Weed Diversity Research Articles

Inventory of Potential Weeds Under Stands of Immature Nutmeg Plants in Allang Country, West Leihitu District Central Maluku Regency

Weeds are plants whose presence is undesirable because it can reduce production. The composition and diversity of weeds also determines the structure of the planting area which will ultimately affect the ecological function. The presence of weeds can be found in all planting areas. This research was carried out in Negeri Allang, Central Maluku Regency in March 2022. This research aimed to inventory the types of weeds under nutmeg plantations. The data collection process in the field was carried out using the quadratic method with sample plots measuring 1 m x 1 m and placed under immature nutmeg plantations. Observation of weeds was carried out destructively, namely the types of weeds in the sample plots were removed to calculate the individual and the biomass of each type.The results of the study found 16 types of weeds in the nutmeg planting area of immature stages. Commelina diffusa (Burm). F. weed type SDR 17.79%. is the dominant weed in the nutmeg plantation area of immature stages.

Effect of Fertilization and Weed Management Practices on Weed Diversity and Hemp Agronomic Performance

The industrial hemp market is rapidly expanding, and best crop practices need to be assessed. This study aimed to determine the effect of fertilization and weed management on hemp crops and weed flora during the 2019 and 2020 growing seasons. Field experiments were laid out in a split–split plot design with three replicates: two hemp cultivars as main plots, three fertilization treatments as sub-plots, and three sub-sub-plots (weedy, weed-free, and herbicide application). For the computation of crop traits, 10 plants were randomly selected by each plot. Weed species were collected by quadrate for density and biomass weight determination. Increased fertilization rate positively affected plant height and dry biomass, while no impact was recorded on yield and yield components. The density and biomass of nitrophilous weeds were enhanced by fertilization, negatively affecting hemp growth. Marked differences were recorded on the competitive ability of cultivars since “Fedora 17” decreased the weed studied traits better than “Uso 31”. Herbicide application decreased the biomass of annual and perennial weeds by 38% and 13%, respectively, while it caused a reduction in hemp growth and yield of “Uso 31” plants. Further research should be conducted to address hemp yield losses under different cultural practices and weed control systems.

In-depth study of tomato and weed viromes reveals undiscovered plant virus diversity in an agroecosystem

BackgroundIn agroecosystems, viruses are well known to influence crop health and some cause phytosanitary and economic problems, but their diversity in non-crop plants and role outside the disease perspective is less known. Extensive virome explorations that include both crop and diverse weed plants are therefore needed to better understand roles of viruses in agroecosystems. Such unbiased exploration is available through viromics, which could generate biological and ecological insights from immense high-throughput sequencing (HTS) data.ResultsHere, we implemented HTS-based viromics to explore viral diversity in tomatoes and weeds in farming areas at a nation-wide scale. We detected 125 viruses, including 79 novel species, wherein 65 were found exclusively in weeds. This spanned 21 higher-level plant virus taxa dominated by Potyviridae, Rhabdoviridae, and Tombusviridae, and four non-plant virus families. We detected viruses of non-plant hosts and viroid-like sequences and demonstrated infectivity of a novel tobamovirus in plants of Solanaceae family. Diversities of predominant tomato viruses were variable, in some cases, comparable to that of global isolates of the same species. We phylogenetically classified novel viruses and showed links between a subgroup of phylogenetically related rhabdoviruses to their taxonomically related host plants. Ten classified viruses detected in tomatoes were also detected in weeds, which might indicate possible role of weeds as their reservoirs and that these viruses could be exchanged between the two compartments.ConclusionsWe showed that even in relatively well studied agroecosystems, such as tomato farms, a large part of very diverse plant viromes can still be unknown and is mostly present in understudied non-crop plants. The overlapping presence of viruses in tomatoes and weeds implicate possible presence of virus reservoir and possible exchange between the weed and crop compartments, which may influence weed management decisions. The observed variability and widespread presence of predominant tomato viruses and the infectivity of a novel tobamovirus in solanaceous plants, provided foundation for further investigation of virus disease dynamics and their effect on tomato health. The extensive insights we generated from such in-depth agroecosystem virome exploration will be valuable in anticipating possible emergences of plant virus diseases and would serve as baseline for further post-discovery characterization studies.5s1csuTeBEFLkorHCziRqaVideo

Biological Control of Weeds in turfgrass: opportunities and misconceptions.

