Effect of Insecticide Usage on Parasitism of Chortoicetes terminifera (Walker) (Orthoptera: Acrididae)

Abstract

Parasitism of adult Chorroicefes terminifera by Trichopsidea oestracea Westwood and BIaesoxiphu rufpes (Macquart) was assessed to discern any effect of chemical control during an outbreak in the 1995-96 season in eastern New South Wales. In the Moree and Gunnedah regions the effects of ground control of bands and aerial control of bands and swarms on parasitism were compared with untreated controls. In the Hunter region only the effect of ground control of bands could be measured. Within both the Moree and Gunnedah regions there were no differences in parasitism rates by either T. oestraceaor B. rufipes which could be attributed to chemical control. Parasitism by T. oestrucea was significantly higher in the Hunter region than in all treatments in the Moree and Gunnedah regions, except untreated sites in the Gunnedah region. Parasitism by T. oestracea was significantly higher in the Gunnedah region than in the Moree region. Regional differences in parasitism by T. oestrucea are attributed to intrinsic climatic and landuse differences between the regions rather than coincident regional differences in insecticide usage. There were no treatment or regional differences in parasitism by B. rufipes. Parasitism levels recorded during the study were atypically low, a fact attributed to a severe drought which preceded the outbreak. Emigration of C. terminifera took place during the study but is not considered to have affected trends in parasitism.