Evaluation of an electrostatic spray charge system implemented in three conventional orchard sprayers used on a commercial apple trees plantation

Electrostatic sprayers can be an option for increasing the effectiveness of treatments and reducing pesticide consumption, but it still requires more verifications, especially in orchards. The spray deposition performances of three different electrostatic sprayers design were compared for apple tree pesticide application, all of them used with the electrostatic system activated and disactivated, as conventional spray application. Despite designs of particular type sprayers were unique, no significant differences were observed in the normalized deposition and droplets density between the conventional and electrostatic spray methods of the same sprayer, but differences were found between the vertical boom and the pneumatic sprayer in terms of coverage. The normalized deposition values of the three sprayers were very similar, ranging between 1.0 and 1.5 μg cm−2. However, the vertical boom sprayer produced the highest spray coverage, followed by the multi-fan sprayer. In general, the measured values of coverage and deposit obtained were in the three cases similar, independently on the use or not of the electrostatic device, being the sprayer type more affecting parameter rather than the electrostatic charging system. Differences in spray deposition qualities on apple trees were observed among three types of sprayers, but were not for the same sprayer with and without activation of the electrostatic charging system. Appropriate design of orchard sprayers according to the canopy structure seems to be more effective rather than the implementation of electrostatic spray charge system to achieve the European challenge of 50% reduction of pesticides by 2030.