Nettle caterpillars, rats and termite: development of control and management strategies

Nettle caterpillars, rats and termites are the main pests of oil palm plantations in Indonesia. The main species of nettle caterpillars often found in the western part of Indonesia are Setothosea asigna, Setora nitens, and Darna trima. In the eastern part of Indonesia Darna catenatus and Thosea monoloncha predominate. Four rat species regularly reported are Rattus tiomanicus, R argentiventer, R. rattus diardi, and R. exulans. Rattus tanezumi was recently sighted. Rat species dominant in oil palm plantation in Indonesia is Rattus tiomanicus, although dominancy of other ral species can occur in specific locations. Termites have been known to be an important decomposer in oil palm plantation; only one species of termite i.e. Coptotermes curvignathus is a pest of oil palm; the pest is mostly restricted to peat areas. Development of control strategies against these pests has evolved from using broad spectrum pesticides to the implementation of integrated pest management (IPM) with biological control agents as the main component. For the IPM of nettle caterpillars, several efforts were reported such as: (1) Development of an appropriate census system as decision support system, (2) Introduction, conservation, propagation and utilization of natural enemies including insect parasitoids, insect predators and entomopathogenic microbes, (3) Conservation and planting of beneficial plants in oil palm areas to encourage the development of insect parasitoids and predators, and (4) Screening of insecticides and development of their application methods which are more selective and safe for the environment. Implementation of these efforts can reduce the frequency of nettle caterpillar outbreaks, while at the same time reduce the quantity of insecticides used. In the IPM against oil palm rats, the planters have persisted using the barn owl, Tyto alba. Minimal use of rodenticides was reported in the successful implementation of barn owl. However, in the certain regions, the establishment of barn owl was problematic. Rat damages exceeding critical level were still observed even where the barn owls were well established. Further studies should be carried out to optimize the impact of barn owl on rat control. For termite control, selective application of fipronyl insecticide based on census system is recommended. The target of control is only specific towards C. curvignathus. Development of new control methods that are more selective and required less insecticide, such as using baiting system and biocontrol agents, are being tested.