Integrated Pest Management of the Leucaena Psyllid. What is Involved?

J.G.D. Ward - Food and Agriculture Organizaton of the United Nations, Nairobi, Kenya
J.G. Mwangi - Forest Health Management Centre, Forest Department, Box 30241, Karura, Muthaiga, Kenya

Abstract

Integrated pest management (IPM) is viewed as a rational approach to reducing the impact of pests (e.g. insects, pathogens, weed) on forest and agroforestry ecosystems. This paper presents the concept and components of IPM as they could apply to the management of the leucaena psyllid, Leucaena leucocephala (Lam.) de Wit. Experience gained from other IPM programmes to manage forest insects provides a basis for developing an IPM approach to managing the psyllid in Africa.

Introduction

Integrated pest management (IPM) has been suggested as an essential approach for managing the leucaena psyllid, Heterosylla cubana Crawford, in Africa (Napompet 1994). IPM is an approach for reducing the impact of insects or other pests in any ecosystem. This concept has been in existence for over thirty years. IPM can be defined as "The maintenance of destructive agents, including insects, at tolerable levels by the planned use of a variety of preventive, suppressive, or regulatory techniques and strategies that are ecologically and economically efficient" (Waters and Ewing 1974).

IPM gained popularity in 1962 following the publication of Rachel Carson’s book Silent Spring.

Its purpose was to alert the world of problems suffered by man and the environment by the indiscriminate use of pesticides. As the informed people of the world became more concerned about the use of chemical pesticides, IPM advocates suggested other options to resource managers for controlling pests. While not eliminating the use of pesticides, IPM considers and encourages possible alternatives to mange pests affecting resources, appeases the environmen-talists and gives managers a more logical approach for reducing the impact of pests on resources. Unfortunately, even today after the philosophy of IPM has been advocated for over three decades, many resource managers routinely resort to chemical pesticides since they may not be familiar with IPM or they may feel that the urgency of the situation justifies their use. This is especially true when farmers or homeowners are faced with the dilemma of controlling an insect pest.

In the past twenty years a number of research and development programmes to design IPM for forest ecosystems have been conducted. In the United States , programs such as the USDA Expanded Douglas-Fir Tussock Moth Program, Gypsy Moth Program, Southern Pine Beetle Program and others developed an IPM approach for managing specific forest insects. The primary purpose of these research, development and applications (RDA) programmes was to collect the necessary information through research and other means to develop and implement practical IPM decision support systems. As a result, IPM approaches were developed and implemented. Improvements have been made a s resource managers gained practical experience and additional research findings became available.

In Africa the first major IPM research, development and applications programme for a forest insect began in Kenya against the cypress aphid, Cinara cupressi (Buckton), in 1992. This insect, which now occurs in a number of East African countries threatens to destroy industrial/commercial plantations as well as ornamental and hedges of Mexican cypress, Cupressus lusitanica. The National Aphid Project, with financial assistance from FAO, UNDP and the World Bank, and in collaboration with institutions such as Kenya Forest Research Institute (KEFRI), International Institute of Biological Control (IIBC), International Centre of Insect Physiology and Ecology (ICIPE), Moi University and the Kenya Forest Department, has made progress towards the development of an IPM system for the cypress aphid. Areas where progress has occurred include the development of survey and sampling methods, importation of an exotic parasitoid, registration of a chemical insecticide, identification of possible resistant or tolerant varieties and removal of severely damaged plantations. Work is continuing to develop and implement an IPM system for cypress aphid in Kenya. Although there has been progress during the past two or three years additional work remains before an adequate IPM system is developed.

Research and development of leucaena psyllid in the Asia-Pacific region has provided treatment tactics suitable for incorporation into an IPM decision support system in Africa. A summary of research information on the psyllid can be found in the proceedings of several workshops held since 1987 (Napompeth 1994, NFTA 1987, Napompeth and MacDicken 1990). Although no formal IPM system has been developed in the Asia-Pacific region, the implementation of non-chemical treatment tactics has reduced the impact of the psyllid in the region.

