Habitat and environmental factors influencing the control of migratory locusts (Locusta migratoria) with an entomopathogenic fungus (Metarhizium anisopliae)

Locusts are important pests in warm, semi-arid regions of the world. Tradit ionally, chemical insecticides have been used to control bands and swarms, but this is coming under great scrutiny. Metarhizium anisopliae is an entom opathogenic fungus, which is formulated in an oil to produce a biopesticide that has been tested in several countries. In Australia, field trials have indicated that efficacy is dependent on rate of application and vegetation cover, while rate of development of both the locust and Metarhizium is inf luenced by temperature. A model has been developed to assess the importance of these factors in the rate and effectiveness of control of migratory loc usts (Locusta migratoria) with Metarhizium using the Australian isolate FI- 985. Model simulations suggest that three application rates may be required in field control operations: a low dose of 1 x 10(12) spores/ha when herba ceous cover was low; a high dose (5 x 10(12) spores/ha) where high cover wi ll reduce the likelihood of locusts receiving spores directly from the spra ying operation or from pickup from the vegetation; and a moderate dose wher e cover is moderate but where locusts are likely to pick up an infection fr om spores on the vegetation. Field efficacy trials are currently underway a gainst the Australian plague locust (Chortoicetes terminifera), spur-throat ed locust (Austracris guttulosa) and wingless grasshopper (Phaulacridium vi ttatum) and this model may be extended to these species in the future. (C) 2001 Elsevier Science B.V. All rights reserved.