Integrated Weed Management Systems Research Articles

Herbicide Strategies for Weed Control in Rice Cultivation: Current Practices and Future Directions

Rice, as a staple food for more than half of the world's population, plays a crucial role in global food security. However, weed competition poses a significant challenge to rice cultivation, affecting yield and quality. To address this challenge, rice farmers have increasingly turned to chemical herbicides as a cost-effective alternative to labor-intensive manual weeding. This review paper explores the current practices and future directions in herbicide strategies for weed control in rice cultivation, with a specific focus on diverse approaches adopted in various agro-ecological regions, particularly in Pakistan. The paper begins by highlighting the importance of rice cultivation in global agriculture and the economic significance of the crop, emphasizing the need for effective weed management to ensure sustainable production. It discusses the impact of labor shortages and rising labor costs on weed control practices, driving the adoption of chemical herbicides, especially in direct-seeded rice cultivation. Additionally, the review underscores the importance of integrated weed management systems, which combine cultural practices, targeted herbicide applications, and legislative measures to optimize crop productivity while minimizing environmental impact. Furthermore, the paper evaluates the efficacy of different herbicides and their timing of application in managing weeds and maximizing rice yield. It synthesizes findings from recent studies to provide insights into the effectiveness of pre-emergence and post-emergence herbicides, as well as their impact on weed-crop competition and overall crop health. By analyzing the strengths and limitations of existing herbicide strategies, the review identifies opportunities for innovation and improvement in weed management practices. Overall, this review paper offers a comprehensive overview of herbicide strategies for weed control in rice cultivation, highlighting the need for sustainable and integrated approaches to address weed challenges while ensuring food security and environmental sustainability in rice-producing regions.

Biology of the invasive species Eragrostis plana in Southern Brazil: What have we learned and how may this help us manage it?

AbstractSince its accidental introduction in 1951, the South African species Eragrostis plana has invaded a large part of the Pampa biome in South America, a highly diverse grassland ecosystem that has coexisted with livestock since its introduction at the beginning of the 17th century. E. plana, a perennial tussock grass with a deep and abundant root system, is resistant to frost and cattle grazing, and a successful competitor for environmental resources. The species is diploid, C4 dispersed endozoochorically, and flowers in late spring and early summer, with optimal germination occurring at 35°C and viability up to 39–40°C. It is allelopathic because it produces several phenols and alkaloids. Extreme soil disturbance or intense grazing favours initial invasion. Nonetheless, grazing exclusion enhances E. plana competition and affects the grassland community and diversity. E. plana is highly tolerant to interspecific competition, especially with grasses exhibiting a similar growth habit. Under water stress, it responds faster by increasing its root system by 66% more than native grass. Moreover, antioxidant system activity increases, and the species recovers quickly through osmolyte production. In non‐invaded fields, avoiding soil disturbance and intensive grazing are key strategies to preserving Biome Pampa. Nonetheless, in fields where the invasion has already occurred, grazing must be maintained, cattle quarantined practiced, along with strategies that reduce cover and prevent the spread of E. plana. Liming and fertilising native grasslands improve their potential to compete with E. plana. The wiper applicator, a device that allows glyphosate herbicide application selectively to E. plana, is an important component of the integrated weed management system, especially with very severe infestations. Establishing strategies to contain or manage E. plana should be a priority to preserve the biodiversity of the Pampa. In the future, innovative options could also help prevent new invasions.

Using integrated weed management systems to manage herbicide-resistant weeds in the Canadian Prairies

