The effect of local fungicides on conidial germination of Spilocaea oleagina in Palestine

Abstract

Olive leaf spot (OLS) disease or peacock disease is caused by the fungus Spilocaea oleagina, it is the most destructive disease on olive trees in most regions of Palestine. The disease is controlled by application of copper containing fungicides. Currently, there are more than 20 different fungicides sold in the Palestinian market. The efficacy of these fungicides was not tested on OLS in Palestine. The aim of this work was to test the efficacy of three major fungicides used against the disease. Fungicide solutions containing Fungran, Copper Antracol, and Kocide®101 were prepared by dissolving 0.5 g of each in 200 ml distilled water (DW) according to manufacturer instruction. Five leaves infected with OLS were soaked in each solution for 30 min. Control leaves were placed in 200 ml DW. Leaves were then placed in 9 cm petri dishes containing 3 ml DW to provide high humidity (> 85%). Each day, one leaf was removed, washed in DW and cut into one-cm2 pieces. Leaf pieces holding OLS conidia were printed on olive leaf extract agar media. Results showed that after 24h of fungicide treatment, Kocide®101 was the most effective fungicide followed by Copper Antracol and Fungran with percent conidial germination 2.08, 2.9 and 25.5%, respectively. Interestingly, Fungran efficacy after 48h (2.8% germination) was higher but not significantly different than Kocide®101 and Copper Antracol. This study showed that the efficacy of the three commonly used fungicides against OLS disease in Palestine diminished after four days of treatment. Further studies are needed to test the efficacy of these fungicides under field conditions for a better control planning of peacock disease in Palestine.