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

doi:10.1016/j.scitotenv.2016.09.200

Science of The Total Environment

Volume 575, 1 January 2017, Pages 1239-1246

https://doi.org/10.1016/j.scitotenv.2016.09.200 Get rights and content

Highlights

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Low-drift nozzles used for pesticide application pose low risk of environmental pollution.
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Biological effect of crop protection obtained by low-drift nozzles is still questioned.
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Efficacy of pest and disease control for standard and low-drift nozzles assessed in apples.
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No explicit effect of nozzle type on pests and disease control efficacy.
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Low-drift air induction nozzles can be efficacious alternative to standards nozzles.

Abstract

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 750 l ha^− 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.

Graphical abstract

Introduction

Pesticide drift is a side effect of chemical crop protection associated with ground and aerial application, and is considered one of the major routes of water, soil and atmosphere pollution with agrochemicals. Due to the way the pesticides are applied by orchard sprayers (radial and upward emission with air assistance, high droplet release, great distance to the target) the risk of environmental contamination is especially high when spraying on three-dimensional crops, such as fruit trees, soft fruit bushes, hop plants or vine crops. Fine, lightweight spray droplets generated by standard hollow-cone nozzles, traditionally used in fruit growing, are very easily carried by air currents which results in relatively high drift. Heavier droplets of coarse spray, produced by air-induction nozzles, are much less prone to drift but at the same time they have also less target coverage potential. This may be compensated by an increased spray volume and therefore reduced pesticide concentration in spray liquid which may result in the reduced efficacy of pest and disease control.

The effect of droplet size and spray volume rate on spray deposit and coverage, that determine the technical performance and biological efficacy of spray applications in fruit crops has always been of concern of the applicators and interest of the researchers. It was long believed that the efficacy of insecticides was inversely proportional to droplet size, i.e. due to better spatial distribution of greater number of small droplets (fine quality spray) they ensured better control of pests compared to the large ones (coarse quality spray) with the same amount of active ingredient. Adams et al. (1990) made a literature review to support this opinion. The data for fungicides cited in the review, although limited (Frick, 1970, Falchieri and Cesari, 1993) led to similar conclusions, while that for herbicides was more complicated (Knoche 1994). Thus, the fine spray hollow cone nozzles, assisted with an air jet, were commonly used as a standard application technique in orchards. However, the fine spray was found very prone to evaporation (Zung 1967) and drift (Walklate, 1992, Reichard et al., 1992), which since the early 1990s has been looked upon as a main diffuse source of environmental contamination by pesticides. Then the spray drift reduction became a hot topic of research and development in the field of plant protection technology. In order to meet the challenge in the mid 1990s, the air induction (venturi) nozzles came on the market. In these nozzles a spray liquid flows through a constricted section of channel resulting in Venturi effect, i.e. creating a negative pressure inside the nozzle body. This makes air be sucked into the nozzle through two holes in the nozzle side, and mixed with the spray liquid before exiting the nozzle. Generated spray contains large droplets filled with air bubbles, and virtually no fine droplets. A mean volumetric diameter of these coarse droplets is at least double that of conventional nozzles (Friessleben, 2004, Heinkel et al., 2000) which makes them less prone to off-target drift (Jaeken et al., 2003, Wenneker et al., 2005, McArtney and Obermiller, 2008). On impact with targets the air-filled droplets tend to explode and fracture into many smaller droplets, increasing the potential for spreading on the leaves, and producing similar (Miller and Lane 1999), or even greater (McArtney and Obermiller 2008) coverage compared to conventional, finer sprays. Also spray deposition in fruit tree canopies, being a quantitative measure expressed by mass of a product per target surface unit, was reported to be at least equal (Świechowski et al. 2014) or significantly greater (Loquet et al. 2009) for applications made with the air induction nozzles compared to those with the conventional nozzles. Heinkel et al. (2000) claimed that because of the drift reducing and coverage favouring properties of the coarse air-filled droplets the air induction nozzles could be successfully used to apply pesticides in fruit growing, especially during unfavourable weather conditions (high wind, low humidity and high temperature) that would result in the suboptimal performance of the standard fine spray nozzles.

