نشریه بوم شناسی علف های هرز
سال سوم شماره 2 (پاییز و زمستان 1394)

In order to evaluate the effects of seed deterioration on capability of seed germination and seedling of three weeds-Malva neglecta L., Echinochloa crus-galli L.and Sorghum halepense L.-under saline stress conditions, an experiment was conducted at university of Ramin in Khuzesatan. The arrangement was factrorial in form of a completely randomized design with 4 replications (RCD) in 2012. In this experiment, The first factor was weed seeds at 3 levels (Malva neglecta, Echinochloa crus-galli and Sorghum halepense), the second factor was deterioration treatments at 4 levels (0, 3, 5 and 7 days), and the third factor was salinity (0,4,8 and 12dSm-1), and the forth factor was moisture stress at 3 levels (saturation field capacity(FC) and 50%FC). The results of experiment showed that seed deterioration and saline stress reduce all measured characteristics including time, speed, uniformity, persentage and emergence index, germination percentage, radicle length, plumul length, vigos index, and seedling dry weight. A significant difference was observed at %1 level. Saline stress resulted in reduction of determined characters in the experiment. Whwrase in Wherase in Malva niglecta moisture Stress of 50% FC, FC and saturation reduced percentage of germination, in barnyard grass and johnsongrass the highest germination percentage was observed in saturation tseated seeds and the least percentage of emergences was observed in %50 FC treated seeds. Our results indicated that seed deterioration increased the effect of salinity on weed seedling establishment and seed germination.

Fields marginal weed can be used as effective factor in dispersion and spatial distribution of pests and work as trap plants to protect the main product or can be a suitable habitat for beneficial insects as well. An investigation was conducted in one of tomato farms in Kalat-miyan village, located in Chenaran city in 2012-13 in order to evaluate the effects of marginal datura weed on the density of tomato important pests such as aphid, thrips, and heliotis. This factorial experiment was done in randomized complete blocks designed with two treatments (presence or absence of weed margins) and four different levels (the distance from the field’s margin) with three repelication. The results showed that after growing tomato plants, aphids and thrips emerged and a significant difference was observed in pest reduction between the plots with presence of marginal datura and those with no marginal datura .About the effect of Helianthis,a significant relationship was observed between the amount of heliothisdamage and presence of marginal datura plant. Since datura contains daturin toxic compounds, it will cause the repelling of suncking insects such as aphids and thrips which feed on the plant. datura had an effective role on Heliothis density. There was also a significant relationship between the distance from weed margin and the pest density so that the more the distance from weed margin, the more density of aphids and thrips and the less density of Heliothis happend. So datura plant can be used in tomato farms as integrated pest management.

To beautify and improve landscape of Mashhad metropolitan city, weed situation of Khorshid Park was studied. Thirty weed species belonging to 15 plants families formed the relatively diverse weed communities established on plains and hillsides of the park most of which belonged to Asteraceae, Poaceae and Fabaceae families, respectively. Sixteen of which (53%) were annuals, 37% were perennials and 10% were biennials. the richness of the plain weed community with 26 species was more than hillsides with 20 species. Weed community in hillside weed was highly uniform while uniformity of weed community in plains was less than hillsides showing signs of dominance at the beginning of the season. The Logarithmic distribution model of species showed the habitats are not relatively demolished, The similarity between weed communities of plains and hillsides was less than the similarity between seasonal weed communities of each habitat indicating more adaption of weeds to habitat conditions. The less similarity was obtained between spring weeds of both habitats while the most similarity was observed between summer weed communities. This survey proved that plains are threatened by noxious weed species such as Acroptilon repens L., Cynodon dactylon L., Hordeum murinum L., Bromus tectorum L. and Setaria viridis L. while hillsides menaced by Acroptilon repens L., Alhagi camelorum Fisch., Cirsium arvense and Xanthium strumarium L.

