Volume Application Rate Research Articles

Validating the MAVIS Model for Optimizing Incorporation of Litter-Based Manures to Reduce Ammonia Emissions

The Manure Ammonia Volatilization and Incorporation System (MAVIS) identifies the optimum method of incorporating solid (litter-based) manures (FYM) to reduce ammonia (NH3) emission following spreading. The model allows the user to specify the geometry of the field to be manured and the parameters of the spreader and incorporator machinery and calculates NH3 volatilization for the defined area. Incorporation machinery work rates depend on the available tractor engine power and the power demand of the cultivation implement. Validation of the output showed an acceptable agreement with survey data of achieved work rates over a range of tractor power availabilities. The work rates achieved by plow types are approximately 40% to 50% of the greatest work rate achievable with disk incorporators for primary cultivation (20 to 25 cm depth). Incorporation by the slow, but efficient, plow always reduced NH3 emissions by more than the faster, but less efficient, disk or tine implements. Typically, incorporation by plowing could limit NH3 emissions to approximately 16% of total ammoniacal-N (TAN); the smallest emissions from incorporation by disk harrow or straw incorporation were approximately 30% and 38% of TAN applied, respectively. These differences were almost unaffected by differences in field size, applicator volume, or manure application rate. It should be noted that, when applied to the field scale, there is still an appreciable loss of NH3 even with the optimum application method, despite reductions in plot experiments of up to 98% of NH3 emissions. The allocation of labor between spreading and incorporation had little effect on model outcome for small fields but led to NH3 emissions ranging from <20% to >40% of TAN on fields >10 ha.

Recent history of Moroccan locust control and implementation of mechanical control methods in northern Afghanistan

Moroccan locust, Dociostaurus maroccanus (Orthoptera: Acrididae), is a univoltine insect and an annual pest of wheat, the staple crop in northern Afghanistan. By 1996, the funds that had supported emergency locust control programmes, based on ultra low volume (ulv) technology (a combination of specific application machinery and insecticide formulation that allows volume application rates of typically around one litre insecticide/ha for locust control work) and implemented by the United Nations since 1990, became exhausted. Donors were reluctant to support further purchases of insecticides for a country in the grip of a civil war. Consequently, mechanical control, used by generations of Afghan farmers to protect their crops, was reintroduced. Mechanical control, which involves the monitoring of egg beds in the spring to predict egg hatch, together with the timely mobilization of communities to dig trenches in front of the advancing bands of hoppers, does not use insecticides. Between 1996 and 1999, about 30 000 ha of locusts were cleared by mechanical control saving the purchase of insecticide worth around US$300 000. Mechanical control worked best when the locust was not in an outbreak phase, when the authorities supported the mobilization of communities and when labour was not in short supply. Where circumstances allow, the timely implementation of mechanical control of Moroccan locust is proposed as a means to protect crops and as a strategy to preserve scarce resources.

IT—Information Technology and the Human Interface: Comparison of Different Spray Volume Deposition Models Using LIDAR Measurements of Apple Orchards

This paper reviews the models of spray volume deposition that have been developed to enable the adjustment of pesticide output from an axial fan sprayer to suit different apple orchards. The review has been limited to the empirical models of leaf deposit D formulated as D= Q/ UL, where L is a length-scale that describes the scaling effect of crop structure and Q/ U is the ratio of the spray volumetric flow rate to sprayer speed which defines the volume application rate on a per unit row length basis. The comparative performance of different models was evaluated using field measurements of leaf deposit on Cox apple trees with different combinations of rootstock, plantation density, age and growth stage. A tractor-mounted light detection and ranging (LIDAR) system was used to record orchard structural detail. Different methods for calculating the length-scale L from this information have been developed based on a range of different orchard crop structural parameters. Linear regression analysis of the measurements showed that the standard method of adjusting pesticide output, based on a linear scaling of the spray volume application rate per unit ground area, accounted for only 9% of the variation in the measurements. The use of other models, based on different geometric scaling parameters of orchard structure were demonstrated to give improved correlation with measurements. Of these models, the best correlation was obtained by using a length-scale proportional to the ratio of the tree volume to total ground area and this accounted for 43% of the variation in the measurements. The use of orchard structure parameters, based on crop area estimates derived from a local Poisson distribution of light transmission, gave further improvements. Of these models, the best correlation was obtained with a length-scale proportional to the tree area density and this accounted for 78% of the variation in the measurements. The tree area density is thus the best single crop structure parameter to use as the basis for pesticide dose expression for the practices of apple orchard spraying represented by these measurements. The calculation of this parameter relies on the availability of LIDAR measurements. Alternatively, a simple method for estimating this parameter might easily be constructed as a pictograph showing the relative tree area density associated with orchard tree images that can be reconstructed from these measurements. This research further identifies the need for this type of crop structural information to improve standardization of the dose recommendations on pesticide labels.

