Status of the alien pathogenParanosema locustae(Microsporidia) in grasshoppers (Orthoptera: Acridoidea) of the Argentine Pampas

Abstract

After experimental introductions from North America in 1978Á1982, the biocontrol agent Paranosema locustae became established in grasshopper communities of the western Pampas region of Argentina. The use and establishment of P. locustae in Argentina constitute both a case of neoclassical or new association biological control (use of an alien species against native pests) and a case of pathogen pollution (anthropogenic introductionÁestablishment of an infectious disease in populations of native species). Since P. locustae is a multihost pathogen among grasshoppers, its presence in the western Pampas represents an additional factor disrupting grasshopper communities according to the differential susceptibility of each species and possibly threatening some species. Microscopic examination of 504 grasshopper samples (the mean number of individuals per sample 0 185) belonging to 43 species from 93 localities throughout the Pampas revealed an establishment area of approximate 90,000 km 2 from about 358 North to 388 South and from 618 East to 658 West. Field infections by P. locustae have now been detected in 21 grasshopper species in the western Pampas. Susceptible species with geographic distributions mostly restricted to the establishment area and with numerically small populations, like the melanopline Scotussa daguerrei, are predicted to be the ones facing higher risks of negative impacts.

Horizontal transmission of Paranosema locustae (Microsporidia) in grasshopper populations via predatory natural enemies

“…Several studies have suggested that P. locustae is a good biological control agent for grasshoppers and locusts, and the long‐term effects of this microsporidian after field application have been reported: P. locustae has been found persisting in grasshopper populations 9 years after application in rangeland of the Qinghai‐Tibet Plateau and Inner Mongolia and after > 10 years in grasshopper populations in Argentina . In our study, we found that grasshopper density decreased significantly by 30 days after treatment and was still low 2 years later, with P. locustae expanding into and persisting in, adjacent untreated areas over the same period (Fig.…”

Microsporidia Biological Control Agents and Pathogens of Beneficial Insects

“…P. locustae has a very broad host range, infecting 122 species of Orthoptera worldwide (Lange 2005(Lange , 2010. After 16 years of monitoring in the Pampas of Argentina, shifts in the relative proportion of grasshopper species were reported but were thought to be part of the inevitable changes to the region as agroecosystems became prevalent (Bardi et al 2012). Nevertheless, grasshopper outbreaks seemed to have ceased in areas where P. locustae established successfully in contrast to similar areas without the microsporidium (Lange & Cigliano 2005, 2010.…”

Alien Insects and Insect Conservation

“…A microsporidian, Paranosema (previously Nosema ) locustae , experimentally introduced to Argentina to control grasshoppers in the Pampas region, was considered to have potential for 'pathogen pollution' (a global threat in biodiversity conservation: Cunningham et al 2003 ). It was introduced with knowledge that it is a generalist, capable of attacking numerous host grasshopper species (Bardi et al 2012 ). About 50 grasshopper species (approximately a quarter of the Argentine fauna) occur in the Pampas, but only about 6 of these are targeted for control as serious pests that cause losses to crops and forage during their outbreaks.…”