Assessment of microbial biocontrol agent (BCA) viability to mechanical and thermal stress by simulating spray application conditions.

BACKGROUND: In order to improve the biological control agent (BCA) efficacy, stress factors threatening the viability of microorganisms during spray application need to be determined. The effect of spray mixture temperature and exposure time on Trichoderma harzianum T 22 and Bacillus amyloliquefaciens QST713 viability were tested. Concurrently the combined effect of mechanical and thermal stress effect on BCA viability were tested at two initial spray mixture temperatures (14 and 25 °C) by simulating a spray application using airblast sprayers featured by different tank capacity and a spray liquid circuit (without and with hydraulic agitation system). To assess the BCA microorganism viability, spray mixture samples were collected at time intervals along trials and plated to count the colony forming units (CFU). RESULTS: The critical temperature threshold that inhibited BCA viability was 35 °C with 30 min of exposure. The sprayer type, the initial temperature of the spray mixture and the temperature increment during the trials significantly decreased the number of CFU recovered. When simulating a spray application, the spray mixture temperature increase rate was determined mainly by the residual amount of spray mixture in the tank. Even if the tank capacity does not substantially affect the final temperature reached by the spray mixture, the higher residual spray mixture in bigger tanks can expose the BCAs for a longer time to critical temperatures. CONCLUSIONS: Experimental trials allowed us to identify the effect of factors affecting the viability of tested BCAs, providing information about the actual chance to guarantee the biological efficacy of BCA treatments. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Evaluationof compact air-induction flat fan nozzles for herbicide applications: Spray drift and biological efficacy.

Nozzles are the most critical component of a sprayer for pesticide applications. Recently, air-induction nozzles and twin flat-fan air-induction nozzles have started to be used for herbicide applications. In order to evaluate the potential of compact air-induction nozzles for herbicide spraying, this paper compares the effects of air-induction nozzles and standard flat-fan nozzles on spray atomization, deposition, drift, and weed control efficacy in maize and wheat. Droplet spectra were measured by a laser particle size analyzer, and drift potential values were determined using a drift test bench (ISO 22401). A field study was conducted to compare the spray drift and biological efficacy between Lechler standard flat-fan nozzles and compact air-induction nozzles including different nozzle sizes. In the range from 0.2 to 0.4 MPa, the droplet size classes of the LU and ST nozzles were very similar and ranged from fine to very fine, while the droplets of the air-induction nozzles IDK and IDKT were medium or coarse depending on the spray pressure and nozzle size. The drift potential trials showed that the droplet size characteristics, mainly V 100, are strongly linked with the drift reduction potential. Both drift potential and field results showed that the compact air-induction nozzles had a good performance in drift reduction. In terms of weed control biological efficacy, there were no significant differences between standard flat-fan nozzles and air-induction nozzles. In all cases, the efficacy values were above 80% both in maize and in wheat. In conclusion, air-induction nozzles are recommended for herbicide applications as they provide good biological efficacy while significantly reducing the amount of spray drift, which is of great significance for the protection of the environment and the surrounding sensitive crops.

Dust drift during mechanical and pneumatic wheat sowing and insights into the physicochemical characteristics of the abraded dust.

BACKGROUND: During sowing, plant protection products (PPP)-laden dust particles can be abraded from coated seeds and emitted into the atmosphere. Drift of these particles is a very complex phenomenon and depends on many factors, including the physicochemical characteristics of the dust. Currently, the available data needed to obtain a better understanding of the phenomenon and to build a risk assessment tool remain very limited. In this study, new data on dust drift and on the physochemical characteristics of dust abraded from wheat seeds generated using a pneumatic and a mechanical seeder were obtained. These data will serve as input to optimize a much-needed computational fluid dynamics (CFD) model. RESULTS: The dust generated by the pneumatic seeder contained a greater volume of smaller particles (<150 µm) than the mechanical seeder dust, which contained a greater volume of larger particles (>1000 µm) than pneumatic seeder dust. Compared to the pneumatic seeder, the mechanical seeder showed lower drift values. With both seeders, the drift depositions decreased with increasing distance from the sowing area but no clear relationship between dust drift and wind speed could be found. CONCLUSION: The gathered physicochemical and drift data for wheat seed drilling extend the current dust drift database, and help to better understand the complex dust drift phenomenon. These data will serve as input to refine and validate a CFD dust drift model. Such a model will allow a better and quicker assessment of different scenarios (e.g. varying wind speeds and direction, treatment, drilling technique) at a lower cost than conducting more field trials. © 2023 Society of Chemical Industry.