Components of an IPM System

Practising IPM is more than a question of selecting from a list of treatment tactics, especially when applied on a large scale. An IPM programme should design an organized system for decision-making that utilizes information on the insect as well as the ecosystem and socio-economic conditions affected. As part of a process to look at the research needs of IPM programmes in the United States, a general conceptual model was developed to show both the research and development components, their relationship to each other and to the operational components (Figure 1).

Figure 1. General conceptual model showing the components and their relationship to one another in an IPM system (modified from Waters and Ewing 1974).

One of the most important aspects of this conceptual model is that pest management is only part of the total resource management for the resource managers or farmers. The Waters and Cowling (1976) version of this model refers to the interior of the model as the research and development components and the outer components as operational components and the outer components as operational components. Research provides information to drive the operational components.

When relating this model to the psyllid problem, a number of questions need to be asked. Do we have the information and methodology needed for the various components and which components should receive priority in terms of research? Is information collected and methodology developed in other parts of the world relevant to Africa? Additional information that may be needed to develop an IPM system for leucaena psyllid in Africa could include the following:

Research and Development Components

1. Pest Population Changes (Population Dynamics)
1. Is the life cycle known in Africa?
2. What factors regulate population fluctuations?
3. Can the influence of these factors be quatifies?
4. Is there a method to predict population changes?
5. Is there a sampling method to quantify populations?
2. Host Susceptibility and Suitability (Forest Stand Dynamics)
1. What are the interactions between pest/host?
2. What are the factors influencing susceptibility?
3. Is there a tree/site hazard rating system?
4. What is the interaction between associated agricultural crops, trees and pest?
3. Impact On Resource Values
1. What is the affect of the pest on reaching management objectives?
2. What is the impact of the pest on growth and yield?
3. What is the impact of the pest on socioeconomic conditions?
4. Can the impact be quantified?
5. What has the impact been in other parts of the world?
6. Are there environmental risks posed by the pest?
7. Are there environmental risks posed by the treatment?
8. What is the impact on associated agricultural/forest crops?
4. Benefit/Cost Integration
1. Do the benefits of developing and implementing an IPM programme equal or exceed the costs involved?
2. Could the funds used for the above be better utilized elsewhere?
3. Could the impact of the pest be positive on the resource?
4. Can the forest manager use this information to make a management decision?
5. Treatment Strategies & Resource Utilization
1. Are any of the following treatment tactics ready for implemention:
1. Biological
2. Cultural
3. Use of resistant or tolerant varieties
4. Use of non-host species
5. Regulatory
6. Chemical
2. Is there scientific or other evidence to show that these treatment tactics were effective in other areas of the world?
3. When is it appropriate to apply a specific treatment tactic?
4. Is there a method to evaluate the treatment tactics?
5. Does the treatment strategy pose environmental risks?
6. Will the problem subside without any treatment?

Operational Components

The operational components shown on the outside of the model include surveys to provide information for making status and prediction determinations, the prediction of impact with and without treatment tactics, the application of treatment tactics and post treatment evaluations. The methodology required for the operational components is usually provided through research and development. Some of the needs and methodology that may be required for the operational components are as follows:

1. Monitoring Pest Populations and Forest Conditions
1. Develop appropriate survey methods for populations and damage estimates.
2. Organize and implement a survey and reporting system.
2. Prediction Models
1. Is there a need to develop a hazard rating system?
2. Develop a method to predict relative population changes.
3. Develop a method to predict outcome with/without treatments.
3. Treatments
1. Implement one or more treatment tactics.
2. Consider no treatment as an option.
3. Conduct post treatment evaluations.

IPM for a specific pest is often referred to as a system or a decision support system. The system serves as an organized means for making a decision on whether to initiate treatment for a pest and, if so, what treatments to use. It may be as simple as using a key expressed as a series of questions or a complicated computer-based model. Some decision support systems require a considerable amount of information gained through research, development and practical experience. Research and development for some of the systems in use today has cost millions of dollars. Although the example of a decision support system shown in Figure 2 may be more complex than needed for the leucaena psyllid, it shows the general process for making pest management decisions.

