Insect biodiversity for sustainable management of natural resources

Georg Goergen,

Insect diversity: Tenebrionidae family checklist. Photo by G. Goergen, IITA.
Insect diversity: Tenebrionidae family checklist. Photo by G. Goergen, IITA.

The conservation of biodiversity and the sustainable use of natural resources are guiding principles of the CGIAR and a recognized thematic priority area. The CGIAR is a major player in the collection, characterization, and unrestricted distribution of agrobiodiversity resources and related information on a global scale. Currently, out of 15 centers, 11 house important genebanks amounting to some 650,000 accessions. These provide scientists with the genetic material needed to significantly increase agricultural productivity.

The conservation of genetic resources at IITA is particularly broad in coverage. Thus, collections encompass a wide range of organisms including plants but also associated nonplant biodiversity. Emphasis is placed on the ex situ preservation of plant genetic material. This is reflected in the maintenance of roughly 28,000 germplasm accessions from 19 agricultural crops and their wild relatives. More than half of the genebank’s holdings represent in-trust collections of cowpea for which IITA has received the world conservation mandate. Free and unrestricted public access to this genetic material is ensured through institutional compliance with the international seed treaty developed through the Food and Agriculture Organization with the strong involvement of the CGIAR centers.

Apart from the use of genetically improved crops, agricultural productivity is also strongly influenced by a rich in-field biodiversity comprising organisms such as fungi, bacteria, viruses, nematodes, mites, and insects. Their beneficial or deleterious impact on crops is relatively well understood when interactions are based on simple associations of organisms. However, when many players are acting sometimes across several trophic (nutrition or feeding) levels, the study of ecosystems becomes complicated and knowledge-intensive.

Immature of the whitefly Paraleyrodes minei. Photo by G. Goergen.
Immature of the whitefly Paraleyrodes minei. Photo by G. Goergen.

Generally, a thorough inventory and characterization process is the requisite condition for the sustainable management of this nonplant biodiversity. Related information is primarily stored in research collections to which IITA has been giving growing attention over the last decade. Today, important nonplant collections allow safe diagnostics of plant pathogenic microorganisms used for resistance screening in breeding programs and arthropods/fungi used for biological control (see Korkaric and Beed, this issue).

A collection that has particularly expanded over the last 15 years is the arthropod reference collection at IITA-Bénin, the largest within the whole CGIAR. It encompasses currently more than 350,000 specimens collected in a wide range of agricultural and natural environments throughout West Africa. More than 5,000 species from 330 arthropod families have been identified from the sampled material, but it is estimated that about 40−50% of all known insect biodiversity of the subregion is preserved in this collection, awaiting further study. Serving as the coordination center for the West African node of the global taxonomic network BioNET-INTERNATIONAL, this biodiversity collection is well placed to provide essential services for sustainable natural resource management at the regional level.

The most important service has been the assistance in arthropod identification. Similar to the safe characterization of germplasm when plant material is transferred under the International Treaty on Plant Genetic Resources for FAO, users need reliable and valid entity names for biodiversity monitoring, pest management, biological control, conservation, and compliance with trade-related controls under the prevailing Sanitary and Phytosanitary regulations of the World Trade Organization.

For scientists, farmers, extension and biosecurity agents, quarantine authorities, and any other user throughout the globe, accurate and timely identification is vital. It represents the unique entry point for access to existing information about any organism. Opportunities in West Africa similar to diagnostics services for plant diseases for identifying arthropods are scarce or nonexistent and fees requested by overseas centers of expertise are not affordable for most local users. Thus, by providing the names of, on average, 1,500 submitted arthropod specimens per year, IITA has been instrumental in responding to the regional need for over a decade.

Adult female of Sri Lanka fruitfly Bactrocera invadens. Photo by G. Goergen, IITA.
Adult female of Sri Lanka fruitfly Bactrocera invadens. Photo by G. Goergen, IITA.

Arthropods form the bulk of the roughly 1.8 million species that have been described until today. It is estimated that this number actually represents only a small fraction of all living organisms, the number of yet unnamed species being particularly large in tropical countries. Thanks to regular faunistic activities, IITA has contributed to the discovery and description of more than 120 arthropod species previously unknown to science. Among them are important pests and their natural enemies.

