IRANIAN JOURNAL OF WEED SCIENCE
Year:2008 | Volume:4 | Issue:1|Papers Count:9

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

Canada thistle (Cirsium arvense) is a noxious weed and one of the most problematic weeds in field crops, orchards, vegetables, pastures and grasslands in Iran. Thistle tortoise beetle (Cassida rubiginosa), an herbivore insect, seems to be an effective agent for suppressing the biomass and survival of Canada thistle. In order to study the efficacy of thistle tortoise beetle for biological control of this weed an experiment was conducted in a randomized complete block design with five replications, in which the populations 0 (control), 5, 10, and 20 larvae per plants were considered as treatments. Results showed that thistle tortoise beetle controlled Canada thistle significantly in all densities. Feeding 20 insects on each plant reduced total biomass and seed production by 78% and 94%, respectively.

In order to control cotton weeds chemically and introducing new herbicides with different modes of action, an experiment was carried out in three locations (Varamin, Golestan, Khorasan) in 2004. The experiment was conducted in randomized complete block design with 11 treatments and 4 replications. trifluralin at 1200 g(ai) /ha (ppi), ethalfluralin at 1160 g(ai) /ha, diuron at 2400 g(ai) /ha (pre emergence), trifloxysulfuron sodium at 11.25 and 15 g(ai) /ha with cytogate 2/1000 (post emergence at the 5- 8 leaf stages of cotton), fluometuron+prometryn at 1232, 1936, 2464 g(ai) /ha (pre sowing) and fluometuron+prometryn at 1499, 2024, 2552 g(ai) /ha (pre emergence) were used. Results showed that fluometuron+prometryn at 2024 and 2552 g(ai) /ha (pre emergence) and trifloxysulfuron sodium at 11.25 and 15 g(ai) /ha and Diuron at 2400 g(ai) /ha increased yield and yield components of cotton. Fluometuron+prometryn at other treatments effectively increased yield components compared with trifluralin and ethalfluralin. Fluometuron+prometryn at 2024 and 2552 g(ai) /ha (pre emergence) and trifloxysulfuron sodium at 11.25 and 15 g(ai) /ha were most effective in decreasing dry weight and density of weeds. Depending on weed species, trifloxysulfuron sodium and fluometuron+ prometryn showed some difference in control of weeds.

This experiment was conducted under pot conditions to investigate competitiveness of spring wheat (Triticum aestium, Chamran cultivar) subject to various plant populations of wild oat Avena fatua, using completely randomized design with three replications in 2006 in the greenhouse of Ramin Agricultural and Natural Resources University, Mollasani Khouzestan. The treatments included pure stands of wheat and wild oat at one level (ratios 4: 0 and 0:4), and density difference ratios wheat and wild oat at seven levels (4:1, 4:2, 4:3, 4:4, 1:4, 2:4 and 3:4). The results showed that relative crowding coefficient (RCC) of wheat to wild oat and wild oat RCC to the wheat were equal. This indicated that competitive ability of the two plants were similar. While relative grain yield of wheat decreased by increasing relative leaf area of wild oat. Ability Aggressivity of wild oat showed that wild oat was more successful in using environmental sources, observed clearly in ratio the 4:4. Moreover mean stem height, mean spikelet number per spike, mean grain number per spike, mean 1000-grain weight, final biomass and grain yield of wheat plant decreased with increasing wild out density.

Field experiments were conducted to investigate the effect of herbicide doses on corn-multiple weed competition.Sixteen weed density combinations consisting of 4 densities of redroot pigweed × 4 densities of common cocklebur under five doses of herbicide were assessed. The two weed species responded differently to herbicide doses.Competitivity of redroot pigweed decreased with increasing herbicide dose and was completely removed by applying herbicide at 0.5 of full recommended dose, but for common cocklebur an initial increase occurred at 0.25 rate of full dosage. The relationship between weed competitivity and herbicide dose was well-described by standard dose response curve and Brain & Cousens model for redroot pigweed and common cocklebur, respectively. A combined model incorporated standard dose response curve and Brain & Cousens function into the multivariate rectangular hyperbola competition model gave a good description of corn yield. When no herbicide was applied, the competitivity of common cocklebur was approximately 1.7 times greater than that of redroot pigweed and 63% of yield loss occurred from the combination of 8 common cocklebur and 12 redroot pigweed plants m-2. Where the density of common cocklebur was low (0 to 4 plants m-2) applying herbicide at half the full recommended dose could save the yield, but with increase in common cocklebur density, the herbicide reduced doses failed to prevent the yield loss. Even at full recommended dose of herbicide, corn yield suffered loss of 6 to 10 percent from high density of common cocklebur.Nomenclature: Nicosulfuron; common cocklebur, Xanthium strumarium L.; redroot pigweed, Amaranthus retroflexus L.; corn, Zea mays L.