Turfgrass systems may offer opportunities for overcoming some constraints on the successful implementation of weed biocontrol. Of the roughly 16.4million ha of turfgrass in the USA, ≈60-75% are in residential lawns and 3% are golf turf. Annual expenditures for a standard herbicide treatment regimen for residential turf are estimated to be ≈US$326 ha-1 , about 2-3-fold greater than that for USA corn and soybean growers. Expenditures can be >US$3000 ha-1 for control of certain weeds such as Poa annua in high-value areas including golf fairways or greens, but those applications are made to far smaller areas. Regulatory actions and consumer preferences are creating market opportunities for alternatives to synthetic herbicides in both commercial and consumer markets, but the size of these markets and willingness-to-pay are poorly documented. Turfgrass sites are intensively managed, yet despite the ability to modify site conditions through irrigation, mowing and fertility management, microbial biocontrol agents tested thus far have not provided the consistently high levels of weed control expected in the market. Recent advances in microbial bioherbicide products may offer a path to overcome many of the obstacles to success. No single herbicide will control the diversity of turfgrass weeds, nor will any single biocontrol agent or biopesticide. Successful development of weed biocontrol for turfgrass systems will require numerous, effective biocontrol agents for the many weed species found in turfgrass environments, as well as a deeper understanding of different turfgrass market segments, and weed management expectations for each segment. © 2023 The Author. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Alley cropping agroforestry systems change weed community composition and reduce dominant weed species associated with corn in southern Mexico

Alley cropping systems can change the weed community composition and reduce common weed species. However, it is unclear how different woody species intercalated with corn can affect weed abundance and community structure and corn yield in the tropics. The present study examined weed species diversity and community composition in alley cropping systems with three woody species associated with corn: Leucaena leucocephala (Lam.) de Wit, Guazuma ulmifolia Lam., and Moringa oleifera Lam. independently, and corn monoculture, as a control. The tree most dominant weed species were Ruellia nudiflora (Engelm. & A. Gray) Urb., Cynodon dactylon (L.) Pers., and Portulaca pilosa L. Our results showed that the alley cropping system compared with corn monoculture reduced the densities of common abundant weed species, changed weed community composition, maintained or increased plant diversity, but did not affect grain yield (t/h). Based on the sample completeness profile we found that Leucaena associated with corn had a higher weed diversity of order q = 1 and 2 (Shannon and Simpson index) and showed higher evenness compared with corn monoculture, which showed the lowest evenness of all treatments. We found nine weed species that only grow in alley cropping systems and Waltheria americana L., Momordica charantia L. and Porophyllum punctatum (Mill) S.F. Blake. with higher densities. Our findings support the hypothesis that alley cropping systems not only changes weed community composition, but also favours biodiversity conservation without reducing corn yield.

Phenology and Diversity of Weeds in the Agriculture and Horticulture Cropping Systems of Indian Western Himalayas: Understanding Implications for Agro-Ecosystems.

