BIOLOGICAL CONTROL OF SPILOCAEA OLEAGINA THE CAUSAL AGENT OF OLIVE LEAF SPOT DISEASE USING ANTAGONISTIC BACTERIA
Olive leaf spot (OLS) caused by the fungus Spilocaea oleagina (Cast.) Hugh. is one of the serious diseases of olive trees in many parts of the world. The disease is controlled by application of copper-containing fungicides prior to winter rains. Timing of fungicide applications and their high costs and possible effects on human health and the environment are critical for an effective control. Since biological control may be a realistic alternative to chemicals, in this work about 176 bacterial isolates were screened for their efficacy against OLS. Six bacterial isolates, belonging to the genera Pseudomonas and Bacillus proved to have an inhibitory effect on conidial germination under in vitro conditions. A Pseudomonas isolate (ORS3) and a Bacillus isolate (BAT) were most effective with inhibition rates of 96.95 and 94.78%, respectively. The length of the germ tube in the presence of the bacteria was three times the length of the conidia in the control treatments. The results of this work provide new possibilities to control using bacteria as biocontrol agents. Further analysis and experiments are required to evaluate the efficacy of the bacteria under field conditions.