Effective Weed Control Research Articles

Evaluation of Autonomous Mowers Weed Control Effect in Globe Artichoke Field

The development of a fully automated robotic weeder is currently hindered by the lack of a reliable technique for weed-crop detection. Autonomous mowers moving with random trajectories rely on simplified computational resources and have shown potential when applied for agricultural purposes. This study aimed to evaluate the applicability of these autonomous mowers for weed control in globe artichoke. A first trial consisting of the comparison of the performances of three different autonomous mowers (AM1, AM2 and AM3) was carried out evaluating percentage of area mowed and primary energy consumption. The most suitable autonomous mower was tested for its weed control effect and compared with a conventional weed management system. Average weeds height, weed cover percentage, above-ground weed biomass, artichoke yield, primary energy consumption and cost were assessed. All the autonomous mowers achieved a percentage of area mowed around the 80% after 180 min. AM2 was chosen as the best compromise for weed control in the artichoke field (83.83% of area mowed after 180 min of mowing, and a consumption of 430.50 kWh⋅ha−1⋅year−1). The autonomous mower weed management achieved a higher weed control effect (weed biomass of 71.76 vs. 143.67 g d.m.⋅m−2), a lower energy consumption (430.5 vs. 1135.13 kWh⋅ha−1⋅year−1), and a lower cost (EUR 2601.84 vs. EUR 3661.80 ha−1·year−1) compared to the conventional system.

Growth Response to Weed Control and Fertilisation in Mid-Rotation Plantations of Eucalyptus pellita in South Sumatra, Indonesia

We report on a study of mid-rotation weed control and nutrient management in Eucalyptus pellita plantations in South Sumatra. The study was established at two contrasting sites (representing high and low productivity for the region) that had previously carried three rotations of Acacia mangium. A combination of weed control, nitrogen (N), and phosphorus (P) fertiliser were applied at 1 and 2 years after establishment. We found that the addition of up to 250 kg N ha−1 applied either at 1 year or 2 years after planting did not improve growth. The application of P (30 kg P ha−1) at age 1 year (in addition to 12 kg P ha−1 applied at planting) did not enhance tree growth either. Keeping the plantation free from weed competition throughout rotation (full weed control) enhanced wood volume up to age 4 years at the high-productivity site, while it improved wood volume up to the end of rotation at age 6 years at the low-productivity site. An additional experiment assessing the effect of weed control in the early phase of plantation establishment revealed that weed competition reduced young tree growth of E. pellita substantially. The results of the studies support the current practice of plantation management of E. pellita in the region that applied only P fertiliser at planting time and that kept trees free from weed competition before canopy closure. Full weed control throughout rotation is worth practicing at lower-productivity sites to achieve maximum productivity.

Effect of integrated weed management on turmeric under mid hill conditions of Himachal Pradesh

A field experiment was carried out on silty clay loam soil, acidic in reaction, high in available phosphorus, medium in available potassium and low in available N during kharif 2017 at the Research Farm of Department of Agronomy, CSKHPKV, Palampur to study effective weed control strategy for this important crop. The results revealed that Alternanthera philoxeroides was the major weed constituting 16% of the total weed flora. This was followed by Cynodon dactylon and Echinochloa colona with 14 and 12% of total weed population, respectively. The count of Echinochloa colona, Alternanthera philoxeroides, Commelina benghalensis, Digitaria sanguinalis and Ageratum conyzoides was maximum at 120 DAP and there after it gradually decreased. All herbicide treatments brought significant reduction in the count on Echinochloa, Alternanthera and Ageratum over weedy check. The lowest count of these weeds was recorded in metribuzin fb straw mulch fb hand weeding and the maximum count was in case of weedy check. All the weed control treatments significantly reduced the total weed count and dry weight of weeds as compared to the weedy check. Amongst different herbicide treatments application of metribuzin @ 0.70 kg/ha fb straw mulch fb hand weeding resulted in significantly lowest weed count at all stages of observation as well as at harvest though this treatment was at par with metribuzin @ 0.70 kg/ha fb two hand weedings and treatments in which atrazine 0.75 kg/ha and hand weedings were applied with or without the use of straw mulch resulted in significantly lower dry matter accumulation by weeds as compared to other herbicide treatments. Weed index calculated at 120 DAP was highest with use of metribuzin @ 0.70 kg/ha and atrazine @ 0.75 kg/ha used along with straw mulch and one or two hand weedings proving effective as compared to other herbicides tested. From the present study it seems that mulching must be included in any effective weed management strategy for turmeric. Also among different herbicides metribuzin and atrazine are effective and their integration with mulching and/or hand weeding gave good control of weeds in turmeric.

