Weed biological control in low- and middle-income countries.

Invasive alien plants have a significant impact on biodiversity, crop and pasture production, human and animal health, water resources, and economic development. As most low- and middle-income countries do not have the resources to actively manage invasive plants, many have intentionally introduced biological control agents to help manage their most important weeds. Some of these introductions have resulted in the successful control of numerous weeds such as Chromolaena odorata, Mimosa diplotricha, Pistia stratiotes, and Salvinia molesta. These successes are partly due to the reliance on biological control agents that have been tested and utilized elsewhere. However, despite the successes in weed biological control to date, many low- and middle-income countries are reluctant to pursue weed biological control, due to poor perceptions of biological control and lack of capacity. This results in missed opportunities to manage many weeds cost-effectively, and in so doing, increasing production costs and a dependency on herbicides.

Recognition pest by image-based transfer learning.

BACKGROUND: Plant pests mainly refers to insects and mites that harm crops and products. There are a wide variety of plant pests, with wide distribution, fast reproduction and large quantity, which directly causes serious losses to crops. Therefore, pest recognition is very important for crops to grow healthily, and this in turn affects crop yields and quality. At present, it is a great challenge to realize accurate and reliable pest identification. RESULTS: In this study, we put forward a diagnostic system based on transfer learning for pest detection and recognition. This method is able to train and test ten types of pests and achieves an accuracy of 93.84%. We compared this transfer learning method with human experts and a traditional neural network model. Experimental results show that the performance of the proposed method is comparable to human experts and the traditional neural network. To verify the general adaptability of this model, we used our model to recognize two types of weeds: Sisymbrium sophia and Procumbent Speedwell, and achieved an accuracy of 98.92%. CONCLUSION: The proposed method can provide evidence for the control of pests and weeds and the precise spraying of pesticides. Thus, it provides reliable technical support for precision agriculture. © 2019 Society of Chemical Industry.

Robotic weeders can improve weed control options for specialty crops.

Specialty crop herbicides are not a priority for the agrochemical industry, and many of these crops do not have access to effective herbicides. High-value fruit and vegetable crops represent small markets and high potential liability in the case of herbicide-induced crop damage. Meanwhile, conventional and organic specialty crop producers are experiencing labor shortages and higher manual weeding costs. Robotic weeders are promising new weed control tools for specialty crops, because they are cheaper to develop and, with fewer environmental and human health risks, are less regulated than herbicides. Now is the time for greater investment in robotic weeders as new herbicides are expensive to develop and few in number, organic crops need better weed control technology and governments are demanding reduced use of pesticides. Public funding of fundamental research on robotic weeder technology can help improve weed and crop recognition, weed control actuators, and expansion of weed science curricula to train students in this technology. Robotic weeders can expand the array of tools available to specialty crop growers. However, the development of robotic weeders will require a broader recognition that these tools are a viable path to create new weed control tools for specialty crops. © 2019 Society of Chemical Industry.

Occupational risks related to vibrations using a brush cutter for green area management.

INTRODUCTION: Weed control is one of the most important issues in the maintenance sectors of both agriculture and green areas. Small tools are employed for controlling grass and other growths on steep verges and river banks. This leads the operators being exposed to many risks among which vibration is one. The purpose of this study is to measure and evaluate hand-arm vibration and to verify the daily exposure to which workers are often subjected while weeding. MATERIAL AND METHODS: Two cutting heads, a brush knife and a mowing head were compared. Both were mounted on the same cow-horn brush cutter. The vibration total value was expressed as the root-mean-square (rms) of three component values according to the axes X, Y and Z. The signal was frequency weighted using the weighting curve Wh, as described in the ISO 5349-1 (2001) standard. In addition, the daily vibration exposure was calculated and compared with the thresholds set by EU Directive 2002/44/EC (2005). RESULTS: The obtained results showed that the exposure action value (EAV) of 2.5 ms-2 was exceeded while using both cutting heads. The exposure limit value (ELV) using the brush knife also exceeded 5 ms-2. CONCLUSIONS: The results highlighted important aspects in terms of exposure values that should be considered with the view of preventing the risk of Hand-Arm Vibration Syndrome (HAVS) to which the operators who frequently use these tools are exposed. Specific measures should therefore be taken to protect the exposed workers.

Optical Sensing of Weed Infestations at Harvest.

