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The present study is conducted to know the effect of certain cultural practices and the variation of
temperature and humidity (continentality, altitude, slope exposure) on the distribution and importance of
Peacock Spot disease, caused by Spilocaea oleagina, in the region of Gharb and Ouazzane (Morocco).
The study was conducted in olive orchards growing in different geographical situations with varying
climatic conditions. The intensity and the presence of the disease were evaluated respectively by
calculating leaf area index and the percentage of diseased trees.
The obtained results showed that as far as continentality augments the severity of the disease decreases
and is increasing in height. The disease is important in the region of Ouazzane than in Gharb. These
variations are due to the humidity and temperature variations. The olive trees cultivated at the western
slope are the most attacked, Leaf area index is 4.54, followed by those of the North, South and East.
Disease decreases in the low slope to the high slope. The presence of rivers leads to increase the intensity
of the disease in South and East slopes, considered as dry slopes. Tillage reduces the intensity of the olive
spot diseases in the grafted olive and cuttings (Leaf alteration index ranged from 1.84) but, increases in
the unmaintained orchards (L.I. is 3.66).
This study allowed us to know the influence of variations of the main climatic factors (humidity and
temperature) and cultural practices (tillage orchards, olive trees origin) on the development of
Peacock Spot disease in Morocco. Taking into consideration of all these factors and the integration of
other factors allow mapping the distribution of the disease in the olive-growing areas and to know those
at high risk.
Key words: Olive tree, Peacock Spot, Spilocaea oleagina, Leaf alteration index, humidity, altitude,
temperature, soil, intensity, orchards.