A field experiment was conducted at the experimental field of Iranian Research Institute of Plant Protection, Karaj city in 2006 to investigate the effect of different doses and application timeing of metribuzin on grain yield of different wheat varieties. The experiment was arranged at factorial in randomized complete blocks design with four replications.The factors investigated were three wheat varieties: Shiraz, Pishtaz and M-79-6 line; 4 metribuzin doses: 1.0, 0.75, 0.5 and 0.0 kg ha-1 and herbicide application times: preemergence and postemergence at three to four- leaf stage of wheat.The results indicated that wheat seed yield and yield components were significantly affected by doses and application timing. The highest wheat yield for all varieties was observed in postemergence metribuzin at 0.5 and 0.75 kg.ha-1.Mean while, postemergence application of metribuzin was better than preemergence. Final deduction from the experiment is that postemergence use of metribuzin at 0.5 kg.ha-1 can be recommended in the above-mentioned wheat varieties.

In order to assess the effects of sulfonylurea herbicides on canola planted in rotation after wheat, this study was conducted in a randomized complete block design with ten treatments in four replications. Treatments included application of herbicides: Total® (metsulfuron methyl+sulfosulfuron), Chevalier (idosulfuron+mesosulfuron), Apirus (sulfosulfuron) at 21, 31.5, 42 and 51 g ai ha-1, Megaton (chlorsulfuron), Bromicide ("bromoxynil+MCPA"+ clodinafop-propargyl), Atlantis (idosulfuron+mesosulfuron), and no-herbicide control. Herbicides were sprayed in the end of tillering stage of wheat. Canola was planted after wheat harvest in the fall. Results showed that Total has indicated a decline up to 20.3 percent in seed yield (highest decrease in yield) versus untreated control. Following Total, Apirus at 51 and 42 g ai ha-1 and Megaton at 15 g ai ha-1 caused 17.3, 13.53 and 13.32 percent yield loss leading to the highest decrease in yield, respectively.

In order to study the effect of different doses of metribuzin and plant density of wheat on weed control, an experiment was conducted at the Iranin Research Institute of Plant Protection, Karaj, Iran during 2007-2008. The experiment was conducted in randomized complete block design with factorial arrangement of treatments. Treatments were wheat densities at three levels of 400, 500 and 600 plant.m-2 and metribuzine doses at five levels of 0.0 0.2, 0.4, 0.6, and 0.8 Kg.ha-1. Results indicated that the best control of weeds and wheat grain yield was obtained in combination treatment of 500 plants.m-2 wheat density and 0.8 Kg.ha-1 metribuize. Results showed that wheat density can be used as a tool for reducing herbicide dose and weed damage in an integrated weed management program in wheat.

Weed survey of irrigated wheat fields is the most important practice in weed management. Based on cultivation area in all counties of Tehran province during six years (2000-2005), 61 sample wheat fields were selected and weed species were counted in each sampling point and population indices were calculated. In each field longitude, latitude and altitude were recorded using GPS. These data were used for producing weed maps using GIS. Results showed that flixweed (Descurainia Sophia [L.] Schur.), knotweed (Polygonum aviculare L.), few-flowered fumitory (Fumaria vaillantii Loisel.) and catchweed (Galium aparine L.) were dominante broadleaf species in irrigated wheat fields of Tehran province. Dominant grass weed species were winter wild oat (Avena ludoviciana Durieu.), wild barley (Hordeum spontaneum C. Koch.) and Feral rye (Secale cereale L.). Field bindweed (Convolvulus arvensis L.), Canada thistle (Cirsium arvense [L.] Scop.) and hoary cress (Cardaria draba [L.] Desv.) were the most important disturbing plants prior to harvesting in irrigated wheat fields of Tehran province.