The Fate of Nosema locustae(Microsporida: Nosematidae) in Argentine Grasshoppers (Orthoptera: Acrididae)

Surveys to detect Nosema locustae,a microsporidian pathogen of orthopterans introduced in Argentina several times from 1978 to 1982 to control pest grasshoppers, were conducted during the 1994 and 1995 seasons at locations in Buenos Aires and La Pampa provinces. A total of 7535 grasshoppers collected from 13 different sites were examined. Infected grasshoppers were found at 4 of the sites, 2 of them 75 km from the closest introduction site. Infections were diagnosed in 10 species: 7 Melanoplinae ( Baeacris punctulatus, Dichroplus elongatus, D. pratensis, D. vittatus, Neopedies brunneri, Scotussa daguerrei,and S. lemniscata), 2 Gomphocerinae ( Staurorhectus longicornisand Rhammatocerus pictus), and 1 Romaleidae ( Diponthus argentinus). Prevalence of infection ranged from 0.7% in D. pratensisto 33.3% in R. pictusand averaged 7.9%. B. punctulatusappeared as the most susceptible species to infection. N. locustaeis well established in grasshopper communities of central Argentina. Some comments are included about concerns that were raised on the use of exotic agents for the control of native pests.