Melon aphids, Aphis gossypii Glover (Hemiptera: Aphididae) is one of the most important pests causing damages in vegetables fields and greenhouses. In this regard, pesticide application is usually considered as the most common forms of pest control. Excessive use of chemical pesticides, leads to an increase in pesticide residue in vegetables, and affects on consumer health. In this study, the sensitivity of the different nymphal instars and adult melon aphids to field recommended dose and half-dose of the insecticides imidacloprid (35% SC) and primicarb (50% WP) was surveyed by leaf dipping. The bioassay was also carried on the third instar of melon aphid. Moreover, based on LC50, the sensitivity of third instar was compared at intervals of 24, 48 and 72 hours, in both insecticides. The results showed that the toxicity of both pesticides was significantly reduced in later stages. Based on the results obtained, LC50 and LC90 of imidacloprid were 71.648 and 365.548 and for primicarb were 212.62 and 457.49 ppm, respectively. The mortality for imidacloprid was 45, 48.89 and 49.45% and for primicarb 43.89, 47.78 and 50.56%, after 24, 48 and 72 hours, respectively. The results also revealed that in both insecticides, the highest mortality were occurred after 24 hours and the passage of time (48 and 72 hours) did not result in higher mortality. According to results, the pest is well controlled by low doses of both insecticides, the issue that can also reduce harmful side effects on consumer health and the environment.

A field study with 3 replications based on RCBD was conducted in order to improve the efficacy of some herbicides using adjuvants in the control of broadleaf weeds of saffron. Oxadiazone, oxyfluorfen, rimsulfuron and dicamba+ tritosulfuron herbicides at recommended rates of 500, 700, 10 and 150 a. i. ha-1, respectively without adjuvants and in reduced rates 375, 480, 8. 75 and 112, respectively were used when they were tankmixed with and without citogate (0. 2% v. v-1) and humix 99 (0. 25% v. v-1) as well as a control plot with no herbicide application and hand weeding. Weed species of Polygonum aviculare and Cardaria draba with relative density of 26% and 20. 5%, respectively were the dominant weeds in the experimental field. The results showed that hand weeding significantly increased the yield of saffron flower and corm. Application of oxyflurfen and oxadiazone in reduced rates decreased saffron damage while addition of citogate to these herbicides increased the phytotoxicity damage in saffron. Addition of humix to these herbicides had no effect on phytotoxicity damage. Although application of rimsulfuron and dicamba+ tritosulfuron in reduced rates reduced phytotoxicity damage and increased yield of saffron, these herbicides have the potential to damage saffron even at reduced rates. Adding citogate to these herbicides can increase the efficacy of these herbicides in weeds control but considering the potential of these herbicides in damage to saffron, application of these herbicides in saffron fields is not recommended even at reduced doses. Application of oxyflurfen at 480 a. i. ha-1 without adjuvant and tank-mixed with humix were best treatments for use in saffron fields. However, it is also possible to use oxadiazone at 375 a. i. ha-1 to control saffron broadleaf weeds.

To evaluate the effect integrated application of mulch with reduced doses of imazethapyr on weeds in bean, a factorial experiment was conducted based on randomized complete block design with three replications and 16 treatments in Tabriz in 2015. The first factor was much application with four levels including straw mulch, living mulch, no mulch and one hand weeding and the second factor was different doses of imazethapyr including 0, 50, 75 and 100 % of recommended dose (100 g ai. ha-1). Results indicated that the interaction effects of herbicide dose and mulch application was significant on weed biomass, plant height, leaf area index and grain yield of bean. The lowest weed biomass was observed in hand weeding +100 % imazethapyr (106. 5 g. m-2) that was not significantly different from straw mulch+100 % imazethapyr and living mulch +100 % imazethapyr. In 100 % dose of imazethapyr treatment, the living and straw mulch significantly increased the leaf area index of bean compared to 100 % imazethapyr. The hand weeding + 100 % imazethapyr treatment produced the highest bean grain yield (78% of weed free) and the straw mulch + 100 % imazethapyr (64% of weed free) and living mulch+ 100 % imazethapyr (53% of weed free) were the next. Generally, it could be concluded that post-emergence application of imazethapyr had low efficacy in bean weed management and using non-chemical treatments such as much and hand weeding could increase the weed control efficacy in this crop.