Weeds are a major threat to agriculture and horticulture cropping systems that reduce yield. Weeds have a better ability to compete for resources compared to the main crops of various agro-ecosystems and act as a major impediment in reducing overall yield. They often act as energy drains in the managed agroecosystems. We studied weed infestation for five different agro-ecosystems in the part of Indian Western Himalayas represented by paddy, maize, mustard, apple and vegetable orchards. Systematic random sampling was done to record flowering phenology and diversity of weeds during the assessment period 2015-2020. We recorded 59 weed species, taxonomically distributed among 50 genera in 24 families. The Asteraceae family has the most species (15% species), followed by Poaceae (14% species), and Brassicaceae (12% species). The Therophytes were the dominant life form followed by Hemicryptophytes. The majority of the weeds were shown to be at their most blooming in the summer (predominantly from June to July). The Shannon index based diversity of weeds ranged from 2.307-3.325 for the different agro-ecosystems. The highest number of weeds was in the horticulture systems (apple > vegetable) followed by agriculture fields (maize > paddy > mustard). Agriculture and horticulture cropping systems were distinguished using indicator species analysis, which was supported by high and significant indicator values for a number of species. Persicaria hydropiper, Cynodon dactylon, Poa annua, Stellaria media, and Rorippa palustris had the highest indicator value in agriculture cropping systems, while Trifolium repens, Phleum pratense, and Trifolium pratense had the highest indicator value in horticulture cropping systems. We found that eleven weed species were unique to apple gardens followed by nine in maize, four in vegetables, two in mustard and one in paddy fields. Spatial turnover (βsim) and nestedness-resultant components (βsne) of species dissimilarity revealed dissimilarity lower than 50% among the five cropping systems. The study is expected to assist in formulating an appropriate management strategy for the control of weed infestation in the study region.

Neighbourhood effect of weeds on wheat root endospheric mycobiota

Abstract Micro‐organisms associated with plants provide essential functions to their hosts, and therefore affect ecosystem productivity. Agricultural intensification has modified microbial diversity in the soil reservoir and may affect plant–microbial recruitment. Weeds develop spontaneously in crop fields, and could influence micro‐organisms associated with crop plants through a neighbourhood effect. We explore the effect of weed species on crop plant microbiota as potentially auxiliary plants that affect agricultural productivity. We combined field and controlled laboratory studies to analyse the neighbourhood effect of weeds on wheat root endospheric mycobiota (i.e. fungi within roots) and growth. First, we analysed the effect of weed species diversity and identity recorded in the neighbourhood of individual wheat plants on soil and wheat root mycobiota in the field. Second, we used a plant‐matrix design in laboratory conditions to test the effect of weed identity (nine weed treatments) and their ability to transmit root mycobiota to wheat roots, and the resulting impact on wheat growth. In contrast to soil mycobiota, we demonstrated that wheat root endospheric mycobiota was influenced by the diversity and identity of weeds developing in their 1 m2 neighbourhood. Wheat root endospheric microbiota strongly differs in terms of richness and composition depending on the neighbouring weed plant species. Weed species transmitted from 13% to 74% of their root microbiota to wheat roots depending on weed identity in controlled conditions. Synthesis. Weed neighbours modified wheat plant performance, possibly as a result of competitive interactions and changes in microbiota. Our findings suggest that crop root mycobiota was variable and was modulated by their weed neighbourhood. Synergistic effects between mycobiota of crops and weeds could therefore contribute to soil biodiversity and sustainable agriculture.

Weed Dynamics in Acid Saline Pokkali Ecosystem of Kerala

Background: Pokkali is a versatile rice- fish system of cultivation, producing naturally organic rice along the waterlogged coastal regions of Kerala. The weed flora of Pokkali rice fields is different from other rice ecosystems. Diverse weed flora appears in low saline phase, when rice is cultivated, but they dry up and decompose in high saline phase. With time, significant deviations have been reported in various climatic parameters and as a result, the weed spectrum has also undergone changes. Methods: Two level stratified surveys and anotomical studies were conducted during Kharif 2017 and 2018 to study the weed flora in five major Pokkali growing blocks of Kerala. Two panchayaths (political village units) from each block and two padasekharams (group farming units) in each panchayath were selected for surveying. To understand the adaptive mechanism of weeds in saline soil condition, anatomical studies were performed on individual weed species. Result: Cyperaceae family dominated in the ecosystem with more number of species. Diplachne fusca and Eleocharis dulcis were the major weeds. Echinochloa crus-galli, a dominant weed reported in earlier weed survey was found confined to very few locations and the frequency got reduced from 80% to 12.5%. In addition, Sphenoclea zeylanica was observed as an emerging weed with notable morphological adaptations. Floating ferns like Najas graminea and Hydrilla verticillata caused problems to aeration in the water in fields.

Integrated omic techniques and their genomic features for invasive weeds.

