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Poster: Epidemiology: Pathogen-Vector Interations


Olive Escudete, caused by Botryosphaeria dothidea, as Result of the Interaction fly-mosquito-fungus
J. MORAL (1), I. Eldesouki-Arafat (2), F. López-Escudero (3), E. Vargas-Osuna (2), T. Antonio (4), H. Aldebis (2) (1) University of California, Davis, Kearney Agricultural Research and Extension Center, U.S.A.; (2) Dpto. Ciencias y Recursos Agrícolas y Fo

The Dalmatian disease or escudete, caused by Botryosphaeria dothidea, is the most important disease of table olive fruit. The typical escudete (small shield) symptom is a sunken, necrotic, and circular (≈8mm) lesion that appears in green fruits. The olive fly (Bactrocera oleae) and mosquito (Prolasioptera berlesiana) whose larvae prey on fly eggs, are disputed as vectors of the pathogen. Here, we study the interaction among these three agents: fly-mosquito-fungus. In the field, we periodically sampled for the presence of the mosquito in fruits, which were naturally punctured by the olive fly or artificially by a needle for three seasons. Under lab conditions, the presence of the fungus in the mosquito and the fly was studied by microscopy, isolation on media, and DNA sequencing. According to our results, the mosquito is attracted by ovipositor punctures on the olive surface made by the olive fly. When the mosquito deposits its own egg adjacent to the fly egg, it also inoculates the fungus in the puncture. This allows the mosquito larvae to feed on B. dothidea mycelium when the fly egg is absent; a need that arises due to frequent false punctures (no oviposition) made by the fly to avoid predation by the mosquito larvae. Microscopic studies show that the mosquito female has a special structure (mycangia) to carry B. dothidea spores in the last abdominal segments close to the ovipositor, which suggests a mutualistic association between B. dothidea and P. berlesiana.