Spray Volume Rate Research Articles

Spray coverage profiles from pecan air-blast sprayers, with a radial air-flow and a volute-generated focused air-flow, as affected by forward speed and application volume

Pecan (Carya illinoinensis) is an important specialty crop in the U.S.A., but yield is limited by several diseases and pests. In mature-tree pecan orchards, large air-blast sprayers are commonly used to apply the pesticides to control these diseases and pests. The spray coverage, deposition and profiles are poorly defined under the range of application scenarios, limiting the recommendations that can be provided to growers to maximize control while minimizing input costs. To explore effects of sprayer setting parameters such as travel speed and spray volume rate on spray coverage on tall targets we set up a system (a simple vertical patternator) using a 19-m-tall pole with cards attached at eight height levels from 5 to 19 m above ground, allowing to determine the vertical distribution pattern of two air-blast sprayers with different air discharge systems. Spray was applied with a standard radial-flow air-blast sprayer during six treatments being combinations of two travel speeds: 2.4 and 3.2 km/h, and three spray volume rates: 470, 940 and 1970 L/ha, as well as with a focused air-flow system (a volute) sprayer during four treatments being combinations of two travel speeds: 2.4 and 3.2 km/h, and two spray volume rates: 470 and 940 L/ha. Results show that using a standard radial air-flow sprayer, application volume affected coverage at heights ≤17 m (higher volumes resulting in more coverage). Higher speed using a standard radial air-flow sprayer resulted in greater spray coverage, but was inconsistent with the focused air-flow system. Using a focused air-flow system more spray coverage occurred at >17 m compared to a standard radial air-flow sprayer. Spray coverage profiles affirmed the rapid decline in coverage with height using a standard radial air-flow sprayer. The results may help guide decisions on volute use, spray volume, and spray partitioning to different parts of the canopy to improve spray profile characteristics for applying more uniform spray coverage to mature pecan tree canopies.

Back Cover Image, Volume 78, Issue 8

The back cover image is based on the Research Article Assessing the application of spot spray in Nanguo pear orchards: Effect of nozzle type, spray volume rate and adjuvant by Shuang Guo et al., https://doi.org/10.1002/ps.6999.image

Assessing the application of spot spray in Nanguo pear orchards: Effect of nozzle type, spray volume rate and adjuvant.

Aerial spray is one of the most important applications of unmanned aerial vehicles (UAVs) in agriculture. This work aimed to promote the use of UAVs as an alternative to knapsack electric sprayers in pesticide application in Nanguo pear orchards planted in mountain terraced orchard scenarios. The spray deposition of four types of nozzles (SX110015, XR80015, IDK90015 and TR80015), two spray volume rates (45 and 90 L ha-1 ) and with or without a commercial surfactant adjuvant were evaluated based on the spot spray mode. The air- assisted IDK90015 nozzle showed significantly higher deposition and penetration, and its large droplet size also reduced the risk of drift. Increasing the spray volume rate can increase the amount of droplets deposition. The adjuvant showed excellent potential to improve spray technology in Nanguo pear trees, with a mean deposition of 0.175-0.574 μL cm-2 and penetration of 3.09-66.73%. The droplet size also increased significantly, with volume median diameter (DV0.5 ) of 469 μm. The nozzle type, spray volume rate and adjuvant should be well considered when using the spot spray in orchard. Compared with increasing spray volume rate, the use of air-induction nozzles and surfactant-based adjuvants can improve the spray deposition better. © 2022 Society of Chemical Industry.

Droplet deposition and pest control efficacy on pine trees from aerial application.

