Neoclassical biological control in Argentina: the introduction of Paranosema locustae (Microsporidia) for the control of grasshoppers (Orthoptera: Acridoidea).

LANGE, C.E.

Recife, Brasil

Simposio; XXI Congreso Brasileiro de Entomología; 2006

Sociedad Entomológica do Brasil

Paranosema locustae, a pathogen of orthopterans developed in the USA as a biocontrol agent of grasshoppers, was introduced into 9 localities of Argentina between 1978 and 1982. Since all grasshopper species of Argentina are native, the case is an example of "New Association or Neoclassical Biological Control". The fate of the pathogen remained unknown for years but following its detection in1991, monitoring of introduction areas has revealed infections in 16 species of grasshoppers of the western Pampas. Infections have not been detected in other areas of the country, except for a few cases in one of the two application sites in northwestern Patagonia (Gualjaina). Grasshopper outbreaks have not been reported in the establishment area since the introductions while they were recurrent before them and still occur outside of the area. A similar trend occurs in Gualjaina. Based on this, plus the higher prevalence in the western Pampas than those known where P. locustae is native (North America), the occurrence of epizootics in several species, and the intensity of infections, it appears that the pathogen is acting as it was originally conceived, as a long-term depressor of grasshopper abundance. Simultaneous to its action as a control agent, P. locustae, by being a generalist pathogen among the Acridoidea, might be altering the structure of grasshopper communities. The decline of what were, previous to the introductions, two abundant species in western Pampas, Dichroplus maculipennis and Borellia bruneri, is given as possible evidence. Four other species, Dichroplus alejomesai, Diponthus communis, Ronderosia forcipata and Scotussa daguerrei, are identified as potentially under risk. Anyway, the degree of ecosystem alteration in the Pampas, from grasslands to agroecosystems, is such that the impact produced by P. locustae, although far from negligible, is just one of many other virtually irreversible factors modeling grasshopper assemblages in the region since long ago.