Kochia (Kochia scoparia L.), Russian thistle (Salsolatragus L.), and prickly lettuce (Lactuca serriola L.) are economically important weeds infesting dryland wheat (Triticum aestivum L.) production systems in the western United States. Those weeds produce most of their seeds post-harvest. The objectives of this study were to determine the ability of an optical sensor, installed for on-the-go measurement of grain protein concentration, to detect the presence of green plant matter in flowing grain and assess the potential usefulness of this information for mapping weeds at harvest. Spectra of the grain stream were recorded continuously at a rate of 0.33 Hz during harvest of two spring wheat fields of 1.9 and 5.4 ha. All readings were georeferenced using a Global Positioning System (GPS) receiver with 1 m positional accuracy. Chlorophyll of green plant matter was detectable in the red (638-710 nm) waveband. Maps of the chlorophyll signal from both fields showed an overall agreement of 78.1% with reference maps, one constructed prior to harvest and the other at harvest time, both based on visual evaluations of the three green weed species conducted by experts. Information on weed distributions at harvest may be useful for controlling post-harvest using variable rate technology for herbicide applications.

Precision Herbicide Application Technologies To Decrease Herbicide Losses in Furrow Irrigation Outflows in a Northeastern Australian Cropping System.

This study compared water quality benefits of using precision herbicide application technologies in relation to traditional spraying approaches across several pre- and postemergent herbicides in furrow-irrigated canefarming systems. The use of shielded sprayers (herbicide banding) provided herbicide load reductions extending substantially beyond simple proportionate decreases in amount of active herbicide ingredient applied to paddocks. These reductions were due largely to the extra management control available to irrigating growers in relation to where both herbicides and irrigation water can be applied to paddocks, coupled with knowledge of herbicide toxicological and physicochemical properties. Despite more complex herbicide mixtures being applied in banded practices, banding provided capacity for greatly reduced environmental toxicity in off-paddock losses. Similar toxicological and loss profiles of alternative herbicides relative to recently regulated pre-emergent herbicides highlight the need for a carefully considered approach to integrating alternative herbicides into improved pest management.

Impact of mechanical mowing and chemical treatment on phytosociological, pedochemical and biological parameters in roadside soils and vegetation.

Many chemical and non-chemical strategies have been applied to control weeds in agricultural and industrial areas. Knowledge regarding the effects of these methods on roadside vegetation is still poor. A 2-year field experiment was performed along a road located near Livorno (Tuscany, central Italy). Eight plots/strips were identified, of which four were subjected to periodical mechanical mowing and the remaining four were treated with a chemical herbicide based on glyphosate (the producer's recommended rates were used for the selective control of broad-leaved weeds). Our results clearly showed that roadside soil and vegetation are a significant reservoir of anthropogenic activities which have a strong negative effect on several phytosociological, pedochemical and biological parameters. Compared with conventional mechanical mowing, chemical treatment induced (i) a significant increase in organic matter in the upper plot layers (+18%), and (ii) a marked reduction in weed height throughout the entire period of the experiment. Irrespectively of the kind of treatment, no significance differences were detected in terms of (i) biological quality of soil (the abundance and diversity of arthropod communities did not change), and (ii) plant elemental content (bulk concentrations of analysed trace elements had a good fit within ranges of occurrence in the "reference plant"). The glyphosate partially controlled broad-leaved weeds and this moderate efficacy is dependent upon the season/time of application. In conclusion, the rational and sustainable use of chemical herbicides may be a useful tool for the management of roadside vegetation.

Would banning atrazine benefit farmers?

Atrazine, an herbicide used on most of the US corn (maize) crop, is the subject of ongoing controversy, with increasing documentation of its potentially harmful health and environmental impacts. Supporters of atrazine often claim that it is of great value to farmers; most recently, Syngenta, the producer of atrazine, sponsored an "Atrazine Benefits Team" (ABT) of researchers who released a set of five papers in 2011, reporting huge economic benefits from atrazine use in US agriculture. A critical review of the ABT papers shows that they have underestimated the growing problem of atrazine-resistant weeds, offered only a partial review of the effectiveness of alternative herbicides, and ignored the promising option of nonchemical weed management techniques. In addition, the most complete economic analysis in the ABT papers implies that withdrawal of atrazine would lead to a decrease in corn yields of 4.4% and an increase in corn prices of 8.0%. The result would be an increase in corn growers' revenues, equal to US$1.7 billion annually under ABT assumptions. Price impacts on consumers would be minimal: at current levels of ethanol production and use, gasoline prices would rise by no more than US$0.03 per gallon; beef prices would rise by an estimated US$0.01 for a 4-ounce hamburger and US$0.05 for an 8-ounce steak. Thus withdrawal of atrazine would boost farm revenues, while only changing consumer prices by pennies.