In order to study the effect of reduced doses of oxadiargyl, on weeds control in potato, a field experiment was conducted at Alaroog Research Station in Ardabil during 2013. Experiment arrangement was factorial based on randomized complete blocks design with three replications. First factor included seven reduced dosages of oxadiargyl (0, 0. 05, 0. 1, 0. 2, 0. 4, 0. 6, 0. 8 L a. i/ha) and second factor included oxadiargyl application timing (potato emergence, stoloning and tuber bulking). The results showed that application of 0. 8 L a. i/ha of oxadiargyl reduced weed density and biomass to 48. 40 and 66. 16 percent, respectively which was not significantly different from applying 0. 6 L a. i/ha. Maximum reduction percentage of weed density and biomass on the different potato growth stages was at potato emergence stage, which provided the best effectiveness of the oxadiargyl. On the other hand, application of 0. 8 L a. i/ha oxadiargyl at potato emergence stage caused the highest mean of tubers weight per plant and total tuber yield, but was not significant on the tuber number per plant.

Field experiment was conducted to study the interaction between imazethapeyr dose and Xanthium strumarium density on soybean yield. Four densities of weed (0, 4, 8 and 12 plant.m-2) × 5 doses of herbicide (0, 25, 50, 75 and 100 g a. i.ha-1) was assigned in a factorial arrange of treatments with four replications. A combined model incorporated standard dose response curve and rectangular hyperbola competition model gave a good description for soybean yield. When no herbicide was applied, soybean yield was decreased by 58, 73 and 80% at densities of 4, 8 and 12 plant.m-2. Where the densities of common cocklebur was low (0, 4 plant. m-2) applying herbicide at half of the recommended dose could save the yield by 90% however; with increasing weed densities to 8 and 12 plant.m-2, 20 and 30% yield loss was caused in soybean yield. No difference was found between herbicide application at 75 and 100 rate of the recommended dose.

Introduction: Weed management is an important agronomic practice. It would be takes 40% of time of small holder farmers, if carried out by hand. Farmers have being interested in more comprehensive programs for weed management that reduce weed populations over time and the use of reduced herbicide doses in order to diminish their production costs. Integrated weed management takes advantages of various methods to suppress weeds in a more common and environmental natural way. Today, it is understood that chemical herbicides are not free of problem. So researchers are working on integrated weed management, which brings all possible methods to control weeds. The use of reduced herbicide doses will cost a fraction of full dose and make them even more affordable to poor farmers who have a limited amount of resources. Researches indicate that there is good potential to reduce the number of herbicide applications and utilize lower herbicide doses within competitive cropping systems. Crop competitiveness advantage is a great potential for weed suppression that provides reducing herbicide dose to avoid its environmental and economic suffers. Therefore, a field experiment was conducted to evaluate the effect of reduced dose of imazethapyr on weed control when two bean cultivars grown in pure stand and intercropping together. Materials And Methods: The field experiment was conducted as split plot based on randomized complete block design at the Research Farm of University of Tehran located in Karaj during 2013– 2014. Main plots were five doses of imazethapyr (0, 25, 50, 75 and 100 percent of the recommended dose) and sub-plots comprised pure stands and intercropping of two bean cultivars include: Akhtar (the growth habit is upright) and Goli (the growth habit is creeping). Also there is a plot as weed free (control). When the plants were at the third trifoliate stage, determined doses of imazethapyr were sprayed. Weed dry weight and bean yield were analyzed by nonlinear regression. In order to obtain the response curves to the doses of imazethapyr, data were fitted by SigmaPlot software (version 11) according to the standard dose-response equation: Where W is the dependent variable, ED50 is equivalent to a dose of herbicide that reduces weed dry matter by 50 percent and b is the curve slope where the trend is linear. The yield data were fitted using a three-parameter logistic equation: where a is maximum yield, x0 represents a dose of herbicide in which the yield reaches 50 percent and b is the slope of the curve. Results And Discussion: The community of weeds in the field mostly consisted of three species; Amaranthus retroflexus, Chenopodium album and Solanum nigrum that all are summer annual weeds. The dose-response model well described the effect of doses of herbicide on weed dry weight. Results indicated that weed species response to herbicide doses differently in bean cultivars and their intercropping. Among dominant weeds, A. retroflexus was determined high sensitive to increasing doses. Bean cultivars were solely different in competition with weeds, as creeping cultivar i. e. Goli with more competitive ability (like: fast early growth and area coverage) was more successful in weed suppression. Herbicide application at reduced dose could also be efficient when we used 75 percent of the recommended dose because led to a yield more than 4000 kg/ha in pure stand of Goli. Pure stand of Akhtar and intercropping showed yields of 3617 and 3641 kg/ha, respectively at 75 percent of the recommended dose. Relative yield total (RYT) for doses of 75 and 100 percent of the recommended dose and weed free control were 0. 95, 0. 87 and 1. 03, respectively. Conclusion: The results of experiment showed that weed sensitivity to herbicide doses vary differently by species. So that, A. retroflexus dry weight was more affected than C. album and S. nigrum in response to reduced doses of imazethapyr. The application of 25 percent of the recommended dose of this herbicide reduced A. retroflexus dry weight more than 50 percent. It seems that if the dominant weed in a field was the A. retroflexus, the farmer could greatly reduce dose of imazethapyr. However, usually weed community of fields are consisted of several species, therefore, to use reduced herbicide doses, sensitivity of all species should be considered. Also, using bean cultivars that potentially have high competitive ability, it could be a good supplement in combination with reduced doses of herbicide. In this experiment, Goli cultivar presented more potential to combine with reduced doses of imazethapyr.

