A study of the floral phenology of cocoa trees was carried out between 2006 and 2008 at Kubease in the Ashanti Region of Ghana, using one hundred cocoa trees from ten farm plots. The objective was to assess the contribution of floral phenology to the productivity of cocoa. Cocoa like all tropical tree species exhibited seasonally-related phenological patterns involving overlapping cycles under both intrinsic and extrinsic controls. However, unlike most tropical plants, flowering was in the rainy season. The production of new pods or cherelles increased during the major rainy season (June, July, and August), but was evenly distributed from the minor to the dry season. Production of small and medium pods peaked in August whereas production of large pods peaked in October. There was a positive correlation between new pod production and pods abortion (r = 0.69; n = 100; P < 0.05). Temperature, light intensity, and rainfall positively affected production of floral buds and production of open flowers. However, rainfall had the greatest influence on the phenological cycle of the cocoa plant. The floral phenological pattern also coincided with the activity of the main pollinators of cocoa which resulted in enhanced reproductive capacity for increased production of cocoa. 1. Introduction Cocoa (Theobroma cacao L.) ranks number three in global export commodities after coffee and sugar and is a major cash crop in many tropical countries [1]. Produced on more than 7.5 million hectares, cocoa provides a means of livelihood for an estimated 40 million people worldwide, ranging from small holder farmers, laborers to employees in processing factories. In the lowland tropics, including parts of Latin America, West Africa, and Indonesia, cocoa is a crop grown largely by smallholder farmers (smallholdings of less than ten hectares) [2]. Compared to other agricultural activities, cocoa has been a leading subsector in the economic growth and development of several West African countries including Ghana [3]. World cocoa production increased at a rate of 2.2 percent a year, from 1998 to 2010 culminating in a production level of 3.7 million tons over the period [4]. Studies in other parts of the world suggest that the yield of cocoa is related to the floral phenology of the trees ([5, 6]). Clarke [7] reported that a good understanding of the floral phenology of tree crops provides significant insights into the functional attributes of growth and reproduction of the trees. Therefore, the synchronization between the phenology of flowering of cocoa trees and the pollinator
References
[1]
World Wildlife Fund, “Developing best practice guidelines for sustainable models of cocoa production. Maximize their impacts on biodiversity protection,” Discussion Paper produced for WWF-Vietnam, 2006.
[2]
M. Franzen and M. B. Mulder, “Ecological, economic and social perspectives on cocoa production worldwide,” Biodiversity and Conservation, vol. 16, no. 13, pp. 3835–3849, 2007.
[3]
B. Duguma, J. Gockowski, and J. Bakala, “Smallholder cacao (Theobroma cacao Linn.) cultivation in agroforestry systems of West and Central Africa: challenges and opportunities,” Agroforestry Systems, vol. 51, no. 3, pp. 177–188, 2001.
[4]
Food and Agricultural Organisation Commodity Projections to 2010, pp. 73-74.
[5]
A. A. F. de Almeida and R. R. Valle, “Ecophysiology of the cacao tree,” Brazilian Journal of Plant Physiology, vol. 19, no. 4, pp. 425–448, 2007.
[6]
A. J. Daymond and P. Hadley, “Differential effects of temperature on fruit development and bean quality of contrasting genotypes of cacao (Theobroma cacao),” Annals of Applied Biology, vol. 153, no. 2, pp. 175–185, 2008.
[7]
P. J. Clarke, “Baseline studies of temperate mangrove growth and reproduction: demographic and litterfall measures of leafing and flowering,” Australian Journal of Botany, vol. 42, no. 1, pp. 37–48, 1994.
[8]
J. B. Hall and M. D. Swaine, Distribution and Ecology of Vascular Plants in Tropical Rain Forest. Forest Vegetation in Ghana. Geobotany, Dr. W. Junk, 1981.
[9]
J. E. Sarfo, B. Padi, F. M. Oppong, I. Y. Opoku, and A. Y. Akrofi, “Effects of two herbicides and four fungicides on insect pollination of cocoa,” in Proceedings of the 14th International Cocoa Research Conference, vol. 2, pp. 1387–1392, Accra, Ghana, 20031983.
[10]
P. Alvim de T., “Flowering of cocoa,” Cocoa Growers' Bulletin, vol. 35, pp. 23–31, 1984.
[11]
P. S. Ashton, T. J. Givnish, and S. Appanah, “Staggered flowering in the Dipterocarpaceae: new insights into floral induction and the evolution of mast fruiting in the aseasonal tropics,” American Naturalist, vol. 132, no. 1, pp. 44–66, 1988.