Following climate change, invasive alien species (IAS) are widely regarded as the second-greatest threat to biodiversity worldwide. They represent a growing concern for biosecurity and quarantine services, especially since increased trade and travel are expected to accelerate the rate of pest introductions. For tropical Africa, data sampled over 100 years show a rate of three introductions every two years. The failure to recognize IAS may have dire economic or ecological consequences. Prevention or early detection of such IAS requires considerable knowledge of native and exotic fauna.

For West Africa, IITA-Bénin is at the forefront of IAS surveillance with the detection of the whitefly Paraleyrodes minei Iaccarino, the Sri Lanka fruitfly Bactrocera invadens Drew et al., and lately the papaya mealybug Paracoccus marginatus Williams & Granara de Willink. Such monitoring also led to the recent detection of a new cashew pest, now awaiting description.

Infestation of the papaya mealybug Paracoccus marginatus. Photo by Manuele Tamo, IITA.
Infestation of the papaya mealybug Paracoccus marginatus. Photo by Manuele Tamo, IITA.

Despite the need to maintain the present services and the opportunities arising to work in new fields, the future of the collection remains unsure because of the lack of external funding. This is all the more surprising since new opportunities for the delivery of public goods are now appearing in various areas with significant impact for the sustainable use of natural resources. Thus, the comparatively young age of the collection makes it particularly well suited for the application of novel identification methods such as DNA barcoding.

IITA’s participation could thereby provide important additions to this publicly accessible DNA database thus advancing the goals set by the Consortium for the Barcode of Life (CBOL). Besides agricultural pests and their natural enemies, this technology will also target crop pollinators because of their vital services to ecosystems and the particular concern raised by their global decline. Thus, a full return from past collection efforts will be achieved by applying molecular techniques.

Opportunities to extend biosystematics services at IITA are manifold and crucial for the region that is known to suffer from scanty local capabilities. These include the development of web-based products, the integration of Geographical Information Systems, the provision of online identification tools using high resolution images of important West African arthropod species, and capacity building in the identification of agriculturally relevant groups at various academic levels.

IITA has already an undeniable comparative advantage in biosystematics. This advantage should be preserved in view of its vital support to the successful deployment of plant genetic material for improving food security and reducing poverty in developing countries.

Why manage noncrop biodiversity

Muris Korkaric, and Fen Beed,

When it comes to the diversity of nonplant taxa, the numbers alone are highly impressive. There are an estimated 5–30 million species of microorganisms globally but only two million have been formally described. In 1 g of soil, over a billion bacteria cells can be found, but fewer than 5% of the species have been named or can be grown on artificial media. For fungi, about 1.5 million species are estimated to exist and yet only 5% have been characterized taxonomically.

Disease symptom caused by Colletotrichum fuscum on lettuce leaf. Photo by F. Beed, IITA.
Disease symptom caused by Colletotrichum fuscum on lettuce leaf. Photo by F. Beed, IITA.

Nematodes remain particularly poorly described with only a fraction of the suspected half million found in nature known to man. For insects, arachnids, and myriapods only 1.1 million have been named from a potential 9 million. These numbers compare with an estimated 420,000 seed plants of which most have been described.

Knowledge of biodiversity is uneven, with strong biases towards the species level, large animals, temperate systems, and the components of biodiversity used by people. Although biodiversity underlies all ecosystem processes, modern agriculture is based on a very limited genetic pool of crops and an even more limited exploitation of the genetic resources of nonplant taxa.

This is surprising, considering that as a consequence of their diversity microorganisms and insects play pivotal roles across ecosystems that far exceed those of plants. They provide critical functions and services for food and agriculture. They are indivisibly connected with ecosystem resilience, crop health, soil fertility, and the productivity and quality of food. Modern agriculture in the developed and especially the developing world uses only a small fraction from this rich pool of genetic resources.

Conserving and using nonplant taxa
One of the vital pillars in the work of the Consultative Group on International Agricultural Research (CGIAR) is the conservation and use of agrobiodiversity and related knowledge. Over 650,000 accessions of crop, forage, and agroforestry genetic resources are stored and maintained through the centers’ genebank system and distributed to researchers and breeders throughout the world.