Many emerging invasive weeds display rapid adaptation against different stressful environments compared to their natives. Rapid adaptation and dispersal habits helped invasive populations have strong diversity within the population compared to their natives. Advances in molecular marker techniques may lead to an in-depth understanding of the genetic diversity of invasive weeds. The use of molecular techniques is rapidly growing, and their implications in invasive weed studies are considered powerful tools for genome purposes. Here, we review different approach used multi-omics by invasive weed studies to understand the functional structural and genomic changes in these species under different environmental fluctuations, particularly, to check the accessibility of advance-sequencing techniques used by researchers in genome sequence projects. In this review-based study, we also examine the importance and efficiency of different molecular techniques in identifying and characterizing different genes, associated markers, proteins, metabolites, and key metabolic pathways in invasive and native weeds. Use of these techniques could help weed scientists to further reduce the knowledge gaps in understanding invasive weeds traits. Although these techniques can provide robust insights about the molecular functioning, employing a single omics platform can rarely elucidate the gene-level regulation and the associated real-time expression of weedy traits due to the complex and overlapping nature of biological interactions. We conclude that different multi-omic techniques will provide long-term benefits in launching new genome projects to enhance the understanding of invasive weeds' invasion process.

Weed control in maize with herbicides and its effect on grain yield

Competition posed by weeds is a major challenge in crop production as weeds cause severe reduction in yield by competing with crop plants for limited resources like light, space applied nutrients and water also. Several researchers and eminent investigators observed that diverse weed flora causes huge losses in maize yield and if the weeds are not managed at right time then it results in huge yield penalty. Among weed management treatments, hand weeding at 15-21 days after sowing and 30-42 days after sowing and integration of pre-emergence application of atrazine 1.5 kg ha-1, pendimethalin at 1.50 kg ha-1, pendimethalin + atrazine both at 0.5 kg ha-1 as pre-emergence spray, atrazine + alachlor at 0.75 + 1.25 kg ha-1, or alachlor at 1.5 kg ha-1fb hand weeding at 30 days after sowing and tembotrione 125 g ha-1+surfactant applied on 20 DAS were proved more effective. In case of sequential treatments, pre-emergence application of atrazine at 1.25 kg ha-1 or pendimethalin at 1.5 kg ha-1 fbparaquat at 0.6 kg ha-1at 3 weeks after sowing or pre-emergence application of atrazine at 1.0 kg ha-1 followed by topramazone at 0.030 kg ha-1 at 30 days after sowing gave higher gross returns, net returns and benefit cost ratio, thus proved more economical.

Effect of Bt traits on transgenic rice’s growth and weed competitiveness

Transgene escape could lead to genetically modified rice establishing wild populations in the natural environment and competing for survival space with weeds. However, whether the expression of the Bacillus thuringiensis (Bt) gene in rice will alter the relationship between transgene plants and weeds and induce undesirable environmental consequences are poorly understood. Thus, field experiments were conducted to investigate the weed competitiveness and assess the ecological risk of transgenic Bt rice under herbicide-free and lepidopterous pest-controlled environments. Results showed that weed–rice competition in the direct-sowing (DS) field was earlier and more severe than that in the transplanting (TP) field, which resulted in a significant decrease in biomass and yield in DS. However, conventional Bt and non-Bt rice yield was not significantly different. The weed number, weed coverage ratio, and weed diversity of conventional Bt rice were significantly higher than those of non-Bt rice at the early growth and mature stages, especially in DS plots, suggesting that Bt traits did not increase the weed competitiveness of transgenic rice and had no negative effect on weed diversity. Grain yield and weed number varied between different hybrid rice lines, but those differences were insignificant between Bt and non-Bt rice. The number of insects increased with the increase of weeds in hybrid rice plots, whereas the insect number and diversity did not display a significant difference between Bt and non-Bt rice. Therefore, the ecological risk of transgenic Bt rice is comparable to non-Bt rice.

