Criteria for Choosing Application Techniques for Desert Locust Control1

Insecticides may be applied in several ways to control desert locusts. The traditional method, of feeding poisoned bait to hopper bands, uses insecticide very efficiently and is inexpensive when put into practice on a limited scale. However, it is both expensive and ineffective when a plague arises. Treating individual bands with contact insecticides is similar and suitable for operations on a modest scale in countries where much of the land is developed for agriculture. Two large-scale methods, matching the size of a locust plague occurring in uncultivated deserts, are the treatment of swarms of adults and spraying dieldrin onto the natural vegetation of the breeding sites. Despite the small dose rate of dieldrin needed - tens of grams per hectare - the last method is very expensive when breeding occurs over the large areas which are susceptible - hundreds of thousands of square kilometres. Although all methods are suitable and used for particular circumstances, the last alone is the only one of general value and practical feasibility that can match the dimensions of a locust plague. Despite its high cost and the use of small dose rates of a persistent organochloride insecticide, the analysis of benefits and costs indicates that it will be the method mostly used in deserts, if a plague occurs again. The arguments leading to this conclusion are presented to illustrate an example of the type of study required to decide how to apply pesticides in practice for more familiar pest management tasks.