The Bahi Plains—An Additional Red Locust Outbreak Area in Central Tanzania?

Gregarious swarms of red locust, Nomadacris septemfasciata (Serville) capable of causing loss to agriculture originate from specific breeding areas in eastern and central Africa often referred to as outbreak areas. Typically these areas are poorly drained grassland plains that flood during the wet season and then dry out, creating sites for egg laying and stimulating growth of specific types of vegetation necessary for nymphal survival. During 1996, a significant upsurge of red locust occurred throughout central and western Tanzania. Populations also appeared in the Bahi Plains west of Dodoma, an area where significant infestations of red locust had not been recorded since the major plague of 1930–1944. Aerial spraying controlled 13,700 ha of nymphal bands and swarms. The 1996 upsurge could have been caused by a number of contributing factors: a prolonged drought leading to changes in vegetation; possible changes to flood water levels through diversion for irrigation; and either an undetected movement of red locust into the area from outside or localised breeding over several seasons. As a result of this outbreak the Bahi is likely to remain as a possible source of red locust swarms in the future and should be monitored closely.