Assessment of electrodynamic spraying as an alternative to ultra-low-volume spraying in western Tanzania

The introduction of ULV (ultra-low-volume) spraying to cotton farmers in western Tanzania in the early 1970s was a major contribution to the cotton industry as the control of cotton insect pests was made easier and possible in many areas. However, spray drift and increased cost of ULV insecticides and batteries have been major constraints to ULV spraying in recent years, so a spraying technique allowing greater efficacy and reduced costs is needed. Trials to assess the potential of electrodynamic spraying as an alternative to ULV spraying started in western Tanzania in 1979. The present study assessed swath width, dosage rates and farmer's reaction to the ‘Electrodyn’® hand-held sprayer as compared with the hand-held spinning-disc sprayer (Micron ULVA), currently used by farmers in Tanzania, in order to identify the optimum combination package to be recommended to farmers. Cypermethrin ED applied at a dosage rate of 15·8–31·6 g a.i./ha by the Electrodyn sprayer over a swath width of 3·0 m gave good control of H. armigera. Yields of seed cotton were comparable to those with ULV cypermethrin applied at a dosage rate of 62·5 g a.i./ha. The spray volume was reduced from 2·5 l/ha applied with the spinning disc to 0·35 l/ha with electrodynamic spraying. Reduced drift, dosage of active ingredient and volume rates, and reduction in the number of batteries needed in a season, were among the major advantages of electrodynamic spraying over ULV spraying in western Tanzania.     

Efficacy of pre and postemergence herbicides on weed suppression in established turfgrass with a conventional and an ultra-low volume sprayer

Previous research has shown the effectiveness of an ULV (Ultra-Low Volume) sprayer compared to a conventional sprayer for weed control in row crop applications. This sprayer produced comparable disease control and foliar nutrient applications to a conventional sprayer in turfgrass, but has not previously been evaluated for weed control in established turf. Four weed control field studies were conducted in the spring and summer of 2012 and 2013 at the University of Nebraska-Lincoln: John Seaton Anderson Turfgrass Research Facility near Mead, NE, USA to compare the weed control efficacy between a novel ULV sprayer and a conventional sprayer. The studies compared the two sprayers for the control of: ground ivy and dandelion in established turf in a summer application; preemergence control of large crabgrass in established turf in a late spring application and ground ivy control in established turf in a late spring application. No differences were observed in weed control between sprayer types in the four studies over both years of the study despite a thirty fold decrease in application volume rate across different herbicide modes-of-action in all of the studies. The Kamterter ULV sprayer system may be a useful and effective management option for control of the weeds in turfgrass.     

热院—30型高扬程喷雾机的研制及应用

在丰收—30型担架式喷粉机的基础上,通过改变风机叶轮叶片的角度,增配汽油机功率输出传动轴和微型输液泵,同时采用加长喷管和特殊雾化器(超低容量喷头)设计出一种新的喷雾机——热院—30型高扬程喷雾机。该机既可进行常规(低容量)喷雾,又可进行超低容量喷雾。射程高度可达16～17m,满足了防治高大乔木病虫害的要求。     

Cotton-pest control: a review of the introduction of ultra-low-volume (ULV) spraying in sub-Saharan French-speaking Africa

Ten cotton-producing countries in sub-Sahara French-speaking African have adopted ULV spraying and by 1985, 97% of the area protected was sprayed using this technique. Compared with knapsack spraying with horizontal booms, ULV sprays gave rise to an equivalent yield of seed cotton, with better or similar bollworm control. In the Ivory Coast, plant coverage obtained by ULV sprays at 3 1/ha with one pass every six rows is insufficient, so a four-row swath with the same amount of insecticide or an increase to 4 or 5 1/ha is recommended late in the season. ULV sprays at 1 1/ha reduce financial expenditure by 15–20% and are used in Cameroon and partly in Chad. This technique may be less effective against certain sucking insects, particularly Polyphagotarsonemus latus in luxuriantly growing cotton.     