In order to evaluate of suitable planting pattern for reduction herbicides dose in corn (Single Cross704) a field experiment was conducted at Faculty of Agriculture and Natural resources, Islamic Azad University, karaj branch in 2010. A factorial experiment was set up on base of randomized complete block design with 3 replications. Treatments include of corn planting pattern in 2 levels (single row and twin row), and herbicide treatments in 2 levels (Nicosulfuron and Foramsulfuron) and herbicide doses in 5 levels (0, 20, 40, 60 and 80 g ai/h) for Nicosulfuron and (0, 14, 28, 42 and 56 g ai/h) for Foramsulfuron. Density and dry weight of weed species were measured in 28 days after herbicide application. Results of statistical analysis showed that different herbicide doses had a various effect on weeds in each planting pattern. Using twin rows planting pattern could able to increase crop competition effect and suppressed weed growth in reduced herbicide doses. Nicosulfuron appeared better effect on weed control than Foramsulfuron. Environmental and economical advantages can be obtained by reducing herbicide doses, and selecting twin row planting pattern.

Reducing herbicide use without compromising performance can lead to lower environmental damage and lower production costs. In this research, the effects of plant density and reduced sulfosulfuron plus metsulfuron-methyl on weed infection and wheat yield, a split plot experiment based on a randomized complete block design with four replications at Agronomy Research Farm, Islamic Azad University during 2012-13, it was evaluated. The main plot consist of various doses of sulfosulfuron 75% + metsulfuron-methyl 5% in three levels of 20, 30 and 40 g a. i. ha-1with weed free and weedy check (control) plots were included for comparison and subplot including different wheat density at four levels of 300, 400, 500 and 600 plant m-2. Results experiments revealed that a fairly acceptable level of weed suppression in wheat fields was achieved with lower doses of sulfosulfuron plus metsulfuron-methyl (30 g a. i. ha-1) in combination with density of 500 plant m-2 that were comparable to results with its label dose. Increased density was able to increased grain yield and number spike m-2. As, the number of spikes (650) and yield (486. 3 g. m-2) were obtained at a density of 600 plant. m-2. 1000-grain weight decreased with increasing density. The results suggested that weeds can be controlled in wheat, for a higher yield, when a reduced herbicide dose (30 g a. i. ha-1) is used in combination with increasing density (500 plant m-2).

Crop-weed competition has a profound effect on the seed yield of mung bean. We evaluated the effects of both the seeding rate and weeding regime on the weed infestation and crop performance of mung bean. Two factors via seed rate (15, 25 or 35 kg ha-1) and different doses of haloxyfop-R-methyl (0, 0. 4, 0. 8 and 1. 2 L ha-1) were included in the experiment. The experiment was implemented in a split-plot design accommodating seeding rate in the main plot and doses of herbicide in the subplot with four replications. Mean data from the experiment showed that weed density and weed dry weight were significantly affected by seeding rate: these two variables decreased with the increase in the seeding rate (p<0. 01). The seeding rate significantly influenced plant height, number of pod per plant, biological yield and seed yield. Different variables that included; plant height, number of pod per plant, 1000 seed weight, harvest index and seed yield were significantly influenced by variations of herbicide doses. Seed yield was significantly improved in dose of 1. 2 L ha-1. Overall, the interaction effect of seeding rate and herbicide doses was not significant in respect to the plant characteristics except harvest index. Nevertheless, a seeding rate of 35 kg ha-1, coupled with volume of 0. 8 L ha-1, illustrated the best seed yield. Therefore, crop competition can be explored as an effective alternative weed management strategy and achieving optimal yield of mung bean.