Weed community dynamics under repeated fertilization with different nutrient sources over 5 years

Soil fertility management through the application of synthetic fertilizer or livestock manures is crucial to maintaining the productivity and profitability of cropping systems. Little, however, is known about the response of weed communities to different livestock manure nutrient sources. As weed communities with increased diversity are considered part of more sustainable agroecosystems, it is necessary to find management practices that result in diverse weed communities of acceptable densities without negative impacts on crop productivity. Here, we monitored the effect of five nutrient sources, with similar goals for nitrogen (N) management, including synthetic fertilizer, liquid pig manure, two types of solid pig manure, and solid dairy manure on the weed community in a five-year (2008-2012) study. The abundance, species richness, Simpson’s diversity, Simpson’s evenness, and species turnover in weed communities were assessed over time. Crop biomass, mid-season plant-accessible soil nitrate-N, and pre-season soil phosphorus were determined. The application of liquid pig manure or synthetic fertilizer enhanced crop biomass likely through increased crop accessibility to N. The continued use of these sources of nutrients over time, contributed to low density, low species richness, and low diversity weed communities, particularly through the decline of broadleaf weed species. Liquid pig manure and synthetic fertilizer treatments were lower in weed density and diversity than solid manures. Solid manure treatments were associated with increased weed densities and reduced crop biomass; however, these nutrient source treatments resulted in more diverse weed communities. Regardless of the nutrient treatments, we observed drastic declines in weed community abundance, species richness, and diversity in drier years. Our study suggests that a management practice that increases the accessibility of N to the crop, possibly through a mixture of solid manures and synthetic fertilizers or liquid pig manure, may be ideal for promoting a profitable cropping system with decreased densities and improved diversity in weed communities. Technological advances that provide more precise placement of solid manures to increase the accessibility of N to the crop, may further contribute to achieving such profitable and multifunctional agroecosystems.

Effect of herbicides on weed dynamics, soil fertility, energetics and productivity of upland rice in an acidic subtropical soil of the Eastern Himalayas, India

ABSTRACT Weed management in upland rice under subtropical climate with high rainfall is challenging. The diverse weed flora in upland rice ecosystem emerges in several flushes, necessitating sequential application of herbicides. A 4-year study conducted in Meghalaya (950 m above sea level), India indicated that sequential application of Cyhalofop butyl [2-{4-(4-cyano-2-fluorophenoxy) phenoxy} propionic acid, butyl ester (R)], a grass weed killer high efficacy low volume herbicide applied 80 g ha−1 at 25 days after sowing (DAS) and 2,4-D, a broadleaf weed killer herbicide applied 0.75 kg ha−1 at 35 DAS was effective for weed control and produced significantly higher grain yield (3572 kg ha−1) of rice with the highest weed control efficiencies than other treatments. Application of Pretilachlor followed by (fb) 2,4-D or Fenoxaprop-p-ethyl fb 2,4-D yielded significantly higher chlrophyll (chl) a, chl b and total leaf chl content compared with other herbicides at 90 DAS. The highest net energy (111,443 MJ ha−1), energy profitability and benefit:cost ratio was recorded with sequential application of Cyhalofop butyl and 2,4-D. Thus, sequential application of Cyhalofop butyl and 2,4-D could provide a sustainable weed management option in upland rice under high rainfall conditions in the Eastern Himalayas, India.

Diversity Of Weeds in Rose Field in District Kasur Punjab Pakistan

In Kasur district an experiment was conducted from 2020 to 2022 in rose field to check the presence of Weed Flora. To conduct this study, 12 locations were chosen, comprising Punjabi Saoda, Kachapacca, Sheikhum, Ghahlan, Jagowala, Pattoki Bypass and Nurseries, Changa Manga, Pattoki railway StationPadhana, Chunia, Nizampura. Five fields from each of the 12 locations were chosen for investigation. A quadrate measuring one metre square was used for testing. A binocular stereo scope was used to examine both macro and micro morphological traits. This study has revealed that most prevalent families of weeds are Poaceae and Asteraceae. This study has significant value for the development of rose industry for the welfare of country economy. This study has shown that the most prevalent of the weed family: Brassicaceae and the most widespread weed is belonged to Brassicaceaefamily.This study have great significant value to develop rose industry. While collecting the data, the researchers encountered numerous challenges that might have affected the study's findings. Since most peasants were uneducated, it was incredibly challenging for them to properly communicate with researchers.