Boom sprayer optimizations for bed-grown carrots at different growth stages based on spray distribution and droplet characteristics.

BACKGROUND: Pesticide losses and uneven spray distribution should be avoided as much as possible as they reduce the effectiveness of spraying and increase environmental contamination as well as costs. Within the H2020-project OPTIMA the goal is to develop a smart sprayer for bed-grown carrots, including optimizations such as air support and variable nozzle spacing. This paper focuses on selecting the most optimal nozzle types, spacing and height for spraying bed-grown crops, while taking into account different target zone widths depending on the growth stage, based on spray distribution and droplet characterization measurements. RESULTS: The results indicate that four bed spray configurations consisting of four nozzles per bed, i.e. XR8004/XR8004/XR8004/XR8004, AIUB8504/AI11004/AI11004/AIUB8504, AI8004/AI8004/AI8004/AI8004 and XR8002/XR8002/XR8002/XR8002, spraying at 300 kPa and recalculated to 12.0 km h-1 forward speed, are appropriate for spraying different target zone widths (ranging from 1.2 to 2.2 m) with high uniformity (CV < 12%) and minimal losses out of the target zone (<17%) when applied at the most appropriate nozzle spacing and height (varying from 0.35 to 0.65 m). Droplet characterization measurements showed that for the same nozzle size and spray pressure, air inclusion nozzles produced larger but slower droplets than standard flat-fan nozzles. Air support increased the droplet velocities but had only a very limited effect on droplet size. CONCLUSION: Laboratory spray distribution and droplet characterization measurements allowed selection of the most optimal nozzle type, spacing and height for bed spray applications in terms of reduced pesticide losses compared to conventional broadcast applications. © 2022 Society of Chemical Industry.

Hyperspectral Classification of Cyperus esculentus Clones and Morphologically Similar Weeds.

Cyperus esculentus (yellow nutsedge) is one of the world's worst weeds as it can cause great damage to crops and crop production. To eradicate C. esculentus, early detection is key-a challenging task as it is often confused with other Cyperaceae and displays wide genetic variability. In this study, the objective was to classify C. esculentus clones and morphologically similar weeds. Hyperspectral reflectance between 500 and 800 nm was tested as a measure to discriminate between (I) C. esculentus and morphologically similar Cyperaceae weeds, and between (II) different clonal populations of C. esculentus using three classification models: random forest (RF), regularized logistic regression (RLR) and partial least squares-discriminant analysis (PLS-DA). RLR performed better than RF and PLS-DA, and was able to adequately classify the samples. The possibility of creating an affordable multispectral sensing tool, for precise in-field recognition of C. esculentus plants based on fewer spectral bands, was tested. Results of this study were compared against simulated results from a commercially available multispectral camera with four spectral bands. The model created with customized bands performed almost equally well as the original PLS-DA or RLR model, and much better than the model describing multispectral image data from a commercially available camera. These results open up the opportunity to develop a dedicated robust tool for C. esculentus recognition based on four spectral bands and an appropriate classification model.

Development of a Stereovision-Based Technique to Measure the Spread Patterns of Granular Fertilizer Spreaders.

Centrifugal fertilizer spreaders are by far the most commonly used granular fertilizer spreader type in Europe. Their spread pattern however is error-prone, potentially leading to an undesired distribution of particles in the field and losses out of the field, which is often caused by poor calibration of the spreader for the specific fertilizer used. Due to the large environmental impact of fertilizer use, it is important to optimize the spreading process and minimize these errors. Spreader calibrations can be performed by using collection trays to determine the (field) spread pattern, but this is very time-consuming and expensive for the farmer and hence not common practice. Therefore, we developed an innovative multi-camera system to predict the spread pattern in a fast and accurate way, independent of the spreader configuration. Using high-speed stereovision, ejection parameters of particles leaving the spreader vanes were determined relative to a coordinate system associated with the spreader. The landing positions and subsequent spread patterns were determined using a ballistic model incorporating the effect of tractor motion and wind. Experiments were conducted with a commercial spreader and showed a high repeatability. The results were transformed to one spatial dimension to enable comparison with transverse spread patterns determined in the field and showed similar results.

