Major Weed Research Articles

Determination of Critical Period of Weed-Crop Competition in Malt <i>Barley</i> (Hordeum <i>vulgare </i>L.) in North Showa Zone, Central Ethiopia

Weeds are the principal limiting biological factor in national barley production, with losses that vary from region to region, depending on the cultivation system, predominant weed communities and weed control methods employed by the farmers. Therefore, field experiment was conducted under rain fed conditions in 2017 cropping season to determine the critical period of Weed-Crop Competition in malt barely (Hordeum vulgareL.) at Debre Birhan University in North Showa Zone, Central highlands of Ethiopia. A total of eighteen treatments were laid out in a randomized complete block design (RCBD) with three replications. The treatments consisted of increasing duration of weedy and weed-free set each consisted weed competition and weed-free durations up to 20, 30, 40, 50, 60, 70, 80 and 90 days after crop emergence (DAE) were compared with two checks namely completely weedy and weed free up to harvest. The major weed families competing vigorously with barley were Compositae and Gramineae and Cyperaceae. According to the current study, the weed density and weed dry weight were decreased, whereas crop parameters like the number of days required to reach heading of barely, the number of days required to reach physiological maturity, number of seed per spike, spike length, thousand seed weight, aboveground dry biomass, grain yield and harvesting index of crop were highly increased, with increasing duration of weed-free periods. The highest yield loss due to weed competition from the weedy check treatment of barely as compared to weed free check. Uncontrolled weed growth significantly reduced barely grain yield by 70.38% compared to the grain yield obtained from the weed-free check plots. The beginning and the end of critical period of weed crop competition were based on 5 and 10 % acceptable yield loss levels, which were determined by fitting logistic and Gompertz equations to relative yield data, representing increasing duration of weed-interference and weed-free periods. In conclusion, the results of the study revealed that, to reduce the loss in the grain yield of barley by more than 10% and higher economic return, it is important to keep the crop weed-free between 33 to 49 days after crop emergence (639 to 1049 GDD) at Debre Berhan.

Characterization of a plant‐pathogenic T3SS‐lacking Xanthomonas strain isolated from common ragweed

AbstractCommon ragweed (Ambrosia artemisiifolia) is one of the leading causes of allergenic rhinitis, as well as a major weed of many crops. Biological control with plant pathogens, such as fungi and bacteria, represents an attractive alternative to the application of synthetic herbicides to control this noxious weed. In this study, we isolated a Xanthomonas strain (designated as 10‐10) from a diseased common ragweed plant collected in southern Quebec, Canada. We characterized the bioherbicidal potential of this strain against common ragweed, and determined whether it can infect other plant species. Its genome was sequenced using PacBio's SMRT technology, enabling us to gain insight into the phylogenetic placement of this strain within the genus Xanthomonas, and to study the repertoire of virulence‐associated genes and clusters. Xanthomonas sp. 10‐10 belongs to a clearly defined subclade within clade C (group 2), which includes X. vesicatoria, X. dyei and X. pisi. While this strain is closely related to X. pisi, it represents a new species within the genus Xanthomonas. Surprisingly, this strain lacks a type III secretion system, which is the main virulence determinant in pathogenic Xanthomonas spp., but harbours an arsenal of cell wall‐degrading enzymes. The addition of the organosilicone surfactant Silwet L‐77 drastically increased the disease symptoms caused by Xanthomonas sp. 10‐10 on common ragweed plants grown under controlled conditions, but the plants remained alive. This strain also caused disease symptoms on tomato, pepper and lettuce. More research is needed to develop Xanthomonas‐based bioherbicide specifically targeting common ragweed.

Weed Control and Physiological Responses in Poplar Plantations: Assessing Glyphosate’s Impact

