Pollination Activity of Elaeidobius kamerunicus (Coleoptera: Curculionoidea) on Oil Palm on Hainan Island

Abstract

Elaeidobius kamerunicus Faust (Coleoptera: Curculionidae), the pollinating weevil, is the most efficient insect pollinator of oil palm, Elaeis guineensis Jacq. (Arecales: Arecaceae). In this experiment, the pollinating activity of E. kamerunicus was observed in an oil palm field in Hainan, China, in order to further understand the dynamics of the weevil's behavior on inflorescences. Both male and female inflorescences emitted an anise-like fragrance. Female inflorescences appeared to reward the weevils with copious nectar production, whereas male inflorescences appeared to do so with both nectar and pollen. The number of weevils visiting an inflorescence was assessed by the use of a sticky trap encircling it, and by counting the weevils present on samples of spikelets of inflorescences. The weevil population peaked on the 3rd day of anthesis on male inflorescences, and on the 2nd day of anthesis on female inflorescences. Weevil activity recorded on the day of highest abundance during anthesis revealed an inactive period during 07:00-08:00, substantial activity during 11:00-12:00, and peak activity during 17:30-18:00. The number of female adult weevils was always much greater than the number of males, both on male and on female inflorescences. Separation of anthesizing male inflorescences into 7 consecutive stages each 1 d long and use of sticky traps baited with anthesizing male flowers that were placed around inflorescences on the plant were optimal techniques for obtaining reliable data on the numbers of pollinating weevils. To increase the population of E. kamerunicus in Hainan, some steps should be taken including releases of adult weevils in oil palm plantations, and control of the weevil's predators and parasites, such as rats and harmful nematodes.