Preliminary observations of the economic importance of rodents in the establishment of oil palm (Elaeis guineensis) plantations in the Eastern Region of Ghana

Preliminary surveys to assess the damage caused to oil (Elaeis guineensis) seedlings were conducted during the first two years after transplanting to the field. Four oil palm plantations in the Eastern region of Ghana were selected for the surveys in 1996 and 1997. A survey of the suspected rodent pests was also undertaken during the latter part of 1997. The rodents gradually chewed the succulent apical buds of the seedlings, eventually causing the death of the palm. The ultimate objectives of this survey were: (i) to assess the damage caused to the young oil palm plants by rodents; (ii) to develop the capability to identify rodent pests through the recognition of the type of damage they cause to the oil palm, and (iii) to correctly identify the rodent pests of oil palm and to investigate their general biology and ecology for effective control. The damage assessment surveys involved periodic inspections of the plantations, the recording of the number of undamaged seedlings, and calculation of annual percentage seedling losses. The rodent survey involved a capture and identification programme using Sherman collapsible live traps placed along designated transects within the plantations. Identifications were confirmed using identification keys, manuals and voucher specimens. All the rodents captured so far have been identified as Dasymys incomtus (shaggy swamp rat), which has also been observed as a serious pest of oil palm in Nigeria and La Côte d'Ivoire. The assessment of rodent damage in the designated plantations indicated a drastic rise in percentage plant destruction of between 0-3% after the first year, to 41-57% after the second year of transplanting. The need to conduct further research, and the specific areas to be investigated in order to design effective rodent management and control strategies to preserve plant stands for maximum yields, have been stressed. JOURNAL OF THE GHANA SCIENCE ASSOCIATION Volume 2 No. 3 (2000) pp. 164-16