The presence of weeds and changes in temperature and precipitation due to global climate change can negatively affect the growth, development, and adaptation of poplars to new places. Experiments were conducted at the Experimental Estate of the Institute of Lowland Forestry and Environment to test glyphosate’s efficacy and phytotoxicity and to assess the impact of glyphosate on physiological parameters in different stages of poplar plantations. A test with glyphosate was set up by a random block system with four replications at three localities, each characterized by different physical soil properties. Glyphosate efficacy was evaluated after 15 and 30 days, while phytotoxicity was evaluated according to the EWRC scale. Net photosynthesis (A), stomatal conductance (gs), transpiration rate (E), and intercellular CO2 concentration (Ci) were measured, and water use efficiency (WUE) was computed. Annual and perennial broadleaf weeds, grasses, and woody shrubs and bushes were identified. The dominant weed species across all poplar plantations were Solidago gigantea L., Solidago speciosa L., and Poa pratensis L. Glyphosate was highly effective against the major weed species, with the total efficacy ranging from 94.29 to 97.67%. The results showed significant differences in all observed gas exchange parameters, except for transpiration rate (E), between the different-aged poplar plantations. The younger poplars showed lower gas exchange rates in the treatment under the environmental conditions of the studied sites. Weed suppression resulted in altered microhabitats for poplar development at various ages, causing variation in the physiological parameters compared to the control.

Allelopathic effects of Ageratum conyzoides leaf aqueous extract on the seed germination along with seedling growth of Phaseolus vulgaris and Cicer arietinum

The agricultural productivity degradation due to toxic weed is one of the various causes of economic losses in developing countries. Ageratum conyzoides L. is major crop weed that is a threat to native flora as it competes with crops for the same resources. The current study was undertaken to investigate the allelopathic action of A. conyzoides on germination and seedling growth of Phaseolus vulgaris L. and Cicer arietinum L. Aqueous extracts of weed at various concentration (control, 10%, 20%, 30%, 50%) were obtained to assess their impacts on test crops. In this experiment, the maximum reduction in seed germination was 37% and 50% for P. vulgaris and C. arietinum respectively. The higher reduction in plumule length (3 cm) and radicle length (2 cm) of P. vulgaris and plumule length (3 cm) and radicle length (2 cm) of C. arietinum was observed at 50% concentration of weed extracts. The phytotoxicity of the A. conyzoides for both crops were increased with elevated concentration and decreased at the low concentration of weed extract. Therefore, the present results revealed that the weed phytotoxicity was concentrations depended. An appropriate weed control strategy is essential to mitigate weed impacts on crops.

Combining a field experiment and literature to model the regrowth probability of perennial storage organs fragmented by tillage: Case study of Cirsium arvense (L.) Scop

Management of perennial weeds has become increasingly difficult with the reduction of herbicide use. Creeping perennials accumulate reserves in specialized belowground organs from which they regenerate new plants after a disturbance. Through tool selection, tillage operations could be optimized to reduce perennial-weed reserves and limit regeneration. In the present study, the effect of five tools on the fragmentation of the creeping roots of Cirsium arvense (L.) Scop. (Canada thistle), a major perennial weed in arable crops, were analysed. A field trial was set up to measure the lengths of the root fragments left after tillage. Five tools were tested: mouldboard ploughing, rotary harrow, disc harrow, rigid-tine cultivator and goose-foot cultivator. Fragment-length distribution varied according to the tool: rotary harrow left the smallest (3.7 cm on average) and least variable fragment lengths, mouldboard ploughing the longest (12.7 cm) and most variable ones. The other tools produced intermediate-sized fragments (8–10 cm). Based on these results and literature, a model was proposed to predict perennial-weed regeneration probability from storage-organ fragments after one tillage run. The effects of six factors, which were agronomic (tillage tool), environmental (soil conditions and temperature) and biological (storage-organ fragment diameter, maximal belowground-shoot length and pre-tillage storage-organ distribution), were tested through a sensitivity analysis. According to the model, the probability of fragment regeneration success is lower for the rotary harrow than for the mouldboard plough. The most important drivers of fragment regeneration success were the biological traits: fragment diameter and maximal belowground-shoot length per unit fragment biomass. The present model should be complemented to predict the effect of tillage on perennial-weed regrowth and help improving non-chemical weed-management strategies. To achieve this, further research is needed on plant regrowth potential from storage organs and their architecture in the soil.

