ABSTRACT

A study on the pollination of seven-year old palms in a plantation in Selangor, Malaysia was made between 1983 and 1987 to determine the relative roles of three types of pollinators, Elaeidobius kamerunicus (Coleoptera: Curculionidae), Thrips hawaiiensis (Thysanoptera) and Pyroderces sp. (Lepidoptera: Cosmopterygidae) as well as to examine their effects on oil palm bunches. Samples were collected monthly from anthesising male inflorescences to provide information on the actual and potential populations of pollinators. The activities of pollinators on anthesising female inflorescences were measured by pan-trapping. All anthesising female inflorescences at the time of population sampling were marked and the fruit bunches which formed were later harvested for analysis. The weevil Elaeidobius kamerunicus had not displaced T. hawaiiensis and Pyroderces sp. as was evident from their co-existence. Their pollination activities had sustained the fruit set and fruit to bunch ratios about 60 per cent. Nevertheless, E. kamerunicus had become the most important pollinator, even during the wet season. During dry periods, T. hawaiiensis played a more important role than E. kamerunicus in pollination. The critical threshold of weevil numbers required for pollination could not be determined because the fruit set had not declined to low levels. Furthermore, a high population was not necessarily beneficial because it resulted in the lowering of fruit set. During the period after the introduction of the weevil into Malaysia, there was no significant change on bunch parameters, with one exception: oil to bunch ratio showed a marked depression in 1985, three years after the introduction of the weevil. Three explanations have been suggested, the most important of which was related to a marked increase in the moisture content of the fruit bunches

KEYWORDS: oil palm, Elaeis guineensis, Elaedobius kamerunicus, Thrips hawaiiensis, Pyrodercers sp, insect pollination, pollinator force