Although herbicides have been a dominant and effective weed control strategy for decades in Western Canada, herbicide resistance and the lack of new modes of action have resulted in weed management challenges. Integrated weed management strategies have been shown to be successful in controlling certain weed species that are problematic in cropping systems. The objective of this study was to investigate integrated weed management strategies that have been successful on individual species to determine their applicability to a multiple weed species that may coexist in a field. In addition, harvest weed seed control was incorporated into these integrated weed management strategies to determine its impact in western Canadian cropping systems. A 5-year rotational study was conducted from 2016 to 2020 at Beaverlodge, Lacombe, and Lethbridge, AB; Scott and Saskatoon, SK; and Carman, MB, that incorporated integrated weed management strategies such as rotational crop diversity (including winter annuals and perennials), increased seeding rates, crop silaging, chaff collection, and with or without in-crop herbicides. This research confirmed success in managing some species of weeds such as wild oat when increased seeding rates, 2 years of early cut silage barley, and competitive winter cereals were incorporated into a cropping system, even when no in-crop herbicides were applied. However, some weed growth morphologies (e.g., twining weeds) or life cycles (e.g., facultative winter annuals) were not managed successfully with this combination of strategies. Chaff collection provided incremental weed control benefits but did not serve as a replacement for herbicidal weed control. Weed densities had an apparent impact on the success of these integrated weed management strategies, suggesting that the sooner they are adopted, the more likely they are to be successful at maintaining or reducing weed densities. This study not only showed the ability to reduce reliance on herbicides with strategies that can be effective in Western Canada but also highlighted the need for further understanding of different weed species and their responses to integrated weed management strategies, as well as the complexity of managing a weed community with integrated weed management.

Direct and indirect effects of Basta®, a glufosinate-based herbicide, on banana plantation soil microbial diversity and function

Herbicide applications have doubled over the past 30 years to control weeds, but their use may influence soil microbial communities, which mediate important ecosystem services. Here, we characterised the direct effects of a single application of Basta® (glufosinate), at 1× and 2× the recommended rate (5 and 10 kg product ha−1), as well as the indirect effects of vegetation loss on the diversity and function of soil microbial communities within a banana plantation. A 10-month pre-experimental period using Basta® to remove additional vegetation from half of the experimental area created conditions for assessing the indirect herbicide effects. Direct assessments on soil microbial communities began when the Basta® herbicide treatments were applied to the areas with and without vegetation and continued over multiple time-points, for 56 days. Herbicide treatment had no significant direct impacts on basal, and substrate induced respiration rates, or the potential activities of microbial enzymes as inferred from fluorescein diacetate hydrolysis (FDA) and β-glucosidase assays. Similarly, phylogenetic marker gene sequencing indicated that Basta® application did not significantly influence the diversity of soil bacterial or fungal communities. Indirectly, Basta® had a greater influence on the soil microbial activity and functions by removing understory vegetation cover around banana plants. This suggested that continual use of herbicides to reduce soil vegetation cover under bananas had a greater impact on soil microbial communities than a single application of the herbicide. Furthermore, the presence or absence of vegetation cover, significantly altered the abundance of Fusarium oxysporum, plus an additional eight bacterial and ten fungal taxa. Our results indicated that a single application of glufosinate as Basta® at the recommended or double the recommended rate, did not adversely affect soil microbial communities or their activities in banana plantations directly. However, application of herbicides, such as Basta® in crops like banana, indirectly alters soil microbial communities and their activities through loss of vegetation cover and should only be used as a component of an integrated weed management system.

Application technology for bioherbicides: challenges and opportunities with dry inoculum and liquid spray formulations.

Bioherbicides offer many potential benefits as part of an integrated weed management system or a totally biological or organic cropping system. A key factor for success is the selection of appropriate formulation and delivery systems for each target weed and cropping/climatic region. For dry inoculum products, we discuss direct implantation as an example for successful control of woody weeds, with benefits in control extending beyond the treated weeds to surrounding weeds. These applications do not require water and will become less labor-intensive with future robotic application platforms. Indeed, all bioherbicide applications are likely to improve and become more cost-effective with the advance of new application platforms with sensors and targeted control at lower application volume rates. Unmanned aerial vehicles, as new application platforms, are one of several such potential progressive application systems for liquid formulations, and we discuss product design to maintain optimum conditioning of the active ingredient(s) and storage stability. The delivery system must not adversely affect the products and the application volume rate must be appropriate for coverage on the target. Where applied with other products, compatibility must be ensured and appropriate mixing orders observed to assure performance and avoid precipitation or settling. Droplet size is important for allowing the active materials to be included in the spray, which may require droplets with diameter >150 μm for some larger particle biologically active agents. However, droplet size should not be too large to achieve target coverage. In some cases, that may be plant stems rather than leaves, or narrow grass weeds which tend to have highest spray collection efficiency for small droplets. Narrow droplet size spectrum nozzles may help optimize droplet size. We propose spray calculators to help optimize performance for coverage, retention and avoidance of drift losses, bounce, shatter and runoff. These include regulatory-supported, validated models. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Different Weed Managements Influence the Seasonal Floristic Composition in a Super High-Density Olive Orchard.