Potato late blight control and top desiccation when pesticides are applied with a controlled droplet and a conventional sprayer

Disease development was observed in field plots to which two different fungicides, each at two rates, were applied regularly with either a conventional or a controlled droplet sprayer. The type of fungicide did not affect disease severity, but more disease damage occurred in the controlled droplet sprayer plots than in conventional sprayer plots. Reduced rates of fungicide resulted in higher disease incidence ratings than recommended rates of fungicides by end of the spraying season. Lower marketable tuber yields and greater incidences of late blight tuber rot were related to foliar disease levels, the different sprayer types, and rates of applied fungicide. No significant differences in terms of potato top desiccation efficacy between the two sprayer types were obtained. In addition, total tuber yield and level of vascular discoloration were similar for both the controlled droplet and conventional sprayer.     

Deposition and biological efficacy of a fungicide applied in charged and uncharged sprays in cereal crops

Barley and wheat crops were both sprayed at growth stages 30 and 61–75 with boom-mounted conventional hydraulic nozzles (250 ?/ha), experimental hydraulic electrostatic nozzles (66 ?/ha), electrically driven spinning discs (2 ?/ha, oil-based sprays and 5 ?/ha, aqueous spray) and ‘Electrodyn’ nozzles (1 and 2 ?/ha, oil). The ULV spray systems (up to 5 ?/haS) were used with or without air assistance. The distribution of both oil and aqueous sprays within the crops was measured with fluorescent tracers on plant parts and on whole plants. An experimental triazole fungicide (mixed with tracer) was applied to the crops by all the spray systems and the degree of control of leaf blotch (scald) caused by Rhynchosporium secalis (Oudem.) J.J. Davis in barley and mildew (Erysiphe graminis DC) in wheat compared with the deposit data. The two highest-volume spray systems gave similar results for disease control and there was no significant difference between the charged and uncharged sprays at 66 ?/ha. The Micron Ulva spinning disc and ‘Electrodyn’ systems with air assistance also performed well. Unassisted ULV sprays were often unevenly distributed within the crops and gave inferior disease control. The ‘Electrodyn’ system often produced large total deposits relative to other spray systems but unassisted sprays were mainly deposited on the upper plant parts. The results indicate that application at volumes as low as 1 ?/h can be as biologically effective as conventional high-volume spraying, when compared at the same dose rate of fungicide (90 g/ha). Relationships between spray distribution within cereals and the sites for pest and disease attack are discussed with regard to different methods of application.     

Sprayer type and water volume influence pesticide deposition and control of insect pests and diseases in juice grapes

In a mature Vitis labrusca L. “Niagara” vineyard, we compared an airblast sprayer and an air-assisted rotary atomizer (AARA) low-volume sprayer for coverage of grape clusters and control of grape berry moth, Paralobesia viteana. In addition, the effect of spray volume on control of fungal diseases was evaluated using the fungicides ziram and azoxystrobin applied with an airblast sprayer. For evaluation of coverage, sprayers applied kaolin clay at 28 kg/ha to grapevines while operating at low, medium and high water volumes. Kaolin residues on grape clusters were analyzed to compare the total amount of spray material deposited, percent of fruit surface covered, number of deposits, size of deposits and distance between deposits. There were no significant differences between sprayers or water volumes in the total amount of kaolin deposited on clusters, but the percent surface coverage was much greater on outside-facing berry surfaces (facing the sprayer) than inside-facing surfaces (facing the rachis). On the outside-facing berry surfaces, the airblast sprayer at 468 L/ha of water (medium volume) provided the highest percent coverage, the greatest density of deposits, the largest deposit diameter, and the smallest distance between deposits. On the inside-facing berry surfaces, the same sprayer–volume combination provided the highest percent coverage and greatest deposit diameter, but deposits from the airblast sprayer operating at 935 L/ha (high volume) had the smallest distance between deposits. No significant differences between sprayers or among water volumes were detected in the deposit density on the inside-facing berry surfaces. Bioassays of grape clusters sprayed with fenpropathrin or methoxyfenozide using the airblast or AARA sprayers at two water volumes revealed the greatest fruit protection from P. viteana at the higher volume for the airblast sprayer, but at the lower volume for the AARA sprayer. Spray volume of the airblast sprayer also affected disease control by the protectant fungicide ziram more than by the systemic fungicide azoxystrobin, with 468 L/ha providing better control than 187 L/ha. However, for most diseases, fungicide type was more influential than spray volume in determining the disease control outcome. The results of this study emphasize the need for appropriate water volumes relative to the sprayer and pesticide being used to optimize pest and disease control in juice grape vineyards.     

