Category Archives: 2010 Vol 22 April

Nutrient absorption by oil palm primary roots as affected by empty fruit bunch application

Various parts of the oil palm primary roots were tested to determine the part which absorbs nutrients. An understanding of this aspect of nutrient absorption by the oil palm will explain why the application of empty fruit bunches (EFB) is important. Applying EFB increases the amount of roots, thus increasing the palm’s ability to absorb nutrients and hence, potentially making fertilizer applications more effective. To determine which part of the roots collects and absorbs nutrients, various locations on the primary roots, starting from the root tip, were treated with a solution of KH2PO4 containing 5 μg P ml -1 and 4 μCi of carrier-free 32P. The various locations were identified based on their colour, i.e. creamy white for the root tip, beige for that part of the root just after the creamy white portion, and dark brown for the oldest part of the root. After 24 hr of exposure, the amount of radioactivity emitted from each location was determined. Another experiment was conducted to determine the nutrient distribution pattern in the root after the nutrient was absorbed. In this experiment, the root tip and the part of the root that was dark brown in colour were treated with potassium chloride solution laced with 86Rb for 24 hr. After that time period, about 1 cm of each treated root, starting from the root tip and moving towards the palm base was cut, and their radioactivity determined. Results show that the part of the root that was creamy white (root tip) was significantly more active (P<0.05) in absorbing the nutrient compared to the other parts of the root. The amount of nutrient absorbed at that part of the root increased over time and was significantly higher (p<0.05) at 72 hr compared to absorption at 24 hr. The nutrient distribution pattern in the root from the point of exposure towards the palm base was different when the nutrient was absorbed from the root tip compared to the older part of the root which was dark brown in colour. When the nutrient was absorbed at the root tip, the distribution pattern of the nutrient along the length of the root from the tip to the base of the palm showed a certain pattern. Nutrient concentration was highest at the tip of the root and gradually decreased along the root towards the palm base. However, the nutrient distribution in the treatment of the dark brown part of the root did not follow the same pattern. It is suggested that the nutrient collected within the spaces in the older brown part of the root and flowed towards the root tip before being absorbed. Application of EFB increased the mass of roots. The results imply that for fertilizer application to be more effective, the fertilizers should be applied to those places where most of the roots are formed, i.e. especially under the heaps of EFB.

Downward movement of chlorpyrifos in the soil of an oil palm plantation in Sepang, Selangor, Malaysia

A study on the leaching of chlorpyrifos in an oil palm agro ecosystem was conducted in an oil palm plantation in Sepang, Selangor. The insecticide chlorpyrifos was sprayed using a knapsack sprayer at the recommended and double the recommended dosage. Soil samples were collected at different depths, viz. 0-10 cm, 10-20 cm, 20-30 cm, 30-40 cm and 40-50 cm at the following inter vals: -1 day (before treatment), 0 day (day of treatment, 6 hr later), 1 day, 3, 7, 14, 30 and 60 days after treatment. Recovery of chlorpyrifos from the soil spiked with chlorpyrifos at 4-50 μg kg-1 ranged from 88%-99% with the coefficients of variation r anging from 2.0% to 7.5%. Chlorpyrifos residue was detected at 0-10 cm and 10-20 cm depths when applied at the recommended and double the recommended dosages, respectively. The residue was only detected in the soil for up to five and seven days after treatment, respectively, when applied at the recommended and double the recommended dosages.

Effect of Beauveria brongniartii and B. bassiana on oil palm bagworm, Pteroma pendula (Joannis)

Beauveria bassiana and B. brongniartii strains 1, 2 and 3, were evaluated for their pathogenicity against the oil palm bagworm, Pteroma pendula. In a laboratory trial, the fungal isolates were found to cause mortality of up to 100% in the first and second larval instars of P. pendula. The lethal dose causing 80% mortality values (LD80) for B. bassiana and B. brongniartii strains 1, and 2 was 1 x 10spores ml-1. The lethal time to 50% mortality value (LT50) of all the isolates was seven days and the lethal time to 80% mortality value (LT80) was 11 days. The results suggested that all four isolates were equally pathogenic to bagworm larvae at a high dose of spore concentrations.

