Brown locust control: we're getting it wrong

The brown locust is one of the most destructive agricultural pests in South Africa, yet our understanding of its habits and our efforts at controlling it are patchy and haphazard. A paradigm shift is needed, says Dr Johannes Henschel, an ecologist and research associate at the University of the Free State and the National Research Foundation.

- Roelof Bezuidenhout

Outbreak and recess phases of the brown locust (Locustana pardalina), which is endemic to Southern Africa, have been recorded for more than 200 years, and efforts have been made to control the pest since the founding of the Locust Research Unit of the Agricultural Research Council (ARC) a century ago.

Surprisingly, after a good start to locust research, when careful observations recorded what happens before outbreaks commence, locust research neglected to do much more along these lines. Instead, scientists focused on refining methods of locust control, even though a workshop in the mid1980s had clearly identified that research should concentrate on the functioning of outbreak centres.

No effort has been made to protect crops, although such methods are being developed elsewhere using pheromones (natural substances that are repulsive to locusts but don’t affect human consumers), and ultrasonic acoustic deterrents.

In 2006, although scientists had identified gaps in research that had not been followed through, the ARC’s Locust Research Unit was shut down. Crops are superfoods for locusts, and can augment swarms immensely; leaving croplands unguarded is therefore neglectful, to say the least. However, the actual economic impact of locusts on crops has never been properly quantified; it is simply assumed to be very severe.

INEFFECTIVE CONTROL