IRANIAN JOURNAL OF WEED SCIENCE
Year:2018 | Volume:13 | Issue:2 |Papers Count:8

A study was conducted to evaluate the impact of farming and management factors on resistance of wild mustard to tribenorun methyl in Golestan province in collaboration with the Iranian Research Institute of Plant Protection and Mohaghegh Ardabili University from 2014 to 2016. Relative resistance was determined by screening the collected seeds of suspicious biotypes from all regions of the Golestan province. The relationship between herbicide resistance and farm records from agricultural, management and technical aspects was evaluated by ordinal logistic regression model of proportional odds models. The result showed that crop rotation and wild mustard density had significant impacts on the development of resistance at 95 percent level of probability. Under regular spring rotation, the risk of resistance was 6. 165 times lower than the reference rotation (autumn rotation). Wild mustard at high density (reference density) had 3. 69 times greater risk of developing resistance than of the lower density. Type of tillage, sowing date and irregular use of herbicides compared with farmer’ s lack of awareness of technical issues had no significant effect on the risk of resistance. Determining the effects of different factors in the development of herbicide resistance might result in more effective management of weeds.

To investigate the effects of winter cover crops and their management on the density and dry matter of weeds in plum orchards, an experiment was conducted during 2014-2015 in Urmia. The experiment was performed in the randomized complete block design with spilt plot arrangement. Four cover crops in main plots included: ryegrass (Secale cereale L. ), barley (Hordeum vulgare L. ), oilseed (Brassica napus L. ) and clover (Trifolium resupintum L. ) and management methods including cutting-off cover crops and using rotivator in sub – plots were experimental treatments. According to the results, the highest and lowest dry matter of cover crops belonged to ryegrass (275 gr. m-2) and clover (97 gr. m-2) and the highest and lowest leaf area index were observed in ryegrass (3. 5) and clover (1. 4) respectively. Comparison of cutting-off cover crop and rotivator revealed that rotivator’ s effect on weed density (%67) and dry matter (%31) is more effective than cutting-off cover crops. Totally, results of this study revealed that ryegrass and barley planting as cover crops, along with using rotivator, is the best recommended method for weed control in Urmia plum orchards.

In order to select the most appropriate morphological characteristics of weeds in wheat fields in Khuzestan province, 16 species of the most common broadleaf weeds were selected. Collected species included: Ammi majus L., Anagallis spp., Beta vulgaris subsp. maritima (L. ), Carthamus tinctorius L., Chenopodium murale L., Convolvulus arvensis L, Lactuca serriola L., Malva spp., Rumex dentatus L., Scorpiurus muricatus L., Silybum marianum L., Sinapis arvensis L., Sonchus tenerrimus L., Stelaria media L., Veronica persica Poir., and Vicia villosa Roth. For any species, five samples (as five replications) were photographed and images were analysed using image processing. Wheat, also, was photographed as control. After isolating images from background and tagging them, seven morphological characteristics including area, perimeter, aspect ratio (length to diameter ratio), rectangularity, area ratio of convex hull, perimeter ratio of convex hull, sphericity, form factor and eccentricity of each weed species and wheat were extracted. Results showed that the best morphological characteristics to distinguish broadleaf weeds from wheat were aspect ratio and sphericity. So that, compared to the weed species, aspect ratio was greatest (19. 79) in wheat. After that, caterpillar-plant (9. 71) and safflower (5. 90) were greatest. The sphericity of wheat was the lowest (0. 05). Considering the narrow shape of wheat leaves and the significant difference in leaf shape with broad-leaved species, this characteristic can be very useful for identifying and distinguishing wheat from broadleaf species at the field.

To increase the rice yield by the interaction of herbicides and humic acid on Azolla control, an experiment was conducted in Amol, Mazandaran, in 2016 as a factorial experiment in randomized complete block design with three replications. Treatments consisted of herbicides application in five levels: 2-4-D SL72%, Bensulfuron methyl DF60% (Londax), bentazon SL48% (Bazagran), Oxadiargyl EC3% (Top Star) and control, and humic acid at three levels: 12, 6 and 0 lit/h (control, no humic acid). The results of this study showed that the simple effect of application of herbicides and humic acid on all traits was significant. Also, tillers number, panicle length, Azolla weight and rice yield were affected by the interaction of herbicides and humic acid. The lowest Azolla weight (115. 33 g m-2) was obtained by the interaction of Oxadiargyl and 12 litha˗ ¹ humic acid, and the highest grain yield (6871 Kg ha˗ ¹ ) was also observed in the same treatment.