Evaluation of Herbicides Efficacy against Weeds in Coffee (<i>Coffea arabica </i>L.) at Jimma Southwest, Ethiopia

Weeds are one of the most serious causes of economic losses in agricultural production. As a result weed completions contributes 60 to 80% yield losses in coffee under Jimma condition. Currently, expensiveness of weed management has been a principle issue in economic analysis of coffee production particularly in large scale farm in Ethiopia. Hence, evaluation of systemic herbicide with different mode of action is essential to effectively control dangerous weeds in coffee production system. The study was conducted in Jimma Agricultural Research Center in 2021 cropping season at Jimma Agricultural Research Center on Station to evaluate the efficacy of newly introduced herbicides (Fascinate 280SL at 3.3l/h, Jimila 480% SL at 3.0l/h and Proper 360 SL at 3.0l/ha) against major weeds in coffee. Tested herbicides (Fascinate 280SL, Jimila 480% SL and Proper 360 SL) were effectively controlled the noxious weeds infested coffee experimental plots. These herbicides also showed significant effect on inhibiting weed density over standard check. The herbicide were effective in controlling weeds in coffee safe for crops if applied at active growth stage of weeds following the instructions on technical guide line of herbicides properly. Therefore, the herbicides were recommended used as management option against weeds in coffee with the application rate mentioned above

Genetic diversity analysis of tropical and sub-tropical maize germplasm for Striga resistance and agronomic traits with SNP markers.

Striga hermonthica (Sh) and S. asiatica (Sa) are major parasitic weeds limiting cereal crop production and productivity in sub-Saharan Africa (SSA). Under severe infestation, Striga causes yield losses of up to 100%. Breeding for Striga-resistant maize varieties is the most effective and economical approach to controlling the parasite. Well-characterized and genetically differentiated maize germplasm is vital to developing inbred lines, hybrids, and synthetic varieties with Striga resistance and desirable product profiles. The objective of this study was to determine the genetic diversity of 130 tropical and sub-tropical maize inbred lines, hybrids, and open-pollinated varieties germplasm using phenotypic traits and single nucleotide polymorphism (SNP) markers to select Striga-resistant and complementary genotypes for breeding. The test genotypes were phenotyped with Sh and Sa infestations using a 13x10 alpha lattice design with two replications. Agro-morphological traits and Striga-resistance damage parameters were recorded under a controlled environment. Further, high-density Diversity Array Technology Sequencing-derived SNP markers were used to profile the test genotypes. Significant phenotypic differences (P<0.001) were detected among the assessed genotypes for the assessed traits. The SNP markers revealed mean gene diversity and polymorphic information content of 0.34 and 0.44, respectively, supporting the phenotypic variation of the test genotypes. Higher significant variation was recorded within populations (85%) than between populations using the analysis of molecular variance. The Structure analysis allocated the test genotypes into eight major clusters (K = 8) in concordance with the principal coordinate analysis (PCoA). The following genetically distant inbred lines were selected, displaying good agronomic performance and Sa and Sh resistance: CML540, TZISTR25, TZISTR1248, CLHP0303, TZISTR1174, TZSTRI113, TZDEEI50, TZSTRI115, CML539, TZISTR1015, CZL99017, CML451, CML566, CLHP0343 and CML440. Genetically diverse and complementary lines were selected among the tropical and sub-tropical maize populations that will facilitate the breeding of maize varieties with Striga resistance and market-preferred traits.

Research on Weed Reverse Detection Methods Based on Improved You Only Look Once (YOLO) v8: Preliminary Results

The rapid and accurate detection of weeds is the prerequisite and foundation for precision weeding, automation, and intelligent field operations. Due to the wide variety of weeds in the field and their significant morphological differences, most existing detection methods can only recognize major crops and weeds, with a pressing need to enhance accuracy. This study introduces a novel weed detection approach that integrates the GFPN (Green Feature Pyramid Network), Slide Loss, and multi-SEAM (Spatial and Enhancement Attention Modules) to enhance accuracy and improve efficiency. This approach recognizes crop seedlings utilizing an improved YOLO v8 algorithm, followed by the reverse detection of weeds through graphics processing technology. The experimental results demonstrated that the improved YOLO v8 model achieved remarkable performance, with an accuracy of 92.9%, a recall rate of 87.0%, and an F1 score of 90%. The detection speed was approximately 22.47 ms per image. And when shooting from a height ranging from 80 cm to 100 cm in the field test, the crop detection effect was the best. This reverse weed detection method addresses the challenges posed by weed diversity and complexities in image recognition modeling, thereby contributing to the enhancement of automated and intelligent weeding efficiency and quality. It also provides valuable technical support for precision weeding in farmland operations.

