Comparison of efficacies of electrostatic and conventional spraying techniques in control of olive leaf spot disease (Spilocaea oleagina (CAST.) HUGHES) in the Aegean region

Olive scab caused by the mitosporic fungus Spilocaea oleagina is the most important foliar disease of olive both in Turkey and other countries where olive are grown in the World. Olive scab disease is gradually increased in years and it is thought that ineffectiveness in control of the disease could be result from misapplication. Studies showed that approximately out of 50-80% of pesticides applied by conventional spraying techniques does not reach to target surface, it could be carried either out of target by drift or moved to soil surface at the same area. Moreover, many diseases could be controlled by electrostatic spraying with less water compare to that of conventional spraying equipment. In this study, conventional and electrostatic spraying techniques individually were being performed to compare against olive scab in 2013 and 2014 in Kemalpaşa, İzmir. For this purpose, amongst registered fungicides copper sulphate pentahydrate and copper calcium sulphate known as ready to use Bordeaux mixture were sprayed with both application techniques individually. Beside biological efficacies of the fungicides, deposit on the leaves, rate of coverage, and the amount of drift were calculated, as well. Electrostatic spraying technique was tested at the first time in olive in this study. At the result of the study, copper sulphate pentahydrate was found 84.82% in conventional spraying technique while this effect was reached to 93.12% in electrostatic spraying technique in control of olive scab. On the other hand, copper calcium sulphate had 82.14% efficacy in conventional spraying technique while electrostatic spraying technique had controlled the disease as 89.60% with the same fungicide. The amount of trace substance drift onto ground was found as average 0.308 µg/cm2 with Conventional spraying technique while there is no accumulation of trace element on the ground with electrostatic spraying technique at all. In consider of accumulation on the tree, 2.5 times more amount was determined in electrostatic spraying technique than that of conventional spraying technique. Electrostatic spraying technique performed maximum efficacies in control of the disease with increasing of accumulation on the olive tree along with providing environmentally friendly approach by minimizing drift to ground and atmosphere with electrostatic spraying technique. In conclusion, better efficacies was obtained from electrostatic spraying technique with better coverage of sprayed fungicides in control of olive scab disease compare to that of conventional spraying technique were resulted in this study.