Abstract. Elaeidobius kamerunicus Faust (Coleoptera: Curculionidae), the pollinating weevil, is the most efficient insect pollinator of oil palm, Elaeis guineen -. Abstract. Elaeidobius kamerunicus Faust (Coleoptera: Curculionidae), the pollinating weevil, is the most efficient insect pollinator of oil palm, Elaeis guineensis. The pollination of the oil palm is assured mainly by the insects. The most effective are Elaeidobius kamerunicus and Elaeidobius plagiatus. Declining.
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African oil palm weevil
When they crawl or move about on the spikelets the pollen grains adhere to their body and during their subsequent visits to the female infloresences the pollen grains are deposited elaeidobiu the stigma of female flowers.
When the weevils crawl over the male inflorescences a large amount of pollen grains are dispersed which are carried by wind Ponnamma et al. Control methods are not appropriate for E. Chew b discussed the reasons why E.
Of the various species of this genus studied in Cameroon, E. Yield increases following the introduction of E. A less efficient existing pollinator, Thrips hawaiiensis was not apparently displaced by E.
The presence of larvae appeared to attract rats. A mill survey revealed that the large compact bunches were difficult to process with the existing machinery, resulting in reduced extraction rates of oil. The advantages of the introduction of E. Greathead stated that in Malaysia, especially Sabah, assisted pollination of oil palm is necessary and even then yields are lower than those in Africa.
One explanation was that in selecting for more female flowers, plant breeders had produced varieties with insufficient male flowers or with less viable pollen. Elaeidobius species are attracted to male flowers only during anthesis when a strong aniseed-like scent is emitted.
When the stigmas are receptive, the female flower emits short pulses of a similar but sharper and more penetrating odour which attracts Elaeidobius species away from the male flowers. On arrival in the female inflorescence, the beetles find no food and after wandering around, they soon leave and return to male flowers. Examination of Elaeidobius species showed that they become covered in pollen which is shed when they clamber about the female inflorescence. Syed estimated that during the period of receptivity, over beetles visit each female inflorescence and that each beetle carries up to pollen grains.
Oviposition takes place after anthesis so that the larvae develop on tissue which has served its purpose and no longer has any function for the palm and, therefore, Elaeidobius species cause no significant damage.
The weevils are extremely beneficial and have been used by man, through introduction to palm plantations, for the pollination of these palms. Previously, hand pollination was required in areas where palms and weevils were not native, at great expense to the growers. In these countries, the inadequacy of pollination has been a major problem.
Besides the low rate of fruit setting, sometimes lack of adequate pollination also results in bunch failure. Two liberations of E. Within a year it had spread throughout the Peninsula and was extremely abundant in all plantations. Freed of competition with other species of Elaeidobius, it breeds in all parts of the male inflorescence and is equally common in all rainfall zones.
However, palm oil factories in Malaysia were designed for the former lower yields and are unable to extract all of the extra oil now available, but this is being remedied by introducing the processing methods used in West Africa. The weevils were taken to Sabah in March,with even more impressive results.
Reports of successful establishment and enhanced yields are now being received from these countries Greathead, The main ecological side effect of weevil introduction is the feeding of three rat species on the larvae which develop in the male flowers. High fresh fruit bunch yields in resulted in the production of a low crop innumbers of bunches being lower, although bunch size was still high.
The higher yields expected where pollination was previously poor and the change in spacing optima now that access for assisted pollination is not needed may affect breeding requirements and fertilizer needs.
Improved set has caused the production of more but smaller fruitlets, but has affected oil yield per bunch very little. The change in numbers of fruit set affects the harvesting standards used for optimizing oil production, as these are based on numbers of loose fruits.
Harvesting all bunches in which fruitlet detachment had commenced every days gave optimum oil production Wood, Wahid and Hassan reported the results of a survey covering Malaysian oil palm estates to assess the increase in rat populations since the introduction of E. Rats in these estates have developed a liking for the larvae of E. The effects of the curculionid, E. The main rat species in the oil palm estates, R.
