Journal of Applied Biosciences (J. Appl. Biosci.) [ISSN 1997 - 5902]
Volume 62: 4582 - 4594 Published February 27, 2013.
Insect assemblage and the pollination system in cocoa ecosystems
*Adjaloo M. K1* and Oduro, W2.1 Technology Consultancy Centre, College of Engineering, KNUST, Kumasi
2 Faculty of Renewable Natural Resources, College of Agriculture and Renewable Natural Resources, KNUST, Kumasi, Ghana.
* Corresponding author: mkadjaloo@gmail.com
ABSTRACT
Objective: An insect survey was
carried out in ten farm plots to determine whether there are other
tropical pollinators of cocoa which are either unidentified or
undescribed, and hence review the pollination system of the crop.
Methodology and results: Ten homogenous farmer managed farm plots were selected. For three consecutive years, a study was carried out to determine the insect species richness and relative abundance in the farm plots during flowering seasons (April to October). It was also to determine which of the insects were pollinators or contributed to the process of pollination of cocoa. Trees used were selected based on availability of flowers. About 2,721 insects belonging to 36 species and 7 orders were recorded. Insect species of the orders viz: Hymenoptera, Diptera, Orthoptera, and Coleoptera were common to all the ten farm plots. These were found on cocoa trees, and on the ground among the cocoa leaf litter. The rest were predominantly aerial or flying insects. The results of focal patch observation indicated that more than half of insect species resident in the cocoa ecosystem did not visit the cocoa flowers. Those which visited did not carry any pollen. Only the ceratopogonid midges (Diptera) showed higher pollinator importance. They were therefore classified as effective pollinators, and hence could be beneficial to the productivity of cocoa. None of the crawling insects ever carried pollen to the stigma. The study showed that the cocoa ecosystem could support diverse insect communities; however, the evolution of the floral structure of cocoa restricts access to all but few pollinators. Cocoa therefore has a specialized pollination system.
Conclusion and application: The study showed that though the cocoa ecosystem could support diverse insect communities the cocoa tree itself has a specialized pollination system. The results therefore suggest that cocoa farmers should be encouraged to incorporate pollinator-friendly practices for sustainable cocoa production.
Key words: Cocoa, pollinators, insect assemblage, Forcipomyia spp, pollination system
Methodology and results: Ten homogenous farmer managed farm plots were selected. For three consecutive years, a study was carried out to determine the insect species richness and relative abundance in the farm plots during flowering seasons (April to October). It was also to determine which of the insects were pollinators or contributed to the process of pollination of cocoa. Trees used were selected based on availability of flowers. About 2,721 insects belonging to 36 species and 7 orders were recorded. Insect species of the orders viz: Hymenoptera, Diptera, Orthoptera, and Coleoptera were common to all the ten farm plots. These were found on cocoa trees, and on the ground among the cocoa leaf litter. The rest were predominantly aerial or flying insects. The results of focal patch observation indicated that more than half of insect species resident in the cocoa ecosystem did not visit the cocoa flowers. Those which visited did not carry any pollen. Only the ceratopogonid midges (Diptera) showed higher pollinator importance. They were therefore classified as effective pollinators, and hence could be beneficial to the productivity of cocoa. None of the crawling insects ever carried pollen to the stigma. The study showed that the cocoa ecosystem could support diverse insect communities; however, the evolution of the floral structure of cocoa restricts access to all but few pollinators. Cocoa therefore has a specialized pollination system.
Conclusion and application: The study showed that though the cocoa ecosystem could support diverse insect communities the cocoa tree itself has a specialized pollination system. The results therefore suggest that cocoa farmers should be encouraged to incorporate pollinator-friendly practices for sustainable cocoa production.
Key words: Cocoa, pollinators, insect assemblage, Forcipomyia spp, pollination system
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