Aerial application, a spraying method with aircraft as the application platform, is one of the most important methods of pest control in pine forests. This work aimed to investigate the movement and distribution patterns of droplets and the pest control effectiveness of helicopter spraying on Masson pine (MP) and Korean pine (KP) trees. In particular, three nozzle types (CP02, CP03 and CP04) were evaluated and compared at the same spray volume rate (15 L ha-1 ) in both wind tunnel and field trials. The CP04 nozzle with a larger orifice size showed significantly better deposition and penetration, but the precision of flight operation parameters must be strictly controlled when using this type of nozzle. The majority (≥48%) of the droplets produced by the three nozzle types were concentrated in the range of <200 μm, and the spray performance of each nozzle type was more stable in the range 201-300 μm. The final pest correction control rate (CR) of MP was in the range 59.24-95.74% and that of KP was 45.41-54.39% by helicopter spraying. This study confirmed that it is necessary to select the appropriate nozzle type and ensure accurate flight parameters for aerial application in mountain pine forests. Meanwhile, it also confirms the importance of the timing of operation which can lead to incorrect implementation, resulting in poor control effectiveness. © 2022 Society of Chemical Industry.

Evaluation of the Effects of Spray Technology and Volume Rate on the Control of Grape Berry Moth in Mountain Viticulture

The current work evaluated spray coverage and pest control effectiveness against the grape berry moth (Lobesia botrana) by two different spray technologies and volume rates: A spray gun (high-volume sprayer—HVS) calibrated at 1000 L ha−1 and a conventional orchard sprayer calibrated at 500 L ha−1 (OS500) or 250 L ha−1 (OS250). Experiments were carried out in three different grape varieties over two years in mountain vineyards on the Mediterranean island of Cyprus. The median coverage for HVS remained above 80% for all three varieties, while that for OS500 ranged from 26% to 56%, and that for OS250 from 18% to 37%. Infestation by the grape berry moth varied from about 2.5% for Palomino, to 8% for Carignan and 3.2% for Xynisteri. Infestation in sprayed plots remained below 1.8% for all treatments, varieties and study years. Although infestation levels in OS250 were not different than the control in two varieties, the infestation levels among sprayer treatments did not differ by more than one percentage point. The current work suggests that lowering application volume and pesticide amount to 50% or more, in some cases, provides adequate control and represents an effective option for reducing pesticide use in vineyards.

Spray Volume and Rate Based on the Tree Row Volume for a Sustainable Use of Copper in the Control of Citrus Canker.

Copper is the most efficient pesticide for the control of citrus canker (Xanthomonas citri subsp. citri). To mitigate the environmental impacts and costs, the copper sprays in citrus orchards are being optimized based on the tree row volume (TRV). A previous investigation allowed for significant reductions of the spray volume and copper rates. Nevertheless, the results also indicated the need for additional studies. The aim of this work was to assess whether both the spray volume and the metallic copper rate based on the TRV may be further reduced. A field trial was carried out during two seasons in a 3-year-old commercial orchard of Pera sweet orange located in the municipality of Paranavaí, Paraná, Brazil. The volumes of 20 and 40 ml of spray mixture per m3 of the tree canopy were assessed in combination with the metallic copper rates of 10.5, 21.0, 36.8, or 52.5 mg/m3. Disease was measured as the temporal progress of canker incidence on leaves, cumulative dropped fruit with canker, and incidence of diseased fruit at harvest. The quality of sprays was assessed by measuring the copper deposition and leaf coverage. The treatment with the highest citrus canker control for the lowest use of water and copper was the combination of 40 ml and 36.8 mg/m3. Regression analyses indicated that the minimum threshold deposition of copper was ∼1.5 µg Cu2+/cm2 leaf area. In addition, the lowest spray volume and copper rate necessary to achieve this deposition are 35 ml/m3 and 30 mg/m3. The use of 20 ml/m3 did not efficiently control the disease due to the deficient coverage of treated surfaces. This study demonstrated that it is possible to use even lower amounts of copper and water without interfering with the efficiency of control of citrus canker.