Since the introduction of E. There was also a steady build-up of R. Ablation or disbudding of oil palm at the immature stage is commonly practised in Malaysia on the assumption that more nutrient will be channelled for vegetative growth, and in order to prevent rotting of the poorly pollinated early bunches. Since the introduction of the pollinating weevil, E.
Millions of dollars have been saved in Malaysia, following the introduction of E. The pollinating weevil, E. As a result of this kamerunnicus, average fruit set increased from An increase in rat damage, particularly to rotting male flowers, was noted following weevil introduction Hutauruk and Ps, The population density of E.
Increases in fruit set of In Indonesia, the introduction of E. There was no significant effect on mesocarp, shell and kernel, but fruits tended to become smaller and bunches more compact. Fruit detachment from the bunch was delayed as a result of pollinating weevil introduction Chairani and Taniputra, In field studies at the Bukit Sentang Estate in Sumatra, Indonesia, the yield of fresh fruit bunches increased in the first year after the release of E.
The increase in yield was due to an increase in the average bunch weight, although the bunch number decreased. During the second kamerunocus production fell because the bunch number was still decreasing, in spite of a slight increase in the average weight.
Increased fertilizer application could not prevent the decrease in yield during the second year. It is estimated that the yield at Bukit Sentang Estate will return to the level of the pre-weevil period Taniputra, In Africa, the curculionids E. In Indonesia, the low pollinating capacity of Thrips hawaiiensis, led to the introduction of Kamerubicus.
Four-year observations after the release of E. Leaf nutrient content of plots with and without extra fertilizer showed no significant difference. It appeared that the weevil did not change the monthly yield pattern. One third of the yield was produced during the first semester and two thirds during the second, with the peak in September-October Taniputra and Muluk, The release of E.
For the first 4 years, yields oscillated, declines being coupled with lowering of bunch numbers and increases with increased bunch numbers.
The average bunch weight doubled compared with that before release of the weevil, and now remains steady, with a tendency to increase further. Applying fertilizers did not reduce bunch numbers. As the yield at Bukit Sentang estate has now returned to the level of the pre-weevil period, it is concluded that it takes 5 years for the oil palm to adjust to the change in pollination system Taniputra kamerunius Muluk, Bunch analysis in oil palms in Indonesia was carried out for 5 years after the introduction of E.
Average bunch weight increased The percentage of kernel to bunch and oil to bunch were and The other components were more or less constant.
The inflorescences which reached anthesis were 6. In the Solomon Islands, the introduced pollinating weevil E.
In Papua New Guinea, components determining the oil and kernel extraction showed no response to density when assisted pollination was used, but with the successful introduction of the pollinator, E. Weevil pollination also decreased parthenocarpy from Although wind, plus assisted pollination was more elaeidobiud than wind plus weevil pollination The pollen carrying capacity and pollen load of adults of the curculionid E.
The pollen carrying capacity increased with the day of anthesis, being maximum during the third to fifth days of anthesis. The viability of pollen carried by the weevils congregating in the male inflorescences and by kamefunicus leaving the male inflorescences were The pollen carrying capacity was inversely proportional to the weevil population per spikelet, too high weevil populations resulted in reduced pollinating efficiency, presumably due to intraspecific competition.
The pollen carrying capacity of males was significantly greater than that of females, which was partially due to the greater surface area of males and especially the presence of pleural setae. The average pollen load of weevils visiting female inflorescences ranged fromand represented only The average viability of the pollen load was Pollination studies initiated at Pamol, Sabah in Decemberindicated that there may be a seasonal trend in the population of E.
High rainfall may elaeidobkus affect pollination elaeidobiua reducing weevil kameruniicus and overall viability of available pollen. Assisted pollination gives good fruit set during the months when natural pollination is poor.
Severe pruning to induce male inflorescence production is being tested as a less labour intensive alternative to improve fruit set Donough et al. However, during their first few years, young oil palms produce elaeifobius female flowers, only producing sufficient male flowers for the establishment and effective activity of pollination insects from the age of months.