In order to evaluate the efficacy of green manure on Egyptian broomrape (Orobanche aegyptiaca. Pers) control and to determin green manure effects on tomato (Lycopersicon esculentum Mill.) growth, a glasshouse experiment was conducted in CRD design with four replications. Treatments consisted of three green manures of wheat (Triticum aestivum L.), barley (Hordeum vulgar L.) and rye (Secale cereal L.) in two levels (50 and 100 biomass return into the soil) and two control treatments of weed free and weed infest treatments. The results showed that among all treatments, the rye manure in both levels (50 and 100 percent return into the soil) reduced significantly the number of broomrape shoot, and nodules on tomato roots; dry weight and the broomrape/tomato dry matter ratio than weed infest treatment. In fact, barley green manure, especially in 100 percent biomass return in many treats, was similar to rye green manure. In spite of reduction in the measured treatments of broomrape, no significant difference was observed among green manure on the dry weight of tomato. Generally, it seems that rye manure in 50 and 100 percent and barley green manure in 100 percent level have the capability to prevent broomrape seed germination and establishment in a better way more research is needed to examine the effects of treatments on tomato growth and quality.

Concerns about environmental pollutions and development of weed resistance to herbicides have attracted the attentions towards the biological control of weeds. In order to evaluate the allopathic effects of different organs of yarrow (Achillea milefolium L.) and lemon-verbena (Lippiacitriodora Kunth.) on germination of redroot (Amaranthus retroflexus ­L.), wild mustard (Sinapis arvensis­ L.), and little seed canary grass (Phalaris minor Retz.), a factorial experiment was conducted in a completely randomized design with four replications at Research Laboratory of Islamic Azad University of Gorgan in 2014. Treatments included medicinal plant at 2 levels(Yarrow and lemon-verbena), organs of medicinal plants at 3 levels (root, stem and leaf), and concentrations of extracts at five levels (0, 25, 50, 75 and 100 v\v%). By increasing the concentration of yarrow and lemon-verbena, the germination rate of seeds, plumule length, radical length and seedling fresh weight in weed species were significantly reduced. Allopathic effects of leaf and shoot extracts of lemon-verbena were severe on seed germination of mustard. Allelopathic effects of leaves and stems of limon-verbena on wild mustard seeds and yarrow extract on the germination of weed seeds was high. Among the three weed species, little seed canary grass was less affected by the extract of yarrow and lemon-verbena. Given the importance of reducing the use of chemical inputs in the management of weeds, use of the potential inherent of some plants and their application in agricultural systems and planning rotation can be very handy and useful.

Weed management systemis a successful approach to reduce weed control cost and gain an acceptable economic performance. Therefore, this study was carried out based on randomized complete block design with four replications in Agro-industry field Dashtenaz Sari, during 2010 to evaluate the effect of weed control and its interference on corn growth properties. Treatments including weed free and weedy check(infested)along with free weed and weedy infestedat 3, 6, 10, 14 were applied with leafy stage tasseling.Logestic non-liner equation was used for critical period of weeds control at start and end of the time.The result showed that most dominant weeds were velvetleaf (Abutilon thophrasti) and pigweed (Amaranthus retroflexus).The interference period did not have significant effect on dry weight and height of weeds; whereas, The control period has significant effect on density of weeds.The interference and control periods did not show significant effect on corn height; whereas, a significant relationship was observed with stem diameter, dry weight, ear length, ear diameter, ear weight, number of kernel rows per ear, number of kernels per row, thousand kernel weight and corn yield. Weed interference compared to weed free showed reduction instem diameter, dry weight, ear length, ear diameter, ear weight, number of kernel rows per ear, number of kernels per row, thousand kernel weights and corn yield. Critical period of weeds was estimated between38-65 days after corn planting or 392-804 GDD (7-8 leaf stage) stage to tasseling at 5% levels reduce seed yield, and at 10% levels reduce seed yield, critical period was estimatedbetween 48-55 days after corn plantingor 534-653 GDD.