Infestation status of invasive coconut leaf beetle, Brontispa longissima (Coleoptera: Chrysomelidae) on coconut palms in three different locations in Malaysia

The coconut plant act as an essential role in the economy of many Asian countries including the Philippines and their economies are recently threatened due to a serious outbreak of the coconut leaf beetle, Brontispa longissima (Gestro). This study was conducted to record the number of populations of B. longissima (Gestro) and their interactions with three different locations, the variety of coconut plants and the weather for 12 months. Coconut leaf beetle infestations were observed in the field on different varieties of coconut palms such as the hybrid, Matag, the aromatic dwarf (locally known as pandan) and the exotic Tagnanan Tall in three locations viz., Parit Botak, Johor, Pasir Mas, Kelantan and Hilir Perak, Perak. Observations on infestations were recorded for one year from January to December 2016. Sampling was conducted based on the symptoms of coconut leaf damage by B. longissima on the coconut trees. A total of 50 to 100 trees of each variety were chosen at random for data collection. Leaves of each frond were examined for the number of larvae and adults of B. longissima. Data was recorded once a month for a period of one year. Data were transformed using the square root of x (√x) for normalisation before analysing using a 3-WAY ANOVA to determine the effect of months, varieties and stages of B. longissima on the extent of coconut leaves damaged. The mean number of coconut leaf beetles was higher and varied significantly (p <0.05) on the aromatic pandan variety compared to other varieties. The mean number of B. longissima larvae was found in larger numbers compared to their adults. Significant differences were seen in the mean number of B. longissima beetles recorded between months. Most beetle infestations were recorded in the middle and at the end of the year, i.e. between July and December 2016. The influence of weather changes on beetle populations is also discussed. We concluded that B. longissima is an economically important pest for the coconut palm industryin Malaysia.