Weed management is not yet environmentally, agronomically, economically and socially sustainable in olive orchards. It is necessary to study appropriate integrated weed management systems (IWMSs) based on the knowledge of weed population and effects of weeding practices over time. The aim of this study was to evaluate the effects of different weed managements on seasonal floristic composition of a super high-density olive orchard, also exploiting the essential principles of an IWMS. Five weeding techniques were compared: chemical control (CHI), mowing (MEC), plastic (nonwoven tissue, TNT and polyethylene, PEN) and organic (with de-oiled olive pomace, DOP) mulching. Weed monitoring was carried out on six dates in a three-year period. The infestation of each of the main 18 weed species recorded (%) and the total infestation (%) on each monitoring date were determined. Results underlined that all weeding practices investigated in this multi-year study affected the floristic composition, weed characteristics (hemicryptophytes, cryptophytes and therophytes) and seed bank. TNT and PEN were the most effective methods for weed management. Particularly, total infestation coefficient was significantly lowest when plots were managed with TNT (13.91%) and PEN (14.38%) and highest for MEC (141.29%). However, DOP also significantly reduced infestation compared to CHI and MEC. Therefore, DOP could constitute an excellent strategy for weed management in super high-density olive groves, since it also has the possibility of distributing mulching materials in a mechanized way in field and can result in improvement of soil fertility and the possibility of valorizing waste. Further studies should be carried out to investigate the mechanism of action (physical and allelochemical) of de-oiled pomace or other organic agro-industrial materials and the recovery time of these mulching materials in super high-density olive orchards.

Evaluation of finger weeder safety and efficacy for intra‐row weed removal in irrigated field crops

AbstractIncreased demand for pesticide‐free food and the development of herbicide‐resistant weed populations have created a need for non‐chemical weed‐control tools. A candidate mechanical tool for controlling weeds in the seeding line (intra‐row zone) is the finger weeder. This study thus aimed to evaluate the safety and weed‐control efficacy of the finger weeder in various irrigated field crops. Eight field trials were conducted in processing tomato, sweet corn, sunflower, cotton, and beetroot over 2 years. The finger weeder treatments were applied as the sole weed‐control method (single or double treatments) and in combination with herbicides. A mini meta‐analysis was used to evaluate the overall effect of the finger weeder treatments on crop stand and yield and on weed control efficacy. Weed density in the control not treated with herbicides nor a finger weeder ranged between 2 and 62 weeds m−2. The finger weeder treatments resulted in a significant reduction in weed density, which ranged between 40% and 90%. The weed density following the double finger weeder treatment was not significantly different from that for the conventional herbicide‐based treatment (p = 0.32) and could therefore be considered as an effective environmentally friendly alternative. Furthermore, a single FW treatment integrated with herbicide application gave better weed control than the conventional herbicide treatment (p = 0.04). This treatment was safe for the crops with no significant stand (p = 0.19) or yield (p = 0.29) reductions compared to commercial treatment. The results of this study demonstrate the promise of the finger weeder as an effective tool within integrated weed management systems for conventional agro‐systems. The tool offers a rational weed‐control solution for sustainable systems under irrigation.

Seed Germination of Three Milk Thistle (Silybum marianum (L.) Gaertn.) Populations of Greek Origin: Temperature, Duration, and Storage Conditions Effects

Milk thistle besides being a highly competitive weed is cultivated as a medicinal plant, and the seeds of which have been clinically utilized in several disorders caused in liver. The present study aims to evaluate the effect of duration and storage conditions, population, and temperature on seed germination. The experiment was conducted in Petri dishes with three replications and three factors: (a) wild populations of milk thistle (Palaionterveno, Mesopotamia, and Spata) originating from Greece, (b) duration and storage conditions (5 months at room temperature, 17 months at room temperature, and 29 months in the freezer at -18 °C), and (c) temperature (5 °C, 10 °C, 15 °C, 20 °C, 25 °C, and 30 °C). All three factors significantly affected germination percentage (GP), mean germination time (MGT), germination index (GI), radicle length (RL), and hypocotyl length (HL) and significant interactions among the treatments were noted. In specific, no seed germination was recorded at 5 °C, while the populations showed higher GP and GI at 20 °C and 25 °C after 5 months of storage. Prolonged storage negatively affected seed germination although, cold storage mitigated this effect. Moreover, higher temperatures reduced MGT and increased RL and HL with the populations reacting differently in storage and temperature regimes. The results of this study should be taken into consideration when proposing the appropriate sowing date and storage conditions of the seeds used as propagation material for crop establishment. Moreover, the effects of low temperatures such as 5 °C or 10 °C on seed germination as well as the high decline rate in germination percentage over time could be utilized in the design of integrated weed management systems thereby indicating the importance of the sowing time and the suitable crop rotation system to weed control.

