The First Trial of a Metarhizium anisopliae var. acridum Mycoinsecticide for the Control of the Red Locust in a Recognised Outbreak Area

The outbreak areas of the red locust are seasonally inundated wetland areas supporting a rich biodiversity. The potential for environmental damage from the repeated use of broad-spectrum insecticides for locust control in these ecologically sensitive wetlands is therefore great. This paper describes the first trial of a Metarhizium anisopliae var. acridum (LUBILOSA isolate IMI 330189) mycoinsecticide as an alternative, more environmentally benign, intervention strategy for managing red locust populations in their outbreak areas. Following initial bioassay tests in the laboratory, which gave 90–93% kill of 3rd instar hoppers within 6–9 days, an oil based formulation of aerial conidia was applied at a rate of 5 × 10 12 conidia/ha using a motorised ‘Solo’ knapsack sprayer to treat 3rd and 4th instar hopper bands in the Buzi outbreak area near Beira in Mozambique. Caged samples of 3rd instars succumbed quickly with a median time to kill of 3.6–3.9 days and 98–100% kill recorded within 8–9 days. The 4th instars took longer to die, with a median lethal time of 5.9–6.1days and > 90% mortality after 21 days. Mortality in control samples was low with 13–23% mortality after 21 days. During this mortality assessment period mean minimum and maximum air temperatures ranged from 26–34°C and relative humidity ranged from 85–100%. Observations on treated bands in the field showed that the cohesion of the 3rd instar bands broke down within 6 days, while controls still behaved normally. Unfortunately observations on the 4th instar band had to be terminated after 10 days due to heavy flooding. This preliminary field trial demonstrated the feasibility of using a Metarhizium mycoinsecticide, applied through conventional spray equipment, for controlling the red locust in its outbreak areas.