Infected fruit as source of inoculum and infection dynamic on olive anthracnose caused by Colletotrichum acutatum

Anthracnose of olive (Olea europaea) caused by Colletotrichum species is the most serious fruit disease of this crop. Mummified fruit are the main inoculum source for olive anthracnose. However, effect of weather conditions on inoculum production by mummified fruit has not been studied. Mummified fruit were independently incubated at several temperatures (from 5 to 35C) for 72 h and various wetness periods (from 0 to 168 h) at 22C. Conidial production reached the maximum at 20C. Conidial production increased linearly with wetness period from 0 to 96 h, although there was an important reduction at 168 h. When mummified fruit were subjected to successive incubation/washing treatments, conidial production decreased exponentially with the number of treatments. On rotted and non-mummified fruit, the pathogen produced significantly more conidia on the susceptible cvs. Hojiblanca (4.7 x 10 super(5) conidia/mm super(2)) and Picudo (4.2 x 10 super(5) conidia/mm super(2)) than on resistant cv. Picual (2.6 x 10 super(5) conidia/mm super(2)). Under field conditions, mummies placed on the olive canopy produced a high number of conidia during all year with peaks occurring in early fall. However, conidial production was greatly reduced when mummies were placed on the soil surface or buried. Disease progress on infected fruit over time was faster for the susceptible cvs. Hojiblanca and Picudo than for the resistant cv. Picual. Besides, there was a positive correlation between rainfall and disease severity for all cultivars during the three years of study.