Identification and Determination of the Spectral Reflectance Properties of Live and Dead Bagworms, Metisa Plana Walker (Lepidoptera: Psychidae) Using Vis/ NIR Spectroscopy

The bagworm is one of main and serious leaf eating insect pest threats of the oil palm plantations in Malaysia. The economic impact from a moderate bagworm attack of 10%-50% leaf damage may cause 43% yield loss. The population of bagworms without control often increases to above its threshold limits, thereby causing a serious outbreak. Monitoring and detection of the oil palm bagworm population is required to ensure proper planning of any control actions in the infested areas. Hence, a study on the determination of the spectral signature of the bagworm species of Metisa plana Walker was initiated by using Visible/Near Infrared (Vis/NIR) spectroscopy. Live and dead bagworm spectral properties were determined under the Vis/ NIR wavelength regions, 350-1050 nm to provide specific infrared detector and band filter for development of an automated counter of the bagworms. The results showed that the live and dead bagworms had specific reflectance spectra at a specific wavelength in the NIR range spectral, ranging from 1032-1051 nm and these were statistically confirmed using the Student's t-Test with two tailed distributions. A principal component analysis (PCA) resulted that the first two principal components, F1 and F2 have eigenvalues greater than 1, at 2.11 and 1.24, respectively. Using a Boxplot Quantiles, the results showed that the lowest and highest means of the reflectance spectra observed for the live bagworms were approximately 3.43% and 26.42%, respectively. Meanwhile, for the dead bagworms, the lowest and highest reflectance spectra observed were 4.02% and 34.29%, respectively. These spectral data were important to determine the suitable infrared (IR) instrumentation for detection of every stage of the live and dead bagworms. This information will be useful, important and crucial for development of an automated detector of insect pest in the future. (author)