Species composition of rare weeds in the south of the Far East

The results of monitoring (2016–2022) of the weed component of agrophytocenoses in the Primorsky Territory of the Russian Federation are presented. The species affiliation of rare weeds was determined, the average occurrence of which in soybeans, early grain crops and corn was less than 5% and with a maximum average abundance of 0.53 pcs/m2. A total of 58 low active weed species were identified, 29 of which were not previously found in the surveyed areas. The data on the average frequency of occurrence of rare species, the density of infestation by them of all surveyed areas and the results of monitoring of crops of individual crops are analyzed. It has been established that the species diversity and abundance of rare weeds depend on the characteristics of cultivated crops. Weed species confined to individual crops and weeds growing everywhere have been identified. Eight species were recorded in areas under all crops: Galinsoga parviflora Cav., Potentilla anserina L., Gnaphalium uliginosum L., Arctium lappa L., Crepis tectorum L., Inula salicina L., Avena fatua L. and Poa pratensis L. Exclusively in 26 rare species were noted in soybean crops. In total, 57 low-active species were recorded in soybean agrocenoses, 26 species in corn crops, and 18 species in early grain crops. The most problematic species with increased occurrence in recent years, representing a potential danger for crop production in Primorsky Krai, have been identified.

A túzok (Otis tarda L.) ízeltlábú táplálékforrás kínálatának vizsgálata alföldi előfordulási területein

We have carried out the tests in the four lowland regions where the Great Bustards are found: (1) Apajpuszta – Csepeli-plain (1985), (2) Mezőnagymihály – Borsodi Mezőség (1991), (3) Nagyiván – Hortobágy (1988) and Dévaványa – Dévaványai-plain (1985, 1987) (Map 1). We have collected the Arthropods in the study areas with BARBER pitfalls. Each of the annually selected habitats had 5 pitfalls in operation, which we have placed along a line at five meters from each other. The traps were in operation from May to July, sometimes until August. We emptied them in two-week (14-14 day) periods. During laboratory processing, we have determined the number of individuals and measured the total mass of individuals of each taxon per period. The individual and mass data were recorded in tables for each measurement (=every two-week period) and the dominance relationships were calculated, then the basic data were used to calculate the various community-ecological indicators (diversity, evenness, etc.). In addition to the calculated individual and mass ratios, we have also calculated the energy value and dominance of the samples. We have applied cluster analysis to group the animal food sources of each habitat. We have used the BRAY-CURTIS index as a similarity index. Based on the results obtained – regardless of the place and time of the examination – if we want to generalize, then we can say the following facts: (1) The mass and energy ratios that most characterize the food source prove that agricultural habitats are more favourable. (2) The food supply of the habitats changes during the reproduction period, partly for biological (seasonal dynamics of the taxa), partly for reasons of cultivation (mowing, harvesting) and with the maturation of the plants (disappearance of green phytomass), shows fluctuations, decreases or increases. The decrease is typical for cereals and natural grasslands, and the cyclical change is typical for mowed grasslands and alfalfa. We have experienced an increase in spring-sown (e.g. maize) habitats. (3) We cannot generally talk about the goodness of food sources within the same year, we must determine and prioritize the food supply in each period. (4) The extent and quality of the supply of Arthropod food sources is also different in the topographically different places of the Great Hungarian Plain. (5) It can be concluded that, based on the trappings, the decisive role of those taxa in the food supply of Arthropods can be demonstrated, which also play a decisive role in the animal food spectrum of the Great Bustards, so above all the Coleoptera and the Orthoptera. (6) Taking all of this into consideration, we should establish that regardless of the year, place, or period, the more favourable Arthropod food supply of agricultural habitats was one of the motivating factors for the habitat change of Great Bustard, and even today it is one of the explanations for the settlement and nesting of Great Bustards on arable land. (7) The examination of the Arthropod food sources of the Great Bustard showed that the Arthropod resource sets of the agricultural habitats are still suitable for the maintenance of Great Bustard populations. (8) Environmentfriendly farming, the restrained use of chemicals, and the increase in the diversity of food weeds increase the diversity and mass of phytophagous Arthropods and their predators, thus increasing the resources of the habitat.