不同施药器械、施药方法防治稻纵卷叶螟效果试验

2010年在长汀县以3wH-36"华盛泰山"牌担架式动力喷雾机、3WF-950"华盛泰山"牌背负式喷雾机、20型电动式喷雾器、3W8S-16型手动喷雾器进行不同施药器械、施药方法防治稻纵卷叶螟的试验.结果表明,3WF-950背负式喷雾机不仅省时省工,而且防治的效果显著高于20型电动喷雾器和3W8S-16型手动喷雾器,是...     

Daily application of ultra-low-volume (ULV) insecticides at low dosages to control insect pests of cotton in Malawi

ULV carbaryl and DDT were applied to cotton (Gossypium hirsutum) at two sites, five times a week, using five swath widths from 4·5 to 18 m, representing high to low dosages. Sprays were applied between 0830 and 1400 h during the day or between 1830 and 2100 h during the evening. Subsequently, Bemisia spp. (whitefly) and Paurocephala gossypii Russell (psyllid) populations were significantly larger on plants treated with lower dosages applied over wide swaths. Yields of seed cotton were significantly lower from plants treated with low dosages (< 0·5 kg a.i./ha weekly) but the results of spraying in the morning and in the evening were comparable, at both sites.     

Droplet deposition and control effect of insecticides sprayed with an unmanned aerial vehicle against plant hoppers

A small unmanned aerial vehicle (UAV) that can spray pesticide with high efficiency and with no damage to crops is required for the timely and effective spraying of small fields and/or those in hilly mountains. The current study aimed to illuminate the influence of spraying parameters, such as operation height and operation velocity, of the UAV on droplet deposition on the rice canopy and protection efficacy against plant hoppers. Droplets of 480 g l⁻¹ chlorpyrifos·(Regent EC) (at a dose of 432 g a.i. ha⁻¹, spray volume rate of approximately 15 l ha⁻¹) were collected using water-sensitive paper, and the coverage rates of the droplets on the rice canopy and lower layer were statistically analyzed. The deposition and distribution of droplets in the late stage of rice growth were closely related to the operational height and velocity of crop spraying as executed by the UAV, further affecting insect control. The spraying parameters for preventing plant hoppers were then optimized. When the spraying height was 1.5 m and the spraying velocity 5 m s⁻¹, the droplet deposition in the lower layer was maximized, and the droplets exhibited the most uniform distribution (CV = 23%). The insecticidal efficacy was 92%–74% from 3 to 10 days after spraying insecticide. Both the insecticidal efficacy and the persistence period were greater than those achieved with a hand lance operated from a stretcher-mounted sprayer (at dose of 432 g a.i. ha⁻¹, spray volume rate of approximately 750 l ha⁻¹), especially on the 5th day, indicating that UAV had a low-volume and highly concentrated spray pattern to enhance the duration of efficacy. This work offers a basis for the optimized design, improved performance, and rational application of UAV.     

茶园农药优化使用技术

雾滴直径、密度和沉积率直接影响着农药在茶园空间的分布。采用机动弥雾、手动吹雾和小喷孔片等低容量喷雾与常规喷雾(常量法)进行比较试验,结果表明,前者对分布在茶树冠面0—10cm的芽叶害虫的农药中靶率高达60%—79%,较后者高10%—17%,但在茶树中下部的农药沉积率则反之(小喷孔片除外),农药在土壤中的流失量,常量法明显高于低容量喷雾。不同喷雾技术农药在茶树上的化学降解速率和半衰期相近,主要差异在于原始附着量的高低,其高低次序为机动弥雾>手动吹雾>小喷孔片>常量喷雾。农药的安全间隔期和对芽叶害虫的防治效果,低容量喷雾的半剂量处理与常量喷雾的全剂量处理相近。单位面积的农药沉积量及雾滴数与害虫的死亡率呈明显的正相关。各种喷雾技术在树冠面的农药沉积量均已超过害虫的致死量,故在芽叶害虫的防效上无明显差异。重点在于通过改进喷雾技术,以提高低容量喷雾对丛内病虫的防效。在研究的基础上,提出了适用于不同类型、地形、集约化程度及不同分布部位病虫的茶园农药优化使用技术方案,按此方案喷药,可获得显著的经济效益及社会效益。     

