Project Team Leader: Dr.Paul P. Bosu
Nauclea diderrichii (local name: Opepe, Kusia) is a valuable timber species found in tropical Africa. Its distribution extends from Sierra Leone through Central Africa to Uganda and some parts of East Africa. In Ghana, the species is found in both the deciduous and evergreen forest zones. The wood is resistant to decay, marine borers and termites and is used extensively in heavy construction, furniture, veneer, as well as many other domestic uses.
In 2001 N. diderrichii was selected as one of the five (5) priority indigenous species for forest plantation development in Ghana. The topmost criteria for selection of the five indigenous species (together with five other exotic species) were fire tolerance and resiliency to pests. However, the impact of opepe shoot borer (OSB) Orygmophora mediofoveata (Lepidoptera: Noctuidae) as a pest on Nauclea was under-estimated due to lack of knowledge on its pest status. Initial attempts to set up Nauclea plantations in Ghana in the last several years had limited success as a result of the pest.
The objective of the project was to develop integrated pest management strategies towards the establishment of sustainable Nauclea plantations in West Africa. The studies undertaken included provenance and genotype assessments; evaluation of OSB impact on Nauclea seedlings in field exclusion cages studies; evaluation of factors affecting seed germination; and an evaluation of the potential of insecticides to protect Nauclea seedlings against shoot borer damage. Fifteen (15) N. diderrichii genotypes from five (5) ecological zones in Ghana and Togo, including Amantia, Begoro, Benso, Berekum and the Plateau Region of the Republic of Togo were established at wet, moist and dry forest zones in Ghana and assessed for growth and OSB damage.
The results of the cage exclusion studies indicate that in the absence of attack by OSB, Nauclea can achieve growth at a rate more than double its current growth rate in plantations. It is recommended that integrated management for Nauclea should begin with the use of tolerant genotypes established on suitable sites. As a result of this study N. diderrichii has been included on the national list of indigenous species for plantation development in Togo. Prospects are also high for increased planting of the species in Ghana. African Forest Research Network (AFORNET) provided sponsorship for this project (Grant number 25/2005).