First Record of the Entomopathogenic Fungus Sorosporella sp. (Deuteromycotina: Hyphomycetes) in Locusta migratoria (Orthoptera: Acrididae) from Madagascar: Symptoms of Infection, Morphology and Infectivity

In Madagascar, a fungal disease was observed in the migratory locust, Locusta migratoria capito, which was caused by the deuteromycete Sorosporella sp. Multiplication of the fungus in locusts results in the formation of brick-red resting spores filling the body of the insect, and in a pale and fragile cuticle which breaks easily, releasing these spores. The conidia of the fungus (only observed in artificial cultures) are cylindrical in shape, measuring 11.0 2.8 mu m. The growth of the fungus was compared on several solid and liquid media, but was invariably slow. The best growth was obtained on a medium containing 3% ground rice, 3% malt extract, 0.3% peptone and 1.5% agar. Attempts were made to initiate artificial infections in L. migratoria migratorioides and Schistocerca gregaria from a laboratory stock. This was carried out by feeding resting spores or through contact with Sorosporella material from agar cultures. However, it rarely resulted in mortalities with typical symptoms. Inoculations by injection were more successful, and resulted in the formation of resting spores in the cadavers 12 to 21 days after inoculation. In Madagascar, Sorosporella sp. seems to be an important, and frequently occurring, locust pathogen. However, the natural mode of infection and the ecology of the fungus are still unclear. Une mycose causee par le champignon deuteromycete Sorosporella sp. a ete observee a Madagascar chez le criquet migrateur Locusta migratoria capito. La multiplication du champignon dans le corps des criquets entraine la formation de spores rouge-briques, qui emplissent celui-ci. Les individus infestes developpent en outre une cuticule pale et fragile, qui se brise facilement, laissant ainsi les spores se disseminer. Les conidies (observees uniquement en cultures artificielles) mesurent 11.0 2.8 mum. La croissance du champignon reste lente sur tous les milieux solides et liquides compares. La meilleure croissance a ete obtenue sur un milieu contenant 3% de riz, 3% d'extrait de malt, 0.3% de peptone et 1.5% d'agar. Des essais d'infection par ingestion de spores d'une part, par contact avec du materiel de culture sur agar d'autre part, ont etes effectues avec L. migratoria migratorioides et Schistocerca gregaria (mate riel d'elevage). Ces essais n'ont abouti que rarement a une mortalite avec des symptomes typiques. Des resultats plus positifs ont ete obtenus au moyen d'inoculations par injection. Ils se forment dans ce cas des spores dans les cadavres des criquets 12 a 21 jours apres l'inoculation. Sorosporella sp. semble etre un agent pathogene des criquets important et frequent a Madagascar. Le mode d'infection naturel, ainsi que l'ecologie de ce champignon restent cependant peu connus.

Keywords:

• Sorosporella Sp.
• Locusta Migratoria
• Madagascar
• Entomopathogenic Fungus
• Locust Control
• Africa