Biology, agricultural impact, and management of Cyperus rotundus L.: the world's most tenacious weed

Purple nutsedge (Cyperus rotundus L.), a troublesome weed, is economically damaging weed, which is widely naturalized in the tropical and subtropical regions of the world. This weed has been reported to cause 20-90% yield losses in various agronomic and horticultural crops across the world. Perennial nature, genetic diversity, ability to tolerate adverse climatic conditions, high rate of reproduction, ease-of-dispersion, strong competitive abilities, and allelopathic potential assist this weed to thrive in a range of agro-climatic regions. Routine cultural approaches, including crop rotation, crop choice, and mechanical cultivation, are ineffective in achieving season-long management of C. rotundus. Pre-emergent and post-emergent herbicides, as well as myco-herbicides, can control its growth but fail to limit the regenerative capacity and tuber viability of C. rotundus in the long term. Integration of herbicides with tillage operations during summer fallows would be a reliable option to desiccate the tubers and rhizomes of C. rotundus. Furthermore, preventive measures as well as complete destruction of nascent foci would be helpful in preventing future spread of this weed. This review will help researchers and scientists in understanding the reproductive biology and future threats of C. rotundus, leading towards the development of improved control methodologies. The information presented in this article will also enable researchers and growers to address the prevailing gaps in the eco-biology of this weed for the long-term control of C. rotundus in economically important field crops

Biology, impact, and management of common sowthistle (Sonchus oleraceus L.)

Common sowthistle (Sonchus oleraceus L.), native to Europe, is widely distributed worldwide as a difficult-to-control weed due to its intermittent and prolonged emergence period, rapid plant maturity, and prolific production of highly dispersive seeds. Genetic diversity, low innate seed dormancy, and evolving herbicide resistance are contributing towards S. oleraceus successful distribution in agroecosystems. In Australia, this weed has raised its status from a relative obscurity to economically damaging weed, particularly in conservation tillage systems. The weed has been reported to evolve resistance against group M and B herbicides, while more populations have been identified as having a moderate risk of developing resistance across Australia. Over the last 10\ua0years, the dominance of S. oleraceus has been increased and has gained the status of second major broadleaf weed. Post-emergent herbicides, such as carfentrazone, florasulam, bromoxynil octanate, and sulfentrazone, either alone or in combination has been found effective against this weed. Double-knock techniques have been considered effective for suppressing S. oleraceus in fallow lands. Despite this, integrated and sustainable approach involving selecting competitive crops, strategic tillage, and herbicide rotation are some of the reliable and efficient techniques for long-term control of this weed. Based on this, an article was designed to highlight the current scenario and future prospects of this highly invasive weed in agro-ecological systems. This article will help in developing understanding related to the eco-physiological aspect regulating the biology, invasion, and management of S. oleraceus

Effect of Soil Moisture Regimes on the Glyphosate Sensitivity and Morpho-Physiological Traits of Windmill Grass (Chloris truncata R.Br.), Common Sowthistle (Sonchus oleraceus L.), and Flaxleaf Fleabane [Conyza bonariensis (L.) Cronq.]

The glasshouse study was conducted with the objectives of (i) investigating the effect of soil moisture variations on the control efficiency of glyphosate on windmill grass (Chloris truncata R.Br.), common sowthistle (Sonchus oleraceus L.), and flaxleaf fleabane [Conyza bonariensis (L.) Cronq.], (ii) evaluating the tolerance of tested weed species under soil moisture variations, and (iii) determining the morphological and physiological characteristics of these species to partially explain herbicide tolerance under periods of reduced soil moisture availability (RSM). The species’ tolerance to glyphosate increased significantly under reduced soil moisture availability (p < 0.001). The lethal dose to cause herbicide injury or biomass reduction by 50% (LD50) and 80% (LD80) in relation to untreated control for water-stressed plants [i.e., moderate soil moisture availability (MSM) and RSM] was significantly higher than that of plants grown under high soil moisture availability (HSM). The tolerance factor (TF) for C. truncata, S. oleraceus, and C. bonariensis, in terms of biomass reduction under RSM, was 2.6, 2.4, and 2.6, respectively, as compared to HSM. The results showed that the glyphosate sensitivity, especially at the sub-lethal rates, of the three weed species under study decreased as soil moisture availability reduced (p< 0.01). Overall glyphosate efficacy, in relation to the recommended rate, was unaffected, except for C. truncata; the weed survived the highest tested glyphosate rate [750 g active ingredient (a.i.) ha−1] under RSM. There was significant interaction between weed species and soil moisture regimes for weed morpho-physiological traits (p < 0.001), with reduced soil moisture having a more influential impact on the growth of C. bonariensis and S. oleraceus compared to C. truncata. Changes in the leaf characteristics, such as increased leaf thickness, higher leaf chlorophyll content, reduced leaf area, and limited stomatal activity for all the tested weed species under MSM and RSM in relation to HSM, partially explain the tolerance of species to glyphosate at sublethal rates

Effect of Soil Moisture Regimes on the Glyphosate Sensitivity and Morpho-Physiological Traits of Windmill Grass (<i>Chloris truncata</i> R.Br.), Common Sowthistle (<i>Sonchus oleraceus</i> L.), and Flaxleaf Fleabane [<i>Conyza bonariensis</i> (L.) Cronq.]