However, scientists from different CGIAR centers are also involved in collection, conservation, and sustainable use of insects and mites, fungi, bacteria, viruses, and nematodes that are either beneficial or antagonistic to crops. These research collections are used in two main areas: (1) crop health and productivity, where the collection supports screening for resistance in breeding programs, pathogen diagnostics, and the development of biological control technologies, and (2) soil health, fertility and ecosystem resilience where for example, collections support the development of biofertilizers.

IITA’s main collections of nonplant taxa are housed at the stations in Ibadan (Nigeria) and Cotonou (Bénin). At the headquarters in Ibadan, the collection and study of plant pathogenic fungi, bacteria, and viruses of important crops are coordinated and collections are maintained. Examples are those for yam and cassava anthracnose, cassava bacterial blight, and soybean rust pathogens.

Aflatoxin-producing fungus Aspergillus flavus growing out of maize grains in a culture medium. Photo by J. Atehnkeng.
Aflatoxin-producing fungus Aspergillus flavus growing out of maize grains in a culture medium. Photo by J. Atehnkeng.

Some of the collections contain large numbers of isolates of the same species which are often unique, not being found elsewhere in the world. International repositories might hold many different species, but tend to store fewer isolates per species and rarely prospect across the developing world. A diverse range of isolates gives a more complete representation of the genetic diversity which can be crucial for understanding evolutionary patterns, pathogen variation, and population dynamics. It helps breeding programs to identify targets for resistance selection.

Collections of isolates of the same species can be used to develop appropriate biocontrol technologies. One such example is IITA’s collection of Aspergillus flavus, a fungus that normally produces aflatoxin, a compound that is toxic to humans and animals. Over 4,500 strains have been collected from Nigeria alone and screened for toxin production and their ability to outcompete other strains when found simultaneously on foodstuffs. The atoxigenic and most competitive strains have been used to formulate aflasafe®, a biocontrol product (see R4D Review September 2009 issue).

Also in Ibadan, collections of beneficial soil microorganisms are studied and maintained. These organisms (such as Rhizobia spp. and mycorrhizae) enhance the nutrient uptake of leguminous crops and can be used as biofertilizers.

At IITA-Bénin, microorganisms and arthropods have been characterized and preserved for use in biological control programs to manage invasive crop pests and weeds. Plant pathogens have been identified and stored since the deployment of appropriate control measures first requires definitive identification of the causal agent of the disease. The biodiversity center maintains over 360,000 insect and mite specimens and is one of the largest reference collections in West Africa (see R4D Review September 2009).

Other IITA stations keep smaller working collections of nonplant taxa. At IITA-Uganda, collections of nematodes, bacteria, and fungi are maintained—mainly those associated with banana production. Certain Fusarium strains, for example, are used for endophyte-improved banana tissue culture for enhanced pest and disease resistance.

Looking like strung beads, these are part of a sample of insects received by the IITA biodiversity center in 12 months. Photo by G. Goergen, IITA.
Looking like strung beads, these are part of a sample of insects received by the IITA biodiversity center in 12 months. Photo by G. Goergen, IITA.

IITA is a lead organization for the conservation and use of nonplant taxa across sub-Saharan Africa. It is now characterizing nonplant taxa collections across the CGIAR as part of the World Bank-funded GPG2 project (Phase II of the Collective Action for the Rehabilitation of Global Public Goods in the CGIAR Genetic Resources System). This is the first system-wide inventory and collation of the existing global, nonplant taxa collections. The aim is to provide a coordinated and harmonized service for research and use of noncrop taxa to support durable farming systems in the developing world.

Future challenges and opportunities
There is a growing appreciation of the fact that farming occurs in an ecological context with complex interactions between crop and nonplant taxa that can be beneficial or antagonistic. There is also increasing demand for sustainable and environment-friendly solutions to manage pests and diseases, with the expectation that the biopesticide market share will increase to over 4.2% by 2010 and, for the first time, reach a market of over US$1 billion. Due to the rate of population increase the World Bank estimates that the global demand for food will double within the next 50 years. At the same time, the amount of arable land is decreasing from pressure from nonfarming activities and the unsustainable farming practices that are causing losses in soil fertility. This scenario is exacerbated by the fact that 40% of what is grown in the world is lost to weeds, pests, and diseases. In developing countries it is common for up to 70% of the yield to be lost due to attacks from insects and microbial diseases.

