FATE OF BIOLOGICAL-CONTROL INTRODUCTIONS - MONITORING AN AUSTRALIAN FUNGAL PATHOGEN OF GRASSHOPPERS IN NORTH-AMERICA

In North America there are two generally recognized pathotypes (pathot ypes 1 and 2) of the fungus Entomophaga grylli which show host-prefere ntial infection of grasshopper subfamilies. Pathotype 3, discovered in Australia, has a broader grasshopper host range and was considered to be a good biocontrol agent, Between 1989 and 1991 pathotype 3 was int roduced at two field sites in North Dakota. Since resting spores are m orphologically indistinguishable among pathotypes, we used pathotype-s pecific DNA probes to confirm pathotype identification in E. grylli-in fected grasshoppers collected at the release sites in 1992, 1993, and 1994. In 1992, up to 23% of E. grylli-infected grasshoppers of the sub families Melanoplinae, Oedipodinae, and Gomphocerinae were infected by pathotype 3, with no infections >1 km from the release sites. In 1993 , pathotype 3 infections declined to 1.7%. In 1994 grasshopper populat ions were low and no pathotype 3 infections were found. The frequency of pathotype 3 infection has declined to levels where its long-term su rvival in North America is questionable. Analyses of biocontrol releas es are critical to evaluating the environmental risks associated with these ecological manipulations, and molecular probes are powerful tool s for monitoring biocontrol releases.