FOREWORD

The rapid spread of the leucaena psyllid, Heteropsylla cubana, across the Pacific Islands, Australia, southeast Asia and the Indian subcontinent during the mid-1980s is legendary in the annals of modern economic entomology. In 1991, new infestations of this destructive insect pest of leucaena trees were discovered on the Indian Ocean Islands of Mauritius and Reunion. These new infestations posed an immediate threat to the leucaena resources of the African continent. One year later, this threat became a reality when infestations of leucaena psyllid were detected almost simultaneously on leucaena plantings in both Kenya and Tanzania. These infestations are spreading rapidly and many African countries are already affected by this pest.

The arrival of leucaena psyllid in Africa follows the introduction of three damaging conifer aphids; the pine woolly aphid, Pineus sp, the pine needle aphid, Eulachnus pini, and the cypress aphid, Cinara cupressi. Cypress aphid, the most damaging of the three has already caused tree mortality equivalent to approximately 10% of Kenya's cypress plantation area since its arrival in that country in 1990. The arrival of leucaena psyllid also coincided with a time when, in several African countries, farmers were just beginning to appreciate the rapid growth and multiplicity of values of the leucaena and were integrating this tree into their agroforestry programmes. Now discouraged by the damage being caused by the psyllid, some farmers are cutting their leucaena trees.

The future viability of leucaena in African agroforestry is not necessarily bleak however. Research by scientists working in Asia, Australia, the Pacific Islands, where the insect has been present for several years and in Mexico and Central America, which are the native habitats for both leucaena and leucaena psyllid, has led to the development of pest management tactics which, with some modification, have potential use in Africa.

The purpose of this sub-regional workshop was to bring together research scientists, forest pest management specialists and foresters from African countries where leucaena psyllid is already established or threatens to become established in the near future. The importance of leucaena, the threat posed by leucaena psyllid and available pest management options were reviewed. During the workshop, emphasis was placed on introducing information gained from years of experience with this insect in the Asia-Pacific Region. Another topic which was discussed during the workshop was the need for improved communication among African forest insect and disease specialists, especially when addressing problems of a sub-regional nature and of the desirability of an African Forest Insect and Disease Network.

This workshop was organized by the Tanzania Forest Research Institute (TAFORI) in technical collaboration with the Food and Agriculture Organization of the United Nations (FAO). Funding for the workshop was provided by USDA Forest Service and the FAO Technical Cooperation Programme, TCP/RAF/4451 - "Assistance for Management of Leucaena Psyllid". Other workshop collaborators were the International Institute of Biological Control (IIBC), the International Centre for Research in Agroforestry (ICRAF) and the Sokoine University of Agriculture in Morgoro, Tanzania.

Approximately 70 experts attended the workshop including representatives from most of the countries of eastern Africa from Ethiopia and the Sudan south to South Africa. Mauritius, Reunion and Nigeria were also represented. In the spirit of Technical Cooperation among Developing Countries (TCDC), a representative from Thailand participated in the workshop and gave a special presentation on the leucaena psyllid in the Asia-Pacific Region.

Sincere thanks are extended to the staff of the Tanzania Forest Research Institute, the Forestry and Beekeeping Division, Sokoine University of Agriculture, the FAO office in Dar- es-Salaam and the White Sands Hotel, whose dedication and hospitality contributed significantly to the congenial atmosphere and the overall success of this workshop. Thanks are also given to Graciela Andrade-Cianfrini, FAO, Rome, for assistance in finalizing the papers for these proceedings.

Co-Editors