Pest Outbreaks in Tropical Forest Plantations
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cover 04202 3/5/02 7:39 AM Page 1 CIFOR The success of exotic tree species in plantations has generally been attributed to P e s effective species-site matching and their t O O freedom from insect pests and diseases. u t b Nevertheless, there is a fear that catastrophic r e a outbreaks of pests and diseases may occur k s I suddenly in exotic plantations. There are two I n T opposing views: that plantations of exotic T r o species are at greater risk compared to p i c indigenous species and conversely that exotics a l F are at lesser risk. This report provides a critical F o r assessment of the risk of insect pest outbreaks e s t P in exotic plantations using an empirical P l a approach. Nine commonly planted species in n t a the tropics, Acacia mangium, Eucalyptus spp., t i o Gmelina arborea, Hevea brasiliensis, Leucaena n s leucocephala, Paraserianthes falcataria, Pinus caribaea, Swietenia macrophylla and Tectona grandis, were selected and their pest problems in natural forest stands, in indigenous species plantations and in exotic plantations were Pest Outbreaks in compared. Growing trees in monoculture increases the pest problem but the risk of pest Tropical Forest Plantations: outbreaks is not solely dependent on the exotic or indigenous status of a species. Pest outbreaks also occur in native plantations. The Is There a Greater Risk for Exotic Tree Species? theory relating to insect population dynamics and causes of pest outbreaks is discussed and several factors are identified that determine the risk of pest outbreaks in exotic monoculture plantations. K . S . S . N N a i r ISBN: 979-8764-87-0 K.S.S. Nair i PEST OUTBREAKS IN TROPICAL FOREST PLANTATIONS: Is There a Greater Risk for Exotic Tree Species? K.S.S. Nair Visiting Scientist Center for International Forestry Research sec0JT.p65 1 2/7/2002, 1:46 AM Black ii Cover photos (from left to right): - Acacia mangium attacked by Apomycera sp. in Indonesia (by Forest Protection Laboratory, Gadjah Mada University) - Eucalypts attacked by Gigantococus maximum in the Peoples Republic of Congo (by C. Cossalter) - Paraserianthes falcataria attacked by termites, Central Java, Indonesia (by L. Santoso) - Young trees dying in an Eucalyptus plantation in Vietnam (by C. Cossalter) © 2001 by Center for International Forestry Research All rights reserved. Published in 2001 Printed by SMK Grafika Desa Putera, Indonesia ISBN 979-8764-87-0 Published by Center for International Forestry Research Mailing address: P.O. Box 6596 JKPWB, Jakarta 10065, Indonesia Office address: Jl. CIFOR, Situ Gede, Sindang Barang, Bogor Barat 16680, Indonesia Tel.: +62 (251) 622622; Fax: +62 (251) 622100 E-mail: [email protected] Web site: http://www.cifor.cgiar.org sec0JT.p65 2 2/7/2002, 1:46 AM Black iii Contents Acknowledgements v Foreword vi Abstract vii 1. Introduction - The Problem and the Approach 1 1.1 Statement of the Problem 1 1.2 Exotics Concept and Definitions 1 1.3 The Tropics3 1.4 Exotic Plantations in the Tropics 3 1.5 Scope and Methods of Study 5 1.6 Presentation 5 2. Case Studies 7 2.1 Acacia mangium 7 2.2 Eucalyptus species 10 2.3 Gmelina arborea 19 2.4 Hevea brasiliensis 22 2.5 Leucaena leucocephala 24 2.6 Paraserianthes falcataria 30 2.7 Pinus caribaea 32 2.8 Swietenia macrophylla 35 2.9 Tectona grandis 38 3. Discussion - Is there a Greater Risk of Pest Outbreaks in Exotics? 47 3.1 Conclusions from Empirical Data 47 3.2 Theoretical Background 49 3.3 Re-examination of Empirical Findings in the Light of Theory 56 3.4 Conclusions 60 4. References 63 sec0JT.p65 3 2/7/2002, 1:46 AM Black iv List of Tables and Figures Tables Table 2.1.1 Main species/species groups feeding on exotic Acacia mangium 9 Table 2.2.1 Most important pests of Eucalyptus plantations in Australia 11 Table 2.2.2 Important pests of Eucalyptus tereticornis and E. grandis in natural forests and plantations in Queensland, Australia 17 Table 2.3.1 Main species of insects causing damage to native plantations of Gmelina arborea 20 Table 2.3.2 Main species of insects recorded in exotic plantations of Gmelina arborea 21 Table 2.5.1 Indigenous insects reported from exotic plantations of Leucaena leucocephala 28 Table 2.6.1 Main species of insects causing damage to exotic plantations of Paraserianthes falcataria 31 Table 2.7.1 Major pests of Pinus caribaea in native plantations33 Table 2.7.2 Major pests of Pinus caribaea plantations in Asia-Pacific 34 Table 2.8.1 Natural distribution of Swietenia species 36 Table 2.9.1 Categories of insects associated with the living teak tree in India and adjacent countries39 Table 2.9.2 Major pests of teak in native plantations 40 Table 2.9.3 Exotic plantations of teak