and tuber. This weed causes damage to more than 92 countries and 50 crop species. In this regard, it is considered as the most damaging weed in the world. The amount of damage varies depending on the crop. One of the most important characteristics of purple nutsedge is the production of the tuber. According to available studies, burial depth of tuber plays an important role in the emergence of the onset of the competition period. Among the physical properties of the soil, soil texture plays an important role on plant growth characteristics, development of underground organs, especially in tuber plants and the amount of water penetration and maintenance. So, given the importance of accurately recognizing the biology and the ability to reproduce of nutsedge in its management, this research is also intended to study the effect of burial depths and the soil texture on the growth of purple nutsedge.

In order to evaluate the effects of soil texture and burial depth on purple nutsedge vegetative characteristics, a trial was conducted at Kerman Natural Resources and Agricultural Research Center, using factorial statistical method and experimental design of randomized complete blocks at three replications. The first factor was burial depth at five levels (2, 12, 22, 32 and 42 cm) and second factor was soil texture at three levels (sandy loam, silty loam and clay loam). The traits of emergence percentage, the time of emergence, the number of produced tubers and dry weight of the underground organs were measured at 130 days after planting. For this purpose, the pots and dumps were emptied, then the underground organs were separated and placed in paper envelopes and finally, paper envelopes were placed in oven with temperature of 75°C for 72 hours. Data were analyzed using SAS v. 9.1 software. Figures are also plotted by Sigmaplot v. 12 and Excel v. 2013.
Results and Discussion The results showed that emergence time, germination percentage, underground organ dry weight and tuber numbers were affected by depth of planting and soil texture. Emergence of C. rotundus was faster in sandy soil and at a lower depth, so that the tubers grew in the sandy loam soil at a depth of 2 cm 7/7 days after planting (the shortest time), and silty loam and clay loam were ranked next lowest. Understanding ecology of germination and weed emergence plays an important role in their management. With increasing depth of sowing, the percentage of germination in the tested soil texture decreased. So that the maximum amount of germination (85%) was obtained at 2 cm depth of sandy loam soil and the lowest germination percentage was observed at depths > 32 cm in silty loam and clay loam soils and the depth of 42 cm of sandy loam soil encountered with no germination and emergence of seedling. According to the results, the underground organ dry weight of C. rotundus in the textures and depths of the soil was quite different. In sandy loam, the highest underground dry weight was obtained at the 2 cm depth and the lowest was at 42 cm depth (0) of sandy loam. The highest underground dry weight of the tuber (63.6 g) was observed at 12 cm depth and the lowest (0) was obtained at 32 and 42 cm depths. The results showed the highest tubers number was observed at 2 cm depth of sandy loam soil and the lowest was obtained at 42 cm depth of sandy loamy and 32 cm and 42 cm depth of sandy loamy. The number of tubers decreased with increasing planting depth in all three texture types. The highest percentage of tuber production in heavy textures (silty loam and clay loam) was formed in layers of 2 to 12 cm of the soil.

The results showed that with increasing depth in all three types of soil texture, all the growth characteristics of purple nutsedge significantly reduced. More than 80% of the distribution and dispresal of underground organs was formed at a depth of 2 to 12 cm. The percentage of emergence decreased by 100 % at 32 and 42 cm depths of clay loam and silty loam. It seems that, the lack of emergence at the high soil depth is due to disruption of gas exchanges and lack of light. Given the importance of tubers in reproduction of this plant, this should be considered in management strategies. The deep plowing by delaying the emergence and growth and decreasing the production of reproductive organs (rhizome and tuber) of purple nutsedge can be considered as a management option. This weed has high emergence ability in the sandy loam soils due to high permeability and porosity.

Modeling fertilizer-herbicide relationship is helpful to minimize the competition of weeds with crops. The goal of present study was to develop the empirical models for predicting crop yield, number and weight of common mallow seed using integrated dose-response curves of herbicide and fertilizer application.

An experiment was conducted in split plot design based on randomized complete block design with three replications in Agricultural Sciences and Natural Resources University of Khuzestan in 2017 growing season. Experimental factors were N-fertilizer as main plot at 5 levels (0, 75, 150, 225 and 300 kg ha-1 of urea) and dose of bromoxynil+2, 4-D as sub plot at 5 levels (0, 0.25, 0.50, 0.75 and 100% rate of recommended dose (1.5 L ha-1)). Common mallow density (50 plant m-2) was fixed in all plots and wheat sowing density was 350 plant m-2. The wheat cultivar was Chamran 2. Spraying was carried out using a 20-liter rechargeable Matabi back Sprayer equipped with a nozzle (11003) and a pressure of 2 bar (calibrated based on 200 to 300 liters of water per hectare) in the post-emergence stage at the middle of the wheat tillering stage (6-4 The leaf of the common mallow). Half of the nitrogen fertilizer was applied at sowing stage and the other half was distributed in the middle of the wheat tillage stage. The plants were then cut at surface and dried in oven (75 °C) and weighted. The four parameters sigmoid model was used to assess wheat and common mallow yield response to herbicide reduced dose and N fertilizer. The three parameters power model was also applied to explain the change of mallow number and weight in response to reduced herbicide dose and different levels of N-fertilizer application.

Wheat grain yield increased in response to increasing herbicide dose and reducing the competitive ability of common mallow in different levels of urea fertilizer application. The grain yield was equal to 202, 277, 329, 408, 443 and 450 g m-2, when 300 kg of urea fertilizer ha-1 with 0.375, 0.60, 0.75, 1.05, 1.35 and 1.50 L ha-1 of the recommended dose of herbicide was employed, respectively. Moreover, the dose required to reduce 50% of the weed competition effects on wheat grain yield was decreasing in urea fertilizer levels. The results showed that the higher levels of urea fertilizer decreased wheat grain yield, but increased the number and weight of the common mallow seeds. The number of common mallow seeds was maximum for the higher levels of urea fertilizer and lesser doses of bromoxynil+2, 4-D, was minimum under low urea fertilizer consumption and the higher levels of bromoxynil+2, 4-D. The density of common mallow seeds under no-herbicide conditions ranged from 4.78 to 35.87 g m-2 for each urea fertilizer level. The number of common mallow seeds produced under no-herbicide application varied between 1915.95 and 16540.76 seeds per m-2 for each fertilizer level. However, in the case of higher doses of bromoxynil+2, 4-D, weight and seed number of common mallow showed a decreasing trend. Thus, under no-herbicide condition, common mallow produced much more seeds when higher N-fertilizer rates were applied. Application of 300 kg of urea ha-1 without herbicide application led to the highest common mallow seed number and weight and the lowest wheat yield. The greatest wheat yield (i.e. 515.40 g m-2) was obtained by consuming 225 kg of urea ha-1 along with 1 L ha-1 bromoxynil+2,4-D. In addition, the higher urea fertilizer levels reduced wheat grain yield, but increased the common mallow seed number and weight.

Increasing the competitive ability of weeds, application of high N-fertilizer rate results in a larger yield loss. However, herbicide application with the application of high N-fertilizer is highly likely to control weed, causing an increase in wheat yield. The combined model helps to lessen the herbicide and fertilizer application.