Factors Influencing Aerial Insecticide Application to Forests

A successful aerial insecticide application is one that provides the desired degree of pest control at an economic cost, with little environmental impact. This paper discusses a broad range of factors that affect treatment efficacy and environmental impact from aerial insecticide application to forests. Efficacy is affected by parameters such as the choice of active ingredient and its application rate, the volume application rate, tank mix characteristics, the spray droplet size spectrum, and the timing of, and meteorological conditions during an application. Environmental impact is influenced by aspects such as active ingredient specificity, meteorological conditions during the application, avionics use and buffer zone width. Key differences between insecticide applications in forestry and agriculture are pointed out.

SPRAY VARIABLE EFFECTS ON ABSCISSION OF ORANGE FRUIT FOR MECHANICAL HARVESTING

An experimental abscission chemical, CMN-Pyrazole (CMN-P), was applied to Valencia orange trees toinvestigate the effects of spray variables on fruit detachment force and mechanical harvesting efficiency of a trunk shaker.Spray variables included sprayer type, spray volume, ground speed, and CMN-P application rate. Harvesting efficacywas assessed in terms of fruit detachment force, pre-harvest drop of fruit, and percent fruit removal by the shaker. Atcomparable volume rates, CMN-P deposition was not significantly different for the Titan tower and AirFlow sprayers;however, harvesting efficacy was slightly better with the latter. Lower volume sprays resulted in higher deposition thanhigher volumes. However, more uniform deposition, lower fruit detachment force, and higher percent fruit removal wereobserved with higher volume sprays. Increasing the ground speed at constant sprayer output improved depositionefficiency, but more uniform spray distribution, better canopy penetration, and higher harvesting efficiencies wereobtained at lower ground speeds.

Comparison of an Organophosphate Insecticide with a Mycoinsecticide for the Control of Oedaleus senegalensis (Orthoptera: Acrididae) and Other Sahelian Grasshoppers at an Operational Scale

Operational scale field trials were conducted in 1996 and 1997, in the east of the Niger Republic, on 50 and 800 hectare plots, to compare the efficacy of an oil based formulation of the entomopathogenic fungus, Metarhizium anisopliae (flavoviride) var. acridum (Deuteromycotina: Hyphomycetes) with fenitrothion for the control of Sahelian grasshoppers. The Senegalese Grasshopper Oedaleus senegalensis Krauss was the most abundant species in the trials. M. anisopliae was applied at 5 x 1012 spores ha-1 at volume application rates of 2 and 0.5 l ha-1 in successive years. Fenitrothion was applied at 220 g/ha-1 at 1.25 and 0.22 l ha-1 volume application rates. Ultra low volume equipment mounted on a vehicle (1996) or a fixed wing aircraft (1997) was used for application. The M. anisopliae treatment reduced the grasshopper population significantly after 7 days and by 93% within 16 days. Fenitrothion caused a population reduction of more than 90% shortly after application, but due to immigration, the grasshopper population recovered to the initial level within 16 days. Grasshoppers treated with the fungus and given the opportunity to thermoregulate in the sun died more slowly than grasshoppers incubated in the shade. The survival of spores in the spray residue of the M. anisopliae plots assessed by exposing grasshoppers to the sprayed vegetation at intervals and monitoring disease levels during subsequent laboratory incubation, showed the spray residue to remain highly infective, for three weeks after spraying. At the end of the 1997 season, egg pod density and viability in the plot treated with the fungus was reduced compared with both untreated and the fenitrothion plots. Compared with the existing practice of large-scale treatment of grasshopper infestations with fenitrothion, use of M. anisopliae would not only be safer to mammals and less damaging to non-target organisms, but also be more effective in the long-term control of grasshoppers.