and occurrence of Hyblaea puera 44 Table 3.1 Segregation of the monoculture effect and exotic effect in pest susceptibility of forest plantation species 48 Table 3.2 Comparison between the numbers of insect species associated with native and exotic plantations48 Figures Figure 3.1 In natural ecosystems, the population size of a species remains in a dynamically steady state (i.e., fluctuates within a moderate range) due to the action of opposing forces 50 sec0JT.p65 4 2/7/2002, 1:46 AM Black v Acknowledgements I am thankful to Prof. Jeffrey Sayer, Mr. Christian Cossalter, Dr. P.M. Ganapathy and Dr. C.T.S. Nair for encouragement to undertake this study. I am indebted to Prof. Julian Evans and Dr. Ross Wylie who reviewed the draft in its entirety, and Prof. Alan Berryman, Dr. Banpot Napompeth and Dr. Devendra Pandey who reviewed parts of the draft and made valuable suggestions for improvement. I thank Dr. J.W. Turnbull for dexterous final editing. Three organisations made this work possible; the Kerala Forest Research Institute, Peechi, India which gave me exposure to forest pest problems for over two decades, the International Union of Forestry Research Organizations which opened a window to pest problems in other countries through its activities and meetings, and the Center for International Forestry Research (CIFOR). I greatly appreciate the help rendered by Ms. Levania Santoso, Technical Assistant, Plantation Forestry Programme, CIFOR for help with literature searches. My wife, Mrs. Sathi Nair deserves special thanks for various kinds of support during this work, including assistance in typing. sec0JT.p65 5 2/7/2002, 1:46 AM Black vi Foreword The world now has 50 million hectares of fast- true that it may encounter new pests to which it has growing timber plantations and the proportion of the no resistance. Dr Nair provides much evidence that worlds wood supplies coming from plantations is runs counter to the conventional wisdom of popular increasing. It estimated that within 30 years the ecology and shows that broad generalisations in this plantation area will have increased by 60% and complex arena are dangerous. By carefully plantations will dominate more and more of our evaluating pest problems in tropical forest plantations landscapes. In the pulp and paper industry a few he has found that patterns do emerge and that many multi-national companies control vast areas of factors must be taken into account in assessing risk. industrial monocultures mainly of exotic species. He has assembled a body of evidence that will enable Even the multitude of small plantations and woodlots forest entomologists to make sensible predictions in the developed and developing world are composed of the types of pest risk to which exotic plantations largely of exotic species. may be exposed. Some species have been widely planted and have not yet suffered from pest The number of species exploited for industrial wood problems. Do we have massive pest problems just is decreasing and with the advent of genetically waiting to happen? modified trees there will be further concentration on a few species and a few varieties of these species It makes sense to be cautious. My own hope is that in plantation forestry. It is frequently claimed that the future will see different approaches to plantation vast areas of land dominated by a few species with forestry. I would like to see less emphasis on speed an ever-narrowing genetic base is creating a risk of of growth and volume of yields. We need a diversity catastrophic pest and disease outbreaks. The risk of approaches to plantation forestry designed to meet increases as trade in logs is globalised and timber local production and environmental needs. harvested on one continent may be found in log yards Plantations and natural forests should complement on another within a few weeks. Also, people who one another in meeting both industrial needs for spend time in forests for work or recreation travel timber and the needs of local livelihoods and of the the world in a matter of hours. All this leads many global environment. One of the attributes of such people to argue against excessive use of exotic multi-functional landscapes is that they could be species and to urge foresters to concentrate on local designed to minimise pest and disease risk. They species. could also provide a better environment for biological control of pest and disease outbreaks when this is Dr K.S.S Nairs book is welcome because it feasible. This is an area of emerging concern and contributes careful analysis and factual information interest. This book provides an excellent overview to a debate that has been dominated by emotions, of what we now know about insect pests in tropical speculation and nostalgia.