INVITATION PAPER (C.P. ALEXANDER FUND): THE POTENTIAL OF BIOLOGICAL CONTROL FOR MANAGEMENT OF GRASSHOPPERS (ORTHOPTERA: ACRIDIDAE) IN CANADA

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Abstract
In Canada biological control of grasshoppers has been studied since the 1930s. Previous attempts at "classical" introductions have not been successful. Native parasitoids, especially sarcophagid flies, have a significant impact on grasshopper populations during certain times but the required conditions and regulatory potential are not understood. Sarcophagids, especially Kellymyia kellyi (Aldrich), and the mermithid nematodes Agamermis decaudate Cobb, Steiner, and Christie and Mermis subnigricans Cobb have some potential as inundative agents. Invertebrate predators appear to impact on egg and early-instar nymphal grasshoppers, and vertebrates, especially birds, help to regulate later instars and adults. The role of microbial pathogens in the population dynamics of grasshoppers in western Canada has long been recognized, particularly with regard to entomophthoran fungi. The possibility of utilizing the microsporidan Nosema locustae Canning for suppression of grasshopper populations has been postulated since the 1970s and field evaluations of its potential have been conducted in Saskatchewan and Alberta. More recently, considerable work, both basic and applied, has demonstrated the potential of various fungus isolates pathogenic to grasshoppers as both "classical" and inundative control agents. Entomopoxvirus isolates from grasshoppers also show potential as biological control agents of grasshoppers but this potential has yet to be investigated in field situations. It is clear, however, that no single microbial pathogen will be the panacea of grasshopper control. It is suggested that future biological control research focus on acquiring a better understanding of the requirements and quantitative effects of parasitoids and predators on grasshopper populations. Emphasis should also be placed on developing integrated pest management programs that utilize local natural enemies (nematodes and microorganisms) for inundative control during outbreaks.

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