Allelopathic Effects of Sugarcane Leaves: Optimal Extraction Solvent, Partial Separation of Allelopathic Active Fractions, and Herbicidal Activities.

The inhibitory potential of allelopathic plants is the subject of increasing research attention for their application in weed management. The sugarcane leaf is an agricultural waste product that has been reported to have allelopathic potential. Therefore, the present study determined the optimal organic solvent system and fractionation procedure to enhance the quantity of this extract and its allelopathic efficiency. Sugarcane leaves were extracted using five ethanol/water solvent ratios (v/v): 00:100, 25:75, 50:50, 75:25, and 100:00. Their allelopathic effects on seed germination and seedling growth were assayed in two major weeds, Echinochloa crus-galli (L.) Beauv. and Amaranthus viridis L. The results showed that the extract concentration, solvent ratio, and their interaction significantly inhibited the growth parameters in A. viridis. Consequently, a crude ethanol/water ratio of 00:100 was used to separate the active fraction via acid-base solvent partitioning. The acidic fraction (AE) exerted the greatest inhibitory effect and completely (100%) inhibited A. viridis at all concentrations, followed by the original crude fraction, neutral fraction, and aqueous fraction. Moreover, all of the fractions had selective effects, inhibiting A. viridis much more than E. crus-galli in the laboratory tests. The chemical analysis using gas chromatography/mass spectrometry indicated that the AE fraction contained 20 different compounds. The five major compounds included alkaloids, organic acids, and phenols. Therefore, the AE fraction was selected for formulation in a concentrated suspension and tested for its herbicidal characteristics. The formulation exhibited early post-emergence activities and had a stronger effect on A. viridis compared to E. crus-galli. The physiological mechanism of the formulation was tested against A. viridis. The thiobarbituric acid reactive substances and H2O2 occurred in the A. viridis leaf, which suggests lipid peroxidation and cell disruption.

Do rotation and fertilization practices shape weed communities and affect rice yield in low input rainfed agroecosystems in the Malagasy highlands?

Weeds are a major threat in tropical regions where climate conditions favor their growth and development. This is particularly true in low-input rice-based cropping systems in the Malagasy highlands, where weed management is mainly done by manual removal. Crop rotation is often promoted as an efficient way to control weed infestations, while the role of fertilization is more controversial. In this study, we compared rice monoculture to three rainfed rice-based two-year rotations: rice followed by groundnut, rice followed by sorghum-cowpea mixture, and rice followed by a velvet-bean crotalaria mixture. Each rotation was tested with two levels of fertilization (5 t DM ha−1 organic manure, sole or in combination with mineral fertilizer - 400 kg ha−1 NPK + 200 kg ha−1 urea). We assessed the effect of rotation and fertilization on weed composition, diversity, biomass and rice yield. Additionally, the farmers’ perception of weed harmfulness and the relation between their assessment of weed harmfulness and rice production was tested. Our results showed that weed biomass significantly decreased rice yield but only under the low fertilization level. The rotation of rice with the velvet bean-crotalaria mixture was efficient in reducing weed biomass, modified weed community composition and allowed to achieve the highest rice yield. A significant negative relationship was found between weed community harmfulness index and weed species richness. Yet, the lowest rice yield was observed under rice monoculture despite a higher species richness over years and under high fertilization level. The lack of significant correlation between the harmfulness index and the actual rice yield is probably because our index is partly based on farmer’s perception, and only on major weeds. More studies on tropical weed harmfulness are needed to support the design of ecologically intensified cropping systems.

First report of target‐site resistance to glyphosate in Amaranthus hybridus L. in the Republic of South Africa

