Spraying Citrus Orchards with Antidrift Nozzles

Spraying Citrus Orchards with Antidrift Nozzles Lucia Dolera 1, Rosa Vercher 1, Cruz Garcerá 2, José Mª Soler 3, Luis Val 1* 1 Universitat Politècnica de València, Camino de Vera s/n, Valencia, 46022 Spain 2 Instituto Valenciano de Investigaciones Agrarias, Carretera Moncada-Náquera km. 4,5, Moncada, 46113 Spain 3 Bayer CropScience España, Paterna, 46980 Spain E-mail: lval@dmta.upv.es Abstract The aim of this work is to estimate the effect of low-drift nozzles on both the biological efficacy of acaricide treatments in citrus orchards and the percentage drift of such applications. An experiment was carried out on a commercial orchard of Clementine mandarins. Two low-drift, air induction nozzles, were compared against one conventional cone nozzle. Different configurations for each nozzle were used in order to obtain an spray application rate of around 3000 l/ha. Two variables were assessed for each nozzle, the biological efficacy against Tetranychus urticae Koch when applying Spirodiclofen-based acaricide and the deposited drift. It could be concluded that low-drift nozzles decreased the percentage of drift without detriment of biological efficacy in the control of Tetranychus urticae in citrus. Key words: drift, air-assisted equipment, air-induction nozzles, Tetranychus 1. Introduction Drift is one of the largest sources of pollution that pesticide applications produce. According to ISO 22866 (ISO, 2005), spray drift is defined as the fraction of plant protection product which is carried out of the treatment area by the effect of air currents during the application process. According to this standard, the methodology for the drift estimation is based on the use of artificial collectors, which are located downwind the treated area, and intercept the aerosols drifting away. This fraction pollutes areas around the crop fields and is now being taken into account to establish measures to protect surface water bodies. Moreover, the last European legislation of sustainable use of plant protection products includes the task of avoiding the spray drift (EU, 2009). Nowadays, the official registration of plant protection products in Spain requires providing drift information. However, such information is not based on empirical results, but rather on estimates. The estimation of drift is based on the research conducted in the Biologischen Bundesanstalt für Land-und Forstwirtshaft, Julius Khün Institut (Ganzelmeier et al., 1995) that is located in central European countries, where the climatic conditions and operating uses are very different to those of southern Europe. In addition, crops such as citrus with very specific canopy characteristics are not represented in these studies. Recently, Salyani et al. (2007) working on citrus crops in Florida have made important contributions this way. However, climatic and agronomical conditions in Florida could not be compared to the Spanish ones. They use to grow citrus for juice, and trees and plantations have very different conformations to ours. In this sense, Meli et al. (2003) studied drift in citrus in Sicilia, but they only measured deposited drift up to 7 m of distance of the sprayed area, and in previous experiments we have found that the deposition of drift may go further. Drift could be especially important when the target pest is supposed to need high spray application rates. Moreover, orchard sprayers used on citrus are of the axial fan-assisted type fitted with disc/core conventional nozzles producing fine droplets. Fine droplets produce more uniform spray coverage than coarse droplets, but are more likely to drift (Fox et al., 1985). Air induction nozzles produce coarser droplets, less prone to drift because they quickly fall to the ground once the air support drops below a critical value (Guler et al., 2006). Air induction 1