Carfentrazone Plus Pyroxasulfone Combinations for Weed Control in Peanut (Arachis hypogaea L.)

Aims: To determine peanut response and weed control following the use of carfentrazone plus pyroxasulfone (C + P).
 Study Design: Randomized complete block design with 3-4 reps depending on location.
 Place and Duration of Study: Studies were conducted during the 2015 and 2016 growing seasons in south Texas near Yoakum (29.276o N, 97.123o W), the High Plains of Texas near Lamesa (32.769o N, 101.977o W) or Brownfield (33.104o N, 102.161o W), and southwestern Oklahoma near Ft. Cobb (35.091o N, 98.275o W).
 Methodology: Plots were infested with naturally occurring weed populations. Pendimethalin was applied either preplant incorporated (PPI) or preemergence (PRE). Early postemergence (EPOST) applications varied according to weather conditions and peanut growth at each location. Postemergence (POST) treatments were applied 26 to 58 days after planting. Weed control and peanut stunting were visually estimated on a scale of 0 to 100 (0 indicating no control or plant death and 100 indicating complete control or plant death).
 Results: Peanut stunting with C + P was only noted at the High Plains and Oklahoma locations in 2015 but not 2016. Urochloa texana (Buckl.) control with C + P (PRE) varied from 75 to 93%. POST applications provided inconsistent control. Amaranthus palmeri S. Wats. control with C + P (PRE) was at least 78% season-long while POST applications were inconsistent (24 to 100%). Pendimethalin plus C + P controlled Cucumis melo L. var. Dudaim Naud. at least 80% late-season. Ipomoea hederacea Jacq. control was excellent season-long (> 80%) in 2015 but poor (< 60%) in 2016. Reduced peanut yields were noted with C + P in Oklahoma in 2015 to excessive season-long injury. 
 Conclusion: The premix of C + P has potential for use in peanut especially for control of many small-seeded annual broadleaf weeds that continue to plague many peanut growers across the southwest. For effective broad-spectrum annual weed control season-long, the addition of pendimethalin to PRE applications will be required.

Seed predation is key to preventing population growth of the weed Alopecurus myosuroides

Abstract Seed predation can reduce the abundance and spread of unwanted vegetation in agricultural and other semi‐natural ecosystems. However, knowledge of how variations in seed predation rates affect plant species population dynamics is needed for decision making and knowledge‐based ecosystem management. We developed a stage‐classified stochastic matrix population model for Alopecurus myosuroides Huds. (blackgrass), an annual plant species thriving as a weed in temperate agroecosystems of Western and Northern Europe. The model was parameterised using empirical demographic data from long‐term experiments in Swedish winter wheat fields, including information on post‐dispersal seed losses by vertebrate and invertebrate seed predators. For agroecosystems with highly effective weed control measures (e.g. chemical and mechanical weed control), model simulations showed that seed losses via seed predation need to reach at least 78% at peak seed shedding to suppress population growth of A. myosuroides. The field experiment showed that vertebrates were most important for seed predation in July, at peak seed shedding. In August, after crop harvest, invertebrates were responsible for almost all seed predation. The model indicated that weed seed predation was much more important for weed regulation when it occurred before crop harvest in July. Vertebrates most strongly reduced population growth of A. myosuroides, although both vertebrates and invertebrates were needed to prevent it entirely. Synthesis and applications. We showed that weed seed predation by vertebrate and invertebrate seed predators is key for reducing the population growth of winter annual weeds like A. myosuroides in intensively managed agroecosystems. Therefore, protection of weed seed predators is essential for making management of unwanted vegetation less dependent on chemical and mechanical measures.