Comparing different techniques to assess the risk of dust drift from pesticide-coated seeds.

BACKGROUND: Although considered as a safe pesticide application method, treated seeds can pose environmental risks when abraded pesticide-laden seed particles are expelled during sowing. This dust drift risk is clearly linked with seed coating quality. Seed coating quality is traditionally assessed with Heubach dust meters, and guidelines are established in terms of the 'Heubach value'. This technique may, however, not take all drift-sensitive particles into account. In this study, results of the Heubach test are compared with two alternative set-ups: mechanical sieving and the individual sowing element. RESULTS: The abrasion potential assessed with the Heubach dust meter was much lower than the total dust fraction generated by mechanical sieving and the individual sowing element. The amount of dust produced and the dust particle size distribution of both the other techniques were comparable. CONCLUSION: It looks as if the Heubach dust meter underestimates the risk of dust drift. Using one of the alternative methods might be a more appropriate way to assess the abrasion potential of seeds. Given the low investment cost required, mechanical sieving seems to be a good approach for non-specialised labs. The individual sowing element set-up is the most realistic simulation of in-field dust drift generation but requires a higher initial investment. Therefore, this set-up is most suitable for specialised labs and is recommended for further research in this area. © 2017 Society of Chemical Industry.

Characteristics of dust particles abraded from pesticide treated seeds: 1. Size distribution using different measuring techniques.

BACKGROUND: Particle size is one of the most important properties affecting the driftability and behaviour of dust particles abraded from pesticide dressed seeds during sowing. Three particle sizing techniques were used determine the particle size distribution of dust abraded from seeds from six different species. RESULTS: Important differences in dust particle size distribution between species were observed with the finest dust for rapeseed and the coarsest dust for barley. Wet laser diffraction and sonic sieving particle size results correlated well while micro-CT is able to deliver three-dimensional information and additional physical particle properties (shape, porosity). CONCLUSION: All particle sizing techniques have their (dis)advantages and none of them is able to perfectly describe the real size distribution of non-spherical particles. The particle size information gathered can be used in dust drift prediction models, risk assessment tools and will help to better understand the dust drift phenomenon. © 2017 Society of Chemical Industry.

Characteristics of dust particles abraded from pesticide treated seeds: 2. Density, porosity and chemical content.

BACKGROUND: Apart from particle size, drift of abraded seed particles during sowing is mainly affected by two other physical properties, viz. particle shape and envelope density. The impact of these abraded seed particles on the environment is highly dependable on their active ingredient content. In this study, the envelope density and chemical content of dust abraded from seeds was determined as a function of particle size for six seed species. RESULTS: Envelope density and active ingredient content both change as a function of particle size. Important differences in these physico-chemical properties were observed between the six species. Functions were fitted to the collected data to describe the physico-chemical properties as a function of particle size. CONCLUSION: The gathered physico-chemical information is essential for the computational fluid dynamics (CFD)-based dust drift prediction models and can be useful for other prediction models as well as for the ongoing risk assessment of active ingredients used for seed treatment on ecosystems and ecosystem-services. In addition, the results can help to better understand the dust drift phenomenon and to develop mitigation strategies. © 2017 Society of Chemical Industry.

Development and implementation of a laboratory spray device and rainfall simulator for retention research using small amounts of agroformulations.

BACKGROUND: Rainfall greatly affects the retention of foliar-applied agroformulations. Improving their resistance to wash-off is therefore of great importance in spray applications. When developing such formulations, small-scale laboratory assays are generally required. A set-up for retention studies using only small amounts of agroformulations (<0.5 L) was developed. The set-up consists of a spray device and a rainfall simulator. The effect of rain quantity (1, 3, 6 mm) on the spray retention of agroformulations was evaluated using this set-up. RESULTS: The data showed that uniform and repeatable spraying was achieved with the small-scale spray device (coefficient of variation 23.4%) on potato pot plants (Solanum tuberosum L.). Rain quantity significantly affected the spray retention. Approximately 40% of the initial deposition was lost after 1 mm of rain at an intensity of 25 mm h-1 . Additional losses decreased with increasing volumes of rain (65 and 80% loss after 3 and 6 mm of rain respectively). CONCLUSION: Future studies could implement the set-up to evaluate the effect of different rainfall characteristics and formulations on spray retention in order to improve the rainfastness of agroformulations. © 2016 Society of Chemical Industry.

