IMPORTATION, RELEASES, AND ESTABLISHMENT OF NEOCHETINA SPP (COL, CURCULIONIDAE) FOR THE BIOLOGICAL-CONTROL OF WATER HYACINTH, EICHHORINIA CRASSIPES (LIL, PONTEDERIACEAE), IN BENIN, WEST-AFRICA

Water hyacinth, Eichhornia crassipes (Martius) Solms-Laubach (Ponteder iaceae) was first reported in Benin in 1977 and about 10 years later b ecame the major floating water weed in the south east, obstructing boa t traffic and fisheries. Water hyacinth multiplies in permanently fres h water in the swampy upper reaches of the S ($) over cap o River and in tributaries of the Oueme River. From there it is moved by wind and water flow to the coastal lagoons. The coastal lagoons are brackish du ring the dry season and water hyacinth eventually dies, In 1991, Neoch etina eichhorniae (Warner) (Col.: Curculionidae) of South American ori gin was imported from Australia via quarantine in Britain to Benin. A small infestation of the fungus Beauveria bassiana (Bals.) Vuill. (Hyp homycetes) was eliminated from the colony before release by sterilizin g eggs and rearing a fungus-free generation. Between late 1991 and mid 1993, about 23,900 N. eichhorniae were released at 11 localities alon g the Oueme River and in the head waters of the S ($) over cap o River . Regular monitoring revealed feeding scars by adults on leaves and tu nnelling by larvae in petioles at all release sites. By October 1993, N. eichhorniae had spread up to 20 km from some release sites. Neochet ina bruchi Hustache was imported in 1992. A total of about 5,700 weevi ls has been released in six localities since mid 1992. Recoveries of o ffspring were made in all but one locality. Despite the negative impac t of water flow wind, penetration of salt water, and removal of infest ed water hyacinth by fishermen, N. eichhorniae and N. bruchi are estab lished in Benin in a situation typical for coastal West Africa.