جستجوی مقالات مرتبط با کلیدواژه « اثر افزایشی » در نشریات گروه « گیاهپزشکی »

Water is the primary carrier for herbicide applications (it usually makes up about 99% of the spray solution) and deliver them to the target weeds that they are intended to control. The quality of water available for spraying will depend on the source of the water on the vineyard, eg. dam or channel. Many chemical elements can be dissolved in water but six major ions make up the dissolved material in most water: Calcium (Ca++), Magnesium (Mg++), Sodium (Na+), Sulfate (SO4-), Chloride (Cl-), and Bicarbonate (HCO3-). Hard water becomes “hard” because of the presence of carbonates, sulfates, and chlorides of calcium, magnesium, and iron. Water containing calcium and magnesium can reduce the effectiveness of post-emergence herbicides that are weak acids include glyphosate (Roundup), paraquat (Gramaxone), bentazon (Basagran), clethodim (Envoy), sethoxydim (Poast), nicosulforun (Cruise) and 2,4-D (many products).Nicosulfuron is a post-emergence sulfonylurea herbicide that act through inhibition of acetolactate synthase (ALS) and controls many difficult-to-manage monocotyledonous weeds at low rates in corn. Also, 2,4-D is a selective herbicide from the group of auxin-like herbicides that act systematically to control broadleaf weeds in cereals. "Mixing herbicides" can be used to reduce the effect of hardness factors in the water carrying herbicides. The purpose of a good mix is to increase the effect of the compound on weeds without damaging the crop. The primary reasons that herbicides are mixed are to improve bioactivity and reduce costs. Therefore, the application of mixing reduces labor costs, the number of crossings across the farm, equipment depreciation, and mechanical damage to the crop and soil. Interactions of two herbicides can occur in three ways: each herbicide has an independent mode of action (additive effect); one herbicide reduces the action of another herbicide (antagonism), and one herbicide increases the presence of another herbicide (synergism). The question is whether the synergistic effects that occur in some conditions in the mixing of two herbicides can be used to reduce the negative effects of hard water on the performance of hard water sensitive herbicides? Therefore, this study was conducted to evaluate the effect of water hardness on the efficacy of nicosulfuron and 2,4-D tank mixing on the control of velvetleaf (Abutilon theophrastis Medicus.).

 The effect of mixing nicosulfuron (Cruse- OD4%) and 2,4-D amine (U46- SL72%) herbicides on velvetleaf (Abutilon theophrastis Medicus.) weed control in the presence of hard agents carried out as factorial arrangement based on randomized complete block design with three replications at the Research Greenhouse of Ferdowsi University of Mashhad in 2019. The first factor of water hardness applied in four levels including deionized water (non-hard), 0.1 M concentrations of CaCl2, MgCl2, FeCl3 salts (Merck, Darmstadt, Germany). The second factor was mixing nicosulfuron and 2,4-D amine herbicides as 6.25, 12.5, 25, 50 and 100% of the recommended dose. The mixing ratios were (0:100), (25:75), (50:50), (75:25) and (100: 0). In addition, 10 pots were considered as control without spraying.Velvetleaf seeds were collected from a heavily infested corn fields in Mashhad, Khorasan Razavi province in northeastern part of Iran. To obtain uniform seedlings, seeds were treated by sulfuric acid 98% during 1 min. Seven seeds pre-germinated in petri dishes were transplanted at 1 cm deep in 1 L plastic pots in a mixture of soil, sand and cocopeat (1 : 1 : 1 wt ⁄ wt ⁄ wt) containing all necessary macro- and micronutrients. The pots were kept in a greenhouse at natural daylength and a temperature around 25°C during the day. The pots were sub-irrigated daily. Prior to herbicide application, plants were thinned to five uniformly sized plants per pot.The herbicide solutions were applied at the 3-4 leaf stage of the weed using a cabinet sprayer equipped with a flat fan nozzle (No.11004) delivering a spray volume of 390 Lha-1. A four-parameter log-logistic model (equation 1) was fitted to the data using the open-source statistical software R 2.6.2 and the drc statistical addition package.   Y=c+[d-c ⁄ 1+exp[b(log x-log e)]]   (1)where Y is the response expressed as percentage of the untreated control, c and d are the responses at very high and very low herbicide rates, respectively, b is the slope of the curve around the point of inflection, and e  is the herbicide rate giving response halfway between d and c (=ED50). If c = 0, then the four-parameter model reduces to the three-parameter model (equation 2), with the lower limit being zero.   Y=d ⁄ 1+exp[b(log x - log e)] .

