Abstract:
Desert locust is one of the most destructive migratory pest in the world. Current methods
of control rely on conventional chemical insecticides during invasion. Some environmentally friendly
biopesticides based on Metarhizium acridum and insect growth regulators have also been deployed
in preventive control operations. They have been tested in sprayers mounted on commonly used
platforms such as vehicles, aircraft, and human. However, despite being used successfully, these
tools present many challenges, hence the need to supplement them with suitable alternatives. The
successful use of drones to control pests such as fall armyworm, planthoppers, aphids, among others,
makes it an attractive technology that has the potential to improve locust management, especially in
inaccessible areas. However, key parameters for the safe and optimal use of drones in desert locust
control are not documented. This study established the key parameters for spraying desert locusts
with a drone. To test the optimum height for spraying Metarhizium acridum on the locusts, the drone
was flown at five different heights: 2.5, 5, 7.5, 10, and 12.5 m. At each height, the drone sprayed the
ink mixture on spray cards pinned to the ground to approximate the droplet density and compare
it to the standard droplet density recommended for desert locust control. To assess the efficacy of
M. acridum and the effectiveness of drones in its application, 50 g of spores were mixed in 1 L of
diesel and sprayed on caged live locusts of different stages (3rd and 4th instars, as well as the adults);
they were monitored for twenty-one days in a controlled room, and their mortality was determined.
Variation in droplet density between the tested heights was significant. A height of 10 m agrees
with the recommended standard droplet density within the 45 droplets/cm2 range. Mortality varied
among the locusts’ developmental stages within and between heights. Survival probability varied
between heights for 3rd instar, 4th instar, and adults. All the developmental stages of the desert locust
were susceptible to Novacrid and the recommended target stage is the 3rd instar. Management of
desert locusts by the use of drone technology appears promising when the pesticides are applied at
an optimum height and standard operating procedures are followed. Further research could explore
the gap in the effects of environmental parameters on flight application efficiency.
