Effect of the Pathogen Nosema locustae (Protozoa: Microspora) on Mortality and Development of Nymphs of the South American Locust, Schistocerca cancellata (Orthoptera: Acrididae)

Abstract

Laboratory procedures previously used by other authors were employed to conduct experimental bioassays with Nosema locustae on cultured Schistocerca cancellata. Third-instar nymphs were individually, per os inoculated with 105 spores and maintained under controlled conditions until their death or termination of the experiment after 30 days. Mortality and development of S. cancellata were affected by N. locustae. Mortality did not differ among treated and control nymphs at 20 days post-inoculation, but was significantly higher for infected nymphs at 30 days post-inoculation. Infections developed in 52.5 % of the treated nymphs. While 92.5 % of control nymphs reached adulthood, no infected individuals reached the adult stage, most succumbing as fifth or sixth instar nymphs. Control insects reached the sixth nymphal instar 6 days before infected nymphs and 4 days before non-infected (but treated) nymphs. Given the current preventive strategy employed in Argentina for locust control, the results obtained in this study suggest that N. locustae could be of value as a long-term biocontrol agent of S. cancellata in the outbreak areas of Northwest Argentina.