AbstractAmaranthus hybridus L. is a major weed for summer crops. Although A. hybridus has been a known crop weed in the Republic of South Africa (RSA) for a long time, herbicide resistance has not been a problem. Nevertheless, A. hybridus populations from KwaZulu Natal (KZN) Province have caught the attention of farmers since glyphosate has been progressively becoming less effective in controlling the species. This study aimed to evaluate herbicide resistance in A. hybridus and the underlying mechanisms of resistance. Seeds from 50 glyphosate‐resistant plants were collected from fields at Bergville and Winterton in KZN and compared with a susceptible population from Hendrina (Mpumalanga Province). Glasshouse screening was conducted where glyphosate (Roundup® PowerMax) was applied at 6‐leaf stage, at doses 0, 540, 1080 (recommended dose), 2160 and 4320 g ae ha−1. Surviving plants were sampled for molecular analysis to establish any target site mutations in the EPSPS gene that confer glyphosate resistance. Dose–response assay indicated 100% control in the Hendrina population, variation in the control of the Winterton population and 100% survival in the Bergville population. Molecular analysis indicated a rare triple mutation (TAP‐IVS) in the KZN populations. This kind of mutation endows a high level of glyphosate resistance, which explains why these populations survived even the 4× dose. These findings confirmed the first cases of glyphosate‐resistant A. hybridus and established the mechanism of resistance as target site mutations in the EPSPS gene reported in the RSA. These findings will serve as a base for other herbicide resistance cases and the development of initiatives to control and minimize the spread of this weed in the RSA.

Phylogenomics-driven host test list selection for weed biological control

A concern in weed biological control research is the potential for candidate biocontrol agents to impact not only the target weed but also native or economically important flora. The degree of evolutionary relatedness between the target weed species and a non-target species is a key predictor of the susceptibility of the non-target to the biocontrol agent. To manage this risk, biocontrol practitioners need to understand the phylogenetic position of the host weed relative to non-target plant species. However, comprehensively sampled phylogenetic trees are often unavailable, with incomplete information scattered across multiple publications. Further, older published phylogenies based on Sanger sequence data often lack branch resolution and support, which increases uncertainty in biocontrol decision making. Decreasing sequencing cost and technological advances have led to phylogenomic approaches being more widely used to understand evolutionary relationships between species. For example, target capture sequencing methods using bait kits such as Angiosperms353 enable cost-effective and timely phylogenomic-level analysis of flowering plant groups at different scales. Here, we introduce a workflow to embed a comprehensive understanding of evolutionary relationships into the efficient development of host test lists in weed biological control. We demonstrate the effectiveness of the workflow through a case study on the major crop weed flaxleaf fleabane (Erigeron bonariensis). Phylogenomic analysis was conducted on 280 species of the tribe Astereae (family Asteraceae) occurring in Australia and New Zealand, clarifying relationships between the target species and related clades of native and non-native Astereae. We consider the phylogenetic tree in the context of a previously proposed host test list and discuss taxonomic implications, highlighting avenues of future molecular-based work to uncover the origin of Australian fleabanes. This study provides a workflow and demonstrates the practical application of target sequence capture for phylogenomic inference to support risk analysis and decision making in classical weed biological control.

Introgression of early shoot vigour in wheat modifies root systems, increases competitiveness and provides options for integrated weed management

Abstract Background and aims Weeds are a major biotic stressor impacting crop production. Improving the competitiveness of wheat (Triticum aestivum L.) could provide a useful tool in integrated weed management. While wheat typically exhibits conservative early growth, early vigour has been increased through long-term recurrent selection for greater early biomass and leaf area. However, the influence of integrating such vigour into breeding lines for improving competitive ability remains to be explored. Methods In replicated controlled environment experiments, the effect of breeding early shoot vigour on root development and below-ground competitiveness was carefully examined. Physical and chemical characteristics of wheat vigour lines were assessed and compared with commercial cultivars in hydroponics and field soil experiments. Measurements included early root growth, rhizosheath size and growth responses in the presence of annual ryegrass, a major weed in wheat production. Results The vigorous lines exhibited larger leaf widths, increased cell file number, increased total root length and larger rhizosheaths compared with commercial parents. Numerous secondary metabolites with known allelopathic effects on weeds were detected in the roots and the rhizosphere, and significant allelochemical level differences observed between distilled water and soil water extract-treated plants. Although the vigour lines were significantly more competitive than the commercial cultivars against ryegrass, they produced similar levels of phytotoxic secondary metabolites. Conclusion Competition below-ground was strongly suppressive of ryegrass for the more vigorous genotypes suggesting that breeding with shoot vigour had pleiotropic effects on key root traits for below-ground wheat competitiveness.