Figure 2. Conceptual design of a decision support process for leucaena psyllid modified from the system used for managing the southern pine beetle in the Southeastern United States (Thatcher et al. 1980).

Similar decision support systems for other forest insects have been implemented. None of them are without problems and they will be constantly changing as additional information becomes available and as the conditions within the forest ecosystems themselves change. Although they are imperfect, their use provides a more logical approach to decision-making, especially in the areas related to the environment and economics of forest pest management.

The development of an IPM system is dynamic because improvements will need to be incorporated as conditions change and new knowledge is acquired. However, the management of forest pests using IPM treatment tactics should not be delayed until the system is completely developed. With regard to the leucaena psyllid, treatment tactics, such as the use of resistant and tolerant varieties of leucaena and biological control, have already proved useful in other countries without the development of a formal IPM decision support system. With some modification these treatment tactics could be used anywhere in the world.

Although every IPM system is unique, a decision support system similar to that shown in Figure 2 could be developed for management of the leucaena psyllid. The management of leucaena is different than a commercial forest plantation tree because it is an agroforestry species and the users are primarily farmers rather than government institutions or industrial managers. Leucaena psyllid causes the most severe problems in developing countries where financial resources for management are scarce and the products from leucaena or similar trees are vital for the well being of the farming community. Therefore, it is important to ensure that the development of an IPM programme for leucaena psyllid will contribute to the well being of the people of Africa and not just to scientific knowledge.

Technology Transfer

Technology transfer is a vital part of an IPM programme. Technology transfer bridges gaps between research, development and applications. Many of the results of an IPM research and development programme must be "translated" from highly technical terms to more easily understood language and reduced to simplest terms to benefit the ultimate user, the farmer managing the leucaena resource. In Africa it will probably be necessary to translate information into several national or local languages. Technology can be transferred in many ways including brochures, television, radio, video, training courses and demonstrations and is usually carried out by people specifically trained and designated for this job.

Constraints to IPM Implementation

The expertise to develop an IPM programme for leucaena psyllid in Africa is available but this in itself will not be sufficient to build a successful IPM programme. Technical and scientific capability is important but other elements including cooperation, organization, coordination, communication, management, transportation and funding are all vital and without them, success will be limited.

Summary and Conclusions

An IPM approach is recommended management of the leucaena psyllid in Africa. This approach should favor non-chemical and long-term treatment tactics such as biological control and the introduction and distribution of resistant and/or tolerant varieties or species of leucaena. A pest management programme for the psyllid in Africa can be built on information that is already available while conducting research to fill information gaps that may be specific for conditions in Africa. The development and implementation of IPM for management of the psyllid should also consider the needs and level of sophistication of the ultimate user, the farmer or resource manager.

Literature Cited

Carson, R., 1962. Silent spring. Houghton Mifflin Co., Boston.

NFTA. 1987. Proceedings of a workshop on biological and genetic control strategies for the leucaena Psyllid. A Special Edition of "Leucaena Research Reports: Volume 7 (2). Honolulu HI.

Napompeth, B., 1994. Leucaena psyllid in the Asia-Pacific Region: Implications for its management in Africa. FAO, RAPA Publication: 1994/13. Bangkok, Thailand. 26 pp.

Napompeth, B. and K.G. MacDicken, eds., 1990. Leucaena psyllid: problems and management. Winrock International/IDRC/NFTA/F-FRED, Bangkok, Thailand. 208 pp.

Thatcher, R.C., J.L. Searcy, J.E. Coster, and G.D. Hertel (eds), 1980. The Southern Pine Beetle. USDA Forest Service - Sci. And Educ. Admin. Tech. Bulletin 1631. Washington, D.C. 266pp.

US AID, 1992. Environmental assessment for implementation of biological control for the leucaena psyllid in Asia and Africa. Office of Forestry and Natural Resources Bureau for Science and Technology. United States Agency for International Development. Washington, D.C. 225 pages.

Water, W.E. and B. Ewing, 1974. Development and role of predictive modeling in pest management systems - insects. Michigan State Univ., East Lansing. Pp 19-27.