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.     

Comparison of ULV with conventional spraying on cotton in Pakistan

ULV and conventional low-volume spraying were compared using ULV and e.c. formulations of deltamethrin, cypermethrin and triazophos to control cotton pests. Both spraying techniques were effective, but Bemisia spp. were controlled better with the low-volume aqueous sprays. The ULV sprayer was much cheaper to use than the conventional knapsack sprayer and covered a five- to six-fold greater area daily.     

Distribution patterns of aerially applied ULV sprays by aircraft over and within the cotton canopy in the Sudan Gezira

A series of experimental ULV sprays by aircraft were conducted over four 35 ha cotton fields in the Sudan Gezira. The aim was to compare the pattern of deposit distribution over and within the cotton canopy when two ULV spray spectra designated for convenience as coarse (120 μm VMD) and fine (80 μm VMD) were released in the early morning (0600 h), mid-morning (0900 h), midday (1130 h) and mid-afternoon (1530 h). Results showed that early morning sprays produced a rather narrow useful swath from both coarse and fine sprays and high risk of drift from fine droplets. Both droplet spectra in the mid-morning spray, on the other hand, provided a good deposit pattern within the cotton canopy and had the least amount in the air at 100 m downwind. Furthermore, the fine spray gave a swath almost 50% wider than the coarse one. At noon the swaths were approximately intermediate to those of the early and mid-morning sprays. However, the variation of deposits at any one point was large and the amounts remaining airborne at 100m downwind were substantial. During mid-afternoon, wind over the Gezira was generally light and variable. As, in practice, the pilot flies invariably along the length of the field rather than across the wind direction, mid-afternoon sprays produced peaky deposits over a narrow swath. With regard to penetration of spray droplets into the canopy, the physical structure of the latter proved to be the determining factor. Turbulence generated by wind or the aircraft had no detectable effect.     

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.     

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.     

Control of Bromus species in winter barley in England using EPTC

EPTC was tested in glasshouse and field experiments for its potential as a herbicide to control Bromus species in winter cereals. Bromus hordeaceus, Bromus commutatus, Bromus pectinatus and Bromus sterilis were all selectively controlled in barley by EPTC. Winter wheat was found to be susceptible but winter barley tolerated doses up to 2·0 kg a.i./ha. The barley cultivar Sonja was more resistant than both Athene and Maris Otter. In the first field trial, 1·0 kg a.i./ha EPTC reduced B. sterilis plant numbers by 75% giving a barley yield increase of 2·84 t/ha. In the following year 2·0 kg a.i./ha reduced B. sterilis numbers by 54% and increased yield by 1·75 t/ha.     

A practical scheme for estimating swath width using ULV sprays

Starting from a simplified model of the aerial dispersion of ULV sprays released from an aircraft perpendicular to the wind direction, a scheme is described for evaluating the total deposition distribution occurring during multiswath spraying. In conditions of overlapping deposition patterns, it is shown that the average concentration generally increases with the downwind distance and is characterized by a pattern of peaks and troughs dependent on the lane spacing. By choosing a suitable reference level on the deposition distribution and matching it to a threshold dose D_t (the minimum area coverage incident on the top of a crop) an optimum swath width can be defined on the basis of minimizing the operational time per unit area sprayed. Estimates of the swath width ω can be obtained by evaluating the expression ω = CQ/ψD_t where C = 0·5 is a derived coefficient, Q is the spray volume emitted per unit distance of flight, and ψ is an overdose coefficient, dependent on meteorological factors—which guarantees D_t to a selected level of probability. For small droplets (diameter 70 μm) the previous expression is fairly insensitive to wind speed, wind direction and atmospheric stability. On an area basis, an overdose (applied dose/threshold dose) is required to take account of both variability in the wind structure and variations in the deposition distribution. A series of worked examples provide insight into the choice of swath width and the associated flying height and demonstrate the practical application of the analysis.     

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.     