Comparison of the effects of ammonium nonanoate and an essential oil herbicide on weed control efficacy and water use efficiency of pumpkin

AbstractWeed management is one of the major challenges responsible for growers’ reluctance to switch from conventional to organic vegetable production. Competition from uncontrolled weeds can significantly reduce the yield and water use efficiency (WUE) of vegetable crops. A field study was conducted during the summers of 2019 and 2020 at the Quaker Research Farm of Texas Tech University, in Lubbock, TX, to determine physiology, plant growth, yield, soil water depletion pattern, and WUE of pumpkin as affected by five weed control treatments: 1) ammonium nonanoate 5% ai, 2) ammonium nonanoate 6% ai, 3) clove oil + cinnamon oil 4.5% ai, 4) clove oil + cinnamon oil 9% ai, and 5) an untreated control. Each plot received the same herbicide treatment at 20 and 30 d after planting (DAP). The experiment was conducted in a randomized complete block design with four replications of each treatment. Both herbicides resulted in significant weed suppression compared to the untreated control and weed control was 88% to 98% with ammonium nonanoate and 39% to 69% with clove oil + cinnamon oil. Photosynthesis rate, stomatal conductance, shoot dry biomass, average fruit weight, total fruit yield, and WUE of pumpkin were significantly higher in plants that were treated with ammonium nonanoate compared to the untreated control. All the aforementioned parameters were not significantly different between clove oil + cinnamon oil and the untreated control. Use of higher active ingredient concentration did not improve the performance of either herbicide. Soil water depletion and evapotranspiration were comparable among all the treatments. Based on the results, ammonium nonanoate at its lower concentration could be an option for effective weed control, and for improving fruit yield and WUE of pumpkin.

Efficacy of Various Mechanical Weeding Methods—Single and in Combination—In Terms of Different Field Conditions and Weed Densities

Public awareness and environmental policies have increased interest in applying non-herbicide weed control methods in conventional farming systems. Even though mechanical weed control has been used for centuries in agricultural practice, continuous developments—both in terms of implements and automation technologies—are continuously improving the potential outcomes. Current mechanical weed control methods were evaluated for their weed control efficacy and effects on yield potential against their equivalent herbicide methods. Furthermore, not much is known about the correlation between weed control efficacy (WCE) of different mechanical methods at varying weed density levels. A total of six experiments in winter wheat (2), peas (2), and soybean (2) were carried out in the years 2018, 2019, and 2020 in southwestern Germany. Harrowing and hoeing treatments at different speeds were carried out and compared to the herbicide treatments and untreated control plots. Regarding the average WCE, the combination of harrowing and hoeing was both the strongest (82%) and the most stable (74–100%) mechanical treatment in the different weed density levels. Whereas, in average, hoeing (72%) and harrowing (71%) were on the same WCE level, but harrowing (49–82%) was more stable than hoeing (40–99%). The grain yields in winter wheat varied between 4.1 Mg∙ha−1 (control) and 6.3 Mg∙ha−1 (harrow), in pea between 2.8 Mg∙ha−1 (hoe slow) and 5.7 Mg∙ha−1 (hoe fast) and in soybean between 1.7 Mg∙ha−1 (control) and 4 Mg∙ha−1 (herbicide). However, there were no significant differences in most cases. The results have shown that it is not possible to pinpoint a specific type of treatment as the most appropriate method for this cultivation, across all of the different circumstances. Different field and weather conditions can heavily affect and impact the expected outcome, giving, each time, an advantage for a specific type of treatment.