热院－3MD4型微型输液泵的研制

热院－３０型高杨程喷雾机垂直喷雾高度能达到１６～１７ｍ，满足了防治橡胶树等高大乔木病虫害的要求，主要是在技术上做了两项较为重要的改进：一是设计和增配了微型输液泵，提高了输液量和输液高度；二是改变了风机叶轮叶片的角度，提高了风机的风量和风压。     

Comparison of application methods for aphicides on sugar beet and swedes

Different designs of electrostatic sprayer (based on hydraulic, rotary atomizer or electrodynamic principles) were compared with uncharged hydraulic sprayers for application of aphicides to sugar beet and swedes. On small plants, the underleaf cover given by low-volume electrostatic systems, ‘APE 80’ and ‘Electrodyn’, enabled effective use of contact-active pyrethroid insecticides. On large plants, electrostatic systems gave no advantage over hydraulic systems and all the systems required the use of aphicides with systemic or fumigant properties to give effective control.     

A spray technique for mass release of eggs of Micromus tasmaniae Walker (neuroptera: Hemerobiidae)

Laboratory and glasshouse tests showed that eggs of Micromus tasmaniae Walker (Neuroptera: Hemerobiidae) can be sprayed at 206 kPa pressure with a specially developed compressed-air sprayer without impairing viability. The effects of five materials (agar, sucrose, gelatin, plant glue and xanthan gum) in water solution on egg hatching were tested and xanthan gum solution (0·03%) was selected as a suitable liquid medium for suspending the eggs and making them adhere to potato foliage. Egg losses during spraying may be greatly affected by wind drift, the amount of exposed soil (which is related to the stage of foliage development) and other environmental factors. The possibility of a spray technique for mass release of M. tasmaniae eggs in the biological control programme for potato pests is discussed.     

Investigations into very-low-volume water-based insecticide application to cotton in Malawi

Field trials in Malawi investigated the effect of swath width, flow rates, voltage and dosage on insect control and yield of seed cotton when applying water-based insecticide formulations to cotton at very-low-volume (VLV) rates through a hand-held spinning-disc sprayer. Halving the dosage of DDT and carbaryl gave poorer control of Heliothis and Earias and low yields. A flow rate of 1·0 ml/s generally gave significantly better insect control, while yield of seed cotton was significantly lower at 1·6 ml/s than at the other rates in only one season. Spraying at high (12−6 V) and low (6−3·5 V) voltage resulted in significant but inconsistent control of Diparopsis and Heliothis, but control of Bemisia, Aphis and Paurocephala nymphs was significantly better at the higher voltage in one season only. At Ngabu, spraying at the higher voltage gave significantly poorer Heliothis control and lower yields in moderately high infestations and poorer control of Bemisia, Aphis and Tetranychus. Only Earias control was significantly better at the narrowest swath. Knapsack spraying gave better Aphis control but yields were similar between the two techniques except in the first year at Ngabu when the knapsack yield was higher. Treated cotton gave higher yields than untreated cotton.     

不同器械施药对水稻白叶枯病防效比较及无人机飞防新技术

以甬优12为材料,进行了水稻白叶枯病不同器械施药防效试验。结果表明,选用相同药剂和药量（20%噻唑锌悬浮剂125 mL/667 m²）,用植保无人机飞防施药对白叶枯病的防效达84.36%,极显著优于用担架式喷雾机或背负式智能电动喷雾器施药,且安全性好。植保无人机施药在水稻生产上具有良好的推广应用前景。文章小结和讨论了无人机飞防白叶枯病新技术。     