The results showed that the net effects of herbicides were affected by hard water factors such as calcium, magnesium and iron III chloride. Besides, their efficiency in controlling biomass, survival percentage and height of velvetleaf were decreased. The inhibitory effect of hardness factors on herbicide performance was different. Calcium chloride and magnesium chloride had the highest reduction effect on nicosulfuron and 2,4-D amine, respectively. Therefore, to reduce the effect of water hardness factors, two herbicides were evaluated by mixing. The results indicated that the type of effect on herbicide mixing in biomass control of velvetleaf was synergistic, and reduced antagonistic effect of water hardness factors. Equal proportions of both herbicides in reducing the effect of calcium chloride and iron III chlorides, high ratio of nicosulfuron in reducing the effect of magnesium chloride, had the best performance in controlling the biomass of velvetleaf. Therefore, depending on the salts involved in the water hardness of the sprayer tank, changing the mixing ratio of the two herbicides nicosulfuron and 2,4-D amine can be achieved the best performance control of velvetleaf.

The assessment of the effect of mixtures could be based on various concepts whether we work within toxicology, pharmacology or weed control. Combinations of certain herbicides can give better weed control than use of the individual herbicide alone and/or loss of weed control when use of certain other herbicides in combination. Predicting the joint action of mixtures is extremely difficult, unless the compounds are known to interact at the same site of action. These most common methods to analyze the joint action of herbicide mixtures are the Additive Dose Model (ADM) or the Multiplicative Survival Model (MSM). The ADM assumes the two compounds have similar modes of action (do not interact) in the receiver plant, i.e. effective doses of each component will not change by mixing. ADM has been widely accepted as a valid method to estimate joint action of mixtures sharing the same or similar action mechanisms in the receiver plant. MSM has been reported to yield more accurate results for mixture toxicity than ADM do when the components exhibited different or dissimilar modes of action in the receiver plant. ADM or Concentration Addition (CA) is used here to test for deviation of additivity of doses using the ADM isoboles as reference; any deviation from the ADM is characterized by antagonism when the efficacy of a mixture is lower than predicted by the reference model and synergistic when the efficacy is higher than predicted.
In order to determine joint action of some usable important broadleaf herbicides in sugar beet, six experiments were conducted at the research glasshouse in Faculty of Agriculture, Ferdowsi University of Mashhad, Iran. The plants were sprayed with seven doses of commercial formulation of desmedipham phenmedipham ethofumesate (Betanal Progress- OF®, 427 g a.i. L-1, Tragusa, Spain), chloridazon (Pyramin®, 1361 g a.i. L-1, BASF, Germany), clopyralid (Lontrel®, 149 g a.i. L-1, Golsam, Gorgan, Iran) either alone or in binary fixed-ratio mixtures of the three herbicides. The ratio of the herbicides of the binary mixtures were chosen with the aim of obtaining a contribution to the overall effect of the two herbicides of 100:0, 75:25, 50:50, 25:75, and 0:100 for seven-mixture-ratio experiments. Spraying was performed by overhead trolley sprayer (Matabi 121030 Super Agro 20 litre sprayer), 8002 flat-fan nozzle at 300 kPa and a spray volume of 200 Lha-1. The plants were treated at 21 days (at the four- to six-true leaf stage) after planting. Dose-response curves were estimated by fitting a three log-logistic dose–response model against dose for ED50 and ED90 response levels. ADM was used as reference model of joint action with their equations. As the results with the herbicide mixtures originate from up to twelve separate experiments it was necessary to standardize the x- and y-axes so that the ED50, ED80 and ED90 doses of the herbicides applied separately were always fixed to 1.
Results The results showed that mixtures of chloridazon and clopyralid were less phytotoxic than predicted by ADM particularly in Amaranthus retroflexus at ED50 and ED80 response levels. These binary mixtures of herbicides were either followed ADM or less than predicted by ADM in Solanum nigrum. In contrast, mixture of desmedipham phenmedipham ethofumesate and clopyralid was synergistic in both species. Whereas desmedipham phenmedipham ethofumesate and chloridazon binary mixture was synergistic in Solanum nigrum to followed according to ADM in Amaranthus retroflexus.
The present study has revealed that mixtures of photosystem II, lipid biosynthesis and auxin inhibitor herbicides either followed ADM, or performed better than predicted by ADM, i.e. applying mixtures of these herbicides will not result in an excessive use of herbicide compared to applying the herbicides separately. In contrast, mixtures of chloridazon and clopyralid were trend antagonistic and the two herbicides should not be applied in mixture.