The phytotoxicity mechanism of florpyrauxifen-benzyl to Echinochloa crus-galli (L.) P. Beauv and weed control effect

Weeds infest rice causing high yield losses, leading to the increasing use of herbicides for weed control. However, many weeds have evolved resistance to common commercial herbicides, including penoxsulam, metamifop and quinclorac. This study investigated the weed control effect and the phytotoxicity mechanism of florpyrauxifen-benzyl, a novel synthetic auxin herbicide registered for weed management in rice fields in China. The greenhouse study showed that florpyrauxifen-benzyl was highly efficient (GR50 < 6 and GR90 < 15 g a.i ha−1) at controlling 10 weed species commonly found in rice fields, including penoxsulam- and quinclorac- resistant(R) biotypes of Echinochloa Beauv. and bensulfuron-methyl-R biotype of Ammannia arenaria. The typical plant hormone content showed that following florpyrauxifen-benzyl treatment, indole-3-acetic acid (IAA) production changed only slightly at 12 h, while abscisic acid (ABA) production increased with time in the treated group, whose content was significantly higher than that of the control. Besides, ethylene biosynthesis was stimulated by florpyrauxifen-benzyl, ethylene production, 1-aminocyclopropane-1-carboxylic acid (ACC) content, and 1-aminocyclopropane-1-carboxylate synthase (ACS) and 1-aminocyclopropane-1-carboxylate oxidase (ACO) activities, which evidently increased in the treated group, and ethylene peaked at 36 h. For the antioxidant enzyme activities and malondialdehyde (MDA) content in the treated group, results showed that MDA content continuously increased with time and was greater than that in the untreated group at 48 h and 72 h, superoxide dismutase (SOD) activity changed with exposure time and was significantly higher in the treatment group than the control at 48 h. A similar phenomenon was observed in peroxidase (POD) activity, which reached a peak at 48 h, and no distinct difference in catalase (CAT) activity was observed among groups except for the higher activity in the treated groups than control at 36 h and 48 h. Our results showed that that the stimulation ethylene biosynthesis and accumulation of ABA and reactive oxygen species (ROS) play important roles in the phytotoxicity mechanism of florpyrauxifen-benzyl in plants. Our findings demonstrate the potential of florpyrauxifen-benzyl to provide an alternative weed management strategy for rice fields.

REVIEW ON HERBICIDES RESISTANCE AND THEIR MODE OF ACTION

Herbicides play a vital role in the reduction of crop yield losses by the use of effective weed control and weed interference capability, their ability to improving soil conservation practices. This review covering herbicide's resistance to specific weed and the mode of action of herbicides in the crops of agronomic fields. In most countries, input-intensive agriculture is adopted. For a better understanding, it is necessary to know about the mode of action of herbicides, management, organization, classification, and weed control capacity of herbicides. On other conditions, it also contributes insight into herbicide resistance; therefore it is a big problem of sustainable agricultural management. However, more use of herbicides, pesticides, and insecticides cause resistance among the weeds and it causing injury in plants and also removes beneficial plants in agricultural fields, industries, and management of lands. This review mainly focuses on the thorough determination of different modes of action of different classes of herbicides. The mechanism of action of various herbicides is as variable as their complex composition as they concentrate on managing the susceptible weeds utilizing different biochemical means. Herbicides based on their specific mode of action, they may involve plant enzymes or a biological system. However, these herbicides may break up thus injury or disturb the uniform plant growth and development, the result affects uneven plant death. For proper weed control, it is essential to know the mode of action of specific herbicides and it is important to choose specific herbicides for a specific crop, also understood the symptoms of injury, and using proper crop management practices.