Aerial spray trials against brown locust ( Locustana pardalina, Walker) nymphs in South Africa using oil-based formulations of Metarhizium flavoviride

A large micro-light aircraft fitted with Micronair AU7000 atomisers was used to apply Metarhizium flavoviride isolate IMI 330189 to brown locust ( Locustana pardalina) populations (mostly Vth instar nymphs) in the Richmond District of the Karoo in South Africa. Dry conidial powder was formulated in a paraffinic oil mixture to apply approximately 2.0 × 10 12 conidia per hectare with volume application rates of 1.0 and 2.5 l/ha. Three different droplet size spectra were produced by setting the pitch of the atomiser turbine blades to 25, 35 and 45 °. A total of ten hopper bands were treated on three separate days. Samples consisted of insects kept in cages under field conditions and sections of hopper bands maintained in open-topped field enclosures. All treated bands showed significantly greater mortality than the controls, with up to 98% mortality in samples maintained in enclosures after 3 weeks. Mortality in caged samples was often faster than with hoppers maintained in field enclosures. The relative efficacy of the various methods of aerial application will need confirmation in further trials; a volume rate of 2.5 l/ha appeared to give more consistent results than 1 l/ha applications. Mortality was probably related to droplet impaction, affected primarily by the wind-speed at the time of spraying.

Development and evaluation of a method for the design of spray applications: aerial tebufenozide applications to control the eastern spruce budworm, Choristoneura fumiferana (Clem.)

A novel approach to the design of insecticide spray applications was developed and evaluated in field trials to assess the efficacy of the insect moulting hormone analog tebufenozide (Mimic ®) against the eastern spruce budworm, Choristoneura fumiferana (Clem.). The pest biology, and habitat and pesticide characteristics were used as a basis to derive the required active ingredient (a.i.) and deposit density. Ingestion is the primary exposure route; an LD 95 acquisition through foliage consumption by fourthinstar larvae was used to establish a target dose of 15 ng a.i. cm −2 in one drop per needle (2.5 cm −2). A range of a.i. and volume application rates were selected based on the required densities, canopy leaf area index and projected spray losses to the understorey and by drift; application rates of 35, 70 and 140 g a.i. 1 ha −1 were employed, with volume application rates of 1, 2 and 4 L ha −1. Coniferous forest plots were aerially treated, resulting in average deposit densities (droplets cm −2) on artificial foliage between 0.8 and 3.7, with averge volumetric deposits between 7 and 30% of volume application rates. Population control was satisfactory, except for those applications at 35 g a.i. in 2 L and 70 g in 4 L ha −1 for which low deposit densities were observed. This approach to spray application design was found to be of scientific value and is adaptable to other insecticide applications.

Spray deposits in a mature oak canopy from aerial applications of nuclear polyhedrosis virus and Bacillus thuringiensis to control gypsy moth, Lymantria dispar (L.)

Aerial spray applications were carried out to evaluate a naturally occurring nuclear polyhedrosis virus (NPV) for gypsy moth control. Mature oak forest plots were sprayed with a repeated application of 5 × 10 10 occlusion bodies (OB) ha −1 per application, and applications at 5 × 10 10 and 10 11 OB ha −1, all with volume application rates of 5 l ha −1 per application. A Bacillus thuringiensis (Bt) treatment comprising a double application at 30 BIU in 2.4 l ha −1 was evaluated as a positive control. Spray applications were made with a fixed-wing aircraft equipped with rotary cage atomizers, in light winds with weak turbulence, moderate air temperatures and high relative humidity. Spray deposits in the treatment areas were assessed by microscopy and fluorometry, by means of a tracer dye. Deposit densities, drop-size spectra and volumetric deposits were quantified on oak leaves and artificial foliage in the tree canopy and on ground samplers. The NPV applications resulted in average deposit densities (number of stains cm −2) on oak leaves, artificial foliage and ground cards of 8, 15 and 11, respectively, and the Bt applications resulted in densities of 13, 10 and 12 on these substrates; coefficients of variation were high at 73–97%. Drop-size spectra on artificial foliage from the NPV applications had number and volume median diameters that averaged 81 and 279 μm. By contrast the foliar drop-size spectra for Bt applications had number and volume median diameters that averaged 31 and 95 μm, due to lower flow rates and faster cage rotation. Volumetric spray deposits on artificial foliage from the NPV applications averaged 11% of the volume application rate compared to 25% on the ground. The Bt applications resulted in average volumetric foliar and ground deposits of 17 and 21% of the application rate. Comparisons with published data are made, and a suggestion for improving NPV applications for gypsy moth control with the use of finer sprays and more turbulent conditions.