A survey was conducted to study the effects of soil and climatic factors on distribution of weeds in 48 parks in 22 districts of Tehranin 2014. 52 weed species from 21 plant families were identified. Multivariate analyses with canonical correspondence analysis (CCA) showed that changes in the weed species distribution were due to soil traits (pH, Phosphorus, Nitrogen, Potassium, %Carbon, %Organic matter, EC) and environmental conditions during previous years. Green foxtail (Setaria viridis), hairy crabgrass (Digitaria sanguinalis), ragweed (Kochia scoparia) and knotweed (Polygonum patulum) had a wide distribution in the areas with high temperature. Where the soil nitrogen were high, Green foxtail (Setaria viridis), Ragweed (Kochia scoparia), Ladino clover (Trifolium repense), Knotweed (Polygonum patulum) and Sow thistle (Sonchus oleraceus ) density was found frequently. Besides, there was a correlation between soil potassium and the density of Broad leaf plantain (Plantago major L. ), Little hogweed (Portulaca oleracea), Watter grass (Echinochloa crus-galli), Procumbent yellow-sorrel (Oxalis corniculata) and Common dandelion (Taraxacum officinale) in turfgrasses. Based on the results of this study, it would be possible to overcome these problems to some extent by predicting future problems of weeds and changing management plans.

A study was conducted to assess the weed flora changes in the irrigated wheat fields during the last decade in 52 fields located in seven cities at Tehran province in 2015. The frequency, Unifromaty and dominance index of species were calculated and they were compared with the mentioned indices from 2005. In 2015, 66 species of weedsfrom 26 families were identified, of which, 55 species were broad-leaf and the others were grasss. 10 species that had been observed in 2005 had been omitted from the fields and 15 new species from 11 families were identified. Amaranthaceae, Dipsacaceae, Plantaginaceae, and Solanaceae were the four families that were for the first times observed in the fields of the province for the first times. Brassicaceae, Poaceae and Asteraceae families were dominant families in the fields. The broadleaf species of flixweed, knotweed, bindweed and fumitory with dominance indices of 117/94, 97/82, 81/09 and 46/11 and the grasss of wild oat, wild barley, annual ryegrass feralrye with dominance indices of 86/59, 50/94, 27/64 and 15/41 had the greatest dominance indices respectively. The differences of dominance index of the most species were negative. The results of study indicated the dominance reduction of the most weeds and their control improvementy although in a few number of weeds such as wild mustard and catchweed, an increase in the dominance index was observed.

Photosynthesis in plants is strongly influenced by stress. Evaluation of chlorophyll a fluoresce is one of the methods for assessment the different stresses effects such as herbicide on photosynthesis. Application of plant growth regulators like salicylic acid (SA), is one of the strategies to overcome for physiological disorders in plant. Therefore, to study the effect of SA mixture with Bentason, Bromoxynil+MCPA and 2, 4-D+MCPA herbicides on physiological behavior of Common lambesquarts (Chenopodium album L. ), a greenhouse experiment was conducted in randomized complete block design with three replications in Agricultural faculty of University of Tabriz in 2016. The results indicated a reduction in maximum fluorescence (Fm), variable fluorescence (Fv), maximum quantum yield of photochemistry (Fv/Fm), efficiency of the water-splitting complex on the donor side of PSII (Fv/Fo), and performance index (PIABS), and an increase in minimum fluorescence (Fo) and photosystem II antenna (Fo/Fm) of Common lambesquarts subjected to Bentason and Bromoxynil+MCPA. Dry weight and chlorophyll index in control treatment (without SA) increased 4. 3% and 2. 1% respectively, but in Bentason and Bromoxynil+MCPA and 2, 4-D+MCPA treatments, these two indexes reduced 41. 6%, 13. 7%, 13. 6% and 32. 2%, 36. 4%, 18. 7%, respectively. SA not only did not reduce the Bentason and Bromoxynil+MCPA efficiency, but also increased efficiency of these two herbicides.

To study the effect of Ethalfluralin, Trifluralin and Pendimethalin on weed control in potato fields and potato yield, a field expriment was carried out in the Ardabil Agriculture and Natural Resources Resarch Station in 2014. Dose-response experiment was performed in an Agria potato cultivar field in Randomized Complete Block Design with three replications. Experimental treatments were: Trifluralin and Etalfluralin at 0. 125, 0. 25, 0. 5, 1, 2 and 4 L/ha, Pendimethalin at 0. 25, 0. 5, 1, 2, 4 and 6 L / ha and two control treatment (weedy and weed free). Weed samplings carried out at 20 and 60 days after treatment. The maximum total weed density reduction was observed 20 days after 6 lit/h Pendimethalin application. After that, 4 lit/h Etalfluralin was at 60 days after spraying, had the greatest effect on reducing the total weed density (94. 4%). Ethalfluralin at 4 lit/ha dose led to the maximum reduction total weed biomass. The application of 4, 6 and 4 L /ha Ethalfluralin, Pendimethalin and Trifluralin respectively reduced the biomass of weeds over a period of 20 days after treatment by more than 90 percent. The maximum mean tuber weight and total tuber yield were achieved by 4 L /ha Pendimethalin that had not significant differences with 6, 2 and 4 L /ha Pendimethalin, Trifluralin and Ethalfluralin, respectivally.