Chemical management of Cyperus rotundus L. and other weeds at sugarcane in PSS system

Among the main weeds with difficult to control in the sugarcane fields can be cited purple nutsedge (Cyperus rotundus L.). This specie was observed in the seed bank in sugarcane fields harvested with or without burning. The objective of this study was to evaluate the efficacy of herbicides in pre-sprouted seedlings (PSS) of sugarcane in the control of C. rotundus and other weeds. The work was carried out in the field, in a randomized complete block design, and four replications. The treatments corresponded to the herbicides applied in pre-planting: sulfentrazone (800 g a.i. ha-1), diclosulam (193.17 g a.i. ha-1), imazapic (133 g a.i. ha-1) and imazapyr (500 g a.e. ha-1); post-planting: halosulfuron (112.5 g a.i. ha-1), ethoxysulfuron (135 g a.i. ha-1), MSMA (1,975 g a.i. ha-1) and 2,4-D (1,340 g a.e. ha-1); besides a control treatment weeding and another without weeding. The symptoms of injury on sugarcane plants, percentage of weed control, variables related to agronomic performance of sugarcane, and yield were evaluated. The herbicides diclosulam, imazapic, and imazapyr caused serious damage to the crop. The halosulfuron, ethoxysulfuron, MSMA, and 2,4-D did not cause symptoms of injury to sugarcane, however, the treatments had a reduced yield due to the low weed control. The sulfentrazone treatment obtained the second highest yield but with effective weed control (&gt;70%) up to 45 days after planting. The best controls were obtained with pre-planting treatments; however, herbicide positioning studies should be performed in relation to PSS.

Classification of weed seeds based on visual images and deep learning

Weeds are mainly spread by weed seeds being mixed with agricultural and forestry crop seeds, grain, animal hair, and other plant products, and disturb the growing environment of target plants such as crops and wild native plants. The accurate and efficient classification of weed seeds is important for the effective management and control of weeds. However, classification remains mainly dependent on destructive sampling-based manual inspection, which has a high cost and rather low flux. We considered that this problem could be solved using a nondestructive intelligent image recognition method. First, on the basis of the establishment of the image acquisition system for weed seeds, images of single weed seeds were rapidly and completely segmented, and a total of 47 696 samples of 140 species of weed seeds and foreign materials remained. Then, six popular and novel deep Convolutional Neural Network (CNN) models are compared to identify the best method for intelligently identifying 140 species of weed seeds. Of these samples, 33 600 samples are randomly selected as the training dataset for model training, and the remaining 14 096 samples are used as the testing dataset for model testing. AlexNet and GoogLeNet emerged from the quantitative evaluation as the best methods. AlexNet has strong classification accuracy and efficiency (low time consumption), and GoogLeNet has the best classification accuracy. A suitable CNN model for weed seed classification could be selected according to specific identification accuracy requirements and time costs of applications. This research is beneficial for developing a detection system for weed seeds in various applications. The resolution of taxonomic issues and problems associated with the identification of these weed seeds may allow for more effective management and control.

Validation of Different Post-Emergence Herbicides for Controlling Wild Oat (Avena fatua L.) and Other Grass Weeds in Wheat (Triticum spp) at Western Oromia

A field experiment on weed control in wheat was conducted at Bako Agriculture Research center during the main season of 2017. Different herbicides were evaluated against the hand weeding and weedy check, for weed competition and grain yield of wheat. The experiment was laid out in randomized complete block design with three replications using the wheat variety “Danda’a” with a seed rate of 150 kg ha-1. The treatments consisted of four post-emergence herbicide; Pallas™ 45 OD, Puma super EW 75, Current 8 EC and Axial, and including Hand weeding and unwedded check for comparison. Significantly lowest weed population (10.7m 2 ) and maximum grain yield of 3306.4 kg ha-1 (with 48.4% increase in grain yield over weedy check) were recorded in the plot pallas was treated in contrary the highest weed population and low grain yield was recorded in weedy check were 54.1 weeds m -2 and 1692.1 kg ha -1 , respectively. Therefore, pallas 45 OD provided significant control of weeds causing significant reduction in density of target weed flora and also significantly improved the grain yield in comparison with other herbicides and weedy check. Hand weeded treatments fetched highest gross income and added income followed by hand weeding and current treatments. However, maximum CBR was calculated for Pallas followed current. The CBR calculated in the hand weeded treatments was though the lowest. pallas therefore recommended for effective weed control as post emergence herbicide respectively for wheat economic yield in western Ethiopia . DOI: 10.7176/JNSR/12-19-01 Publication date: October 31 st 2021

