Abstract
Regular and often intense outbreaks of the brown locust, Locustana pardalina (Walker), in the semi-arid Nama Karoo region of South Africa present a formidable pest control problem. Outbreak patterns over a 64-year period (1941–2005) were reviewed indicating a very high frequency of outbreak years with regular ‘plague’ periods being experienced, while a more detailed analysis of the numbers of locust targets controlled during a 22-year period (1983–2005) described the intensity and scale of the outbreaks. The operational constraints associated with the traditional ground-based control strategy employed against the thousands of individual roosting brown locust hopper band and swarm targets in the Karoo are discussed. A brief review of laboratory and field trials of alternative methods of controlling the brown locust, such as insecticide baits, barrier treatments and the Green Muscle® myco-insecticide, as an alternative to broad-spectrum pyrethroid insecticides are described. In addition, alternative control strategies to the current ‘Commando’ system of ground-based control operations are discussed. The recommendation is for a modernised and technology-equipped integrated brown locust management strategy (IPM), combining ground and aerial tactics that will have the flexibility and the capacity to deal effectively with outbreaks. The integrated management strategy should focus on ground-based control of hopper bands and fledgling swarms in the Upper and eastern Karoo, while outbreaks over most of the Central Karoo and arid Bushmanland areas should be left to fledge and coalesce into large-sized swarms that could then be targeted by spray aircraft as they migrate along their known swarm flight paths. The introduction of electronic reporting and GIS mapping technologies for brown locust campaign management is essential.
Highlights
The aim of this review article is to summarise the outbreak history of the brown locust, Locustana pardalina (Walker) along with the control tactics currently employed and alternative control methods evaluated, and to discuss possible alternative strategies for more effective management of outbreaks
The Nama Karoo occupies the central plateau of the western half of South Africa at an altitude of 500–2000 m, so frost is common in winter
The rainfall mainly falls in late summer and autumn, with a rainfall gradient ranging from approximately 100 mm in the western arid areas to 400 mm per annum in the eastern Karoo, rainfall is typically erratic and extended droughts are common
Summary
The aim of this review article is to summarise the outbreak history of the brown locust, Locustana pardalina (Walker) along with the control tactics currently employed and alternative control methods evaluated, and to discuss possible alternative strategies for more effective management of outbreaks. The brown locust has a recognised outbreak area that covers approximately 250,000 km of the semi-arid Nama Karoo biome region of South. The rainfall mainly falls in late summer and autumn, with a rainfall gradient ranging from approximately 100 mm in the western arid areas to 400 mm per annum in the eastern Karoo, rainfall is typically erratic and extended droughts are common. Solitaria phase females only lay diapause eggs, with the obligate diapause being broken after 9–45 days under dry soil conditions, while gregaria swarming females only lay non-diapause eggs that develop continuously under moist soil conditions. Gregarious brown locust populations requiring chemical control could be found somewhere or other in the Karoo in approximately 90% of years throughout the entire twentieth century, the intensity and extent of outbreaks varied greatly [19].
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