Optimization of the polymerase chain reaction (PCR) method for the detection of Orystes rhinoceros virus

Optimization of the polymerase chain reaction (PCR) method for the rapid detection of Oryctes rhinoceros virus (OrV) was studied. The virus DNA was extracted from the gut tissues by a robust method. Using a pair of specific primers, Primer 15a and 15b, infection was confirmed when the PCR product produced a single 945 bp DNA band. The optimized concentrations of the PCR components were at 2.0 mM MgCl2, 1.0 mM 10X PCR buffer, 0.2 mM Primer 15a and15b, 0.5 U Taq-DNA polymerase and 0.4 mg bovine serum albumin (BSA). All tested virus DNA concentrations at 0.085, 0.170 and 0.255 μg μl-1 were suitable for virus detection. Addition of BSA (20 mg ml-1) at 0.4 mg in the reaction increased the PCR sensitivity. The method is capable of detecting OrV infection from DNA diluted one million times or equivalent to a virus DNA concentration as low as 2.23 pg μl-1. The PCR detected 83.2% adult beetles from pheromone traps as being infected by OrV, 13.6% higher (P< 0.05) than the results based on observations on the gut morphological appearance (69.6%). A typical OrV infection symptom is a swollen gut filled with milky fluid. Of the 839 guts with this symptom, 97.6% were diagnosed to be infected which was not significantly different (P>0.05) compared to the method based on gut morphological appearance. The PCR was also capable in detecting virus at an early infection stage and in dead adults with decayed tissues. Of the 307 adults that appeared to be healthy, 36.1% of them were found to be infected. As much as 61.6% of dead adults with decayed tissues (N = 428) were diagnosed to be infected by the OrV. The method can be used in further research studies relating to OrV for the management of the rhinoceros beetle.

Empty fruit bunch application and oil palm root proliferation

The benefits derived from the application of empty fruit bunches (EFB) included better yields and improved palm nutrient status. These benefits were the result of better soil conditions after applying EFB. Root proliferation resulting from EFB application was observed to be an important factor that led to the better yields and palm nutrient status. The study was conducted on three-year-old DxP palms. Treatments followed an arrangement for the paired t-test with one side of the palm receiving EFB (treatment) at 100 kg per palm while no EFB was applied to the other side of the same palm (which acted as the control). Root samples were collected at three and six months after EFB application. The root masses from both treatment and control were then analysed as a total of all root orders, and also according to each root order, i.e. primary, secondary and tertiary. Comparison of quaternary roots was made using density/unit tertiary root length. Results showed that there was a proliferation of roots at a depth of 30-45 cm three months after EFB were applied. This proliferation occurred in a soil environment which was significantly improved (p<0.05) in terms of total and exchangeable K and total Ca at 15-45 cm soil depth. Significant (p<0.05) improvements in soil pH, soil moisture and P at 0-15 cm soil depth may also have influenced this proliferation of roots. It is postulated that the increased root mass under improved soil conditions implies an enhanced nutrient uptake process which explains the increased yields and better nutrient status.

Interactions of the bagworm, Pteroma pendula (Lepidoptera: Psychidae), and its natural enemies in an oil palm plantation in Perak

Bagworms are one of the important leaf-eating pests of oil palm in Malaysia and Indonesia, causing high yield losses up to 43% over two years after a serious infestation. Parasitoids and predators play an important role in regulating bagworm numbers. The propagation and establishment of the natural enemies depend on some suitable species of flowering plants as sources of nectar. Cassia cobanensis, a leguminous nectar producing plant is recommended to be grown in oil palm plantations as a food source for parasitoids related to the bagworm. An observation on the interactions of the bagworm pest and its natural enemies was conducted at an oil palm plantation in Perak, Malaysia. A bagworm (Pteroma pendula) infested block, with C. cobanensis planted along the roadside, and a control block with no C. cobanensis within their vicinity, were chosen for the trial. In late 2006, the population of the bagworms increased to 60 live larvae per frond (LPF) in the control block, while in the C. cobanensis block it remained below 30 LPF. A chemical control operation in early 2007 reduced the population of bagworms to negligible levels for about two years. The natural enemies (predators and parasitoids) were monitored using sticky traps and sweep nets in all the plots. Results show that due to the negligible bagworm hosts in the block, activities of the insect parasitoids shifted to the C. cobanensis plants planted along the roadsides. In the control block, the natural enemies still dwelt within the ground covers because of the absence of C. cobanensis plants in the vicinity. Activities of predators were seen to be more prominent on ferns while parasitoids preferred to dwell on plants with nectar sources (C. cobanensis and Asystasia gangetica). These observations strongly suggest the importance of establishing C. cobanensis within the vicinity of oil palm plantations in order to sustain the population of natural enemies for long-term control of bagworms.