Estimating economic thresholds for site-specific weed control using manual weed counts and sensor technology: an example based on three winter wheat trials.

BACKGROUND: Precision experimental design uses the natural heterogeneity of agricultural fields and combines sensor technology with linear mixed models to estimate the effect of weeds, soil properties and herbicide on yield. These estimates can be used to derive economic thresholds. Three field trials are presented using the precision experimental design in winter wheat. Weed densities were determined by manual sampling and bi-spectral cameras, yield and soil properties were mapped. RESULTS: Galium aparine, other broad-leaved weeds and Alopecurus myosuroides reduced yield by 17.5, 1.2 and 12.4 kg ha(-1) plant(-1) m(2) in one trial. The determined thresholds for site-specific weed control with independently applied herbicides were 4, 48 and 12 plants m(-2), respectively. Spring drought reduced yield effects of weeds considerably in one trial, since water became yield limiting. A negative herbicide effect on the crop was negligible, except in one trial, in which the herbicide mixture tended to reduce yield by 0.6 t ha(-1). Bi-spectral cameras for weed counting were of limited use and still need improvement. Nevertheless, large weed patches were correctly identified. CONCLUSION: The current paper presents a new approach to conducting field trials and deriving decision rules for weed control in farmers' fields.

Potential use of ground-based sensor technologies for weed detection.

Site-specific weed management is the part of precision agriculture (PA) that tries to effectively control weed infestations with the least economical and environmental burdens. This can be achieved with the aid of ground-based or near-range sensors in combination with decision rules and precise application technologies. Near-range sensor technologies, developed for mounting on a vehicle, have been emerging for PA applications during the last three decades. These technologies focus on identifying plants and measuring their physiological status with the aid of their spectral and morphological characteristics. Cameras, spectrometers, fluorometers and distance sensors are the most prominent sensors for PA applications. The objective of this article is to describe-ground based sensors that have the potential to be used for weed detection and measurement of weed infestation level. An overview of current sensor systems is presented, describing their concepts, results that have been achieved, already utilized commercial systems and problems that persist. A perspective for the development of these sensors is given.

MULCHES AND OTHER COVER MATERIALS TO REDUCE WEED GROWTH IN CONTAINER-GROWN NURSERY STOCK.

Due to the recent EU-wide implementation of Integrated Pest Management (IPM), alternative methods to reduce weed growth in container-grown nursery stock are needed to cut back the use of herbicides. Covering the upper layer of the substrate is known as a potential method to prevent or reduce weed growth in plant containers. As a high variety of mulches and other cover materials are on the market, however, it is no longer clear for growers which cover material is most efficient for use in containers. Therefore, we examined the effect on weed growth of different mulches and other cover materials, including Pinus maritima, P. sylvestris, Bio-Top Basic, Bio-Top Excellent, coco chips fine, hemp fibres, straw pellets, coco disk 180LD and jute disk. Cover materials were applied immediately after repotting of Ligustrum ovalifolium or planting of Fagus sylvatica. At regular times, both weed growth and side effects (e.g., plant growth, water status of the substrate, occurrence of mushrooms, foraging of birds, complete cover of the substrate and fixation) were assessed. All examined mulches or other cover materials were able to reduce weed growth on the containers during the whole growing season. Weed suppression was even better than that of a chemical treated control. Although all materials showed some side effects, the impact on plant growth is most important to the grower and depends not only on material characteristics (e.g., biodegradation, nutrient leaching and N-immobilisation) but also on container size and climatic conditions. In conclusion, mulches and other cover materials can be a valuable tool within IPM to lower herbicide use. To enable a deliberate choice of which cover material is best used in a specific situation more research is needed on lifespan and stability as well as on economic characteristics of the materials.

Development and evaluation of a combined cultivator and band sprayer with a row-centering RTK-GPS guidance system.