Effect of Spray Volume and Active Ingredient Rates on Insecticidal Control of a Rice Stink Bug (Hemiptera: Pentatomidae) Complex in Florida Rice

Effect of Spray Volume and Active Ingredient Rates on Insecticidal Control of a Rice Stink Bug (Hemiptera: Pentatomidae) Complex in Florida Rice

The relations of leaf area index with the spray quality and efficacy of cotton defoliant spraying using unmanned aerial systems (UASs)

Leaf area index influences on the spray quality and efficacy, and has relationships with the spray quality and efficacy in agricultural spray application. The aim of the present study was to sought the relations of LAI with the spray quality and efficacy of cotton defoliant spraying using unmanned aerial systems (UASs). A TRAC-II instrument was used to measure the LAI of cotton plants. Three different types of UASs with different spray volume rates (48 L·ha−1, 72 L·ha−1 and 96 L·ha−1), flight altitudes (1.5 m, 2.0 m and 2.5 m), and flight speeds (1 m·s−1, 2 m·s−1 and 3 m·s−1) were tested. Results showed the following: (1) There were exponential relationships between LAI and droplet deposition at volume rates of 48 L·ha−1, 72 L·ha−1 and 96 L·ha−1. There were cubic relationships between LAI and cotton defoliation rate at volume rates of 48 L·ha−1, 72 L·ha−1 and 96 L·ha−1. (2) The multiple regression model between LAI and volume rate, and droplet deposition was D = −0.02896 − 0.08055 L + 0.01226 V, the R2 and RMSE values of the training and test sets were 0.81 and 0.08, and 0.83 and 0.07, respectively. The multiple regression model between LAI and volume rate, and cotton defoliation was C = 100.8524 − 4.0617 L + 0.05482 V, the R2 and RMSE values of the training and test sets were 0.72 and 0.17, and 0.75 and 0.06, respectively.

Effect of spray volume, application timing and droplet size on spray distribution and control efficacy of different fungicides against circular leaf spot of persimmon caused by Plurivorosphaerella nawae

In recent years, Spain has been the scenario of the largest production growth of persimmon worldwide. However, circular leaf spot of persimmon, caused by Plurivorosphaerella nawae, was responsible for causing severe yield and economic losses. This work studied the effect of spray volume rate, droplet size, and application timing on spray distribution and disease control efficacy for mancozeb, pyraclostrobin and difenoconazole applications. Also fungicide degradation dynamics on persimmon leaves were studied. A method to inoculate persimmon plants using natural inoculum of P. nawae was developed. Results showed that spray volume influenced canopy spray coverage regardless of the fungicide used, but it did not influence disease control efficacy, except when pyraclostrobin was applied as pre-inoculation spray. Pyraclostrobin also showed a good post-inoculation activity. Influence of droplet size on spray coverage depended on the leaf side considered but it did not affect disease control efficacy except for pyraclostrobin applied 14 days after inoculation, when coarse droplets had lower control than fine ones. In general, slight degradation dynamics of fungicide residues on leaves were observed at 14 days.

Leaf area, spray volumes and applicable quantities of fungicide during the protection period for control of Asian soybean rust

ABSTRACT The purpose of this study was to check the influence of leaf area index, spray volumes and applicable quantities of fungicide during the protection period, and for control of Asian soybean rust. All tests were conducted in the field and in the laboratory between 2014 and 2016. The quantity of fungicide and the spray volume were varied in the application of fungicides on soybean plants with different leaf area index. Rainfall simulation tests were also carried out at different times after application of fungicide. The spray volume and application rate of fungicide should be adequately proportioned according to the leaf area index of the soybean cultivar. The closer to the time of application that the rain occurs, the lower the control obtained by applying the fungicide. The leaf area index, the fungicide application rates, and the spray volumes influenced the protection period of fungicides and the control of Asian soybean rust.