Integrated Weed Management in Turmeric (Curcuma longa)

The experiment was conducted at Regional Spices Research Centre, BARI, Magura during the cropping season of 2021-22 and 2022-23 to find out the best management practices for controlling the weed of turmeric. The experiment was laid out in a randomized complete block design with three replications. Nine different treatments and a control plot were studied. Significant differences regarding yield and yield attributes were observed among different treatments. The results revealed that Cyperus rotundus was the major weed constituting 51% of the total weed flora. All treatments brought significant reduction in the count of weeds over control. The lowest number of these weeds was recorded in glyphosate @ 10 ml/L+ 1 HW at 70 DAP + straw mulch @ 5 t/ha treated plot. The highest fresh yield (64.63 t/ha in 2021-22 and 58.28 t/ha in 2022-23) was found from treatment T5 (glyphosate @ 10 ml/L+ 1 HW at 70 DAP + straw mulch @ 5 t/ha) and the lowest yield (20.16 kg/ha in 2021-22 and 20.07 in 2022-23) was found from control plot T10. Maximum weed control efficiency (91.97%) was found from treatment T5 (glyphosate @ 10 ml/L+ 1 HW at 70 DAP + straw mulch @ 5 t/ha). Benefit cost ratio (BCR) was highest under glyphosate @ 10 ml/L+ 1 HW at 70 DAP + straw mulch @ 5 t/ha (3.75) followed by T6 (Paraquat @ 10 ml/L+ 1 HW (70 DAP) + straw mulch 5 t/ha (3.33).

Application and Effects of Different Herbicides against Weed Flora in Wheat Crop for Sustainable Agriculture

Weed management is a sustainable approach which promotes the majority of crop production. To control weeds in various cropping systems, farmers employ a variety of techniques, although nowadays, the most popular method is the application of herbicides, which can be attributed to labour shortage. Application and effects of different herbicides against weed flora in wheat crop for sustainable agriculture," was conducted in 2020 and 2021. The experiment's goal was to assess how many herbicides performed against complex weed flora in wheat crop. The experiment was planned and laid out with nine treatments which are pre-emergance application of pendinethalin 1.0 kg a.i. ha-1 at (3 DAS) (T2) and post emergence application of metribuzin 0.3 kg a.i. ha-1 (T1), sulfosulfuron 0.03 kg a.i. ha-1 (T3), metsulfuron-methyl 0.005 kg a.i. ha-1 (T4), clodinafop-propargyl 0.04 kg a.i. ha-1 kg (T5), 2,4-D 0.6 kg a.i. ha-1 (T6), carfentrazone-ethyl 0.025 kg a.i. ha-1 (T7), weed free (T8) and weedy check (T9) and four replications under randomized block design. The major weeds infesting the wheat crop field were Anagallis arvensis, Chenopodium album, Phalaris minor, Parthenium hysterophorus and Cyperus rotundus. The post-emergence application of carfentrazone-ethyl 0.025 kg a i/ha at 33 days after sowing was most efficient in controlling the weeds (both grassy and non-grassy) among the various applied herbicides. Weed growth suppression effect of carfentrazone-ethyl 0.025 resulted significant increase the growth parameters, yield attributes and higher economic yield of wheat over check control in order to promote the sustainability.

Weed seedbank as influenced by tillage and herbicide in direct seeded rice‐mustard cropping sequence in lateritic soil of eastern India