Therefore, agricultural production needs to be intensified and more marginal land used to produce sufficient food. This requires the deployment of improved land management techniques combined with the selection and distribution of appropriate crop and noncrop germplasm to exploit interactions with beneficial nonplant taxa and resist increased pressure from antagonistic nonplant taxa. Other factors such as climate change are likely to add new layers of complexity to these challenges. To predict risk and develop appropriate adaptation strategies, CGIAR and governments will become increasingly reliant on knowledge of and access to nonplant taxa genetic resources for food and agriculture. This will be used for research, training, or direct use in agriculture and originate, or be found, in a range of countries or centers.

Collections form the mechanism through which information and access to nonplant taxa can be obtained, but the survival of these collections is under threat from funding constraints. Appropriate policies, investments, and collaborations among CGIAR centers and with international collections are urgently needed to recognize noncrop taxa as global public goods. This would facilitate the conservation of collections, increase their visibility, and maximize their use for the benefit of sustainable farming systems. Especially in Africa, where the biodiversity is high, but the taxonomic and technological capacity is limited, work is needed to manage the full potential of nonplant taxa for food and agriculture.

Sunday Ekesi: Partnership is about respect

Sunday Ekesi of icipe
Sunday Ekesi of icipe. Photo from icipe

Sunday Ekesi is a research entomologist from Nigeria working at the International Centre of Insect Physiology and Ecology (icipe). He is currently leading a continent-wide initiative on the African fruit flies that threaten the production and export of fruits and vegetables. Its aim is to develop a cost-effective and sustainable technology for controlling the pest.

What are your research interests and focus?
I have a lot of curiosity for all aspects of reducing damage to crops by arthropod pests to raise productivity, increase income, and improve the livelihood of smallholder growers across Africa. I am interested in integrated pest management (IPM), the development and application of entomopathogens and baiting techniques for managing arthropod pests and their integration into habitat management and other IPM approaches.

The goal is to develop effective, economical, and environmentally sound approaches for managing arthropod pests and to reduce dependence on chemical pesticides.

My research center on the development of an IPM package that encompasses baiting techniques, classical biological control, application of augmentorium, entomopathogens, and postharvest treatment for quarantine fruit flies.

Tell us about the project on fruit flies
icipe and IITA are the pioneering institutions that address the fruit fly menace in Africa. The project, funded by the German Federal Ministry for Economic Cooperation and Development (BMZ), involves developing and implementing an IPM program for three major mango pests—tephritid fruit flies (e.g., Bactrocera invadens and Ceratitis cosyra), mango seed weevil (Sternochetus mangiferae), and mealybugs (Rastrococcus iceryoides). These tree pests ravage mango, causing losses ranging from 30 to 80%, depending on locality, variety, and season. Fruit flies and mango seed weevil are also quarantine pests and quarantine restrictions limit the export of fruits to lucrative markets abroad.

In the project, icipe, IITA, and the University of Bremen, together with national agricultural research system (NARS) and advanced research institute (ARI) partners in Africa, Asia, Europe, and the USA are developing and implementing IPM programs in Kenya, Tanzania, and Bénin. The project aims to minimize the use of pesticides that lead to unwanted residues, and so to facilitate compliance with the standards required for domestic urban and export markets.

Any insights about partnership?
Partnership is about having common and complementary interests. Capacity and expertise can be strengthened only through partnerships and shared commitments. Partners have to believe that their work will make a difference. The scale and scope of work are usually amplified by the collaboration and it is in the interest of all scientists and centers to work with one another to solve pertinent problems to benefit the growers.

Above all, partnership is about respect for opinion and one another, affection, trust, and generosity. There is a lot that icipe and IITA can do together—projects that take a holistic approach to crop problems in which IPM is only one component.

Sunday Ekesi and a PhD student discuss fruit fly control methods with a mango grower
Sunday Ekesi and a PhD student discuss fruit fly control methods with a mango grower

Who are your other collaborators?
We work with the World Vegetable Center largely on managing red spider mite; also with the International Atomic Energy Agency in developing attractants for fruit fly management and rearing methods in support of the sterile insect technique and with the SP-IPM and other CGIAR centers that are interested in applying IPM for pest suppression.

I work with farmers with established orchards and involve them in formulating any research agenda from day one. Our national partners in all the target countries are the key to identifying farmers and farmer groups. They work with us from project planning to implementation and are vital to the success of the project.