The Potential of Cover Crops for Weed Management: A Sole Tool or Component of an Integrated Weed Management System?

Cover crops are an important component of integrated weed management programs in annual and perennial cropping systems because of their weed suppressive abilities. They influence weed populations using different mechanisms of plant interaction which can be facilitative or suppressive. However, the question often arises if cover crops can be solely relied upon for weed management or not. In this review we have tried to provide examples to answer this question. The most common methods of weed suppression by an actively growing cover crop include competition for limited plant growth resources that result in reduced weed biomass, seed production, and hence reductions in the addition of seeds to the soil seedbank. Cover crop mulches suppress weeds by reducing weed seedling emergence through allelopathic effects or physical effects of shading. However, there is a great degree of variability in the success or failure of cover crops in suppressing weeds that are influenced by the cover crop species, time of planting, cover crop densities and biomass, time of cover crop termination, the cash crop following in the rotation, and the season associated with several climatic variables. Several studies demonstrated that planting date was important to achieve maximum cover crop biomass, and a mixture of cover crop species was better than single cover crop species to achieve good weed suppression. Most of the studies that have demonstrated success in weed suppression have only shown partial success and not total success in weed suppression. Therefore, cover crops as a sole tool may not be sufficient to reduce weeds and need to be supplemented with other weed management tools. Nevertheless, cover crops are an important component of the toolbox for integrated weed management.

Allelopathy and its application as a weed management tool: A review.

Weeds are a serious threat to crop production as they interfere with the crop growth and development and result in significant crop losses. Weeds actually cause yield loss higher than any other pest in crop production. As a result, synthetic herbicides have been widely used for weed management. Heavy usage of synthetic herbicides, however, has resulted in public concerns over the impact of herbicides on human health and the environment. Due to various environmental and health issues associated with synthetic herbicides, researchers have been exploring alternative environmentally friendly means of controlling weed. Among them, incorporating allelopathy as a tool in an integrated weed management plan could meaningfully bring down herbicide application. Allelopathy is a biological phenomenon of chemical interaction between plants, and this phenomenon has great potential to be used as an effective and environmentally friendly tool for weed management in field crops. In field crops, allelopathy can be applied through intercropping, crop rotation, cover crops, mulching and allelopathic water extracts to manage weeds. Accumulating evidence indicates that some plant species possess potent allelochemicals that have great potential to be the ecofriendly natural herbicides. This review is intended to provide an overview of several allelopathic species that release some form of the potent allelochemical with the potential of being used in conventional or organic agriculture. Further, the review also highlights potential ways allelopathy could be utilized in conventional or organic agriculture and identify future research needs and prospects. It is anticipated that the phenomenon of allelopathy will be further explored as a weed management tool, and it can be a part of a sustainable, ecological, and integrated weed management system.

Impact of Rotational Sequence Selection on Weed Seedbank Composition in Australian Broadacre Crops

The use of competitive crops in successional rotations has been shown to reduce the growth and establishment of annual weeds by the depletion of the weed seedbank in broadacre cropping systems. However, the impact of specific crop rotational sequences contributing to weed seedbank density has not been quantified in the Riverina region of southern Australia. Trials were established in two locations in 2014–2018 to quantify the impact of selected annual rotations featuring grain, pulse, and pasture crops on weed infestation and seedbank dynamics with a focus on winter and summer annual weeds. The weed seedbank dynamics were evaluated by a twice-annual soil sampling regime (at planting and harvest), followed by soil sample screening for weed propagule germination and seedling establishment in a subsequent controlled-environment screening performed from 2014–2020. The weed seedling density decreased in the cereal rotations in years experiencing average to above-average rainfall, as crops established a dense canopy leading to reduced weed establishment and fecundity. Several rotational treatments were effective in suppressing the weed propagule numbers over time, including those using dual-purpose cereals only or a canola break-crop along with the cereals. Rotational selection can be an important and cost-effective tool in integrated weed management systems when applied over multiple growing seasons.

