Control of the brown locust, Locustana pardalina (Walker) (Orthoptera: Acrididae), using a mycoinsecticide : addressing the issues of speed-of-kill, dose rate, mortality and reduction in feeding

Metarhizium anisopliae var. acridum (Deuteromycotina: Hyphomycetes) mycoinsecticide acts through direct contact and provides control equal to that of chemical insecticides in current use, although the speed-of-kill is slower. To test the dose-mortality response, doses ranging from 10 3 -10 8 conidia per insect Were tested in the laboratory against fifth instar brown locust hoppers, Locustana pardalina (Walker). At the highest dose (10 8 ), all insects died after 3-4 days, while 100 % mortality was achieved with the 10 7 and 10 6 dosage rates after five and six days, respectively. The 10 5 dose took 6-10 days to achieve 100 % mortality and a dose of 10 4 took 12-14 days to achieve mortalities of 75-87 %. The lowest dose rate (10 3 ) produced no significant mortality before 9-10 days after inoculation, with final mortality reaching only 60 % after 21 days. This was a classic dose response. Locusts are pests because of the crops and pastures that they consume and any reduction in food consumption is consequently of great value. All preliminary laboratory treatments caused a reduction in food consumption, even at a dose rate of 10 4 conidia per locust. These results may influence the future operational implementation of the mycoinsecticide in the field.