What are your challenges?
I work mostly with alien invasive species where the first choice of management is classical biological control. This involves exploration for natural enemies in their aboriginal home. There are enormous challenges arising from the movement of biological control agents because of restrictions related to the Convention on Biological Diversity. No country is willing to allow any living organism to be taken from their environment for use in another country. Classical biological control is all about international public good yet it is becoming increasingly difficult to take natural enemies from one place to help in another country facing a devastating pest problem. We have not been able to bring in parasitoids of B. invadens to Africa from its putative aboriginal home of Sri Lanka. Similarly, it has been extremely difficult to obtain parasitoids of R. iceryoides from India for managing the pest in Kenya and Tanzania.

Another challenge is working on three complex insect pests at the same time. None of these pests is easy to deal with but by prioritizing the activities, sharing the tasks among partners, and ensuring that the milestones are achievable, we have been able to address the challenges. Coordination has been challenging but the partnership has been wonderful.

There are rewards as well. Being able to find affordable solutions to pest problems and seeing farmers apply the technologies—those make me happy. For example, in one of our project benchmark sites in Kenya, farmers previously could not sell mangoes to urban markets or export to lucrative markets in the Middle East because of the B. invadens problems. They are now able to do so by adopting technologies from the project. This is motivating and rewarding!

Unraveling the diversity of African insects

“A problem identified is half-solved.” — Anonymous

The IITA insect center in Bénin houses one of the largest reference collections of arthropods and microorganisms in West Africa. An insect identification hub, it plays the role of a “gatekeeper” by facilitating the discovery and monitoring of invasive pests in the region. The resulting information helps to locate the probable area of origin where promising natural antagonists may be found.

Entomologist Georg Goergen, IITA-Benin
Entomologist Georg Goergen, IITA-Bénin. Photo by IITA

Several invasive insect pests have recently been identified by the center, among which are fruit flies, whiteflies, and moths. An example was when a myriad of caterpillars and moths invaded Liberian farms early this year, providing entomologists a puzzle. The identity of this pest that devastated crops and contaminated water supply in northern Liberia had been established through the joint efforts of FAO, IITA, and CABI. It was later identified as Achaea catocaloides by Georg Goergen, IITA entomologist and biosystematist. The insect is a member of the Lepidoptera group and known as a fruit-sucking moth.

Goergen says that proper identification is a starting point for any basic or applied research and a prerequisite for any successful biocontrol program. “Any biocontrol approach without proper identification of the insect pests will fail,” he says.

Rapidly accelerating human trade, transport, travel, tourism, and porous borders have dramatically contributed to the introduction, ease of movement, and spread of invasive pests thereby overwhelming the capacities of quarantine services in West Africa.

IITA works with national and international partners to control the spread of these invasive species. In addition to its role of identifying insects, the center is also helping scientists to unravel and conserve the rich diversity of African insects.

Through the identification of insect specimens, scientists get more insight on the species richness of the African insect diversity in various ecosystems, the structure of their populations, their interrelationships, and interactions with their habitats.

Insect collection, IITA Benin
Insect collection, IITA Bénin. Photo by IITA

Insects represent the majority of living organisms, accounting for about two-thirds of all living animals on earth and filling many niches in both terrestrial and aquatic ecosystems. They thus play an important regulatory role in all ecosystems including agricultural environments. Many of them can become notorious pests of agricultural, medical, and veterinary importance.

However, existing knowledge on insect diversity is still inadequate for large parts of the globe and no one knows exactly how many species of insects exist. The situation is worse in Africa where much of the planet’s biodiversity occurs, but where traditionally the scarcity of biosystematists is the strongest.

Goergen says, “Biosystematics is important in all phases of a control program starting from a reliable pest identification, assessment of native antagonists, monitoring faunal changes following the use of exotic beneficials, and detection of eventual nontarget effects. To do that, you need to have a reference collection such as the one we have here in Cotonou.”

IITA has developed a strong regional capacity in biosystematics through the West African Network for Taxonomy, BioNET-INTERNATIONAL.

The center continues to attract students from different parts of the world while offering capacity building and ensuring a requisite contribution to countries seeking to comply with the sanitary and phytosanitary agreement of the World Trade Organization and to fulfill the objectives anchored in the Convention on Biological Diversity.