Typically, low-pressure sprayers are used to uniformly apply pre- and post-emergent herbicides to control weeds in crop rows. An innovative machine for weed control in inter-row and intra-row areas, with a unique combination of inter-row cultivation tooling and intra-row band spraying for six rows and an electro-hydraulic side-shift frame controlled by a GPS system, was developed and evaluated. Two weed management strategies were tested in the field trials: broadcast spraying (the conventional method) and band spraying with mechanical weed control using RTK-GPS (the experimental method). This approach enabled the comparison between treatments from the perspective of cost savings and efficacy in weed control for a sugar beet crop. During the 2010-2011 season, the herbicide application rate (112 L ha(-1)) of the experimental method was approximately 50% of the conventional method, and thus a significant reduction in the operating costs of weed management was achieved. A comparison of the 0.2-trimmed means of weed population post-treatment showed that the treatments achieved similar weed control rates at each weed survey date. Sugar beet yields were similar with both methods (p = 0.92). The use of the experimental equipment is cost-effective on ≥20 ha of crops. These initial results show good potential for reducing herbicide application in the Spanish beet industry.

Configuration and specifications of an Unmanned Aerial Vehicle (UAV) for early site specific weed management.

A new aerial platform has risen recently for image acquisition, the Unmanned Aerial Vehicle (UAV). This article describes the technical specifications and configuration of a UAV used to capture remote images for early season site- specific weed management (ESSWM). Image spatial and spectral properties required for weed seedling discrimination were also evaluated. Two different sensors, a still visible camera and a six-band multispectral camera, and three flight altitudes (30, 60 and 100 m) were tested over a naturally infested sunflower field. The main phases of the UAV workflow were the following: 1) mission planning, 2) UAV flight and image acquisition, and 3) image pre-processing. Three different aspects were needed to plan the route: flight area, camera specifications and UAV tasks. The pre-processing phase included the correct alignment of the six bands of the multispectral imagery and the orthorectification and mosaicking of the individual images captured in each flight. The image pixel size, area covered by each image and flight timing were very sensitive to flight altitude. At a lower altitude, the UAV captured images of finer spatial resolution, although the number of images needed to cover the whole field may be a limiting factor due to the energy required for a greater flight length and computational requirements for the further mosaicking process. Spectral differences between weeds, crop and bare soil were significant in the vegetation indices studied (Excess Green Index, Normalised Green-Red Difference Index and Normalised Difference Vegetation Index), mainly at a 30 m altitude. However, greater spectral separability was obtained between vegetation and bare soil with the index NDVI. These results suggest that an agreement among spectral and spatial resolutions is needed to optimise the flight mission according to every agronomical objective as affected by the size of the smaller object to be discriminated (weed plants or weed patches).

Personal air sampling and risks of inhalation exposure during atrazine application in Honduras.

PURPOSE: To assess occupational inhalation exposure to the herbicide atrazine during pesticide application in a developing country. METHODS: Personal air samples were collected during atrazine application using a personal sampling pump equipped with an OSHA Versatile Sampler (OVS-2) sorbent tube. Samples were collected from 24 pesticide applicators in Honduras. Application was observed during sampling, and a survey was completed in the home. RESULTS: Fourteen of the 24 participants used pump backpack sprayers to apply atrazine and 10 used tractor/boom systems. Despite applying about 15 times as much atrazine, the tractor/boom participants (11.5 µg/m(3)) had only slightly higher (not statistically significant) time-weighted averages (TWA) than participants using backpack sprayers (9.6 µg/m(3)). Within the backpack sprayer group, those that used a cone spray nozzle (11.54 µg/m(3)) had nearly double the TWA than applicators using a flat spray nozzle (5.98 µg/m(3); P = 0.04). In the tractor/boom group, the participants that rode on the boom or the back of the tractor monitoring nozzles (15.0 µg/m(3)) had almost double the average TWA than tractor drivers (8.0 µg/m(3); P = 0.097). CONCLUSIONS: Since tractor/boom pesticide application decreases the number of man-hours required to apply pesticides, and does not increase inhalation exposure significantly, it decreases the overall population occupational exposure. Monitoring nozzles on booms from a distance rather than on the back of a tractor or boom may decrease or eliminate inhalation exposure. Use of flat spray nozzles for herbicide application among pump backpack sprayers may reduce their inhalation exposure.