Farmers usually combine various herbicides with the aim of reducing the number of machinery passes across the field, preventing weed resistance to herbicides, and saving time and money. Combination of herbicides is not only recommended for the management of herbicide resistance, but for increasing efficacy compare with a single herbicide application and expanding spectrum weed control.
In order to assess the mixing herbicides that used in wheat, several experiments were conducted in the Research greenhouse and Farm of Agricultural Faculty of Ferdowsi University of Mashhad, Iran in 2013. The greenhouse experiments were arranged in a completely randomize design with a factorial arrangement of treatments with four replications. Greenhouse studies were included two combination experiments. Experiments included of 7 doses (0, 2.25, 4.5, 9, 13.5, and 18 g ai ha-1) of mesosulfuron-methyl誇梲몺 and (0, 5.6, 11.25, 22.5, 33.75, and 45 g ai ha-1) of pinoxaden (Axial 10% EC, EC; Syngenta, Switzerland) alone on wild oat (Avena ludoviciana Durieu) and littleseed canarygrass (Phalaris minor Rtez.). Wild oat seeds were sown in pots directly. Littleseed canarygrass seeds were placed in petri dishes with 9 cm diameter which contains a layer of filter paper then 6 ml of KNO3 solution (2 g L-1) was added to each petri dish. Petri dishes were kept for 10 days at 4 to 5 °C in the refrigerator in darkness condition and then transferred to a germinator with 20/10 °C temperature in 45/65% relative humidity for a 16/8 h day/night. Then, they were planted in 1L plastic pots filled with a mixture of clay, loam soil, and sand (1:1:1 v/v/v). The pots were irrigated every two days. The seedlings were thinned to 4 plants in per pot. The spray treatment was done at the three to four-leaf stage by using an overhead trolley sprayer (Matabi 121030 Super Agro 20 L sprayer; Agratech Services-Crop Spraying Equipment, Rossendale, UK), equipped with an 8002 flat fan nozzle tip delivering 200 L ha-1 at 2 bar spray pressure. Four weeks after spraying, the plants of the experimental units were harvested and oven-dried at 75°C for 48 h, then weighed. The greenhouse temperature varied from 18–25 °C during the day and 14–21°C at night. Field trial was conducted in completely randomized block design with three replications at Research Farm of Agricultural Faculty of Ferdowsi University of Mashhad, Iran in 2014. Because the appropriate ED50 obtained in the greenhouse therefor he recommended doses were used for field trial. Minitab 16.0 software was used for variance analysis and Mean comparison also for regression analysis, R software was applied.
Greenhouse experiment results showed that pure application of mesosulfuron-methyl誇梲몺 and pinoxaden herbicide was effective on wild oat and littleseed canarygrass. The results of mixing experiments on wild oat and littleseed canarygrass showed that mixture of mesosulfuron-methyl誇梲몺 with pinoxaden had additive effect of both species. ED50 of different ratios of the two herbicides showed that maximum efficacy (maximum intensity effect) in decreasing dry weight of wild oat was related to ratio 100: 0 mesosulfuron-methyl誇梲몺 and pinoxaden with ED50= 2.16 and minimum efficacy (minimum intensity effect) was related to ratio 75:25 mesosulfuron-methyl誇梲몺 and pinoxaden with ED50= 4.22. The results of the field almost were consistent with the results of the greenhouse so that the different ratios no significant difference was observed in both species of wild oat and littleseed canarygrass. All herbicide treatments resulted in at least 85.4% and 86.86% reduction biomass and population of wild oat. Except control treatments, all tank mixing ratios of mesosulfuron-methyl誇梲몺 and pinoxaden weren’t significantly different. On the other hand, jointed effects of the two herbicides on wild oat in field experiment had the same effect as when each herbicide applied separately. Also, comparisons between greenhouse and field results showed that twice condition have same response. The results of yield and yield components showed that parameters of grain yield and biological yield was significant at the 5% level.
None of herbicides had effect on others and the results of greenhouse were consistent with field experiment. It may be possible without diminished performance, these herbicides were used to postpone weed resistance in weed management.

The tomato leafminer moth (Tutaabsoluta M.) has been identified as a major pest of Solanaseous especially tomato crops. According to risks of pesticide residue and environmental damage using biological control agents, especially‌Bacillusthuringiensis is considered. In this study, the henna powder was used for enhancing effects. In this research work the interaction between bacterium and henna were assessed by using LC50 and LC25 values of both agents on different larval stages. After determining the LC50 and LC25 values of both agents, to evaluate the combined effects of bacterium and henna, an experiment was conducted in the form of completely randomized design with four treatments including LC50 (He), LC50 (Bt), LC25 (B) plus LC25 (H) and control. The result showed that in three larval stages additive effects was observed; percentage of mortality mixture of bacteria and henna treatments was increased in compare bacteria and henna alone. So that the average mortality in1st larval stage with Henna LC50, bacterial LC50 and LC25 mixture of bacteria and henna, after 24, 48 and 72 h were calculated (20, 26.67and 50), (23.33, 30 and 63.33) and (26.67, 33.33 and 66.67), in 2nd instar larvae (20, 26.67 and 56.67), (23.33, 30, 60) and (26.67, 33.33 and 63.33) and in 3rd instar larvae (20, 23.33and 56.67), (23.33, 30, 60) and (26.67, 33.33 and 63.33) percentage, respectively. Our current study indicated that the integrating B. thuringiensis with henna and other control tactics, especially with environmentally acceptable agents has opened further opportunities for their uses as integrated pest management.