Hypsipyla Shoot Borers of Meliaceae in Sri Lanka - Australian ...

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The Forest Resource of Ghana and Research on Hypsipyla robusta (Moore) (Lepidoptera: Pyralidae) Control in Mahogany Plantations in Ghana S.K.N. Atuahene 1 Abstract The forestry sector is a major contributor to the national economy of Ghana, employing some 75 000 people and contributing between 6% and 8% of the Gross Domestic Product. Overexploitation of the timber resource, particularly from the unreserved forests, has led to severe depletion of the highly desirable, traditional mainstays of the Ghanaian timber trade such as Pericopsis elata (Harms) van Meeuwan (‘Aformosia’), Milicia spp. (‘Odum’ or ‘Iroko’) and the Meliaceae. Previous management policy promoted the sustained supply of forest produce for the timber industry. There are currently 50 000 ha of plantations in Ghana, of which nearly 90% are exotic species, mainly Tectona grandis L., Cedrela odorata L. and Gmelina arborea Roxb. Attempts by the Forestry Department to establish indigenous tree species in open plantations have failed for several reasons, including poor tending operations, poor seed sources, fire, and pests and diseases. Overall success rates in all plantations were poor, ranging from 20–58%, but were particularly so among native Meliaceae, of which only 9% survived, largely as a result of damage by the shoot borer Hypsipyla robusta (Moore). With a projected increase in demand for wood and increasing interest in plantation development among individuals and private companies, there is an urgent need for an effective method of control of H. robusta. This paper outlines past and current research on H. robusta in Ghana, and discusses future research strategies that could help to reduce shoot borer impact on plantations of native Meliaceae in Ghana and the rest of West Africa. THE HIGH forest of Ghana is located in the south and southwest of the country and covers an area of 82 580 km 2 or 34% of the total land area (Hawthorne 1995). Some 16 340 km 2 of the forest estate has been demarcated as reserves managed by the Forestry Department. Of this area, 7600 km 2 are said to be reasonably well stocked, and have been set aside for timber production. The rest of the reserved forests are either permanent protection areas (3500 km 2 ) or conversion areas (1220 km 2 ) where the forest is degraded but could be rehabilitated through natural regeneration and protection over one felling cycle (about 40 years). The remaining reserve area is so degraded that it requires replanting (Aninakwa 1996). The unreserved forest has been declining at about 750 km 2 per year since the turn of the century. This 1 Forestry Research Institute of Ghana University PO Box 63, Kumasi, Ghana 58 deforestation has resulted from conversion to agriculture, logging and fuelwood gathering, mining, infrastructure development, and fires (World Bank 1988). Importance of the Forestry Industry in Ghana West Africa is home to some of the most valuable timber species in the world. The export trade in timber began in 1891 and initially focussed on the Meliaceae (Taylor 1960). The Meliaceae species of greatest economic importance in Ghana today are species of Khaya and Entandrophragma, although Lovoa species are also harvested (Table 1). Timber from native Meliaceae is extracted from the natural forests. The forestry sector employs 75 000 people and provides a livelihood to some 2 million people. The sector contributes between 6% and 8% of Ghana’s
Gross Domestic Product, a contribution exceeded only by cocoa and gold. In 1994, exports of forest products amounted to US$244 million or about 18% of total export earnings of that year. Native Meliaceae contributed substantially to these as over 34 000 m 3 of wood, valued at approximately US$20 million were exported, mainly as sawn lumber or sliced veneer, plywood and furniture parts (Table 1). Like most sub-Saharan countries, Ghana consumes more wood internally than is exported (Forest Products Inspection Bureau 1995). The major domestic markets for timber are the construction industry and fuelwood; thus economic and population growth are key factors leading to increased domestic consumption of wood. Real economic growth rates are currently 3.8% per year and population growth rate is 3.3%. It is estimated that at 3.5% economic growth, future levels of domestic demand of wood would rise from around 0.7 million m 3 in 1995 to nearly 1.0 million m 3 in 2005 (UK Forestry Commission 1995). Although the annual allowable cut of timber set by the