AbstractThe above‐ground community dynamics of weeds represent the soil weed seedbank in an agro‐ecosystem. Hence, understanding the seedbank will offer an idea for future weed management tactics. We aimed to determine the density of weed seedbank and emergence of major weeds in direct seeded rice (DSR) (Oryza sativa L.)—mustard (Brassica campestris L. var. yellow sarson) cropping sequence under varied tillage and herbicide combinations. The present study on weed seedbank was conducted using seedling emergence method after collecting the soils at the harvest of mustard at the completion of 2 years field experimentation. The experiment was conducted in split‐plot design with two tillage practices [zero tillage (ZT) and conventional tillage (CT)] in main plot and eight weed management practices in DSR [oxadiargyl followed by (fb) bispyribac‐sodium, penoxsulam + cyhalofop‐butyl, oxadiargyl fb penoxsulam + cyhalofop‐butyl, fenoxaprop‐p‐ethyl + ethoxysulfuron, oxadiargyl fb fenoxaprop‐p‐ethyl + ethoxysulfuron, pendimethalin fb bispyribac‐sodium, unweeded control, and weed free check] as subplot. The carry‐over effect of tillage and weed management practices were recorded in mustard crop. Seed emergence study revealed that ZT reduced the emergence of grassy weeds (by 13.7%) and total weed emergence (19.5%) in comparison to the CT (p &lt; 0.05). However, emergence of broadleaf weeds was 24.5% higher in ZT than in CT. The higher infestation was recorded for Ludwigia parviflora (Jacq.) Raven under penoxsulam + cyhalofop‐butyl, fenoxaprop‐p‐ethyl + ethoxysulfuron, Cyperus iria (L.) under fenoxaprop‐p‐ethyl + ethoxysulfuron, and Eleusine indica (L.) Gaertn. under pendimethalin fb bispyribac‐sodium, oxadiargyl fb bispyribac‐sodium. Sole application of post‐emergence (POE) herbicide decreased the total weed emergence by 22.2%–28.1% than unweeded control (p &lt; 0.05). Whereas, sequential application of PRE + POE herbicides decreased the total weed emergence by 32.8%–36.9% than unweeded control (p &lt; 0.05). Notably, sedge weeds such as Cyperus iria (L.) and Fimbristylis miliacea (L.) Vahl were lower in ZT than in CT under herbicide treated plots (by 66.6%–84.3%) than unweeded control. Thus, ZT with oxadiargyl 90 g a.i. ha−1 fb fenoxaprop‐p‐ethyl + ethoxysulfuron (90 + 15 g a.i. ha−1) as tank‐mix can be effectively used to lower the weed seedbank density vis‐à‐vis managing complex weed flora in DSR and rice‐mustard cropping sequence.

Unraveling the influence of environmental factors on fireweed (Senecio madagascariensis) germination and its management implications

AbstractFireweed (Senecio madagascariensis Poir.) has invaded and colonized numerous habitats in the coastal areas of southeastern Australia and is a major weed in cultivated lands as well as in poorly grassed, neglected, and highly grazed pastures. To examine the seed germination ecology of two populations (Felton and Gatton) of S. madagascariensis, experiments were conducted in the laboratory and screen house. The germination of both populations increased as the alternating temperatures increased from the coolest temperatures (15/5 C) to warmer temperatures (25/15 C). However, the highest temperature regime (35/25 C) resulted in the lowest germination rates. The Gatton population exhibited greater tolerance to higher temperatures, resulting in significantly higher germination (2.4 times) than the Felton population at the highest alternating temperature of 35/25 C. Compared with the Felton population, the Gatton population demonstrated higher tolerance to salt and water stress. In comparison to alternating light and dark periods (12 h each) (97% to 98%), the germination of both populations of S. madagascariensis was significantly reduced under complete darkness (24 h) (33% to 39%). A screen house seed burial depth experiment revealed similar emergence of S. madagascariensis seedlings between the populations. The maximum emergence (60%) was observed for seeds placed at the soil surface, followed by a dramatic decline in seedling emergence with an increase in depth. No seedlings emerged from a burial depth of 4 cm. With the addition of wheat (Triticum aestivum L.) crop residue to the soil surface at rates comparable to 4,000 to 8,000 kg ha−1, seedling emergence of S. madagascariensis decreased significantly. Information acquired from this study could be utilized to manage and develop effective weed management strategies for controlling S. madagascariensis in different agroecological conditions.

Efficacy of pyroxasulfone and its combinations against weeds in wheat (Triticum aestivum)

A field experiment was conducted during the winter (rabi) season of 2021–22 at the research farm of Jawaharlal Nehru Krishi Vishwa Vidyalaya, Jabalpur, Madhya Pradesh to study the efficacy of pre-emergence herbicides against weeds in wheat (Triticum aestivum L.). The experiment was laid out in a randomized block design with 3 replications and 8 weed control treatments. Major weed flora in the experimental site, viz. Medicago polymorpha (L.) (28.97%) and Cichorium intybus (L.) (26.19%) were predominant in dicot weeds and in monocot weeds, Phalaris minor (17.82%) was dominant. The weedy check plot had the higher density and dry weight of weeds. Hand weeding (once) was done at 25 DAS (day after sowing) in wheat, reducing weeds density and dry weight to the maximum extent at 40 DAS with a weed control efficiency (WCE) of 92.8%, proving superiority over other treatments. Among the herbicidal applications, pyroxasulfone + metribuzin at 127.5 + 280 g a.i./ha significantly reduced the monocot and dicot weeds density and dry weight, followed by pendimethalin + pyroxasulfone at 1250 + 127.5 g a.i./ha. Pyroxasulfone + metribuzin at 127.5 + 280 g a.i./ha resulted in maximum values of growth parameters, viz. plant height (66.38 cm), number of tillers/m2 (403.14) and yield attributing characters, viz. grains per earhead (51.00) and grain yield (5.65 t/ha) as compared to other herbicidal treatments.

