PHYTOPHAGOUS INSECTS ASSOCIATED TO REPRODUCTIVE STRUCTURES OF MESQUITE (PROSOPIS SPP) IN ARGENTINA THEIR POTENTIAL USE IN BIOLOGICAL CONTROL IN SOUTH AFRICA

Authors: MC KAY, FERNANDO - USDA/ARS/SABCL; GANDOLFO, DANIEL - USDA/ARS/SABCL

Submitted to: African Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/6/2007
Publication Date: 3/20/2007
Citation: Mc Kay, F., Gandolfo, D. 2007. PHYTOPHAGOUS INSECTS ASSOCIATED TO REPRODUCTIVE STRUCTURES OF MESQUITE (PROSOPIS SPP) IN ARGENTINA THEIR POTENTIAL USE IN BIOLOGICAL CONTROL IN SOUTH AFRICA. African Entomology. 15(1):121-131.

Interpretive Summary: Mesquite is a thorny shrub or tree native to predominantly North and South America. Several species were introduced into South Africa during the XIX century, for shade, wood fuel, and fodder. Some species have become weedy. Mechanical and chemical methods to control mesquite plants have been only marginally effective. In order to preserve the beneficial attributes of mesquite while arresting its spread, biological control programs were restricted to the use of seed-feeding insects. Between 1987 and 1993, three species of beetles were introduced from the USA, but they have not provided the desirable level of control, because livestock forage on the ripe pods before they can be damaged by the beetles. With the aim to overcome this problem, an agreement for cooperation on mesquite research was signed between the Plant Protection Research Institute (PPRI) of South Africa and the USDA-ARS-SABCL. In four extensive exploratory trips throughout Argentina, nine beetles, four moths and one gall midge species were found attacking flower buds, flowers and pods of mesquite. Among these potential biocontrol agents, a new species of seed-feeding weevil was selected for further studies. A petition to release it in South Africa is expected to be submitted to the regulatory authorities in 2006.

Technical Abstract: Mesquites (Prosopis spp.) are thorny leguminous shrubs or trees native to Southwest Asia, Africa, and, predominantly, North and South America. Introduced as beneficial plants in India, Pakistan, South Africa, Egypt, Kuwait, Australia, USA (Hawaii) and Brazil, some Prosopis species have become weeds in some of these countries. In South Africa, mesquite plants have been ranked in the top category amongst other alien weeds, because of their use of underground water. Mechanical and chemical methods to control Prosopis species implemented in the USA, Australia and South Africa have been only marginally effective. In an attempt to preserve the beneficial attributes of mesquite while arresting the spread, biocontrol efforts in South Africa have been focused on seed-feeding agents. Between 1987 and 1993, three species of bruchids were introduced from the USA, but their impact has been limited as ripe pods are eaten by livestock soon after falling to the ground. In this paper we present a list of insects that attack reproductive structures of Prosopis species in Argentina, with special attention to those insects that feed in green unripe pods and flowers. We provide information on the biology, distribution and host plants of nine beetles, four moths and one gall midge species. Their potential as biological control agents against mesquite in South Africa is discussed. A new species of the weevil Coelocephalapion was selected for further studies. The adults feed and oviposit on green pods, and the larvae develop and destroy the seeds, apparently without causing a substantial reduction on the value of pods as fodder. This would solve the competition problem for the ripe pods between livestock and the introduced bruchids in South Africa.