Spray deposition and distribution on the targets and losses to the ground as affected by application volume rate, airflow rate and target position

Greenhouse crop production in China has in the recent years expanded widely. To minimize compromised pesticide use and adverse environmental impact in these structures, it is essential to optimize the working parameters and settings of sprayers. Experiments using an air assisted greenhouse sprayer and artificial plants with attached fruits were conducted to investigate the effects of volume rate, target location, and airflow rate on spray deposition and distribution uniformity on leaves, fruits and losses to the ground. Three spray volume rates (530, 368 and 220 l ha−1) and three nozzle's outlet volumetric airflow rates (374.4, 289.4 and 234.7 m3 h−1) were evaluated. Ground speeds were set at 0.36 and 0.31 m s−1 for volume rate and airflow rate trials, respectively. Artificial targets (filter-paper collectors) were attached on either sides of leaves, fruits and the ground to collect deposits of a food colourant used as a tracer (Spray solution). Deposition was quantified through UV-VIS spectroscopy at a wavelength of 508 nm. Results indicated that volume rate significantly influenced deposition and distribution uniformity. Reducing the volume rate reduced deposition but improved distribution homogeneity. Quantified absolute deposits on upper leaf surfaces declined by 27.4% (MV) and 43.3% (LV). Normalized deposition displayed under-leaf to upper-leaf deposition ratios of between 16.1% (HV) to 20.0% (LV). Ground deposits were reduced by roughly 37.3% (MV) and 54.7% (LV). Similar to volume rate, airflow rate influenced spray deposition on leaves but followed an opposite trend. Reducing airflow rate improved deposition although the effect attained a threshold at medium airflow rate beyond which further reduction the deposition decreased though the reduction was not statistically significant (P = 0.069). Airflow rate did not significantly affect ground deposits (P = 0.315) it reduced the quantity of spray lost by 7% (MF) and 8.4% (HF).

Spray Tip Configurations with Pulse-Width Modulation for Glufosinate-Ammonium Deposits in Palmer Amaranth (Amaranthus palmeri)

Abstract. A commercial sprayer operated at a field speed of 24 km h-1 simultaneously applied glufosinate-ammonium through seven spray tip treatments spaced along a 30.5 m boom for measured foliar deposits of herbicide in 35 cm tall Palmer amaranth weeds and spray deposits on foliar-mounted water-sensitive paper (WSP). The experiment followed one that found increased herbicide deposits for dual tips with an adjacent, fore-aft mount, downward-pointed pre-orifice tip (Extremely Coarse) operated with blended pulse-width modulation (bPWM) and a pre-orifice tip (Fine) operated constant (non-bPWM) under moderate ambient wind velocities from 3.1 to 4.1 m s-1. Additional dual-tip treatments were added to the dual-tip configuration for the current experiment to expand droplet Coarseness and to add dual tips operated constant to isolate bPWM effects. Tested treatments in common with the previous experiment included the original dual-tip bPWM and non-bPWM combination, Y-adapter fore-aft-mounted pre-orifice tips with diverging spray patterns both operated bPWM, and an air-induction extended-range tip operated constant. Palmer amaranth weeds, total spray volume rate of 93.5 L ha-1, sprayer speed of 24 km h-1, and test methods were similar between studies, except for negligible wind in the current experiment. Conditions were clear and sunny during spraying without indicators of a stable atmosphere. Overall mean glufosinate-ammonium deposits recovered from leaves were greatest for dual-tips operated constant at reduced droplet size (Very Coarse and Fine) due to reduced required tip size operated without bPWM, and for increased droplet size for Y-adapter-mounted pre-orifice tips (Extremely Coarse and Coarse) operated with bPWM, resulting in overall mean glufosinate-ammonium leaf deposits of 15.9 and 15.0 µg a.i. cm-2, respectively. The combination of dual tips at reduced droplet size or the Y-adapter fore-aft spray pattern divergence of bPWM tips coupled with high sprayer speed enhanced droplet interception by Palmer amaranth plants under negligible wind conditions, since the collected deposits, even without summed integration over foliage height, significantly exceeded the applied rate of 8.2 µg a.i. cm-2. An air-induction extended-range tip non-bPWM (Very Coarse) provided the next highest mean in overall glufosinate-ammonium deposit. One increased-droplet size dual-tip, pre-orifice tip bPWM and non-bPWM (Ultra Coarse and Coarse) resulted in a mean deposit that was not significantly different from the air-induction extended-range tip operated non-bPWM. Other dual-tip combinations with bPWM and non-bPWM, including the original dual-tip configuration in the previous study, resulted in significantly reduced mean herbicide deposits. Considering all tested tips, advantages of bPWM depended on spray tip droplet size classifications and Y-mounted fore-aft divergence of spray patterns. Overall mean WSP spot deposits were greatest for reduced droplet size (Very Coarse and Fine) dual pre-orifice tips operated non-bPWM, corresponding with the highest numerical overall mean of glufosinate-ammonium deposit. This correspondence of highest spot deposits and highest mean glufosinate-ammonium deposit also occurred in the previous study. Increased Palmer amaranth control correlated with increased glufosinate-ammonium deposit and decreased volume median diameter (Dv0.5) determined with WSP electronic scans, with the air-induction extended-range tip operated constant and the Y-adapter pre-orifice tip operated as bPWM providing the highest weed control. Overall mean WSP spot deposits ranged from 42.3 to 81.1 spots cm-2, compared to 14.0 to 47.0 spots cm-2 previously reported for similar spray conditions, with spot deposits attributed to negligible wind versus wind, respectively. Thus, the spray environment, particularly wind, exhibited effects on nozzle tip comparisons for foliar deposition and may offer some rationale for the conflicting published data beyond the examined treatments. Keywords: Application technology, Blended pulse-width modulation, Herbicide, Herbicide resistance, Nozzle, Spray deposition, Water-sensitive paper, Weed.