Assessment of the abrasion potential of pesticide-treated seeds using the Heubach test.

During sowing of pesticide-treated seeds, pesticide-laden dust and abraded seed particles may be emitted to the environment, possibly leading to environmental contamination and posing health risks. In many countries there is currently no legislation concerning the acceptable amount of dust of treated seeds. This study aimed to gain insight in the abrasion potential of available pesticide-treated seeds and its associated factors. The abrasion potential of 45 seed samples of 7 different species (viz. sugar beet, oat, barley, wheat, spelt, pea, and maize) was determined using the Heubach test and amounts of dust were expressed as g 100 kgseeds-1, g 100,000 seeds-1, and g ha-1. The abrasion potential fell generally within the boundaries of maximum permissible values adopted by different countries. Species, seed treatment company, number of active ingredient (AIs) and combination of AIs had significant effects on the abrasion potential, whereas little or no effect of agitation and conservation was found. However, species were situated differently with respect to each other depending on the unit in which the abrasion potential was expressed. A standard unit that takes into account the species' seed rate is suggested to give the fairest assessment of dust drift risk and would allow international comparison.

Spray Droplet Characterization from a Single Nozzle by High Speed Image Analysis Using an In-Focus Droplet Criterion.

Accurate spray characterization helps to better understand the pesticide spray application process. The goal of this research was to present the proof of principle of a droplet size and velocity measuring technique for different types of hydraulic spray nozzles using a high speed backlight image acquisition and analysis system. As only part of the drops of an agricultural spray can be in focus at any given moment, an in-focus criterion based on the gray level gradient was proposed to decide whether a given droplet is in focus or not. In a first experiment, differently sized droplets were generated with a piezoelectric generator and studied to establish the relationship between size and in-focus characteristics. In a second experiment, it was demonstrated that droplet sizes and velocities from a real sprayer could be measured reliably in a non-intrusive way using the newly developed image acquisition set-up and image processing. Measured droplet sizes ranged from 24 µm to 543 µm, depending on the nozzle type and size. Droplet velocities ranged from around 0.5 m/s to 12 m/s. The droplet size and velocity results were compared and related well with the results obtained with a Phase Doppler Particle Analyzer (PDPA).

Volatilisation of pesticides under field conditions: inverse modelling and pesticide fate models.

BACKGROUND: A substantial fraction of the applied crop protection products on crops is lost to the atmosphere. Models describing the prediction of volatility and potential fate of these substances in the environment have become an important tool in the pesticide authorisation procedure at the EU level. The main topic of this research is to assess the rate and extent of volatilisation of ten pesticides after application on field crops. RESULTS: For eight of the ten pesticides, the volatilisation rates modelled with PEARL (Pesticide Emission Assessment at Regional and Local scales) corresponded well to the calculated rates modelled with ADMS (Atmospheric Dispersion Modelling System). For the other pesticides, large differences were found between the models. Formulation might affect the volatilisation potential of pesticides. Increased leaf wetness increased the volatilisation of propyzamide and trifloxystrobin at the end of the field trial. The reliability of pesticide input parameters, in particular the vapour pressure, is discussed. CONCLUSION: Volatilisation of propyzamide, pyrimethanil, chlorothalonil, diflufenican, tolylfluanid, cyprodinil and E- and Z-dimethomorph from crops under realistic environmental conditions can be modelled with the PEARL model, as corroborated against field observations. Suggested improvements to the volatilisation component in PEARL should include formulation attributes and leaf wetness at the time of pesticide application. © 2015 Society of Chemical Industry.

Efficacy of entomopathogenic nematodes against larvae of Tuta absoluta in the laboratory.