Legacy Effects of Contrasting Long-Term Integrated Weed Management Systems

To reduce reliance on herbicides and maintain crop productivity, integrated weed management (IWM) seeks to optimize synergies between diverse sets of weed management practices combined at the cropping system scale. Nevertheless, data on weed community response to the long-term implementation of IWM practices remain scare. Here, we assessed the effects of four IWM systems with contrasting objectives and practices (S2: transition from superficial tillage to conservation agriculture; S3: no-mechanical weeding; S4: mixed mechanical and chemical weeding; S5: herbicide-free; all with 6 year rotations) compared to a conventional reference (S1: herbicide-based with systematic plowing and a 3 year rotation) on taxonomic and functional weed community composition and structure after 17 years of continuous implementation. We examined the legacy effects of these systems with a uniformity trial consisting of winter wheat managed uniformly across the systems as well as with a novel in situ weed seedbank approach involving tilled strips. We found that resulting weed communities in IWM systems were more species rich (species richness from 1.1 to 2.6 times greater) and more abundant (total density from 3.3 to 25 times greater) than those observed in the reference system, and differed in term of taxonomic and functional composition. In addition, we found that, when systems shared the same weed species, germination patterns of two thirds of the species differed between systems, highlighting the selection pressures some IWM practices exert on weeds. We showed that analyzing the superficial germinable seedbank in situ with tilled strips could provide a comprehensive view of resulting weed communities and be helpful in developing cropping systems that foster agroecological weed management.

A REVIEW ON NON-CHEMICAL WEED MANAGEMENT IN MAIZE (ZEA MAYS L.)

Weed is omnipresent species that compete with major crops for light, nutrients, space, and water for their growth and development and ultimately deteriorate the ideal environment for crops growth. In the present context, herbicide application is the easiest and seemingly economical approach for weed control in south-Asian countries. In contrary, the side effects of herbicide on health and environment impose to adopt for the non-chemical method of weed management. This paper reviewed the menace of herbicide, crop weed association, the critical period of crop-weed competition, and different methods of organic weed control implemented especially for maize. The main objective of this review is to maneuver a weed control strategy for maize other than the chemical application. The findings of different research suggested that a critical period of crop-weed competition in maize lies between 2 to 8 weeks after crop sowing. Many mechanical methods for weed control in maize proved efficient but seemed labour intensive and biological methods provided maximum security against specific weed species. The cultural method in combination with other methods effectively reduced the weed population in the maize field. It was found that, if various components of non-chemical weed management are implemented systematically, we can control the weed population with higher economic return and achieve the goal of organic food production with sustainable solutions. Weed control in the organic system focuses on management techniques designed to prevent weed emergence, give a competitive advantage to the main crop, and act for sustainable solutions. The non-chemical integrated weed management system is recommended to reduce the use of herbicide and for sustainable production. A review of non-chemical weed management in maize could be helpful for researchers to provide useful, sustainable, and environmentally friendly solutions to farmers to solve the problem of weed infestation in the maize crop along with substantial yield improvement.

Integrated Weed Management Strategies for Sustainable Rice Production in Bangladesh