Low-drift nozzles vs. standard nozzles for pesticide application in the biological efficacy trials of pesticides in apple pest and disease control

The coarse spray air-induction nozzles have documented pesticide drift reducing potential and hence pose lower risk of environmental pollution than the standard fine spray hollow cone nozzles. However, it is questioned that use of the low-drift nozzles might not provide as effective crop protection as the standard nozzles. The objective of work was to assess the pest and disease control efficacy as affected by spray volume rate and nozzle type. The experiment was carried out in apple orchard, cv Jonagold/M26. The evaluated treatments were combinations of three spray volume rates: 250, 500 and 750lha−1, and two types of nozzles: hollow cone nozzles generating very fine spray, and flat fan air induction nozzles producing coarse droplets. The biological performance of treatments was determined based on severity of diseases: apple scab (Venturia inaequalis), powdery mildew (Podosphaera leucotricha) and bull's eye rot (Pezicula spp.), as well as population or damage caused by pests: green apple aphid (Aphis pomi), rosy apple aphid (Dysaphis plantaginea Pass.), woolly apple aphid (Eriosoma lanigerum), apple rust mite (Aculus schlechtendali) and apple blossom weevil (Anthonomus pomorum L.). In general apple scab was equally controlled by all treatments. Only in the years of high infection pressure efficacy of powdery mildew control was better for fine spray nozzles and high volume rates. Green and rosy apple aphids were better controlled with higher volume rates, though significance of the advantage over the lower rates was occasional. No effect of spray quality on efficacy of aphid and mite control was found for any spray volume rate. Better control of apple blossom weevil and woolly apple aphid was achieved with the high spray volume rate providing heavy coverage to the point of run-off. The air induction nozzles having drift reducing potential are biologically efficacious alternative to conventional hollow cone nozzles.

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.

Spray volume and fungicide rates for citrus black spot control based on tree canopy volume

