Phytophagous insects associated with the reproductive structures of mesquite (Prosopis spp.) in Argentina and their potential as biocontrol agents in South Africa

Mesquites (Prosopis spp.) are thorny leguminous shrubs or trees native to Southwest Asia, Africa, and predominantly North and South America. Introduced as beneficial plants to India, Pakistan, South Africa, Egypt, Kuwait, Australia, U.S.A. (Hawaii), and Brazil, some Prosopis species have become invasive in some of these countries. Mechanical and chemical control methods implemented in the U.S.A., Australia and South Africa have been only marginally effective. In an attempt to preserve the beneficial attributes of mesquite while arresting its spread, biocontrol efforts in South Africa have only focused on seed-feeding agents. Between 1987 and 1993, three species of bruchids were introduced from the U.S.A., but their impact has been limited as ripe pods are eaten by livestock before the agents have had a chance to eat the seeds. In this paper we present a list of insects that attack the reproductive structures of Prosopis species in Argentina, focusing on those that feed on green, unripe pods and flower buds. We provide information on the biology, distribution and host range of nine beetles, four moths and one gall midge species. Their potential as biological control agents against mesquite in South Africa is discussed with special reference to that of a new weevil species, Coelocephalapion gandolfoi Kissinger which was selected for further studies. The adults feed and oviposit on green pods, while the larvae feed on the immature seeds, apparently without causing a substantial reduction in the value of pods as fodder.