Survey of Olive Leaf Spot in New Zealand

Olive leaf spot (OLS) 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 December 1999 and January 2000 to measure the prevalence and severity of olive leaf spot in the Auckland, Waiheke Island, Wairarapa, Marlborough and Canterbury growing regions of New Zealand. The susceptibility of six cultivars (Barnea, Manzanillo, Frantoio, Leccino, Nabali and Souri) to OLS was assessed. OLS was found in all study areas with Auckland and Marlborough the worst affected. OLS 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. Souri and Nabali were the worst affected cultivars while Frantoio and Leccino were least affected.