Weed causes huge reduction in crops yield, increases cost of cultivation, reduces input efficiency, interferes with agricultural operations, impairs quality, act as alternate hosts for several insect and diseases .Yield loss due to improper weeding at farmer’s field ranged from 4 to 22% depending on different rice ecosystem in Bangladesh. But at present considering all the cultivable land across the country and other issues; yield loss due to weeds considered about 2% in a consultation meeting.The present weed control practices in Bangladesh are characterized by intensive use of manual labour, use of herbicide and certain mechanical weeding. Manual weeding, besides laborious is inefficient as it is not done in time in most of the cases and always not practical because of various adverse conditions. Cost effective and integrated weed management system should be adopted to increase economic gain and sustainable rice production. Adopting timely and effectively appropriate weed management techniques we can reduce a significant amount of yield loss and about 0.43 million ton (MT) additional yield could be increased by 2030. To achieve the target weed management should be done from the very beginning of rice production and up to 30-35 DAP (days after planting) for Aus season, 35-40 DAT (days after transplanting) for T. Aman season and 40-45 DAT for Boro season which indicates critical period of weed infestation in Aus, T. Aman and Boro season. The main approach is that rice field have to keep free from weed up to that days by 2/3 hand weeding (HW) or application of herbicide fb (Followed by) 1HW or applying weeder fb 1HW which is called integrated weed management. Herbicide should be applied at proper time and dose which reduce 61% weeding cost. Mechanical weeding (MW) reduces 50% weeding cost that keeps environment friendly. Future weed science research specially herbicide efficacy with correct time and dose, new molecule herbicide with low environmental effect, herbicide residues in soil plant system, bioherbicide, allelopathic variety, weed competetive variety, mechanical weeder with related technological developments need a multidimensional approach for ecologically sustainable integrated weed management. Such a system will work toward a socially permissible, environmentally sound, economically feasible, productive and sustainable agricultural system. Bangladesh Rice J. 24 (2): 133-159, 2021

Defining Integrated Weed Management: A Novel Conceptual Framework for Models

Weed population dynamics models are an important tool for predicting the outcome of alternative Integrated Weed Management (IWM) scenarios. The growing problem of herbicide resistance has increased the urgency for these tools in the design of sustainable IWM solutions. We developed a conceptual framework for defining IWM as a standardised input template to allow output from different models to be compared and to design IWM scenarios. The framework could also be used as a quantitative metric to determine whether more diverse systems are more sustainable and less vulnerable to herbicide resistance using empirical data. Using the logic of object-oriented programming, we defined four classes of weed management options based on the stage in the weed life cycle that they impact and processes that mediate their effects. Objects in the same class share a common set of properties that determine their behaviour in weed population dynamics models. Any weed control “event” in a system is associated with an object, meaning alternative management scenarios can be built by systematically adding events to a model either to compare existing systems or design novel approaches. Our framework is designed to be generic, allowing IWM systems from different cropping systems and countries to be compared.

Main drivers of broomrape regulation. A review

Orobanchaceae—broomrapes—are a family of parasitic plants that represent an ecological and agronomic challenge because some of them cause significant damage to many monocots or dicots. Weedy broomrapes infest different crops in the Mediterranean basin, leading to substantial yield losses. Besides, they quickly adapt to new host plants, so that new crops are more and more under threat. Control methods are lacking because as plant parasites they cannot be considered as a common weed in agriculture. It is therefore important to characterize the main drivers of their regulation to identify sustainable management strategies. We reviewed all the possible interactions of Orobanchaceae species with surrounding organisms in an agricultural landscape, with a focus on the Orobanche and Phelipanche genera. Our main findings are that (1) broomrapes successfully co-evolve with their host through tight interactions ranging from the molecular to the tissue level, resulting in a unique strategy in their interactions with their host; (2) broomrapes have to face natural regulatory mechanisms such as host plant defenses, allelopathic interferences, and pest attacks from both the rhizosphere and phyllosphere; (3) alternative methods combining these natural mechanisms with existing conventional methods should be used to control broomrape. Conventional methods have shown limited results with parasitic weeds. By considering their life cycle and biotic and abiotic environment, management methods will target their weak point(s). Combining different control methods needs to be considered in an integrated weed management system. Furthermore, future studies on biocontrol will bring out new products to be used in addition to cultural techniques. Modeling approaches would help predict the evolution of broomrape-infested plots and the available potential management strategies.

Future efficacy of pre-emergence herbicides in corn (Zea mays) is threatened by more variable weather.

