The thesis was defended on 9 May 2016, in front of a jury comprising

• Mr Bhen Sikina TOGUEBAYE, Professor, UCAD, Senegal, Chair
• Dr Dominique BORDAT, Researcher HDR, France, Rapporteur
• Dr Mame Samba MBAYE, Lecturer, UCAD, Senegal, Rapporteur
• Mr Mbacké SEMBENE, Professor, UCAD, Senegal, Rapporteur
• Ms Corinne ROULAND-LEFEVRE, Professor, IRD, France, Examiner
• Dr Makhfousse SARR, Researcher, FAO, Senegal, Examiner
• Dr Jean-Yves REY, Researcher, CIRAD, France, Examiner
• Mr Karamoko DIARRA, Professor, UCAD, Senegal, Director

Abstract

Mango production plays a major socioeconomic role in Senegal. In recent years, producers have increasingly frequently observed dieback of mango trees, at least partly caused by termites. Despite the positive role played by termites in ecosystems, several species have become crop pests. It is now vital to take account of the functional elements of agrosystems if pests are to be managed sustainably. This work set out to i) assess the biodiversity of and damage caused by termites within agrosystems, ii) characterize the functioning of fruit tree-based agrosystems, and iii) assess the effects of agrosystem characteristics on termite damage and biodiversity.
It was conducted in 85 orchards in the Thiès and Dakar regions, Senegal. Orchard design, management practices, vegetation and hedge composition were characterized for all the orchards, before inventorying termite species, qualitatively and quantitatively. Lastly, tree condition and termite damage were assessed qualitatively.
This served to define four cropping systems, based on orchard design and management practices. Relatively substantial biodiversity (90 termite species) was recorded in Senegal, including 54 in orchards. Termite damage was observed on several fruit species such as mango, cashew, citrus, etc. Mango tree dieback was due to termite damage at the base of the trunk and on the roots. The attack rate was lower in well-irrigated, pruned orchards given moderate amounts of fertilizer and pesticides. Termite biodiversity was positively correlated with the vegetative state of the trees, and fell when organic fertilizers were used. Certain soil types were more or less favourable to relative termite abundance. These results should serve to develop an effective, sustainable orchard management strategy to reduce the impact of termites by managing their biodiversity and knowing more about orchard design and management practices.