Sprayed barriers of diflubenzuron (ULV) as a control technique against marching hopper bands of migratory locust Locusta migratoria capito (Sauss.) (Orthoptera: Acrididae) in Southern Madagascar

Diflubenzuron was applied to vegetation using handheld Micro-Ulva spinning disc sprayers in barriers. Volume application rate was 0.8 l ha −1 in the barriers and mass application rate was 93.7 g a.i. ha −1 in the barrier, equivalent to 7.8 g a.i. ha −1 overall. A total of 8 barriers, 50 m wide, were sprayed with a 600 m barrier spacing. The approximately square plot of 1649 ha was infested with transiens phase marching hopper hands of Locusta migratoria capito (Sauss.) (Orthoptera: Acrididae). The effects on hopper bands within the plot were monitored and compared with bands from an untreated control plot. Observations of hopper density, hopper band area, age structure and band displacement were made daily. Diflubenzuron effects were observed within 3 days of spraying. All hopper bands in the treated plot and all nymphal stages were affected. In both treated and control plots population decreases were observed in all monitored bands. The decrease in hopper bands in the treated plot was mainly due to diflubenzuron effects whereas that in the control was due to dispersal and some natural mortality. Hopper bands in the treated plot showed decreased displacement rates especially when encountering diflubenzuron barriers. Quadrat studies of locust populations in the plots showed a marked reduction in locust numbers in the treated plot that was significantly different from the control.

Field Efficacy and Deposit Analysis of Bacillus thuringiensis, Foray 48B, Against Gypsy Moth (Lepidoptera: Lymantriidae)

Four aerial treatments of Bacillus thuringiensis (Foray 48B) were evaluated against gypsy moth, Lymantria dispar L., infestations to determine their field efficacy and foliar deposits. From an initial average density of 2,000 egg masses per ha (EM/ha), gypsy moth populations in the untreated (control) blocks increased to 6,570 EM/ha. At a dose of 30 Billion International Units of insecticidal activity per hectare (BIU/ha) applied in 2.3 and in 7.0 liters, the populations decreased significantly to 337 EM/ha (95% control) and to 280 EM/ha (96% control), respectively. At 60 BIU/4.6 and at 90 BIUI 7.0 liters/la, they decreased to 1175 EM/ha (89% control) and to 50 EM/ha (99% control), respectively. EM density differences between treatments after spray were not significant and all were significantly less than the controls. The mean drop density, estimated volume deposit, drop size (Dv05) and relative span (RS) measured on the foliage were 2 drops per cm2, 1.5 nl/cm2, 134 mm Dv0.5, and 0.54 RS for the 2.3 liter/ha application and 8 drops per cm2, 2.2 nl/cm2, 103 mm Dv0.5, and 0.81 RS for the 7.0 liter/ha volume application rates. Nine percent of the leaves collected from blocks sprayed at 2.3 liter/ha had no B. thuringiensis , compared with 2% of the leaves collected from blocks sprayed at 7.0 liter/ha. At 5 or fewer drops per cm2, the differences were 83% and 43%, respectively. The remaining 8% of the leaves collected from the blocks sprayed at 2.3 liter had between 5 and 20 drops per cm2, compared with 49% of the leaves from blocks sprayed at 7.0 liter/ha. The remaining 8% of the leaves collected from blocks sprayed at 7.0 liters/ha were covered with >20 drops per cm2.

