Citation
Ibrahim, Ishaq
(2016)
Application of sonic tomograph for basal stem rot detection in oil palm.
Masters thesis, Universiti Putra Malaysia.
Abstract
Basal stem rot (BSR) has been known as a silent killer to the oil palm industries
especially in Malaysia as the disease symptoms can only be observed once the
infected tree is highly damaged from the inside. Losses have reached up to
millions of ringgit per year due to high reduction of fresh fruit bunch production.
The main objective of this study was to improve the BSR disease detection
technique by sonic tomography (SoT) assisted by Ganoderma selective medium
(GSM). Hence, a sonic tomography was used to measure and to reveal the
internal condition of 51 selected oil palm trees, as well as to classify the
percentage of damage detected in each selected trees at a measuring level
between 0 and 100 cm near the ground level. Eight trees were selected as the
focal tree by using purposive sampling, while 43 neighboring trees were selected
nearby the focal trees via adaptive sampling. Four sensors were mounted
around the circumference of the tree trunk. Then, the measuring points were
nailed into the trunk. Next, each measuring points was tapped by an electronic
hammer to generate sound waves. Subsequently, the sonic waves were
captured by the sensors and were measured to produce tomogram. The
tomogram contain information on the percentage of damage and the general
location of the decayed area within the scanned tree. The percentage of
damages from each selected trees was classified into 0%, 1 to 20%, 21 to 40%,
41 to 60%, and 61 to 100% damage. Afterwards, trunk samples were extracted
by using an increment borer from the 51 scanned trees (excluding the three
control trees) at the same elevation from four directions of north, south, east, and
west by referring to tomogram images. Then, each sample was cut into five
portions of 2 mm size each, isolated onto the GSM, and stored inside a closed
box under room temperature for five days. Subsequently, the occurrence of
Ganoderma mycelium inside the Petri dishes was counted and the percentage of
the occurrence was determined and classified into 0%, 1 to 20%, 21 to 40%, 41
to 60%, and 61 to 100% occurrence. Lastly, the tomogram were corroborated
with the occurrence of Ganoderma mycelium to determine if the damages found
in the trees were caused by Ganoderma, and at the same time, to determine the accuracy of SoT to locate Ganoderma inside the tree trunk. As a result,
tomographic images revealed that among the 51 selected trees, two trees had
0% damage, nine trees had between 1 and 20%, 19 trees had between 21 and
40%, 15 trees had between 41 and 60%, and six trees had between 61 and
100%. Other than that, the occurrence of Ganoderma mycelium in the Petri dish
had been discovered in 3 trees with 1-20%, 19 trees with 21-40%, 14 trees with
41-60%, and 6 trees with 61-100%. This study concluded that the SoT was able
to detect damages caused by Ganoderma at a total percentage of 82%.
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