Volume Rate Adjustment for Pesticide Applications against Aonidiella aurantii in Citrus: Validation of CitrusVol in the Growers’ Practice

Abstract

Aonidiella aurantii is one of the most damaging armored scales in citrus crops worldwide. To control this pest, high water volume rates are conventionally used. In order to rationalize the pesticide applications in citrus, IVIA developed CitrusVol, a tool that recommends the optimal volume rate based on the vegetation, the pest or disease and the active ingredient. In this study the objectives were: (i) validate CitrusVol as a tool to adjust the spray volume to control A. aurantii and (ii) quantify its environmental and economical advantages. For this, the spray volume adjusted with CitrusVol was compared with the one conventionally used by farmers in 18 applications in seven orchards during two years. The following parameters were evaluated: (i) spray distribution in the canopy, (ii) A. aurantii males trapped per day, and (iii) number of scales per fruit at harvest. CitrusVol reduced the spray volume and the amount of pesticide by 35% on average. Despite this reduction, a satisfactory spray distribution was achieved, and the volume was found to control the pest in a comparable way to the conventional volume. Moreover, CitrusVol saved per application and on average 31.25 h/100 ha of spray operating time, 241.83 L/100 ha of fuel consumption and consequently, the reduction of emissions of CO2 was 631.18 kg/100 ha. Therefore, CitrusVol allows for efficient, low-input and low-impact pesticide applications.

Influence of mechanical and manual pruning on the incidence of pests in ‘Clemenules’ mandarins

“…The highest percentage of damaged fruit inside the canopy could be a consequence of the fact that, in the PPP applications, the interior of the canopy receives a lower spray coverage than the outer part of the canopy, as usually happens in citrus applications. 45,46 Regarding A. aurantii, there were no statistical differences between pruning strategies during the 3 years studied. In addition, the number of scales per fruit at harvest in the experimental Note: Mean value with standard error in parenthesis.…”

“…plot was low, as found in previous years in a nearby manually pruned 'Clemenules' orchard, in which no scales were found in 2016 and fewer than one scale per fruit on average was found in 2017. 46 In conclusion, pests associated with sprouting (as in the case of aphids) increased their incidence following mechanical pruning and therefore it is fundamental to monitor these pests to carry out the treatments in the adequate moment. However, the pests unaffected by sprouting (T. urticae and A. aurantii) were unaffected also by the pruning strategy (manual/mechanized) under the conditions tested in 'Clemenules' clementine trees.…”

“…In general, most of the damaged fruit was internal fruit, and most of the damage was light, with which fruit can be marketed fresh, regardless of the pruning strategy and in the 3 years of experiment, although most notably in the last year. The highest percentage of damaged fruit inside the canopy could be a consequence of the fact that, in the PPP applications, the interior of the canopy receives a lower spray coverage than the outer part of the canopy, as usually happens in citrus applications 45,46 …”

Design and experimental assessment of a field‐spraying system with nozzles employing reciprocating up‐and‐down movements

“…To improve the definition of the droplet images, a camera (model 7D; Canon Company,Tokyo, Japan) with a macro lens was used to capture the images of the paper cards. Using the image processing method (in MATLAB software), the droplet number density (the number of droplets per unit area of the paper card) and droplet coverage rate (the ratio of the entire droplet area to the area of the paper card) were calculated according to standard procedures used by other authors 17–19 …”

Effect of the Airblast Settings on the Vertical Spray Profile: Implementation on an On-Line Decision Aid for Citrus Treatments

“…Sprayer adjustment, sometimes referred to as calibration, is aimed at: (i) adjusting the fan airflow rate and its orientation to the tree canopy to minimize off-target losses [35,36,38,39], (ii) balancing the distribution of spray volume between the right and left side of the airblast sprayer [40], (iii) selecting the proper number of active nozzles and setting their orientation to produce a spray vertical profile that matches the targeted canopy as closely as possible [9,36], and (iv) applying the most appropriate spray volume [18,[41][42][43][44][45].…”