BACKGROUND: Previous studies have indicated the control potential of entomopathogenic nematodes (EPNs) against Tuta absoluta. Here, the potential of Steinernema feltiae, S. carpocapsae and Heterorhabditis bacteriophora is studied when applied against larvae of T. absoluta inside leaf mines in tomato leaf discs by means of an automated spray boom. RESULTS: The studied EPN species were effective against all four larval instars of T. absoluta but caused higher mortality in the later instars (e.g. fourth instar: 77.1-97.4% mortality) than in the first instars (36.8-60.0% mortality). Overall, S. feltiae and S. carpocapsae yielded better results than H. bacteriophora. Steinernema carpocapsae and H. bacteriophora performed better at 25 °C (causing 55.3 and 97.4% mortality respectively) than at 18 °C (causing 12.5 and 34.2% mortality respectively), whereas S. feltiae caused 100% mortality at both temperatures. Under optimal spraying conditions and with the use of Addit and Silwet L-77 adjuvants, a reduced dosage of 6.8 infective juveniles (IJs) cm(-2) yielded equally good control as a recommended dosage of 27.3 IJs cm(-2) . CONCLUSION: Under laboratory conditions, S. feltiae and S. carpocapsae showed good potential against the larvae of T. absoluta inside tomato leaf mines. Results need to be confirmed in greenhouse experiments. © 2015 Society of Chemical Industry.

Drift from the Use of Hand-Held Knapsack Pesticide Sprayers in Boyacá (Colombian Andes).

Offsite pesticide losses in tropical mountainous regions have been little studied. One example is measuring pesticide drift soil deposition, which can support pesticide risk assessment for surface water, soil, bystanders, and off-target plants and fauna. This is considered a serious gap, given the evidence of pesticide-related poisoning in those regions. Empirical data of drift deposition of a pesticide surrogate, Uranine tracer, within one of the highest potato-producing regions in Colombia, characterized by small plots and mountain orography, is presented. High drift values encountered in this study reflect the actual spray conditions using hand-held knapsack sprayers. Comparison between measured and predicted drift values using three existing empirical equations showed important underestimation. However, after their optimization based on measured drift information, the equations showed a strong predictive power for this study area and the study conditions. The most suitable curve to assess mean relative drift was the IMAG calculator after optimization.

Quantitative 3D shape description of dust particles from treated seeds by means of X-ray micro-CT.

Crop seeds are often treated with pesticides before planting. Pesticide-laden dust particles can be abraded from the seed coating during planting and expelled into the environment, damaging nontarget organisms. Drift of these dust particles depends on their size, shape and density. In this work, we used X-ray micro-CT to examine the size, shape (sphericity) and porosity of dust particles from treated seeds of various crops. The dust properties quantified in this work were very variable in different crops. This variability may be a result of seed morphology, seed batch, treatment composition, treatment technology, seed cleaning or an interaction of these factors. The intraparticle porosity of seed treatment dust particles varied from 0.02 to 0.51 according to the crop and generally increased with particle size. Calculated settling velocities demonstrated that accounting for particle shape and porosity is important in drift studies. For example, the settling velocity of dust particles with an equivalent diameter of 200 µm may vary between 0.1 and 1.2 m s(-1), depending on their shape and density. Our analysis shows that in a wind velocity of 5 m s(-1), such particles ejected at 1 m height may travel between 4 and 50 m from the source before settling. Although micro-CT is a valuable tool to characterize dust particles, the current image processing methodology limits the number of particles that can be analyzed.

Effect of spray angle and spray volume on deposition of a medium droplet spray with air support in ivy pot plants.

BACKGROUND: Spray boom systems, an alternative to the predominantly-used spray guns, have the potential to considerably improve crop protection management in glasshouses. Based on earlier experiments, the further optimization of the deposits of a medium spray quality extended range flat fan nozzle type using easy adjustable spray boom settings was examined. Using mineral chelate tracers and water sensitive papers, the spray results were monitored at three plant levels, on the upper side and the underside of the leaves, and on some off-target collectors. In addition, the deposition datasets of all tree experiments were compared. RESULTS: The data showed that the most efficient spray distribution with the medium spray quality flat fan nozzles was found with a 30° forward angled spray combined with air support and an application rate of 1000 L ha(-1) . This technique resulted in a more uniform deposition in the dense canopy and increased spray deposition on the lower side of the leaves compared with the a standard spray boom application. Applying 1000 L ha(-1) in two subsequent runs instead of one did not seem to show any added value. CONCLUSION: Spray deposition can be improved hugely simply by changing some spray boom settings like nozzle type, angling the spray, using air support and adjusting the spray volume to the crop.

