Abstract

Olive leaf spot or peacock spot, caused by the fungal pathogen Spilocaea oleagina, can cause reduced growth and yield in olive trees (Olea eurapaea). Investigations were carried out during 2007-2010 to measure the prevalence and severity of olive leaf spot in the northern olive growing regions of Iran. The susceptibility of ten cultivars (Amygdalifolia, Blaidy, Koronakei, Mary, Manzanillo, Mission, Rooghany, Valatolina, Wild olive, Zard) to the disease was assessed. Olive scab was found in all study areas and with the worst affected in high relative humidity (Y= -21.058 + 0.794X, p<0.001 r=0.952, Y= disease percent and X= Annual rainfall Mean monthly) and appeared to be particularly severe on trees that were growing in sheltered parts of an olive grove. Severity increased with age and a correlation between prevalence and severity was found. Native olive (Rooghany, Zard and Mary) and Manzanilla were the worst affected cultivars while Valatolina and Wild olive were least affected. The rate of conidial germ tube elongation on leaves affected by temperature and olive cultivars.

Key words: Peacock spot, Spilocaea oleagina, disease prevalence, disease severity, Iran.