Off‐target glyphosate from aerial silvicultural applications, and buffer zones required around sensitive areas

AbstractOff‐target glyphosate deposits were measured downwind of aerial silvicultural applications which used D8‐46 hollow‐cone hydraulic nozzles, ‘Micronair’ AU 5000 rotary atomisers, and the ‘Thru Valve Boom’ (030), with volume application rates of 35, 20 and 20 litre ha−1 respectively, and a glyphosate application rate of 2·1 kg ha−1. Crosswind spray lines were released 10 m above ground level over a short forest canopy, from a fixed‐wing aircraft flying at 45 m s 1 in atmospheric boundary layers with average wind speeds and air temperatures of 2·2‐3·7 m s−1 and 8‐23°C at release height. Ground sheets and artificial foliage clusters were exposed at downwind distances of between 50 and 300 m. Glyphosate deposit measurements at various downwind distances (x) were fitted with non‐linear regression lines; deposits were attenuated at rates inversely proportional to x at powers of 1·3‐2·3. For a particular trial, deposits on ground sheets and artificial foliage were generally similar, and ranged between 19 and 0·04 mg m−2 over the sampling distances used. For 100‐ha applications the estimated buffer‐zone widths around water bodies were less than 50 m, whereas those around non‐target vegetation ranged between 75 and 1200 m, depending on the application method and the meteorological conditions.

Airborne permethrin and off-target deposits from an aerial ultra-low-volume silvicultural spray

A 16 ha forested site with canopy height averaging 7 m was aerially sprayed with an aqueous permethrin emulsion, using active ingredient and volume application rates of 70 g ha −1 and 41ha −1 respectively. A fixed-wing aircraft equipped with Micronair AU 3000 atomizers dispersed a spray with a volume median diameter of 65 μm in a stable atmospheric boundary layer with a wind speed of 2.3 m s −1 and air temperature of 19°C at the spray height of 18 m above ground level. Measurements were made of airborne permethrin and off-target spray deposits on spruce foliage and fine-toothed combs at 2 m above ground level, and glass plates and Kromekote cards placed horizontally on the ground at various distances up to 250 m from the treatment area. Airborne permethrin was reduced by 60% between 0 and 250 m; over this distance the drop numbers per spruce needle decreased from 17 to 2.6 and drop densities on Kromekote ground cards and combs from 22 to 5.6 and from 87 to 18 drops cm −2. Volume median diameters on the Kromekote cards and combs were 49 and 38 μm, and showed no significant change between 0 and 250 m. Permethrin deposits on glass plates and aluminium combs decreased from 23 to 6 ng cm −2 and from 52 to 10 ng cm −2 between 0 and 250 m. Deposits on glass plates were compared with values calculated using a published swath superposition model and found to be in good agreement.

Variations in insecticide dose received by settled locusts: a computer model for ultra-low-volume spraying

A computer model has been devised to examine the variation in the insecticide dose received by settled locusts resulting from change in the primary application variables [volume and mass application rate, spray drop size distribution, emission height and wind speed (with logarithmic wind profile)], while taking into account formulation differences, i.e. specific gravity and volatility. A buoyancy factor can be incorporated, but has been omitted from most of the present calculations. The size and collection efficiency of the locust target are estimated, and drop collection has been computed as the sum of the contributions of the two component processes, i.e. inertial collection on the vertical projected area and sedimentary collection on the horizontal projected area. The lethal swath is shown to be narrowest at very low wind speeds, when dose is mainly dependent on the sedimentary component of deposition. There is progressive widening of swath forecast for increasing wind speed and emission height, coupled with decreasing drop size, until the increasing dilution limits the realization of the lethal dose level. In addition, fall-off in collection efficiency can place a limit to the lowest effective size. For any wind speed there is shown to be a particular volume median drop diameter which maximizes the lethal swath; however, the downwind displacement of the lethal swath is shown to increase progressively with increasing wind speed, emission height and decreasing drop size. Thus the choice of optimum size depends on a trade-off between these effects and accurate targeting in strong winds requires either (a) an appropriate upwind offset in the line of emission (or decrease in emission height), or alternatively (b) some increase in drop size to limit displacement. For aerial spraying from 10 m height at a flow rate of 151 min −1, a volume median diameter (VMD) ⩽ 120 μm is forecast to justify the recommended 100 m track spacing, but the crosswind velocity component should exceed 2 m s −1. The lethal effect is shown to be lost if the emission height is increased to 20 m, unless there is a compensatory increase in flow rate. The VMD may have to be increased to 180 μm to maintain precision in winds above 5 m s −1 if a low emission height is not feasible; however, if the target bands are diffuse, it may be preferable to retain the advantage of the wider swaths accruing from the smaller VMDs (i.e. large reduction in application rate if allied to wider track spacing), while accepting some accompanying uncertainty in placement.