Ganoderma boninense is the causal agent of a devastating disease affecting oil palm in Southeast Asian countries. Basal stem rot (BSR) disease slowly rots the base of palms, which radically reduces productive lifespan of this lucrative crop. Previous reports have indicated the successful use of Trichoderma as biological control agent (BCA) against G. boninense and isolate T. virens 7b was selected based on its initial screening. This study attempts to decipher the mechanisms responsible for the inhibition of G. boninense by identifying and characterizing the chemical compounds as well as the physical mechanisms by T. virens 7b. Hexane extract of the isolate gave 62.60% ± 6.41 inhibition against G. boninense and observation under scanning electron microscope (SEM) detected severe mycelial deformation of the pathogen at the region of inhibition. Similar mycelia deformation of G. boninense was observed with a fungicide treatment, Benlate indicating comparable fungicidal effect by T. virens 7b. Fraction 4 and 5 of hexane active fractions through preparative thin layer chromatography (P-TLC) was identified giving the best inhibition of the pathogen. These fractions comprised of ketones, alcohols, aldehydes, lactones, sesquiterpenes, monoterpenes, sulphides, and free fatty acids profiled through gas chromatography mass spectrometry detector (GC/MSD). A novel antifungal compound discovery of phenylethyl alcohol (PEA) by T. virens 7b is reported through this study. T. virens 7b also proved to be an active siderophore producer through chrome azurol S (CAS) agar assay. The study demonstrated the possible mechanisms involved and responsible in the successful inhibition of G. boninense.
Bagworms (Lepidoptera: Psychidae) are one of the important leaf-eating pests of oil palm in Malaysia and Indonesia. Crop losses, due to the extensive defoliation by a serious bagworm attack are inevitable. The establishment and propagation of the bagworm's parasitoids, depend very much on species of flowering plants as sources of nectar. Cassia cobanensis, was proven suitable due to its attractiveness to most bagworm parasitoids. A study to assess the diversity of bagworm's natural enemies (hymenopterous parasitoids and reduuvid predatory bugs) on the C. cobanensis plant and within the undergrowth of the oil palm planting block was evaluated by sweep net and sticky trap sampling. Environmental parameters such as light intensity, temperature and relative humidity were also recorded during the sampling to determine their possible range of influence towards the activity of the insect natural enemies. The Shannon-Wiener diversity index of insect natural enemies occurring on the C. cobanensis plant was 2.32. Among the dominant parasitoids observed on C. cobanensis plants are chalcids (Brachymeria lugubris and Brachymeria carinata) and braconids (Dolichogenidea metesae and Apanteles aluella), besides the reduuvid predator, Cosmolestes picticeps. In contrast, within the oil palm planting block, the undergrowth within the non-harvesting path only recorded a much lower diversity index of 1.09 and 1.12 each, in a block with C. cobanensis at the roadside and without, respectively. However, C. picticeps was shown to be much more dominant within both oil palm planting blocks, up to two-to threefold , with much lesser numbers of hymenopterous parasitoids (less than five individuals). This indicates the important contribution of C. cobanensis plant towards enriching the diversity of the parasitoids, which are normally not found within the oil palm block, due to much less intense sunlight. In terms of insect activity, they are significantly more active in the moderate or medium light intensities (<8000 fc), medium humidity levels (50%-69%) and medium temperatures (30°C-34°C).
The oil palm environment in Malaysia is rich in many ecosystem services which can be beneficial to control pests and diseases. Some examples are the soil microbes which consist of entomopathogenic fungi and bacteria which can be exploited for insect control, especially bagworms, rhinoceros beetle and termites. The bagworms (Lepidoptera: Psychidae) are currently severely infesting oil palm plantations in Malaysia. The Integrated Pest Management (IPM) of bagworms includes aerial spraying of Bacillus thuringiensis (Bt), cultivation of beneficial plants and fixing of natural pheromone traps. The rhinoceros beetle (Coleoptera: Scarabaeidae), can be managed with the soil fungus Metarhizium and the Oryctes nudivirus (OrNV). The subterranean termite (Isoptera: Rhinotermitidae) can be controlled with two entomopathogenic fungi, Beauveria bassiana and Metarhizium anisopliae which perform similarly as an insecticide. The soil microflora, rich in soil antagonists, can be useful for the control of Ganoderma disease. The Integrated Ganoderma Management (IGM) approach is advocated, which aimed at minimising disease incidence in replanting and prolonging the productive life of the infected palm. Birds are also examples of ecosystem services which can be further exploited for the control of rodents and also insect pests. There are several endemic nocturnal and diurnal bird species inhabiting the oil palm plantation which have the potential to control pests, especially rats and bagworms. This article deliberates on some of the endemic ecosystem services in Malaysia which have been exploited towards the management of major pests and diseases in oil palm. The enhancement of existing and introduced ecosystem services would ensure better management of pests and diseases for the sustainable cultivation of oil palm.
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