Sains Malaysiana 48(1)(2019): 15–21

http://dx.doi.org/10.17576/jsm-2019-4801-03

Effects of Rainfall, Number of Male Inflorescences and Spikelets on the Population Abundance of Elaeidobius kamerunicus (Coleoptera: Curculionidae)

(Kesan Hujan, Bilangan Jambak Bunga Sawit Jantan dan Spikelet ke atas Kelimpahan Populasi Elaeidobius kamerunicus (Coleoptera: Curculionidae))

NURUL FATIHAH, A.L.¹*, MUHAMAD FAHMI, M.H.¹, LUQMAN, H.A.¹, SYARIFAH NADIAH, S.M.D.¹, TEO, T.M.², IZFA RIZA, H.¹ & IDRIS, A.B.¹

¹Centre for Insect Systematic, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor Darul Ehsan, Malaysia

²Advanced Agriecological Research Sdn. Bhd., No 11, Jalan Teknologi 3/6, Taman Sains Selangor 1, Kota Damansara, 47810 Petaling Jaya, Selangor Darul Ehsan, Malaysia

Received: 30 March 2018/Accepted: 4 September 2018

ABSTRACT

Elaeidobius kamerunicus was first introduced to Malaysia from Cameroon as an oil palm pollinator in 1981. Since then, oil palm pollination has improved and the need for assisted pollination has reduced. Fruit set development and fruit production also saw significant improvements, until a reported decline that began in the late 1980s. Several factors may have contributed to such decline, but most researchers believe it is due to the low E. kamerunicus population. Therefore, a study was conducted to determine whether the amount of rainfall and the number of male inflorescences and spikelets influenced the population abundance of E. kamerunicus in Ladang Lekir, Perak, Malaysia. Sampling was performed each month in oil palm subplots, three for each age of palm age, from October 2015 to September 2016. A total of nine spikelets (three from the top, middle and base of a male inflorescence) were randomly selected from each male inflorescence on each chosen palm. They were cut early in the morning to avoid the weevil’s most active time, thus making collection easier. The number of weevils congregating on each spikelet was then counted. The average number of E. kamerunicus per hectare (ha) living on oil palms aged four and six were 21,086 and 25,712, respectively. The amount of rainfall and the number of male inflorescences and spikelets were found to positively correlate with the E. kamerunicus population. The number of male inflorescences showed strong correlation with the E. kamerunicus population. However, in-depth study is needed to determine the relationship between E. kamerunicus and fruit set.

Keywords: Coleoptera; Elaeidobius kamerunicus; oil palm; oil palm pollinator; population abundance

ABSTRAK

Elaeidobius kamerunicus mula diperkenalkan ke Malaysia dari Cameroon sebagai serangga pendebunga kelapa sawit pada tahun 1981. Sejak daripada itu, pendebungaan kelapa sawit bertambah baik dan keperluan untuk pendebungaan berbantu telah berkurang. Pembentukan set buah dan pengeluaran buah juga menunjukkan peningkatan yang ketara, sehingga terdapat laporan penurunan bermula pada akhir 1980-an. Beberapa faktor mungkin menyumbang kepada kemerosotan pendebungaan ini tetapi kebanyakan penyelidik percaya kemerosoton ini disebabkan oleh kelimpahan populasi E. kamerunicus itu sendiri. Oleh itu, satu kajian telah dijalankan untuk menentukan sama ada jumlah hujan, bilangan jambak bunga sawit jantan dan spikelet mempengaruhi kelimpahan populasi E. kamerunicus di Ladang Lekir, Perak, Malaysia. Pensampelan dilakukan pada setiap bulan di subplot kelapa sawit, tiga untuk setiap umur kelapa sawit, dari Oktober 2015 hingga September 2016. Sebanyak sembilan spikelet (tiga dari atas, tengah dan bawah bunga sawit jantan) telah dipilih secara rawak daripada setiap bunga sawit jantan matang yang dipilih. Spikelet dipotong pada awal pagi untuk mengelakkan waktu paling aktif kumbang pendebunga supaya proses pensampelan menjadi mudah. Bilangan kumbang yang terkumpul di setiap spikelet bunga jantan matang kemudiannya dihitung. Purata kelimpahan populasi E. kamerunicus setiap hektar pokok kelapa sawit berumur 4 dan 6 tahun masing-masing adalah 21,086 dan 25,712 kumbang. Jumlah hujan, bilangan jambak bunga sawit jantan dan spikelet didapati berkorelasi positif dengan populasi E. kamerunicus. Bilangan jambak bunga sawit jantan menunjukkan korelasi yang kuat dengan populasi E. kamerunicus. Walau bagaimanapun, kajian yang lebih mendalam diperlukan untuk menentukan hubungan antara E. kamerunicus dengan set buah.

Kata kunci: Coleoptera; Elaeidobius kamerunicus; kelapa sawit; kelimpahan populasi; pendebunga kelapa sawit

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*Corresponding author; email: nurulfatihahabdlatip@gmail.com