Management of weed diversity through organic mulching and alternative weed suppression practices on ginger (Zingiber officinale)

Management of weed diversity through organic mulching and alternative weed suppression practices on ginger (Zingiber officinale)

Management of weed diversity through organic mulching and alternative weed suppression practices on ginger (Zingiber officinale)

A field experiment was conducted at the Regional Research Station (Hill Zone), Uttar Banga Krishi Viswavidyalaya, Kalimpong, Darjeeling, West Bengal, during 2019 and 2020 to study the effect of weed diversity, growth and yield of ginger (Zingiber officinale Rose) as influenced by organic mulching and alternative weed management practices. The randomized block design, having seven varying treatments with three replications was used. The treatments consisted of dry weed biomass mulch @ 5.0 t/ha (T1), paddy straw mulch @ 5.0 t/ha (T2), FYM Mulch @ 5.0 t/ha (T3), dry leaves of Schima wallichi@ 5.0 t/ha (T4), dry leaves of Artimesia sp. and Eupatorium sp. @ 5.0 t/ha (T5), hand weeding (twice) at 45 and 90 DAS (T6) and unweeded control (T7). The result showed that hand weeding twice at 45 and 90 DAS (T6) appreciably reduced the total weed population/m2 and total dry weight of weeds than unweeded control plot (T7) at all the stages of crop growth. The highest plant height (82.10 cm), number of leaves/clump (65.41), number of pseudo stem/clump (5.17), rhizome length (7.22 cm), rhizome width (5.50 cm), number of fingers/rhizome (6.42), yield/plant (0.268 kg/plant), yield (20.33 t/ha) and weed control efficiency were recorded under the hand weeding twice at 45 and 90 DAS (T6) compared to other treatments. The results showed that it is necessary to cover the soil surface with different mulch materials and manual weed control practices to achieve a good control of weeds along with enhanced yield attributes and yield.

Impact of 40 Years Use of Different Herbicide Strategies and Crop Rotations on Weed Communities in Two Sites of the Czech Republic

Understanding the impact of farming practices on the composition of weed communities has important implications for the sustainability of weed management strategies. This study analyses data from a 40-year experiment established at two sites in the Czech Republic in 1972. The impact of herbicide strategies on the weed communities was evaluated in multi-crop rotation (MCR) with 50% cereals, and simple crop rotations (SCR) with 75% cereals. The following two herbicide strategies were compared: (1) simple treatment with synthetic auxins only in the simple crop rotation, and (2) targeted herbicide combinations with particular use of sulfonylureas, triazines, ureas and synthetic auxins. Untreated plots were included for reference purposes. Results showed that crop was the major factor determining weed community composition and explained 18% of the total variation in the case of untreated controls. However, herbicide treatment reduced the crop effect to 11%. The highest average increase of Shannon’s diversity index was by 25.4% after 44 years at the untreated plots in SCR, and it decreased by 15.1% at the treated plots in MCR. Weed species evenness € increased at all plots by an average of 23%. Simpson’s dominance index decreased at untreated plots in both crop rotations and plots treated with auxins, with the highest 44.8% decrease at the untreated plots in SCR. On the contrary, Simpson’s index increased by 33,3% on the treated plots in MCR. Herbicide selection depended on the occurrence and density of target weed species, and led to greater decrease in weed diversity and population densities in the diversified crop rotations.

Global patterns of herbicide resistance evolution in Amaranthus spp .: an analysis comparing species, cropping regions and herbicides

Herbicide resistance in weeds is an evolutionary process. Although there is a great global diversity of weeds, independent origins of herbicide resistance evolution have been shown to converge into similar molecular and physiological resistance mechanisms in geographically distant weed populations. Amaranthus species have shown an extraordinary ability to evolve herbicide resistance and invade new environments at a global scale, which represents an opportunity for identifying adaptive evolutionary patterns. The most frequent cases of herbicide-resistant Amaranthus species have been identified [...]