Involvement of the shore fly Scatella stagnalis (Diptera: Ephydridae) in expansion of Fusarium crown and root rot disease from diseased to healthy tomato seedlings in greenhouse hydroponics
2009
Matsuda, Y.(Kinki Univ., Nara (Japan). Faculty of Agriculture) | Nonomura, T. | Toyoda, H.
The present study was conducted to examine aerial transmission of the plant pathogen of Fusarium crown and root rot disease by algae-reared flies to tomato seedlings hydroponically cultured in greenhouses. First the symptom of Fusarium crown and root rot appeared on a limited number of tomato seedlings, and then the disease expanded to the seedlings grown in other culture troughs in the same greenhouse. The pathogen was isolated from the diseased seedlings using a selective medium and then identified as Fusarium oxysporum f. sp. radicis-lycopersici according to the morphological characteristics of microconidia and conidiophores. Green algae proliferated vigorously on sponge cubes to support the seedlings in the holes of the plate floated on the culture solution in the hydroponic trough. Eggs, larvae and pupae of the flies (shore flies) inhabited the algae on the sponge supports of both healthy and diseased seedlings, and the adults flew to different sponge supports to oviposit in fresh algae. These flies were separately collected to trace their holding and transmission of the conidia of the pathogen. In addition, some morphological characteristics of the flies were examined for identification. As a result, the fly was identified as Scatella stagnalis (Diptera: Ephydridae). The present study indicated that the pathogen was carried only by the shore flies captured from the diseased seedlings, suggesting that the shore flies living in green algae on the sponge supports may have transmitted the pathogen to tomato seedlings in neighboring culture troughs in the same greenhouse.
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