Effects on young american kestrels (Falco sparverius) exposed to Beauveria bassiana bioinsecticide.

Abstract

Wide-area spraying of insecticides for control of grasshopper outbreaks on western rangelands has exceeded 5 million hectares in a single year (USDA 1987). Effects of insecticides on non-target fish and wildlife are of concern to conservation organizations and to the general public. The U.S. Department of Agriculture has developed a Range Grasshopper Integrated Pest Management Program (GHIPM) that seeks to integrate chemical, biological, and cultural methods for regulating grasshopper populations while reducing ecotoxic effects on non-target animal life. Beauveria bassiana fungus is a pathogen that holds promise as a biological control material for a major rangeland grasshopper pest species (Melanoplus sanguinipes) (Marcandier and Khachatourians 1987; Moore and Erlandson 1988; Inglis et al. 1995). Biological controls are useful for reducing high grasshopper populations in environmentally sensitive areas such as lake and stream borders, nest sites of endangered bird species, and other endangered species habitats where chemical insecticides are restricted. Grasshopper control with biological materials may be more target-pest specific and pose lower risk to other animal life inhabiting treated areas (USDA 1987). In this paper we report the results of field tests in which wild American kestrel (Falco sparverius) nestlings were exposed to acute oral dosages of B. bassiana spores. The young kestrels were observed through the post-fledging stage in Colorado during the 1992 breeding season. Null hypotheses tested were: (1) mean growth parameters and survival would not differ between treated and untreated nestlings, (2) timed responses to systematic behavior/reaction tests would not differ between treated and untreated nestlings, and (3) mean distances moved and survival would not differ between treated and untreated fledglings. Juvenile kestrels were chosen for this study because the optimal timing (June) of application of B. bassiana spores to late instar grasshopper populations coincides with the kestrel nestling stage. Grasshoppers are important prey for kestrels and are a valuable food source for the young (Bent 1961).