Pre-transplant herbicides for weed control in irrigated onion (Allium cepa L.) in northern Nigeria

Field trials were conducted at Samaru in the northern Guinea and at Bakuta and Kadawa in the Sudan Savanna ecological zones of Nigeria to identify suitable herbicides for weed control in irrigated onion. The herbicides tested were chlorthal-dimethyl, fluorodifen and oxadiazon. In the trials each herbicide treatment was compared with an identical treatment which received supplementary hand-weeding. The results of these experiments show that oxadiazon at 1·0–2·0 kg a.i./ha, with or without supplementary hoe-weeding at 6 weeks after transplanting, combined effective weed control with high bulb yields in irrigated dry season onions. While fluorodifen at 1·5 kg a.i./ha followed by supplementary hoe-weeding may be effective at sites with low weed infestation, a higher rate (3·0 kg/ha) may be desirable at sites with a higher broad-leaved weed infestation. Chlorthaldimethyl at 10·0 kg a.i./ha effectively controlled weeds at all the sites and gave high onion yields at sites with 6–12% clay; the selectivity was, however, lower at Bakura with very light soil. Uncontrolled weed growth caused 49–86% reduction in the bulb yields compared with the best herbicide treatments.     

Phytotoxicity of isazophos,lindane and heptachlor to sorghum applied as in-furrow and broadcast-incorporated treatments

Isazophos applied as an in-furrow spray at 0·5, 0·75 and 1·0 kg a.i./ha (4·65, 6·98 and 9·3 g a.i./100 m of row) reduced the establishment of Yates NK 212 sorghum by 37, 61 and 75% respectively. Similarly, heptachlor at 1·12 kg a.i./ha (10·42 g a.i./100 m of row) and lindane at 0·29 kg a.i./ha (2·7 g a.i./100 m of row) reduced establishment by 24 and 57% respectively. Heptachlor and isazophos, applied at the same rates but as broadcast-incorporated sprays and the lowest rate of isazophos applied as an in-furrow spray (0·25 kg a.i./ha, 2·33 g a.i./100 m of row) were not phytotoxic.     

Effects of spray adjuvants on swath patterns and droplet spectra for a flat-fan hydraulic nozzle

The effects of seven agricultural adjuvants and two polymeric drift retardants on the distribution of spray were compared with water applied through a multiple nozzle boom. Similarly, the effects on droplet spectra from a single XR80004VS nozzle operating at 276 kPa (40 p.s.i.) were compared. Except for two adjuvants, swath pattern relative to water was significantly altered. With one exception, droplet spectra parameters relative to water were shifted to both smaller and larger frequency distributions. The polymers, whether sprayed alone or in mixture, had the greatest effect on swath pattern. The polymers sprayed alone had the greatest effect on droplet spectra, but the mixtures gave a more variable response. Swath patterns and droplet spectra derived using water are not, therefore, representative when spraying pesticides with adjuvants. Dynamic surface tension (DST) and viscosity at high shear rates were measured for all spray solutions. Analysis to determine the feasibility of predicting quality of swath pattern and various spray spectra parameters (e.g. VMD, NMD) showed that the interaction between the two physicochemical parameters and the results of atomization are complex. DST and viscosity were poor predictors when applied to the mixtures of polymers and conventional adjuvants tested.     

Effects of application methods,spray volumes,pressures and herbicide rates on weed control in spring cereals

Herbicides were sprayed in spring cereals with conventional and low pressure hydraulic flat-fan spray nozzles and rotary atomizers. The biological effects were measured on weeds and oats. In addition, some spray retention studies were performed. Conventional flat-fan spray nozzles at a spraying pressure of 2 or 4 bar (200 or 400 kPa) gave the best effect. There was no difference in effect between spray volumes of 125 1/ha and 250 1/ha. In most field situations, 200 kPa and 125 1/ha should be preferred. However, when the spray volume is reduced from 250 to 125 1/ha, the droplet size decreases and the drift hazard increases. Where great care has to be taken, the use of conventional flat-fan spray or low-pressure nozzles at 100 kPa and 250 1/ha may be a compromise between effect and safety.     

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.     

