Novel Copper Nanoparticles for the Control of Olive Foliar and Fruit Diseases ^†

Peacock spot caused by Spilocaea oleagina and anthracnose caused by Colletotrichum spp., are the most important foliar and fruit diseases of olives. Applications of copper-based fungicides are the main control measures for these pathogens. However, the replacement of copper-based products with more eco-friendly alternatives is a priority. In this study, we investigated the efficacy of five novel nano-copper (Cu-NPs) formulations against the two major olive diseases. Two commercial copper-based formulations were included as reference treatments. The efficacy of Cu-NPs against Spilocaea oleagina was evaluated in one-year-old olive trees (cv. Chondrolia Chalkidikis) under controlled environmental conditions in plant growth chambers, while the efficacy against Colletotrichum spp. was evaluated under field conditions on the same cultivar. Results showed that the most effective Cu-NPs against Colletotrichum spp. was 110_CN_S4_X1 which provided a mean control efficacy value of 61.03%, while the two commercial formulations of conventional copper products provided significantly lower control efficacy values of 35.06% and 45.45%. Similarly, three of the Cu-NPs tested (110_CN_S4_X1, 109_CC_S4_X2, 108_CN_S1_X1) were found to be highly effective against Spilocaea oleagina, with control efficacy values ranging from 60% to 67.5%. The results of this study are expected to contribute to the optimization of olive disease control and reduce the yield losses caused, using a new generation of biocides.