Weed science research achievements on maize in Ethiopia: a review

Recent research into assessing and combatting maize weeds was reviewed based on scientific and working reports from the year 2011 onwards in Ethiopia. This review paper covered two main topics: assessment of major weed types and their impacts, and research results of weed management in the maize cropping system of the country. More than 80 major weed floras dominated by broad leaved weeds were found infesting maize fields in different localities. By competing, toxifying and/or parasitizing maize plants, they reduce the crop germination, growth and productivity. Several experiments indicated that maize yield loss due to uncontrolled weed growth varied from 35 to 87.5%, indicating that weed management is a critical factor for maize production in the country. Hoeing, hand weeding and pre-emergence herbicides application have been the most frequently used weed control practices to minimize the competition effect of weeds. So far, there has been no effective and sustainable individual weed control method for maize fields. Thus, future research should focus on developing integrated weed management that effectively reduce weed infestation and associated impacts, and improve productivity of the crop considering socio-economic condition of a specific maize producing agro-ecology of the country.

Distribution of Mosaic Disease in Ridge Gourd (Luffa acutangula (L.) Roxb.), Characterization of Associated Virus and Screening for Virus Resistance

Aims: A survey was conducted in the ridge gourd growing areas of Kasaragod, Kannur and Kozhikkode district, India, to assess the prevalence of virus diseases. Molecular detection and characterization indicated the presence of mixed infection of Tomato leaf curl New Delhi virus (ToLCNDV) and Cucumber mosaic virus (CMV) in infected samples of ridge gourd collected from surveyed locations. Additionally, a screening of popular varieties/hybrids was undertaken to identify resistance sources against the Begomovirus in Ridge gourd.&#x0D; Study Design: CRD design for screening for resistance genotype.&#x0D; Place and Duration of Study: Department of Plant Pathology, College of Agriculture, Padannakkad. November 2022 - 2023.&#x0D; Methodology: Twenty-five ridge gourd plants were selected from a field and scored during survey. Major weeds and insects in and around the location were collected and identified. Screening for resistance was carried out in vitro by grafting infected scion on to healthy ridge gourd plants. Begomovirus infections were confirmed by polymerase chain reaction (PCR) using specific coat protein primers. Presence of CMV was detected using specific primers.&#x0D; Results: Disease incidence (DI) of surveyed locations ranged from 5.3-100 per cent and vulnerability index (VI) from 26.57-84.08. Kunjathur, Thalangady, and Hosabettu areas of Kasaragod district recorded the highest incidence (100%). The highest VI (84.08) was recorded in Thalangady (Kasaragod). Bemisia tabaci and Aphis gossypii were the associated insects and Synedrella sp., Ageratum conizoides and Alternanthera sp. were the associated weeds.&#x0D; Screening of varieties indicated moderately susceptible reactions of RG7 and RG10 after 60 days of grafting. PCR based molecular detection of ToLCNDV using coat protein specific primers yielded amplicons of approximately 575 bp. All the isolated sequences were found to be related to ToLCNDV on sequencing and blast analysis. Phylogenetic studies revealed that isolates from Thrikaripur, Mavichery, and Poolacode were closely related to each other. Cucumber mosaic virus, a RNA virus was also detected from isolated samples using specific primers of CMV with an amplicon size of 400 bp.&#x0D; Conclusion: The study revealed that the ridge gourd cultivated in areas of Kasaragod, Kannur and Kozhikode were infected with ToLCNDV and CMV; RG7 and RG10 were moderately susceptible among the varieties and hybrids screened. The presence of the begomovirus was detected in weeds indicating its role in perpetuation and spread of the virus disease in the field.