The control of citrus black spot (CBS) caused by Phyllosticta citricarpa relies mainly on fungicide sprays. Generally, high and non-standardized spray volumes are adopted and the sprays are based on litre per tree or per hectare. However, the tree canopy volume may vary with age, density and variety, and this is expected to impact on the spray volume and fungicide rates needed for disease control. This study evaluated the efficacy of different fungicide spray volumes and rates for CBS control based on the tree-row-volume (TRV) concept. Two field trials were carried out during three seasons in São Paulo state, Brazil. Trials were set up in commercial orchards of late-maturing ‘Valencia’ sweet orange grown for juice production. In field trial 1, the volumes tested were 125 (standard), 100 (internal runoff point), 75 (intermediate) and 50 (half the internal runoff point) mL of spray mixture/m3 of the tree canopy. In field trial 2, 100 and 50 mL/m3 were evaluated. The fungicide rates ranged from 40 to 110 mg of metallic copper/m3 and from 1.9 to 4.7 mg of pyraclostrobin/m3. Untreated control trees (UTC) were kept unsprayed. CBS incidence and severity, premature fruit drop, yield, fungicide deposition and spray coverage were evaluated. All spray volumes tested reduced CBS incidence and severity on fruit at 75–95% and resulted in 1.6–3.0-fold higher yields than the UTC. However, a slight trend of more CBS symptoms and fruit drop, and lower yield was observed for trees treated with 50 mL/m3 compared to those treated with higher volumes. Spray volume change, from 125 to 75 mL/m3, irrespective of fungicide rate correction, led to a 40% reduction of CBS spray costs and water usage and increased the financial return of the control by up to 35%. TRV-based sprays may contribute to sustainable citrus production by reducing costs and environment impacts while maintaining efficient CBS control.

Flat fan and air induction nozzles affect soybean herbicide efficacy

Fifteen field experiments were conducted from 2002 to 2005 to determine the influence of the nozzle type, spray volume, spray pressure, and herbicide rate on herbicidal efficacy in soybean. There was no effect of the nozzle type on herbicidal efficacy with fomesafen, bentazon, glyphosate, and cloransulam‐methyl when applied at the manufacturer's recommended rate. The control of Echinochloa crus‐galli (barnyardgrass) with quizalofop‐p‐ethyl was improved when applied with flat fan (FF) nozzles compared with air induction (AI) nozzles. There was an increase in weed control with the FF nozzles compared with the AI nozzles in four of the 13 comparisons when the herbicides were applied at half the recommended rate, while in two situations, application with the AI nozzles resulted in improved weed control. With the FF nozzles, there was no effect of the water carrier volume on weed control with bentazon, glyphosate, and cloransulam‐methyl. The control of Abutilon theophrasti (velvetleaf) and Chenopodium album (common lambsquarters) with fomesafen and E. crus‐galli with quizalofop‐p‐ethyl was improved at the higher water carrier volume. With the AI nozzles, the control of A. theophrasti and Ambrosia artemisiifolia (common ragweed) with fomesafen and E. crus‐galli with quizalofop‐p‐ethyl was improved at the higher water carrier volume, while the control of A. theophrasti and Polygonum persicaria (ladysthumb) was improved with glyphosate at the lower water carrier volume. With the AI nozzles, the control of C. album with bentazon and E. crus‐galli with quizalofop‐p‐ethyl was improved at the higher spray pressure. There was no effect of the nozzle type on the soybean yield with glyphosate, cloransulam‐methyl, and quizalofop‐p‐ethyl. The use of the FF nozzles compared with the AI nozzles to apply fomesafen and bentazon increased the soybean yield by 6 and 7%, respectively. Based on this study, the optimum nozzle type, water carrier volume, and spray pressure is herbicide‐ and weed species‐specific.

Investigation on the Correlations between Droplet and Particle Size Distribution in Ultrasonic Spray Pyrolysis

In this study, the measurement of droplet size distribution by means of a laser diffraction technique in ultrasonic spray pyrolysis was investigated. Effects of precursor temperature, spray volume rate, carrier gas flow rate, and physicochemical properties of precursors were analyzed in detail. The results showed that the mean size of precursor droplets decreased with increasing precursor temperature, concentration, and addition of alcohol, while it increased with increasing spray volume rate and carrier gas flow rate. Bimodal droplet size distribution was observed probably due to droplet coagulation effect. A cyclone or an impactor was used to control the droplet size distribution. Uniform droplets were obtained using a cyclone that removed large droplets. For comparison, spray pyrolysis of salt aqueous solutions, such as ZrO(NO3)2 and Ni(NO3)2, were also conducted. Particle size distribution of the spray pyrolyzed powders was analyzed using scanning electron microscopy. The results showed that the particle size distribution of prepared solid particles was strongly dependent on, and could be controlled by, variation in the corresponding properties of the sprayed droplets.