Hot foam and hot water for weed control: A comparison

Thermal weed control plays an important role in managing weeds in synthetic herbicide-free systems, particularly in organic agriculture and in urban areas where synthetic herbicides are prohibited. This study compares the impact on weed control of increased doses of hot water and hot foam (i.e. 0, 0.67, 1.67, 3.33, 5.00, 6.67 and 8.33 kg m–2). The doses were applied using the same machine. The temperatures, weed control effectiveness, weed regrowth after the death of the aboveground vegetative weed tissues, and weed dry biomass 30 days after the treatments were studied in two experimental fields with a different weed composition (i.e. Site I and Site II). The results showed that difficult weeds to control, such as Cynodon dactylon (L.) Pers., Digitaria sanguinalis (L.) Scop. and Taraxacum officinale Weber, like all the other species in the initial weed populations in the two experiments, died after lower doses of hot foam compared to hot water. Adding foam to hot water made it possible to lower the required dose of water by at least 2.5-fold compared to hot water used alone. By insulating the weeds, the foam led to higher peak temperatures and slower temperature decay, thus determining an effective weed control with lower doses compared to hot water. Starting from 11 days and 16 days after treatments (for Site I and Site II, respectively), there were no statistically significant differences in weed regrowth between hot foam and hot water at all the doses applied. There were no differences between the dry biomass of weeds collected 30 days after treatments when the same doses of hot foam and hot water were used.

OPTIMIZATION OF TECHNOLOGICAL METHODS OF CULTIVATION OF WINTER BARLEY IN CONDITIONS EXPERIMENTAL FIELD WNAU

The spread of areas under crops of winter barley is associated with great national economic importance, since its products include malt, feed grain, hay and are used in the food industry. The main reasons for the production of an insufficient amount of winter barley grain is a violation of cultivation technologies. Among the main ones are the untimely use of means of protection or the absence of these measures to regulate the number of harmful organisms in crops of winter barley to an economically imperceptible level. Violation of the scientific foundations of agriculture and changes in weather and climatic conditions led to an increase in the development of diseases, the number of weeds in winter barley crops. During seed dressing with modern highly effective dressing agents, conditions are created under which winter barley plants better tolerate stress, improve the development of their root system, which is important for plants in preparation for winter entry. The infestation of winter barley fields is accompanied by the appearance of both early and late crops, a certain periodicity of the appearance of weeds of different biological groups. Accordingly, in different conditions and in different fields, the weed structure can differ significantly. Therefore, the development of highly effective systems for protecting winter barley crops from weeds largely depends on the completeness of the study of phytocenoses and the species composition of weeds. The introduction of herbicides on crops of winter barley contributed to a sharp decrease in weeds. Dicotyledonous weeds were almost completely destroyed, in the agrocenoses of winter barley, mainly cereal weeds remained, but they did not pose a threat to barley plants. Control of barley and weed plant diseases in agrocenoses provides an increase in crop yields, as well as an improvement in grain quality. To obtain the planned level of grain yield of winter barley of appropriate quality, it is recommended before sowing barley seeds to treat with a disinfectant Scenik 80 FS at a rate of 1,5 l/ha, and for effective weed control in winter barley crops, spray with herbicide Caliber 75 c. g. + South Africa Trend 90 at a rate of 50 g/ha + 0,2 l/ha, which helps reduce weeds to 96,5% and will allow to obtain a grain yield of winter barley at 6,24 t/ha.

Diminishing weed control exacerbates maize yield loss to adverse weather.

