Preventive control and Desert Locust plagues

The original locust control strategy assumed that plagues arose when swarms escaped from outbreak areas and bred successfully in the surrounding invasion area. Thus, control within outbreak areas could prevent plagues. Plague prevention was achieved for species with small, relatively accessible outbreak areas providing resources allocated to preventive control allowed continuous monitoring and rapid treatment as outbreaks appeared. Plague prevention was less successful for species such as the Australian Plague Locust and the Desert Locust in which pre-plague bands and swarms develop and migrate within very large geographical areas. The success of preventive control can be demonstrated, however, by comparing population size and distribution before and after the strategy was implemented using effective control techniques. Some but not all recent plagues of the Australian Plague Locust have been prevented and, although the frequency of Desert Locust plagues has not declined in the last 40 years, their duration and extent has been sufficiently reduced to achieve the original objective of keeping major agricultural zones in the invasion area locust free. In Australia, substantial resources and the latest technology were available to implement early intervention and its success has been clearly demonstrated. We used a simple model to quantify the case for early intervention in Desert Locust campaigns and our simulations suggest that applying even a conservative rate of control from the beginning of an upsurge as part of early intervention would further reduce the size of upsurges and plagues and would contribute to a better managed Desert Locust population. (C) 2008 Elsevier Ltd. All rights reserved.