Development and Testing of a Recommendation System to Schedule Copper Sprays for Citrus Disease Control

Abstract Copper (Cu) fungicides are contact action products commonly used for control of citrus fungal diseases. Cu residues are subject to weathering (rain and wind) and dilution from fruit expansion during early growth. Growers often over-spray, which leads to inadequate disease control, or under-spray, which leads to environmental concerns and Cu phytotoxicity to fruit. Fruit surface Cu residue data were collected, developed into an expert recommendation system, and tested for accuracy in predicting fruit surface residues to determine need to re-spray. Trees were sprayed with different amounts of copper fungicides using different water volumes per tree. Cu on fruit surfaces was analyzed over time. These data were used to build a Cu spray scheduling recommendation system (CuSSRS) that predicts initial residue after spraying, depending on spray volume rate and Cu content and then predicts dilution and loss of the Cu residue as fruit grow and rainfall weathering occurs. The model indicates a warning and a danger level of low residual Cu based on necessary levels of Cu for disease control, thus providing the grower with advanced notice of the need to re-spray. The system was grower tested for six years. Verification data on actual versus predicted residues were collected over a three-year period. Success in preventing fungal disease fruit blemishes was determined also. These tests indicated the CuSSRS works reasonably well and in some years can reduce the number of copper fungicide sprays needed.

A SYSTEM TO ASSESS THE MASS BALANCE OF SPRAY APPLIED TO TREE CROPS

The measurement of pesticide spray losses from air blast sprayers as they apply to tree crops is required to providethe industry with information on sprayer efficiency. Spray loss, however, is often difficult to measure using currentstandardized methods. Test procedures are often time consuming and too costly to be extensively used. To facilitate samplingof spray losses during application to tree crops, a device consisting of an adjustable metal frame and a grid has beendeveloped. The grid supports artificial targets. The frame stands in the vineyard or orchard over two adjacent rows, allowingthe sprayer to pass below the structure, while applying a predetermined spray volume rate. Spray deposit on the collectorsenables assessment of the amount of spray droplets dispersed in the atmosphere around the plant target. On one hand, thesystem aims to develop an alternative procedure to the presently proposed ISO methodology (DIS 22369.2) for classificationof orchard/vineyard sprayers according to drift risk. On the other hand, it could facilitate the study of the spray mass balancedischarged to target plants, ground, and atmosphere, integrating ISO standard CD 22522 concerning field measurement ofspray distribution in tree and bush crops. This article reports the first experimental results related to the use of the device.

SPRAY PENETRATION INTO THE CITRUS TREE CANOPY FROM TWO AIR–CARRIER SPRAYERS

Field experiments were conducted to investigate the effect of sprayer type, application volume rate, and airflowrate on spray deposition along depth of the citrus canopy. The trees were sprayed from one side using a tower sprayer withcrossflow fans and rotary atomizers (Curtec) at three spray volume rates and a tower sprayer with an axialflow fan andhydraulic nozzles (Titan) at two spray volume rates and two airflow rates. Spray deposition was determined with fluorometryusing cotton ribbons as targets within the entire canopy depth at two heights.<br><br>For both sprayers, deposition decreased with canopy depth, and spray penetration was improved as the volume rateincreased. The effect of volume rate became significant after about 1 m and 2 m depths for the Curtec and Titan sprayers,respectively. At the highvolume rate, mean depositions of the two sprayers were not significantly different. In general,operating the Titan sprayer at 1600 rpm (lower airflow) gave mean deposition comparable to that at 2225 (rated) rpm (higherairflow). The effect of airflow on spray penetration was significant beyond about 2 m depth.