Both weed interference and adverse weather can cause significant maize yield losses. However, most climate change projections on maize yields ignore the fact that weeds are widespread in maize production. Herein, we examine the effects of weed control and weather variability on maize yield loss due to weeds by using machine learning techniques on an expansive database of herbicide efficacy trials spanning 205 weather environments and 27 years. Late‐season control of all weed species was the most important driver of maize yield loss due to weeds according to multiple analyses. Average yield losses of 50% were observed with little to no weed control. Furthermore, when the highest levels of weed control were not achieved, drier, hotter conditions just before and during silking exacerbated maize yield losses due to weeds. Current climate predictions suggest much of the US maize‐growing regions will experience warmer, drier summers. This, coupled with the growing prevalence of herbicide resistance, increases the risk of maize yield loss due to weeds in the future without transformational change in weed management systems.

Characterisation of a 4A QTL for Metribuzin Resistance in Wheat by Developing Near-Isogenic Lines.

Wheat (Triticum aestivum L.) production is constantly affected by weeds in the farming system. Chemical-based weed management is widely practiced; broad-spectrum herbicides such as metribuzin have been successfully used to control weeds in Australia and elsewhere of the world. Breeding metribuzin-resistant wheat through genetic improvement is needed for effective control of weeds. Quantitative trait loci (QTLs) mapping efforts identified a major QTL on wheat chromosome 4A, explaining up to 20% of the phenotypic variance for metribuzin resistance. The quantitative nature of inheritance of this QTL signifies the importance of near-isogenic lines (NILs), which can convert a quantitative trait into a Mendelian factor for better resolution of the QTL. In the current study, NILs were developed using a heterogeneous inbred family method combined with a fast generation-cycling system in a population of Chuan Mai 25 (resistant) and Ritchie (susceptible). Seven pairs of NILs targeting the 4A QTL for metribuzin resistance were confirmed with a molecular marker and phenotyping. The resistant allele from the resistant parent increased metribuzin resistance by 63–85% (average 69%) compared with the susceptible allele from the susceptible parent. Segregation analysis in the NIL pairs for thousand grain weight (TGW) (g), biomass per plant (kg), tillers per plant, plant height (cm), yield per plant, and powdery mildew visual score (0–9) indicated that these traits were linked with metribuzin resistance. Similarly, TGW was observed to co-segregate with metribuzin resistance in most confirmed NILs, signifying that the two traits are controlled by closely linked genes. The most contrasting NILs can be further characterised by transcriptomic and proteomic analyses to identify the candidate genes responsible for metribuzin resistance.

Effects of Various Environmental Conditions on the Growth of Amaranthus patulus Bertol. and Changes of Herbicide Efficacy Caused by Increasing Temperatures

Understanding the effects of climate change on weed growth and herbicide activity is important for optimizing herbicide applications for effective weed control in the future. Therefore, this study examined how climate change affects the growth of Amaranthus patulus and the efficacy of soil and foliar herbicides at different temperatures. Although the control values for A. patulus differed between herbicides and temperature, the control values increased with increasing time after the herbicide treatments. Under growth conditions in which the temperature remained constant, the efficacy of soil-applied herbicides, ethalfluralin, metolachlor, linuron, and alachlor, on A. patulus was highest when the weeds were grown at high temperature. In particular, 100% control values of A. patulus were achieved in response to metolachlor treatments at the total recommended dosage in growth chambers at 35 °C. The efficacy of foliar herbicides, glufosinate-ammonium, bentazone, and mecoprop, on A. patulus was also highest when the plant was grown at high temperature, except for glyphosate isopropylamine, which had similar efficacy rates regardless of the temperature. A. patulus was 100% controlled in response to glufosinate-ammonium, bentazone, and mecoprop at the recommended dosages in growth chambers at 30 and 35 °C. Under growth conditions in which the temperature changed from day to night, the efficacy of soil-applied herbicides, alachlor and linuron, on A. patulus was highest when the weeds were grown at high temperature. On the other hand, the efficacy of the soil-applied herbicides metolachlor and linuron on A. patulus was similar regardless of the temperature. The efficacy of foliar herbicides, glyphosate isopropylamine, glufosinate-ammonium, bentazone, and mecoprop, on A. patulus was highest when the weeds were grown at high temperature. Although herbicide efficacy varied depending on whether the weeds were grown at constant or alternating temperatures, herbicide efficacy was generally highest when the temperature was high.