Controle de plantas invasoras em cultivo orgânico e convencional de capim-limão (Cymbopogon citratus (DC) Stapf. ) / Weed control in organic and conventional crops of lemongrass

O cultivo orgânico é preconizado para o capim-limão (Cymbopogon citratus (DC) Stapf.) como planta medicinal promissora ao desenvolvimento de fármacos no Brasil. Objetivou-se avaliar técnicas de controle de plantas invasoras sobre componentes de produção de capim limão em cultivos orgânico e convencional. Dois experimentos foram instalados sob delineamento inteiramente casualizado, com quatro repetições, em esquema fatorial 2x2x3, considerando-se duas áreas (orgânico e convencional) e os tratamentos combinando cobertura morta (presente e ausente) e técnicas de controle de plantas invasoras (capina manual, roçada e nenhuma). Altura, perfilhamento, teor e rendimento total de óleo essencial de capim-limão no cultivo orgânico foram superiores ao convencional, mas a produtividade de biomassa aérea seca não diferiu entre ambos. A capina, com ou sem cobertura morta, favoreceu o rendimento de óleo no cultivo orgânico.

Organic farming is recommended for lemongrass as a promising medicinal plant for drug development in Brazil. The purpose of this paper was to evaluate the effect of the techniques to control weed on the plant height, tillering, biomass productivity, content and yield of the essential oil of lemon grass in organic and conventional crops. Two experiments were set in a completely randomized design with four replications, at a 2x2x3 factorial scheme, considering two areas (organic and conventional) and treatments combining mulching (present and absent) and weed control techniques (hoeing, skimming and none). Plant height, tillering, content and yield of the essential oil of lemongrass were better in the organic crop, but the biomass productivity did not differ between both areas. The biomass production was better in the conventional crop as to weed control, with or without mulching, and for organic crop under hoeing or skimming with mulching. Hoeing or skimming with no mulching improved the oil content in organic crops. Hoeing or skimming with mulching was better than any other weed control technique with no mulching, and hoeing was better than skimming, justifying its recommendation as a technique for this crop system.

Tank mixture additives approach to improve efficiency of bentazon against broadleaf weeds in peas.

Efficiency of different tank-mixed additives with bentazon at half rate was investigated on (Malva parviflora) and other broad leaf weeds compared with bentazon at the full recommended rate without additives in peas in open field. All the tested additives enhanced the efficiency of bentazon at the half rate. Nonyl phenol and toximol S proved to be the most effective additives in comparison with the full rate treatment. The tested treatments did not show any significant effect on chlorophyll content and soil microorganisms. Bentazon residues were determined in certain treatments to investigate the effect of the tested additives on bentazon deposition. Samples were extracted using QuEChERS method and residues were determined using LC-MS/MS. Residues after 24 hours in the half rate treatment reached 4 times lower than the Maximum Residues Limit (MRL) (0.11 mg kg(-1)), compared to the full rate treatment (0.51 mg kg(-1)), that was slightly above the MRL.

Ergonomic interventions in weeding operations for drudgery reduction of hill farm women of India.

Weeding is an important time consuming and drudgery prone task mainly performed by hill farm women for almost all crops grown. This directs for interventions in terms of improved technologies (weeder, kutla and hoes) to relieve women from high energy demands, time spent and associated drudgery particularly for weeding activity. The study was conducted in two hill states of India viz. Himachal Pradesh (35 villages and 1500 representative samples) and Uttrakhand (10 villages and 500 representative samples). Experimental data were conducted on representative sub sample of 60 hill farm women of both states to assess physiological workload and musculo-skeletal problems both while working with traditional tools along with improved tools by employing selected parameters viz. physical fitness level, physiological parameters etc. The results showed that heart rate values were more than acceptable limits for task performed with the traditional tools as compared with improved tools. Significant reduction in the heart rate was observed while working with improved tools. Analysis of MSDs showed that the postural stress and severity of pain in various body parts was reduced by adopting new technology. Hence, the use of improved weeding tools is recommended over the existing ones for drudgery reduction.

Optimization of the spraying equipment and technology used in ornamental crops.

In 2006, a research project concerning the optimization of the spraying equipment and technology used in ornamental crops was started. First, several greenhouse growers were surveyed on the spray equipment and technology they were using for their plant protection. Later on, different parts of their equipment were evaluated. It this way, we could advice the connected growers on how to improve their own techniques and equipment. Additionally, the survey showed that growers predominantly use knapsack sprayers and lances for crop protection purposes. These techniques are often proven to be less effective compared to spray booms, which could explain the high application rates (up to 6650 L ha(-1)) used by most growers. Since spray boom equipment could enhance spray distribution and minimize labour cost, operator exposure; the usability of this technique in ornamental crops was studied by means of laboratory tests, field trials and bio-efficacy experiments.