nozzles are usually known as anti-drift nozzles. Because of the larger size of the droplets that are produced by air induction nozzles, they are thought to influence the spray coverage and consequently the efficacy of the treatments. However, in general, results obtained until now do not confirm this point (Frießleben, 2004; Heinkel et al., 2000; McArtney & Obermiller, 2008). This work is aimed at the comparison of the performance of conventional and air induction nozzles fitted to an axial fan sprayer in a Mediterranean citrus orchard. First, their performance regarding the quantification of the drift that they produce, to study the drift that could be averted with air induction nozzles. Second, the performance regarding the effectiveness in the control of a citrus pest that needs a good penetration inside of the canopy. 2. Material and methods The experiment was carried out in a 12-years-old Clemenules mandarin orchard located in Lliria (Valencia, Spain). The planting framework was 6 x 3.6 m and the average size of the trees was 3.1 m high, 3.5 m long and 4.4 m wide. The tractor used was an Agroplus 90 (Same Deutz Fahr, Treviglio, Italy), with a power of66 kw. The applications were done with an air-assisted sprayer (mod. Futur Pulverizadores Fede S.L., Cheste, Spain), with the following characteristics: - Pump: FDR 1203, with 3 diaphrams, flow of 120 l/min and pressure 50 bar - Nozzle distribution: 2 semi-archs with 10 nozzles - Fan: 915 mm diameter and 10 blades The tested nozzles were two anti-drift nozzles (one air induction hollow cone nozzle, model TVI 80º, and one air induction flat fan nozzle, model AVI 110º, Albuz, Saint-Gobain Solcera, France), and one full cone nozzle, considered as the conventional nozzle (model 1553, Hardi, Taastrup, Denmark). The configuration of each nozzle type was designed to deliver almost the same spray application rate. It was around 3000 l/ha with a forward speed of 1,4 km/h (Table 1). Meteorological data were collected with a weather station. TABLE 1. Nozzle configuration on each semi-arch used in the trial (Diameter of the corresponding nozzle) Nozzle (Position) Semi-arch 1 Semi-arch 2 1553 TVI AVI 1553 TVI AVI 1 - - - - 2 14 grey 80-025 80-025 14 grey 80-025 80-025 3 14 grey 80-025 80-025 14 grey 80-025 80-025 4 14 black 80-025 80-025 14 black 80-025 80-025 5 14 black 80-030 80-025 14 black 80-025 80-025 6 14 grey 80-025 80-030 14 grey 80-030 80-030 7 - - - - - - 2

Drift assessment The experimental design for the drift assessment was based in the ISO Standard 22866 (ISO, 2005), which was adapted to the conditions of the orchard. The total area of the experimental site was 7600 m 2, and it was divided into two parts: - Spray area: It accounted for the area where the applications were made. It consisted of four rows, 50 m long, perpendicular to the dominant wind direction. - Drift-collection area: It accounted for the area where deposited drift was collected. To do so, artificial collectors were placed at known distances from the spray area (2, 3, 4, 8, 9, 10, 14, 15, 16, 20, 21, 22, 26, 27, 28 m). Three replicates were placed at each distance. The fluorescent colouring Brilliant Sulfo Flavine (BSF) (Biovalley S.A., Marne-La-Vallée, France) was used at a concentration of 1 g/l as a tracer for the drift assessment. Blotting paper pieces (51.5 cm 5 cm) were used to collect the deposits. The quantification of the spray tracer deposited in the collectors was made by washing off it and estimating the BSF concentration in the washing water by fluorometry (mod. Cary Eclipse, Varian, Santa Clara, California; excitation wavelength of 425 mm and emission wavelength of 500 mm). BSF concentration was then used to calculate BSF deposit and, consequently, spray deposit in the corresponding collector. These deposits were then expressed as µl/cm 2 and as the corresponding percentage of the spray application rate. The accumulated deposited drift for each nozzle was calculated adding up the values obtained at each distance. Data analysis was performed by means of an Analysis of Variance of the percentage drift data at each distance with the factor Nozzle with three levels (TVI, AVI and Hardi). An ANOVA was also performed to study the influence of the nozzle on the accumulated deposited drift. Biological efficacy The target of treatments was the two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae). This mite causes significant damage to citrus and lives generally grouped in colonies on the underside of the leaves. It has a very fast life cycle, completing a generation optimally in 10 days. The pesticide was an spirodiclofen-based acaricide, applied at a concentration of 0.2 g/l when the mite population started to grow. An untreated control was also included in the study. Efficacy was assessed by monitoring presence-absence of mites in five leaves of the inside of the canopy. Four replicates were performed, using a Randomized Block Design. Each replicate consisted of