Severity of Associated Weeds in Rabi Crops and their Control Measures Perceived by Farmers

Purpose: The study was conducted to identify the associated weeds of Rabi (winter) crops and their control measures used by the farmers at Dumuria and Batiaghata upazila in Khulna district of Bangladesh. Research Method: Data were collected from purposively selected 73 respondents using structured interview conducted from 4 January to 20 April, 2019. Findings: In the study area, Echinochloa crussgalli and Cynodon dactylon were found as dominant within rice fields with the highest severity index of 25.34% and 20.54% respectively. In sesame fields, Cucumis melo var. agrestis and Cynodon dactylon were found with 16.78% and 12.33% severity index respectively. The severity index of Cynodon dactylon was the highest in majority of the vegetable crops. The weeding of rice, potato, bitter gourd, spinach, country bean was done within the critical weeding regime but in the rest of the crops weeding was not done during the critical weeding regime. Originality/value: Farmers spend about 40% of the total production cost on weed control and the critical weeding regime has a major impact on effectiveness of weed control, overall economic benefit and net income.

Post‐sowing weed control technique can affect woody seedling numbers, with early hand‐weeding potentially more beneficial than early spraying

SummaryDirect seeding is increasingly being used as a cost‐effective revegetation technique. Successful outcomes from direct seeding rely on effective weed control, particularly during the vulnerable seedling establishment phase. Post‐sowing weed control options are constrained by the need to protect seedlings from damage and few studies have compared the effectiveness of different weed control techniques. We evaluated the effect of preliminary hand weeding (with subsequent spraying), spraying monthly or spraying quarterly with glyphosate, on woody seedling emergence, survival and growth in trials sown either in spring or autumn at a riparian site in Victoria, southeastern Australia. Seedling numbers were recorded monthly for 6 months and at 12 months after sowing, with seedling survival and heights assessed at 12 months. Total seedling numbers were higher in subplots initially hand weeded than in subplots sprayed on either a monthly or quarterly basis, regardless of when direct seeding occurred, but weed control treatment had no effect on seedling survival. These results indicate that post‐sowing spraying limited rates of seedling emergence, either directly or indirectly. For direct seeding, hand weeding in the first few months after sowing may maximise rates of woody seedling emergence, while spraying with glyphosate may inhibit seedling emergence.

Effects of plastic film mulching on soil quality, growth of Angelica sinensis, and weed occurrence in cold and humid areas

We analyzed the growth dynamic and bolting rate of Angelica sinensis, soil quality and enzyme activities and weed density and control effect in a field experiment under different mulching patterns, to provide theoretical basis for the application of plastic film in genuine producing area of A. sinensis. The planting patterns were conducted as hole seeding under ridging with plastic-film mulching (LS), trenching and slant planting under film-side cultivation (MC) and trenching and slant planting in open field (LD). Our results showed that, 1) compared with LD, soil organic matter content in top layer under the treatments of LS and MC was increased by 4.4% and 14.3%, respectively, with that under MC being statistically significant. Soil bulk density was significantly decreased by 11.6% and 8.5%, while pH was significantly decreased by 4.6% and 1.7%. The activities of soil sucrase, phosphatase and urease were significantly increased by the two mulching methods, but that of catalase was inhibited to a certain extent. 2) Mulching film improved the speed of returning green after transplanting, the early bolting rate, and the individual medicinal quality of A. sinensis. MC showed the fastest, the most uniform, and the highest greening rate. LS bolting rate was the highest, and the fresh mass of MC and LS was significantly increased by 20.4% and 58.4%, respectively. 3) Weed density under the treatment of MC and LS was significantly reduced by 34.0% and 25.8%. Compared with LS, MC significantly increased the control effect of plant and fresh mass by 21.7% and 63.4%, respectively. In conclusion, film cultivation methods could improve the environment for root growth, reduce weed density, improve weed control effect, and promote growth process and substance accumulation, but could promote the bolting of A. sinensis in early phase.