[12]
A. M. Young, “Cocoa pollination,” Cocoa Growers' Bulletin, vol. 37, pp. 5–23, 1986.
[13]
J. Y. Ewusie, Phenology in Tropical Ecology, Ghana Universities Press, Accra, Ghana, 1992.
[14]
E. E. Southwick, “Photosynthate allocation to floral nectar: a neglected energy investment,” Ecology, vol. 65, no. 6, pp. 1775–1779, 1984.
[15]
A. A. Snow and D. F. Whigham, “Costs of flower and fruit production in Tipularia discolor (Orchidaceae),” Ecology, vol. 70, no. 5, pp. 1286–1293, 1989.
[16]
R. R. Valle, A. A. F. de Almeida, and R. M. O. Leite, “Energy costs of flowering, fruiting and cherelle wilt in cacao,” Tree Physiology, vol. 6, pp. 329–336, 1990.
[17]
M. M. Bos, I. Steffan-Dewenter, and T. Tscharntke, “The relative importance of cacao fruit abortion, insect attacks and pathogens depends on shade tree management,” Agriculture, Ecosystems and Environment. In press.
[18]
A. M. Young, “Ecological notes on cacao-associated midges (Diptera: Ceratopogonidae) in the “Catongo” cacao plantation at Turrialba, Costa Rica,” Proceedings of the Entomological Society of Washington, vol. 86, no. 1, pp. 185–194, 1984.
[19]
M. Falque, A. Vincent, B. E. Vaissiere, and A. B. Eskes, “Effect of pollination intensity on fruit and seed set in cacao (Theobroma cacao L.),” Sexual Plant Reproduction, vol. 8, no. 6, pp. 354–360, 1995.
[20]
G. Mossu, D. Paulin, and P. De Reffye, “Influence de la floraison et de la pollinisation sur les rendements du cacayer. Liaisons mathematiques entre les donnees experimentales. Equation du rendement,” Café, Cacao, the, vol. 25, pp. 155–168, 1981.
[21]
G. A. R. Wood and R. A. Lass, Cacao, Longman, New York, NY, USA, 4th edition, 1985.
[22]
H. Mohr and P. Schopfer, Plant Physiology, Springer, New York, NY, USA, 1994.
[23]
S. S. Omolaja, P. Aikpokpodion, S. Adedeji, and D. E. Vwioko, “Rainfall and temperature effects on flowering and pollen productions in cocoa,” African Crop Science Journal, vol. 17, no. 1, pp. 41–48, 2009.
[24]
T. C. Whitmore, Tropical Rain Forest of the Far East, Oxford University Press, London, UK, 1975.
[25]
G. Vaughton and M. Ramsey, “Pollinators and seed production,” in Seed Development and Germination, J. Kigel and G. Galili, Eds., pp. 475–490, Marcel Dekker, NewYork, NY, USA, 1995.
[26]
R. G. Hurd and R. K. Cunningham, “A cocoa shade and manurial experiment at the West Africa Cocoa Research Institute, Ghana. III. Physiological results,” Journal of Horticultural Science, vol. 36, pp. 126–137, 1961.
[27]
J. K. Owusu, “Light requirements of cocoa: a review,” in Proceedings of the International Conference on Cocoa and Coconuts, pp. 112–121, Kuala Lumpur, Malaysia, 1978.
[28]
S. J. Taylor and P. Hadley, “Relation between root and shoot growth in cocoa (Theobroma cacao) grown under different shade regimes,” in Proceedings of the 10th International Cocoa Research Conference, pp. 77–183, Cocoa Producers Alliance, Santo Domingo, Dominican Republic, 1987.
[29]
G. J. Anim-Kwapong, K. Opoku-Ameyaw, F. M. Amoah et al., “Cocoa agronomy: a review,” Cocoa Research Insitute of Ghana, New Tafo-Akim, (unpublished).
[30]
E. J. A. Asomaning, R. S. Kwakwa, and W. V. Hutcheon, “Physiological studies on an amazon shade and fertilizer trial at the Cocoa Reearch Institute of Ghana,” Journal of Agricultural, vol. 4, pp. 47–64, 1971.
[31]
S. T. Ampofo and E. E. N. A. Bonaparte, “Flushing, Flowering and pod-setting of hybrid cocoa in a cocoa shade/spacing/cultivar experiment,” in Proceedings of the 7th International Cocoa Research Conference, pp. 103–108, Douala, Cameroon, 1981.
[32]
A. H. Brew, “Cocoa pod husk as a breeding substrate for Forcipomyia midges and related species which pollinate cocoa in Ghana,” 1988, Cocoa Growers Bulletin no. 40, November, 1988.
[33]
C. P. van Schaik, J. W. Terborgh, and S. J. Wright, “The phenology of tropical forests: adaptive significance and consequences for primary consumers,” Annual Review of Ecology and Systematics, vol. 24, pp. 353–377, 1993.