BACKGROUNDBy 2050, weather is expected to become more variable with a shift towards higher temperatures and more erratic rainfall throughout the U.S. Corn Belt. The effects of this predicted weather change on pre‐emergence (PRE) herbicide efficacy have been inadequately explored. Using an extensive database, spanning 252 unique weather environments, the efficacy of atrazine, acetochlor, S‐metolachlor, and mesotrione, applied PRE alone and in combinations, was modeled on common weed species in corn (Zea mays L.).RESULTSAdequate rainfall to dissolve the herbicide into soil water solution so that it could be absorbed by developing weed seedlings within the first 15 days after PRE application was essential for effective weed control. Across three annual weed species, the probability of effective control increased as rainfall increased and was maximized when rainfall was 10 cm or more. When rainfall was less than 10 cm, increasing soil temperatures had either a positive or negative effect on the probability of effective control, depending on the herbicide(s) and weed species. Herbicide combinations required less rainfall to maximize the probability of effective control and had higher odds of successfully controlling weeds compared with the herbicides applied individually.CONCLUSIONSResults of this study highlight the importance of rainfall following PRE herbicide application. As rainfall becomes more variable in future, the efficacy of common PRE herbicides will likely decline. However, utilizing combinations of PRE herbicides along with additional cultural, mechanical, biological, and chemical weed control methods will create a more sustainable integrated weed management system and help U.S. corn production adapt to more extreme weather.© 2021 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Development of a Mechatronic System for Plant Recognition and Intra-row Weeding With Machine Vision

In this paper, an electro-mechanical integrated weed management system was designed, constructed, and tested. This laboratory-scale solution integrated elements of machine vision, controls, and mechanical actuation to selectively remove weeds from within a crop row. The device was validated in a controlled environment using corn crops. Various crop conditions were considered to ensure the robustness of the design. Though some design aspects should be reworked for improved results, the device can effectively be used to facilitate small-scale research for automated weeding strategies.

Integrated Weed Management Systems to Control Common Ragweed (Ambrosia artemisiifolia L.) in Soybean

As resistance to herbicides limits growers' weed management options, integrated weed management (IWM) systems that combine non-chemical tactics with herbicides are becoming critical. A 2 year integrated weed management (IWM) study was conducted at three locations in VA, USA. The factorial study evaluated: (1) soybean planting date (early or late planted) (2) with or without winter cover (cereal rye/wheat or no cover), and (3) with or without harvest weed seed control (HWSC). Prior to soybean planting in the first year, winter cover resulted in a 22% reduction in common ragweed density compared to no cover. At soybean harvest in the first year, the lowest common ragweed densities were in the late planted plots following winter wheat, and common ragweed aboveground biomass was reduced by 46 and 22% at two locations in late planted compared to early planted soybean. To evaluate the impact of the first year's treatments and HWSC, full season soybeans were planted across the trial in the second year. Prior to soybean planting in the second year, late planting in the first year common ragweed density was reduced by 83% at one location, but significant reductions were not observed elsewhere. When comparing winter cover to no cover, common ragweed densities were reduced by 31 and 49% at two locations and densities were similar at the third location. Harvest weed seed control reduced common ragweed density by 43% at one location compared to the conventional harvest plots but no significant reductions were observed at the other locations or at other rating timings. However, there was a significant location by planting date by winter cover interaction and the overall lowest common ragweed densities (4.1 to 10.3 plants m−2) were in the late planted plots with winter cover. This research indicated that winter cover, late planting, and HWSC can reduce common ragweed populations with late planting being the most influential. Therefore, double-cropping soybean after wheat is likely the most viable means to better control common ragweed using IWM as it combines both winter cover and late planting date.

Developing a multispecies weed competition model for high-yielding cotton

AbstractGlyphosate-tolerant and glyphosate-resistant weeds are becoming increasingly problematic in cotton fields in Australia, necessitating a return from a glyphosate dominated system to a more integrated approach to weed management. The development of an integrated weed management system can be facilitated by identifying the critical period for weed control (CPWC), a model that enables cotton growers to optimize the timing of their weed control inputs. Using data from field studies conducted from 2003 to 2015, CPWC models using extended functions, including weed biomass in the relationships, were developed for the mimic weeds, common sunflower and Japanese millet, in high-yielding, fully irrigated cotton. A multispecies CPWC model was developed after combining these data sets with data for mungbean in irrigated cotton, using weed height and weed biomass as descriptors in the models. Comparison of observed and predicted relative cotton-lint yields from the multispecies CPWC model demonstrated that the model reasonably described the competition from these three very different mimic weeds, opening the possibility for cotton growers to use a multispecies CPWC model in their production systems.