Pollination activity of Elaeidobius kamerunicus (Coleoptera: Curculionoidea) on oil palm on Hainan island

Jianjun Yue, Zhen Yan, Cheng Bai, Zetan Chen, Weifu Lin, Fangzhen Jiao

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.

 

Resumen

Elaeidobius kamerunicus Faust (Coleoptera: Curculionidae), el gorgojo de polinización, es el insecto polinizador más eficiente de la palma de aceite, Elaeis guineensis Jacq. (Arecales: Arecaceae). En este experimento, se observó la actividad polinizadora de E. ka­merunicus en un campo de la palma de aceite en Hainan, China con el fin de comprender mejor su dinámica. Se evaluó el número de gorgojos que visitan las inflorescencias mediante el uso de trampas adhesivas que rodean las inflorescencias, y contando los gorgojos presentes en muestras de espiguillas. Las inflorescencias machos durante el antesis fueron atractivas para los gorgojos durante 6 días, en comparación con 5 días para las inflorescencias femeninas. La población de gorgojos alcanzó su punto máximo en el tercer día de antesis en inflorescencias machos, y en el segundo día de antesis en inflorescencias femeninas. La actividad de los gorgojos registrada en el día de mayor abundancia durante la antesis reveló un período de inactividad entre 07:00–08:00 y la actividad constante entre ambos 11:00–12:00 y 17:30–18:00. El número de hembras adultas de gorgojos siempre fue mayor que el número de machos, tanto en las inflorescencias machos y hembras. Para aumentar la población de E. kamerunicus en Hainan, se deben tomar algunas medidas que incluye la liberación de adultos de gorgojos en las plantaciones de palma de aceite, y el control de depredadores y parásitos del gorgojo, como las ratas y nematodos nocivos.

 

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Keywords


anthesizing male inflorescence; Elaeis guineensis; pollinating weevil; pollinating activity; spikelet; sticky traps

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