three adjacent rows with 16 trees each, monitoring the population in the central ten trees of the central row. To define the blocks, the initial level of the pest was evaluated, carrying out a prior sampling of the population of the mites (T). To monitor the evolution of the pest and of the efficacy of the treatments, sampling of leaves was carried out each seven days after treatment (DAT) (T+7/T+14/T+21/T+34). Data analysis was performed by means of an Analysis of Variance of the infestation data at each sampling date with the factor Treatment with four levels (TVI, AVI, Hardi and Control). A Multifactor Analysis of Variance (MANOVA) with two factors, Treatment and Sampling Date with five levels, was applied to analyze if the evolution of the pest with time was the same for all the treatments. 3. Results and Discussion Drift assessment There were significant differences between the nozzles in the percentage of deposited drift. The differences between anti-drift and conventional nozzles were significant for all the distances except at 20 and 26 m (Table 2), where there were not differences between nozzles. The conventional nozzle (Hardi) presented the highest levels of drift in all the monitored distances. AVI anti-drift nozzle generated the lowest drift almost up to the distance of 25 m. Finally, the behaviour of the TVI anti-drift nozzle was similar to the AVI nozzle, although it 3

Drift (% applied dose) generated higher levels of drift in almost all the collection distances. It could be observed that the canopies influenced the deposited drift in the sampling points located just behind them, where the deposits were lower than on the other points of the same swath. This effect could be due to the movement of the spray cloud and the shadow effect produced by the canopies. 9 8 7 6 5 4 3 HARDI TVI AVI 2 1 0 0 5 10 15 20 25 30 Distance (m) FIGURE 1: Percentage of drift deposited as a function of distance in the application on September 20, 2011 in the study plot located in Liria (Valencia). TABLE 2. Percentage of deposited drift at different distances % drift Nozzles Distance (m) TVI AVI HARDI media ± ee media ± ee media ± ee 2 3,806 ± 0,38 (b) 1,620 ± 0,53 (c) 7,610 ± 0,74 (a) 3 2,336 ± 0,53 (b) 0,966 ± 0,28 (b) 6,304 ± 0,78 (a) 4 1,945 ± 0,36 (b) 0,635 ± 0,09 (c) 4,684 ± 0,50 (a) 8 0,549 ± 0,13 (b) 0,448 ± 0,09 (b) 1,136 ± 0,20 (a) 9 0,917 ± 0,23 (b) 0,326 ± 0,04 (b) 2,454 ± 0,21 (a) 10 0,842 ± 0,20 (b) 0,208 ± 0,05 (c) 2,564 ± 0,09 (a) 14 0,245 ± 0,05 (ab) 0,059 ± 0,02 (b) 0,502 ± 0,18 (a) 15 0,325 ± 0,12 (b) 0,051 ± 0,01 (c) 1,181 ± 0,05 (a) 16 0,233 ± 0,06 (b) 0,069 ± 0,02 (b) 1,185 ± 0,42 (a) 20 0,082 ± 0,01 (a) 0,150 ± 0,03 (a) 0,483 ± 0,36 (a) 21 0,122 ± 0,02 (b) 0,128 ± 0,05 (b) 0,877 ± 0,36 (a) 22 0,038 ± 0,02 (b) 0,169 ± 0,12 0,626 ± 0,21 (a) 26 0,081 ± 0,03 (a) 0,358 ± 0,26 (a) 0,317 ± 0,11 (a) 27 0,083 ± 0,01 (b) 0,153 ± 0,03 (b) 0,631 ± 0,04 (a) 28 0,063 ± 0,01 (b) 0,163 ± 0,06 0,330 ± 0,07 (a) Total general 0,778 0,367 2,059 *Different letter in a column indicates that there were significant differences between treatments for each sampling day according to the LSD test (p<0.05) 4

There was a significant effect of the nozzle in the accumulated drift (F = 65.19; d.f.: 2, 8; P = 0.0001), with values (mean ± SE) of 9.09 ± 0.72 µl/cm 2 for the conventional nozzle, 3.43 ± 0.37 µl/cm 2 for TVI nozzle and 1.62 ± 0.20 µl/cm 2 for AVI nozzle. According to these data, the antidrift AVI and TVI nozzles reduced the deposited drift by 82% and 62% respectively compared to the conventional nozzle. Biological Efficacy There were no significant differences in the distribution of the pest between the treatments prior to the applications (T) (F = 0.10; d.f.: 3, 12; P = 0.9592), with 49,3±3,3 % of leaves occupied by the pest (Table 3). TABLE 3: Percentage of occupied leaves (mean ± SEM) in the efficacy trial conducted on September 15, 2011 for control of T. urticae with acaricide (spirodiclofen) in the study plot located in Liria (Valencia). Thesis % occupied leaves T T + 7 T + 13 T + 22 T + 34 TVI 51,5 ± 7,81 a 18,5 ± 4,19 b 17,5 ± 3,31 a 10,5 ± 2,07 b 9,0 ± 4,36 a AVI 47, 5 ± 9,11 a 27, 5 ± 4,43 ab 19,5 ± 3,40 a 14,0 ± 2,45 b 10,5 ± 1,90 a HARDI 51,0 ± 5,26 a 23,0 ± 7,55 ab 18,0 ± 3,65 a 17,5 ± 3,40 ab 12,0 ± 1,83 a Control 47,5 ± 5,13 a 37,0 ± 4,80 a 17,5 ± 5,19 a 27,0 ± 4,44 a 21,0 ± 7,86 a *Different letter in a column indicates that there were significant