Ghana Forestry Department is 1.0 million m 3 , since 1989 the forest has been consistently over cut, with between 1.2 and 2.0 million m 3 harvested per year. As a result, supply of many of the highly desirable, traditional mainstays of the Ghanaian timber trade, such as Pericopsis elata (Harms) van Meeuwan (‘Aformosia’) Milicia spp. (‘Odum’ or ‘Iroko’) and the Meliaceae, are severely limited (Ghartey 1989). Internationally, demand for African mahogany is likely to increase as supplies of hardwoods from Southeast Asia and Brazil decline (Elliot and Pleydell 1992). However, supply from natural forests is limited; at current rates of extraction, the resource is likely to be exhausted within 20 years (Alder 1989). The Government has recently taken legal measures to restrict the exploitation and depletion of the offreserve forests, which will further restrict supply and export revenue. 59 Forest Plantations in Ghana As the forest reserves alone are inadequate to sustain a viable timber industry and meet the growing domestic demand for timber, the FAO proposed for Ghana a national forest plantation estate of 59 000 km 2 commencing with the planting of 50 km 2 in 1968 (FAO/UNEP 1981). This figure was later revised downward by a national land use planning committee which targeted an estate of 1000 km 2 to be established over a 10-year period from 1970/71 (Nsenkyire 1992). A plantation program involving indigenous hardwood species including the Meliaceae was widely undertaken in eastern and western regions of Ghana. The annual target was set at 65 km 2 and limited to the forest reserves where the stocking of current valuable species was poor. Native Meliaceae that have been planted in Ghana include the native species Entandrophragma utile (Dawe and Sprague) Sprague, E. cylindricum (Sprague), E. angolense (Welw.), DC, K. ivorensis A. Chev., K. anthotheca (Wehu) C.DC, and K. grandifoliola C.DC (Table 2). Most native Meliaceae were established in the forest reserves by enrichment planting in previously logged forests or in ‘Taungya’ systems (Osafo 1970). Cedrela odorata L. and Swietenia spp. from Latin America have also been planted. Swietenia macrophylla King and S. humilis ZUCC. were planted in experimental pure stands at Pra-Anum Forest Reserve between 1961 and 1967 from seeds obtained from Costa Rica. The oldest C. odorata plantation was established at Dunkwa in the Central Region in 1922. Since then, there have been other plantations at Offin Headwaters and Pra-Anum Forest Reserves. Cedrela odorata has been planted largely as pure stands, although it has sometimes been included in mixed species plantation established in the Taungya systems (Quaynor 1971). Enrichment planting was found to be costly to manage and frequently produced poor growth due to Table 1. Volume and value of native species of the subfamily Swietenioideae of family Meliaceae exported in 1994 and 1995 (Forest Products Inspection Bureau, Takoradi 1996). Species Volume m 3 Value (US$) 1994 1995 1994 1995 Khaya spp. 17 130 12 753 9 146 969 6 000 407 Entandrophragma utile (Dawe & Sprague) Sprague 6 966 2 855 5 465 827 1 998 354 E. candollei (Harms) 429 470 198 870 213 128 E. cylindricum (Sprague) 4 065 2 877 2 441 543 1 614 440 E. angolense (Welw.) DC 5 186 3 819 2 510 157 1 658 984 Lovoa trichiliodes (Harms) 801 639 399 636 297 101
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Hypsipyla Shoot Borers of Meliaceae
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Mayhew and Newton (1998) have revie
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Page 7 and 8: Table 1. Summary of current and pas
Page 9 and 10: 26° 21° WEST BENGAL (INDIA) PACHA
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Page 19 and 20: them are species of the subfamily S
Page 21 and 22: T. ciliata grows in dry deciduous f
Page 23 and 24: Table 1. Area of forestry plantatio
Page 25 and 26: S. macrophylla and Swietenia mahago
Page 27 and 28: plantings of S. macrophylla, K. sen
Page 33 and 34: Table 1. Major plantation areas and
Page 37 and 38: mixing seedlings of S. macrophylla,
Page 41 and 42: of these species, plantings have be
Page 43 and 44: 45 Table 5. Continued. Description
Page 45 and 46: 47 Table 6. Description of on-going
Page 47 and 48: locations were generally poorer, wi
Page 51 and 52: growth response and resultant form
Page 53 and 54: Mr David Spolc (University of Queen
Page 55: Haley, C. 1954. Forestry in Tropica
Page 59 and 60: A number of parasitoids have been b
Page 61 and 62: A Review of Hypsipyla grandella Zel
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