Improving the biocontrol potential of Steinernema feltiae against Delia radicum through dosage, application technique and timing.

BACKGROUND: The potential of the entomopathogenic nematode (EPN) Steinernema feltiae Filipjev as a biocontrol agent against the cabbage maggot Delia radicum (L.), was assessed in three field tests, focusing on EPN dosage, application technique and timing. RESULTS: Spraying cabbage plant trays with different doses of infective juveniles (IJs) (50,000, 100,000 and 200,000 per plant) generated a similar reduction of plant mortality. Spraying plant trays with 200,000 IJs of Steinernema feltiae per plant temporarily reduced the number of maggots around the plants' roots, while neither spraying a lower dose (50,000 IJs/plant) nor soil drenching with 200,000 or 50,000 IJs/plant) reduced maggot numbers. When applied as a plant tray spray, IJs of S. feltiae took 1-2 weeks to spread through the soil surrounding the roots. The pathogenicity of the EPNs, as evaluated by a Galleria mellonella bait test, was highest (up to 100% mortality) until up to five weeks after application, and declined to control levels after 4-7 weeks. Follow-up drench applications with EPNs, applied one and/or two weeks after the first EPN application, did not influence control of Delia radicum. CONCLUSION: Plant tray spraying provides better placement of Steinernema feltiae than soil drench treatments for control of Delia radicum. Plant mortality was not dose-dependent in the presented trials, unlike the reduction of maggot numbers. Further research into timing and application technique of follow-up treatments with S. feltiae is required to increase efficacy to commercial standards.

Improving the biocontrol potential of entomopathogenic nematodes against Mamestra brassicae: effect of spray application technique, adjuvants and an attractant.

BACKGROUND: Steinernema carpocapsae Weiser, an entomopathogenic nematode (EPN), is a potential biological control agent for the cabbage moth (Mamestra brassicae L.). This research aimed to identify a suitable spray application technique, and to determine whether yeast extract added to an EPN spray has an attracting and/or a feeding stimulant effect on M. brassicae. The biological control capabilities of EPN against this pest were examined in the field. RESULTS: Good coverage of the underside of cauliflower leaves, the habitat of young instar larvae (L1-L4) of M. brassicae was obtained using different spray boom configurations with vertical extensions that carried underleaf spraying nozzles. One of the configurations was selected for field testing with an EPN spray. Brewer's yeast extract stimulated larval feeding on leaves, and increased the mortality of these larvae when exposed to EPN. The field trial showed that a spray application with S. carpocapsae, Addit and xanthan gum can effectively lower the numbers of cabbage heads damaged by M. brassicae. Brewer's yeast extract did not significantly increase this field performance of EPN. CONCLUSION: Steinernema carpocapsae, applied with an appropriate spray technique, can be used within biological control schemes as part of a resistance management programme for Bt.

Pesticide-laden dust emission and drift from treated seeds during seed drilling: a review.

Dressing seeds with pesticides to control pests is a widespread practice with important advantages. Recent incidents of bee losses, however, have directed attention to the emission of abraded pesticide-coated seed particles to the environment during sowing. This phenomenon of drift of pesticide dust can lead to pesticide contamination of air, water and other natural resources in crop-growing areas. This review article presents the state of the art of the phenomenon of dust emission and drift from pesticide seed dressing during sowing and its consequences. Firstly, pesticide seed treatment is defined and its pros and cons are set out, with the focus on dust, dust emission and dust drift from pesticide-coated seed. The factors affecting emission of pesticide dust (e.g. seed treatment quality, seed drilling technology and environmental conditions) are considered, along with its possible effects. The measuring techniques and protocols and models currently in use for calculating the behaviour of dust are reviewed, together with their features and limitations. Finally, possible mitigation measures are discussed, such as improving the seed quality and the use of modified seed drilling technology, and an overview of regulations and stewardship activities is given.