The glasshouse study was conducted with the objectives of (i) investigating the effect of soil moisture variations on the control efficiency of glyphosate on windmill grass (Chloris truncata R.Br.), common sowthistle (Sonchus oleraceus L.), and flaxleaf fleabane [Conyza bonariensis (L.) Cronq.], (ii) evaluating the tolerance of tested weed species under soil moisture variations, and (iii) determining the morphological and physiological characteristics of these species to partially explain herbicide tolerance under periods of reduced soil moisture availability (RSM). The species’ tolerance to glyphosate increased significantly under reduced soil moisture availability (p 50) and 80% (LD80) in relation to untreated control for water-stressed plants [i.e., moderate soil moisture availability (MSM) and RSM] was significantly higher than that of plants grown under high soil moisture availability (HSM). The tolerance factor (TF) for C. truncata, S. oleraceus, and C. bonariensis, in terms of biomass reduction under RSM, was 2.6, 2.4, and 2.6, respectively, as compared to HSM. The results showed that the glyphosate sensitivity, especially at the sub-lethal rates, of the three weed species under study decreased as soil moisture availability reduced (p 0.01). Overall glyphosate efficacy, in relation to the recommended rate, was unaffected, except for C. truncata; the weed survived the highest tested glyphosate rate [750 g active ingredient (a.i.) ha−1] under RSM. There was significant interaction between weed species and soil moisture regimes for weed morpho-physiological traits (p C. bonariensis and S. oleraceus compared to C. truncata. Changes in the leaf characteristics, such as increased leaf thickness, higher leaf chlorophyll content, reduced leaf area, and limited stomatal activity for all the tested weed species under MSM and RSM in relation to HSM, partially explain the tolerance of species to glyphosate at sublethal rates

Weed management in sorghum [Sorghum bicolor (L.) Moench] using crop competition: a review

The food security of many developing countries relies on sorghum production due to its low input requirements and ability to endure extreme climatic stresses. This C grass species is widely cultivated for grain, feed/fodder, and bio-fuel uses in tropical and semi-arid areas of the world. A high efficiency water utilization mechanism and tolerance to drought and high temperatures favours it as an alternative crop to maize in areas with marginal water availability. Despite of its potential, this crop is underutilized given few weed management options. In addition to other biotic and abiotic factors, weeds are considered to be a major constraint, causing 15–97% losses for sorghum growth and yield under different climatic conditions. Previous studies where the crop spacing, seeding rate, and selection of competitive cultivars were altered, highlighted the importance of weed management through cultural practices or crop competition. Narrowing the crop rows and increasing plant densities were found effective in reducing the growth, biomass, and competitive ability of several weed species in sorghum. In addition, selection of competitive and allelopathic sorghum cultivars affected the weed seedling emergence by decreasing light interception and by releasing numerous allelochemicals. However, a review of the literature directed our attention towards some neglected points of weed management through crop competition in sorghum. For instance, crop row orientation has not been studied yet to investigate its influences on weed competitiveness against sorghum around the world. There is a dire need to diversify cultural practices in agro-ecosystems as much as possible to provide competitive advantage for the sorghum crop. Future research should be planned to evaluate the effectiveness of different sowing rates, dates, and directions on the crop yield and weed suppression under different cropping systems. Furthermore, cultural practices should be integrated with other weed management techniques for the development of a more reliable and sustainable weed control program in sorghum

Biology, impact, and management of Echinochloa colona (L.) Link

Echinochloa colona (L.) Link. is one of the most problematic weeds across the world. It is an annual C summer grass, native to tropical and subtropical Asia, emerged as a serious and persistent threat in 35 cropping systems in more than 60 countries. E. colona is reported as an important associated weed species in transplanted and direct-seeded rice. Diverse ecotypes, high seed production, short seed dormancy, rapid growth, competitive potential, allelopathic interaction, and resistance against several herbicides makes it a more adaptable and persistent challenge in various agro-ecosystems. Development of resistance to recommended or higher doses of numerous herbicides, including ametryn, atrazine, bispyribac-sodium, clefoxidym, cyhalofop-butyl, fenoxaprop-p-ethyl, glyphosate, metribuzin, propanil, and triazine, is a serious concern for the farming and scientific community. Crop infestation with resistant E. colona biotypes may ultimately increase the weed control cost. Unfortunately, investigations on seed dormancy release, genetic diversity, allelopathic interference, and competitive ability of this weed are inadequate in accomplishing its appropriate control in different environments. Therefore, a comprehensive review is presented here to gather the existing information, to pin point key findings, and to highlight the research gaps in the biology, interference, and management of E. colona. Different management options have been discussed in relation with eco-biology of this noxious weed. The potential research endeavours have also been highlighted in order to provide an insight of its existing scenario and to facilitate the future management strategies

