Optimizing Fungicide Application Timing to Control Olive Peacock Eye Disease: Impact on Current and Succeeding Growing Seasons

We recently provided new insights into the etiology of Venturia oleaginea, the causal agent of peacock eye disease in olive. We identified two distinct periods of infection events during each growing season: the first in autumn and the second in spring. In addition, we reported the occurrence of two episodes of disease development: the first at the end of autumn/beginning of winter, and the second in the spring and early summer. The main goal of the current study was to experimentally examine the practical implementation of these new insights. Four experiments were performed in the 2021/2 and 2022/3 seasons in commercial groves under natural epidemics. The results demonstrated that application of 1 or 2 sprays before or after the first major rain event in the season (the presumed time of infections that generate the second disease episode) significantly reduces disease development. The level of disease suppression achieved by these sprays was not inferior to the level of disease control achieved by 9 consecutive sprays in a season. The effect of the application in one season on peacock eye development in the following season was evaluated in the same groves, and it was found that if the disease is not controlled during two consecutive seasons, its severity increases markedly in the succeeding season, but if the disease is properly managed in the first season, its severity in the succeeding season may be minute or even non-existent.