Effects of sprayers and nozzles on spray drift and terminal residues of imidacloprid on wheat

In pesticide application, it can be obtained by using appropriate nozzles and sprayers to reduce spray drift and pesticide residues. In this study, a field trail was conducted to determine the spray drift and pesticide residue of imidacloprid on wheat, using three types of flat fan nozzles from the LECHLER Company (LU120-02, AD120-02, IDK120-02) and two types of sprayers (guided-baffle shield sprayer (GBSS) and conventional sprayer (CS)). The spray drift (measured with both airborne and sediment samplers) and terminal residues on wheat were analyzed by liquid chromatography triple-quadrupole mass spectrometry. The results show that both the sediment drift and airborne spray profile were greatest for the LU120-02 nozzle, intermediate for the IDK120-02 nozzle, and lowest for the AD120-02 nozzle. The shielded sprayer gave one third of the drift recorded by airborne samplers and one half of the drift recorded by sediment samplers, compared with results from the CS. Airborne spray drift decreased with increasing height. The imidacloprid residues on wheat grain from different application methods were all below the maximum residue limit (MRL) suggested by EU (0.1 mg/kg) or China (0.05 mg/kg) and no imidacloprid residue was detected on wheat straw. Considering the factors on environment protection, food safety, and biological efficacy, the AD120-02 nozzle and GBSS performed better compared with other nozzles and sprayers. The combination of AD120-02 nozzle with a GBSS is likely to be the optimum application method on wheat.     

Effects of fungicides applied at seeding on stripe rust and common bunt of wheat

Control of stripe rust (Puccinia striiformis) and common bunt (Tilletia caries and T. foetida) of wheat (Triticum aestivum), with fungicides applied on or adjacent to seed at sowing, was studied. Etaconazole pellets (2800 g a.i./ha), fenfuram liquid seed treatment (17 · 5 g a.i./ha) and imazalil granules (5000 g a.i./ha) were phytotoxic, reducing the number of heads per plot. All treatments reduced the incidence of common bunt although benomyl granules (2500 g a.i./ha), benomyl pellets (1400 g a.i./ha) and imazalil granules (5000 g a.i./ha) were not as effective as the registered smut fungicides carboxin, fenfuram, fenaminosulf and triadimefon. Triadimefon pellets (7000 g a.i./ha), PP347 pellets (1400 g a.i./ha), triadimefon granules (1500 g a.i./ha), flutriafol pellets (1400 g a.i./ha) and etaconazole pellets (2800 g a.i./ha) reduced stripe rust severity 17 weeks after sowing by 90, 89, 88, 86 and 74%, respectively.     

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.     

The effect of the air blast sprayer speed on the chemical distribution in vineyard

A study was conducted to determine the spray deposition patterns for air blast sprayers used to apply chemicals to the canopy of Semillon grapevine in vineyard. The application carried out in 12 bars and three sprayer speed (2.1-4.9-7.7 km h(-1)). The spray deposition was measured on the point in the different distances (1.5-3-6-9 m). Tartrazine were applied as tracer material. Maximum spray deposit was obtained 66.1 mg cm(-2) at sprayer speed of 2.1 km h(-1) and minimum deposit was obtained 37.1 mg cm(-2) at sprayer speed of 7.7 km h(-1). The results showed that the sprayer speeds had significant effect on spray deposit distribution and increasing of the sprayer speed increased drift.     

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.     

Comparative performance of recycling tunnel and conventional sprayers using standard and drift-mitigating nozzles in dwarf apple orchards

The use of tunnel sprayers should be encouraged because they can potentially reduce pesticide input and drift in orchards. They could also allow smaller plot size in multifactorial trials in which fully randomized or randomized block designs are recommended. However, the effectiveness of plant protection products applied with tunnel sprayers cannot be reliably assessed without a thorough investigation into spray distribution in tree canopies. A set of three experiments was undertaken in an apple orchard to compare a new type of recycling tunnel sprayer with a standard axial fan sprayer, both of them fitted with either conventional hydraulic hollow cone nozzles (ATR) or drift-mitigating air induction cone nozzles (TVI). Its performance was assessed in terms of 1) spray deposit and coverage in the canopy, 2) sedimentation drift (spray drift to the ground) and 3) collection and recycling rate of the liquid sprayed in the tunnel. Artificial targets composed of cellulose papers and water-sensitive papers were used to evaluate the spray deposit and coverage at similar target positions for each treatment. A fluorescent dye was used as the spray tracer.     

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。