Survey of Spilocaea oleagina, causal agent of olive leaf spot, in North of Iran

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.

Fungal Communities Associated with Peacock and Cercospora Leaf Spots in Olive

“…In both cases, under favorable conditions, sunken brown lesions may appear on petioles and fruits. Trees affected by olive leaf spots caused by V. oleaginea and P. cladosporioides show defoliation of leaves and weakness or death of branches, resulting in reduced fruit set and a decrease in oil yield in the following years [13,14,15,16,17,18]. These fungi survive in leaf lesions and spread through conidia, by rain, wind, or insects, which is the main source of inoculum for primary infection in spring [19,20].…”

Dodine an effective alternative to copper for controlling Venturia oleaginea, the causal agent of pea-cock eye disease, in highly infected olive trees

“…The high levels of defoliation recorded in early spring confirmed that Moraiolo is a very susceptible cultivar to V. oleaginea ( Raggi and D'Armini, 1996 ). The importance of resistance/susceptibility of olive varieties to the pathogen in determining the level of attack is well known ( Agosteo and Schena, 2011 ; Sanei and Razavi, 2011 ; Rongai et al., 2012 ; Abuamsha et al., 2013 ; Buonaurio et al., 2023 ). The high levels of infections observed at the beginning of the experiments in symptomatic and asymptomatic leaves (15% + 50% = 65% of infected leaves) is due to the high susceptibility of the Moraiolo cultivar, the abundant rainfalls recorded in 2014 and 2015 and the orchard position which is located at the base of a hill where high relative air humidity occurs.…”

“…The high levels of infections observed at the beginning of the experiments in symptomatic and asymptomatic leaves (15% + 50% = 65% of infected leaves) is due to the high susceptibility of the Moraiolo cultivar, the abundant rainfalls recorded in 2014 and 2015 and the orchard position which is located at the base of a hill where high relative air humidity occurs. These are all factors known to promote fungal attack ( Obanor et al., 2008 ; Trapero and Blanco, 2010 ; Salman et al., 2011 ; Sanei and Razavi, 2011 ). The observed percentage of diseased leaves (65%) at the beginning of the trial is very high, considering that a value of 20% can be used as a threshold to execute treatments to keep the disease under control and keep the trees in a suitable physiological state ( Almadi et al., 2024 ).…”

First Report of Nigrospora Species Causing Leaf Spot on Olive (Olea europaea L.)

“…cercospora leaf spot) [3]. Olive leaf spots caused by V. oleaginea and P. cladosporioides result in the defoliation of leaves and weakness or death of branches, a reduced fruit set, and a decrease in the oil yield in the following years [4][5][6][7][8].…”