Weed management using crop competition in Pakistan: a review

Agriculture occupies an important place in improving the living standards of farmers in Pakistan. About 90% of farm earnings rely on the cultivation of sugar, fibre, cereals and legumes. Due to lack of essential resources and technical expertise, every year thousands of farmers fail to reach maximum yield potential. Over 70% of farmers own less than 5 ha in Pakistan; therefore, it is uneconomic to employ costly mechanical and chemical strategies for the control of pests in their crops. Among these pests, we eds are considered to be the major obstacle to crop production, and can ultimately result in crop failure. Traditionally, manipulation of cropping techniques was employed for the control of weeds; later on, development of synthetic chemical herbicides made it easier to control weeds in a very short time period. However, over time the increased use of herbicides has led to the development of herbicide resistant weeds. Furthermore, increasing environmental concerns, weed population shifts, and increased managerial costs have made it difficult for farmers to control these weed species within their limited economic resources. Nowadays, scientists and research organizations are being urged to provide innovative weed management solutions, with minimal ecological impacts. Studies have revealed the importance of cultural strategies for the management of weeds in different cropping systems. Research has proved that alternation of cultural practices, and selection of competitive crop cultivars, could be a possible strategy to minimize the competitiveness of weeds. Increased crop densities, narrower row spacing, intercropping and alternation in row directions are among the weed control strategies gaining rapid attention in many countries. Unfortunately, limited information is available about weed management using crop competition in Pakistan. This review article focusses on the importance of these agronomic practices in reducing the competitive potential of weeds, for their effective and appropriate management in major crops of Pakistan. It is intended to assist researchers in the design of economically viable and eco-friendly weed management strategies, which will aid in eliminating the burden of herbicides and mechanical cultivation from farmer’s production costs

Biology and management of two important Conyza weeds: a global review

Jabran, Khawar/0000-0001-8512-3330; Peerzada, Arslan Masood/0000-0003-3577-4906; Bajwa, Ali/0000-0002-7171-3118; Chauhan, Bhagirath/0000-0003-1540-4668; ALI, HAFIZ HAIDER/0000-0002-8262-6327WOS: 000389301700020PubMed: 27798798Weed management is one of the prime concerns for sustainable crop production. Conyza bonariensis and Conyza canadensis are two of the most problematic, noxious, invasive and widespread weeds in modern-day agriculture. The biology, ecology and interference of C. bonariensis and C. canadensis have been reviewed here to highlight pragmatic management options. Both these species share a unique set of biological features, which enables them to invade and adapt a wide range of environmental conditions. Distinct reproductive biology and an efficient seed dispersal mechanism help these species to spread rapidly. Ability to interfere strongly and to host crop pests makes these two species worst weeds of cropping systems. These weed species cause 28-68 % yield loss in important field crops such as soybean and cotton every year. These weeds are more prevalent in no-till systems and, thus, becoming a major issue in conservation agriculture. Cultural practices such as crop rotations, seed rate manipulation, mulching, inter-row tillage and narrow row spacing may provide an effective control of these species. However, such methods are not feasible and applicable under all types of conditions. Different herbicides also provide a varying degree of control depending on crop, agronomic practices, herbicide dose, application time and season. However, both these species have evolved resistance against multiple herbicides, including glyphosate and paraquahe use of alternative herbicides and integrated management strategies may providt. Te better control of herbicide-resistant C. bonariensis and C. canadensis. Management plans based on the eco-biological interactions of these species may prove sustainable in the future

Challenges in organic component selection and biochar as an opportunity in potting substrates: a review

Plant production in potting substrates provides maximum profit on the applied inputs, and hence, directly improving the socio-economic condition of the grower/nurserymen. The main challenge in this industry is sourcing of materials for their potting substrates. Peat and perlite have been widely preferred materials. However, recently higher prices, more restrictive legislation of many countries and wetland ecosystem destruction through its extraction has limited peat use. Nowadays, producers focus towards peat alternatives that provide good performance, are readily available, inexpensive and environment friendly to attain sustainability in potted plant production. In an effort to grasp sustainability during the last few decades, many industrial and agricultural waste materials were reviewed for their use in potting substrates. In these studies, the major focus remained on material characterization, neglecting their economics, technical aspects and environmental impacts. Thus, switching from peat and perlite to alternatives requires material exploration. In the present review, we summarize a clearer and practical approach for substituting different materials especially biochar to fulfill the need of modern potting substrate industry. Biochar has the potential to sustain the substrate production on a long-term basis