Several field evaluations of the biological efficacy of the air induction nozzles in apple orchards have been performed for the last two decades. Heinkel et al. (2000) reported equivalent control of apple scab (Venturia inaequalis) and powdery mildew (Podosphaera leucotricha) for treatments made with air induction or conventional hollow cone nozzles. Also Knewitz et al. (2002), based on seven trials in the years 1998–2001, found no principal differences in control efficacy of apple scab and powdery mildew, as well as spider mite (Panonychus ulmi) and rosy apple aphid (Dysaphis plantaginea) between those two types of nozzles. An equal effect of spider mite and rosy apple aphid control obtained by both types of nozzles was also reported by Lešnik et al. (2005). In the same study he observed, however, a worse control of codling moth (Cydia pomonella), green apple aphid (Aphis pomi), and leaf miner (Leucoptera malifoliella) with the air induction nozzles. Friessleben (2003) reported a summary of 8 years of data (130 trials over the years 1995–2002), comparing the efficacy of pesticides applied in apple orchards with air induction nozzles and conventional hollow cone nozzles used under commercial conditions, and he concluded that no definite difference in biological performance was found between the nozzles for any of examined diseases (apple scab and powdery mildew) or pests (mites and aphids).

In most efficacy trials with the air induction nozzles the effects of changes in drop size (variable factor) were investigated at the unchanged spray volume rate (constant factor) in order not to confound the effects of both factors. However, the effect of different combinations of the factors on the efficacy of pest and disease control in apples is an interesting subject to study, and the results of the investigations are of great practical value. The fruit growers are awaiting scientifically supported recommendations on nozzle selection that would ensure satisfactory biological performance. Their attention has recently been turned towards the air induction nozzles since, according to legal regulations in many European countries, they allow the growers to reduce no spray buffer zones for surface water and other sensitive areas, or in some countries/regions they permit pesticide applications in densely populated fruit growing areas.

The objective of this work was to evaluate the efficacy of pests and diseases control on apples as affected by spray volume rate and spray quality in order to provide evidence that the satisfactory level of plant health status can be ensured with up-to-date plant protection products applied with coarse spray air-induction nozzles having recognised and documented pesticide drift reducing potential and hence posing lower risk of environmental pollution than standard fine spray hollow cone nozzles.

Section snippets

The experimental orchard

The investigation was carried out over the years 2010–2013 in the experimental orchard of the Research Institute of Horticulture, Skierniewice, Poland (51°57′36.49″N/20°09′34.16″E). The apple trees of cv. Jonagold/M26 were planted in the year 2000, in single rows with 4 m spacing. The trees were 3.0 m tall and 1.8 m wide resulting in tree row volume (TRV) 13,500 m³ ha^− 1. Every three rows of apple trees were separated by 5.5 m tall hedgerow of black alder (Alnus glutinosa) serving as an isolation of

Apple scab

Due to very humid and rainy weather in 2010 there were as many as 14 events of risk of strong infections in critical months of spring (April–June) (Table 3) which resulted in an extremely high infection pressure and intensive production of conidia that initiated secondary infections. Thus, the fungicide applications needed to be continued after the fruitlet abscission during the June drop. In summer (July–August), however, events of several rainy days in a row prevented spray applications from

Discussion

The spray application technique is one of the principal factors having an impact on efficacy of plant protection products, just next to other factors such as choice of the product and its dose, timing and weather conditions at the time of application. Since the product and timing are determined mainly by pests or diseases the application technique, or to be more precise the application parameters need to be adjusted according to weather conditions and target characteristics. The weather

Conclusions

No definite conclusions may be drawn based on the obtained results for the effect of nozzle type on efficacy of control of the harmful organisms was demonstrated to be not clear. However, some findings were noteworthy:

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in the years with adverse weather conditions and extremely high infection pressure powdery mildew was better controlled with fine spray nozzles and higher volume rates,
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green and rosy apple aphids were better controlled with higher volume rates, though significance of the advantage

Acknowledgements

The described research and the article preparation were made within the statutory research task S 11.5 of the Research Institute of Horticulture, Skierniewice, Poland, subordinated to the Ministry of Agriculture and Rural Development, and in the mentioned research area financed by the Ministry of Science and Higher Education of the Republic of Poland.

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

Highlights

Abstract

Graphical abstract

Introduction

Section snippets

The experimental orchard

Apple scab

Discussion

Conclusions

Acknowledgements

Crop. Prot.

Crop. Prot.

J. Agric. Eng. Res.

A method for computing the effectiveness of the insecticides

J. Econ. Entomol.

Droplet spectra for some agricultural fan nozzles, with respect to drift and biological efficiency

Relationship between deposit characteristics, modes of action of pesticide and efficacy

The effects of volume, drop size and concentration, and their interaction on the control of apple powdery mildew by Dinocap

Br. Crop Prot. Councis Monogram

Influence of coarse droplet application via injector nozzles on the biological efficacy in apple production

Balancing drift management with biological performance and efficacy

The effect of air injector nozzles on crop penetration and biological performance of fruit sprayers

Asp. Appl. Biol.