Life history traits and damage potential of an invasive pest Brontispa longissima (Coleoptera: Chrysomelidae) on Satakentia liukiuensis

The coconut hispine beetle Brontispa longissima has been causing serious damage to the coconut palm Cocos nucifera in the Pacific, and Southeast and East Asia. This beetle also attacks Satakentia liukiuensis, an endemic palm on Ishigaki and Iriomote Islands, Japan. To assess the potential impact of B.longissima on S.liukiuensis, we examined the development period, survival rate, egg production and body size of B.longissima on S.liukiuensis at 22-31°C and consumption of S.liukiuensis leaf at 28°C. We also examined these life history traits on C.nucifera at 28°C to compare with those on S.liukiuensis. Brontispa longissima completed their development and reproduced on S.liukiuensis at 22-30°C. Linear regression analysis was used to estimate the effective cumulative temperature (k) as 891.2 degree-days, and the lower developmental threshold as 13.3°C. On the basis of these values and monthly average temperatures on Ishigaki Island, it was estimated that B.longissima has four generations per year on the island. Satakentia liukiuensis was less suitable for B.longissima than C.nucifera in terms of immature survival, development time, resultant adult size and reproduction. The low quality of S.liukiuensis as a host-plant may prevent the outbreak of B.longissima, which has not occurred yet on Ishigaki and Iriomote Islands.