THE RESPONSE OF FLOWER-VISITING INSECTS ON DIFFERENT CANOPY DENSITIES AND INSECT POLLINATION SUCCESS

• Main Author: Ainun, Khairunissa
• Format: Theses
• Language: Indonesia
• Subjects: Ilmu hayati ; Biologi
• Online Access: https://digilib.itb.ac.id/gdl/view/67957
• Institution: Institut Teknologi Bandung

Cocoa bean production is determined by the success in pollination, so the role of pollinating insects is needed. The presence of pollinating insects is strongly influenced by certain conditions, one of which is the density of the canopy. Canopy density in cocoa plantations can be different because in cocoa cultivation systems canopy management is very necessary. Canopy management in the cocoa cultivation system aims to control plant-disturbing organisms and induce flowering. The purpose of this study was to aim the impact of canopy density on the presence of visitor insect and the pollination success on the formation of cocoa beans. This research was conducted in February-March 2020 and April-July 2021 at the PT Pasir Ucing Timur cocoa plantation, West Java. Observation was carried out from the flowering phase (n=375) until the formation of seeds on 45 trees. This research was conducted in three stages, namely: (1) insect pollination, (2) hand-pollination and (3) self-pollination. In insect pollination, observations of insect diversity, perch behavior and environmental factors were carried out. Diversity was observed by carrying the scan sampling method and collection of insects by carrying the removal method to be identified in the laboratory. Perch behavior was done by observing the location of the insect perch on the flower and the handling time. The removal method was carried out again to determine the amount of pollen load on the visitors. Observations on hand-pollination and self-pollination experiments were carried out until the 7th week by harvesting the formed fruit to compare the pollination level of selfpollination, hand-pollination, and insect pollination by looking at the size of the fruit and the number of seeds formed. The results of observations showed that there were 112 individuals divided into four orders. There were 61 individuals visiting the open canopy cocoa plot and 51 individuals visiting the dense canopy cocoa plot. Based on the results of the Diversity index (H') it shows that in the open canopy and the dense canopy there is no difference with values of 1.46 and 1.08 respectively. However, in the evenness index, there were differences in the two types of canopy which showed that there were species that dominated in dense canopy (E=1) compared to the open canopy (E?0). Based on the frequency of visits, it was found that there was a significant difference (P<0.05) in the visits of Oecophylla smaragdina and Dolichoderus thoracicus between the canopies. Species O. smaragdina was found to have an almost 2 times higher of visitation frequency than D. thoracicus in the open canopy while in the dense canopy the opposite occurred. In the behavioral test, it was found that the species Forcipomyia sp. and D. thoracicus pollinated by perching on the cocoa pistil and anther with an average pollen load calculated on Forcipomyia sp. 1,171.87±302.58 grains/ml and D. thoracicus 545.50±243.50 grains/ml. Based on three types of pollination, the results showed that hand-pollination produced more with a percentage of 10.40% compared to insect pollination as much as 7.20% and self-pollination as much as 1.60%. Although the fruit yield in hand pollination (32.80 ± 1.85 seeds/fruit) was higher, the cocoa beans was not significantly different from insect pollination (37.20 ± 1.85) and significantly different from self-pollination (26.50). ± 1.50 seeds/fruit). Based on the results of the study, it can be said that the canopy condition can affect pollination success indirectly by increasing the types of pollinating insects. Then, the role of pollinator insects is more efficient than other pollination methods in dense cocoa canopy conditions.