differences between treatments for each sampling day according to the LSD test (p<0.05) Once the treatments were applied, 7 DAT (T+7) only TVI nozzles showed a significant difference with the Control, and there were no significant differences among the nozzles (F = 2.12; d.f.: 3, 12; P = 0.1515). In the sampling performed 13 DAT (T+13) all the treatments showed a reduction in the infestation, including the Control, possibly reflecting inconsistent data due to an unidentified error during the course of the sampling. In the subsequent sampling (T+22) the mean infestation of all the treatments was lower than in T+7 sampling. In this date, TVI and AVI nozzles showed significant differences with the Control. No significant differences among nozzles were found (F = 5.07; d.f.: 3, 12; P = 0.017). The sampling performed 34 DAT (T+34) showed that the average population of each treatment had decreased compared to the previous sampling, and no significant differences between the treatments, although control treatment had a population higher than the other treatments. This could be due to the great variability between the replicates. The evolution of the pest with time was the same for all treatments, that is, the interaction between Treatment and Sampling Date was not significant (F = 9.48; d.f.: 9, 48; P = 0.61). The result showed that there were differences among dates (F = 6.9; d.f.: 3, 48; P <0.001) and among treatments (F = 5.10; d.f.: 3, 48; P <0.001), showing a lower infestation of the three nozzles than the Control, but no significant differences among them. 4. Conclusions 1. The three types of nozzle achieved significantly lower pest levels than the untreated control. 5

2. No significant difference between the anti-drift nozzles (AVI and TVI) and conventional nozzle was found on the level of infestation, leading to the conclusion that all the nozzles presented similar efficiencies in the control of Tetranychus urticae. 3. Deposited drift depended on the type of nozzle and the distance. 4. It could be concluded that anti-drift nozzles decreased the percentage of drift without decreasing biological efficacy when applying Spirodiclofen-based acaricide to control Tetranychus urticae in citrus. Acknowledgements This research was partially funded by Spain Ministerio de Ciencia e Innovación (project AGL2010-22304-C04-01), Fondo Europeo de Desarrollo Regional (FEDER) and Bayer CropScience. References EU (European Parliament and Council of the European Union) (2009) Directive 2009/128/EC of 21 October of 2009 establishing a framework for Community action to achieve the sustainable use of pesticides. Official Journal of the EU, L309, 71-86. Fox, R.D., Reichard, D.L., & Brazee, R.L. (1985) A model study of the effect of wind on air sprayer jets. Trans. Amer. Soc. Agr. Eng. 8, 83-88. Frießleben, R. (2004) Balancing drift management with biological performance and efficacy. Invited presentation to the International Conference on Pesticide Application for Drift Management, Washington State University. 27-29 October 2004, Waikoloa, (Hawaii). http://pep.wsu.edu/drift04/pdf/proceedings/pg72-79_frie%dfleben.pdf Acceded 04/05/2012 Ganzelmeier, H., Rautmann, D., Spangenberg, R., Streloke, M., Herrmann, M., & Wenzelburger, H.J. (1995) Studies on the spray drift of plant protection products. Berlin: Blackwell Wissenschafts-Verlag GmbH. Guler, H., Zhu, H., Ozkan, H.E., Derksen, R.C., Yu, Y., & Krause, C.R. (2006) Spray characteristics and wind tunnel evaluation of drift reduction potential with air induction and conventional flat fan nozzle. Amer. Soc. Agr. Biol. Eng., Annu. Intl. Mtg., Paper No. 06111. (Abstr.) Heinkel, R., Fried, A., & Lange, E. (2000) The effect of air injector nozzles on crop penetration and biological performance of fruit sprayers. Aspects Appl. Biol. 57, 301 307. ISO (2005) Equipment for crop protection Methods for field measurement of spray drift. ISO/FDIS 22866. Geneva. 22p. Salyani, M., Muhammad, F., & Sweeb, R.D. (2007) Mass balance of citrus spray applications. ASABE Annual International Meeting June 2007, Paper Nº071037. McArtney, S.J., & Obermiller, J.D. (2008) Comparative Performance of Air-induction and conventional nozzles on an axial fan sprayer in medium density apple orchards. HortTechnology 18 pp: 365-371 Meli, S.M., Renda, A., Nicelli, M., & Capri, E. (2003) Studies on pesticide spray drift in a Mediterranean citrus area. Agronomie, 23, 667-672. 6