Pest management challenges for smallholder vegetable farmers in Zimbabwe

Smallholder vegetable production is expanding rapidly in Zimbabwe both for local sale in urban markets and for export. Pest management practices of 12 small-scale vegetable farmers in two areas of Zimbabwe were surveyed over a five-month period to gather information on crops, pests, diseases and crop protection methods. A range of serious pests and diseases affects non-indigenous vegetables such as Brassicas, tomatoes, onions and cucurbits. Although farmers use some cultural control methods and occasionally botanical pesticides, pest control is predominantly by the use of conventional synthetic pesticides. These are usually applied through lever operated knapsack sprayers although some less orthodox application methods are occasionally used. Results are variable and there are concerns about risks to sprayer operators, consumers and the environment (including natural enemies) due to shortcomings in protective clothing, large deviations from recommended doses and excessive run-off to the soil. Field trials were carried out to evaluate a modified sprayer lance which directs the spray upwards rather than downwards in an attempt to place more of the spray under the leaves where most of the arthropod pests are found. The ‘V lance’ as it is called improved the uniformity of spray coverage on the upper and lower leaf surfaces and is expected to improve efficacy of spraying and/or offer the opportunity to reduce doses or spray frequencies. Farmers who tested the device reported good results and gave constructive feedback for future improvements. The smallholder vegetable sector requires support in the form of improved access to existing pest management information (in an appropriate form) and focused research targeted at the knowledge gaps which currently impede implementation of sustainable IPM.     

Assessment of spray deposition and recycling rate in the vineyard from a new type of air-assisted tunnel sprayer

A new, two-row, air-assisted tunnel sprayer was tested in the vineyard in comparison to a conventional, broadcast sprayer. The tunnel was fitted with external axial flow fans (airflow rate: 2.23 m³ s⁻¹ per row) and lamellate separating panels, designed to filter the excess spray and recover its liquid fraction for recycling, while discharging the air to the outside. Two field tests were performed, at end of flowering and beginning of ripening. Mean deposits on the leaves and on leaf undersides at twelve canopy locations (three height ranges, two depths and the two sides of the row) were assessed using a soluble colour dye (Tartrazine) as a tracer.Mean foliar deposition from the tunnel sprayer and the reference sprayer was not statistically different at either growth stage. The tunnel sprayer gave increased deposit variability on leaf undersides in the first test, associated with uneven deposition over the canopy heights and significant differences between the two sides of the row. This was corrected by a different adjustment of the nozzles and air outlets in the second test when, as a whole, the overall performances of both sprayers could be considered comparable. Penetration into the canopy was similar despite smaller airflow rate of the tunnel sprayer, and coverage of undersides was also comparable and in line with previous tests performed with air-assisted vineyard sprayers.The recycling rate of the tunnel sprayer was 50.1% of spray volume applied in the first experiment, and 34.0% in the second experiment. This confirmed the potential of this technique for substantial spray saving and reduction in chemical input, without compromising deposition.     

Spray deposition assessment using different application techniques in artificial orchard trees

Seven orchard spray application techniques were compared in terms of within-tree deposition quality and off-target losses to the ground and behind the target trees. The studied spray techniques included different sprayer types, fan speeds and air deflector settings. An artificial pear canopy was realized for this purpose. Filter papers and a multiple tracer methodology were used to evaluate deposition. All measurements were conducted indoor and will be used as an input and to validate a CFD orchard spray model.Results showed that spray application technique has an effect on spray deposition. Sprayer design caused major differences in spray distribution and off-target losses. A sprayer with individual spouts gave the highest deposits on the tree (0.15 L), followed by an axial sprayer (0.10–0.12 L). Changing settings on the axial sprayer only caused minor differences, although the high fan gear performed significantly better than the low gear. Lowest tree depositions were found for a cross-flow sprayer (0.08–0.09 L). A significant portion of the spray liquid was lost to the ground and directly behind the trees with all spray techniques. The axial fan sprayer and the sprayer with individual spouts caused higher ground deposits than the cross-flow sprayer. The cross-flow sprayer on the other hand gave higher losses behind the trees, especially when a high fan speed was applied.     

Deposition patterns of small droplets applied to a tomato crop using the Ulvafan and two protoype electrostatic sprayers

The deposition patterns of droplets applied to tomatoes using the commercially available Ulvafan and two prototype hand-held ultra-low volume (ULV) electrostatic sprayers have been compared. A high ratio of droplets on the upper:lower (U:L) leaf surfaces was recorded at most sampling sites after spraying with the Ulvafan. However, a U:L approaching unity was common with the electrostatic sprayers and it rarely exceeded 4:1. Air-assistance was necessary in order to obtain suitable penetration of the foliage using charged droplets. The combination of small droplets (15–20 μm vmd) with a narrow droplet spectrum (vmd/nmd 1·06-1·15) with an even U:L coverage shows great promise for the development of machinery providing truly controlled droplet application in glasshouses.