Ecofriendly bioherbicide approach for Striga control

Abuelgasim Elzein,, and Fen Beed

Root parasitic weeds of the genus Striga are a significant constraint to cereal and cowpea production in sub-Saharan Africa. They can cause total crop losses particularly during drought, in infertile soils and cereal monocropping. Striga causes annual losses of US$7 billion and affects incomes, food security, and nourishment of over 100 million people mostly in sub-Saharan Africa.

Each Striga plant can produce thousands of seeds, viable for over 10 years. Their intimate interaction with different host plants prevents the development of a silver bullet control technology that subsistence farmers can adopt. Hence, it is widely accepted that an integrated approach to Striga management is required for which biocontrol represents a crucial component.

Bioherbicide innovation
A bioherbicide is a plant pathogen used as a weed biocontrol agent (BCA), which is applied at sufficient rates to rapidly cause a disease epidemic that kills or severely suppresses the target weed. The use of biocontrol technology to manage Striga is a desirable control method as it is environmentally friendly, safe to farmers and crop consumers, specific to the target host, and has the potential to be economically viable. In addition, biological control also assists in the development of a balance of nature, the creation of more biodiversity, and sustaining of complex ecological interactions.

Since the early 1990s, a series of intensive disease surveys in many countries of sub-Saharan Africa has evaluated hundreds of microorganisms for their pathogenicity and virulence against Striga. Fusarium oxysporum Schlecht isolates have been the most promising. However, the discovery of a highly effective pathogen is only one step in the process of developing bioherbicides, for which the inoculum mass production, formulation, delivery, and storage ability must be optimized, and the mode of action, host specificity, and biosafety evaluated and fully understood.

The most widely studied and used fungal isolate that met all requirements for a potential bioherbicide for Striga is F. oxysporum Schlecht f. sp. strigae Elzein et Thines (isolates Foxy2 and PSM197). These are highly virulent, attack Striga in all growth stages—from seed to germination, from seedling to flowering shoot; protect the current crop yield; and prevent seed formation and dispersal.

F. oxysporum f. sp. strigae is highly host-specific to the genus Striga, and does not produce any known mycotoxic compounds. Thus, its use does not pose health risks to farmers, input suppliers, traders or consumers or threaten crops or the environment. Its unique DNA constitution differs from other forms of F. oxysporum deposited in GenBank, known to cause crop diseases. Indeed, this ensures its biosafety and greatly facilitates its wider application and use as a bioherbicide.

In addition techniques for massive production of inoculum of F. oxysporum f. sp. strigae was optimized based on simple and low-cost methods and using inexpensive agricultural by-products available in sub-Saharan Africa. The chlamydospores produced by this fungus have the advantage of being able to survive extreme environmental events while still remaining viable. This is an important feature required for a BCA suited to hot and dry climatic conditions of cereal production in sub-Saharan Africa, and to produce stable, durable, and pathogenic propagules.

Extensive research by the University of Hohenheim (UH, Germany), IITA (Benin), McGill University (Canada), and Institute for Agricultural Research – Ahmadu Bello University (Nigeria), has enhanced application of F. oxysporum f. sp. strigae, its formulation into bioherbicidal products, and its delivery for practical field application. The Striga bioherbicide contains the Striga host-specific F. oxysporum f. sp. strigae, applied in massive doses to create a high infection and disease level to kill or severely suppress Striga.

Promotion in West Africa
The bioherbicide is a component of the IITA-led project, Achieving sustainable Striga control for poor farmers in Africa, funded by the Bill & Melinda Gates Foundation to intensively promote technologies to combat Striga in sub-Saharan Africa. The project will validate the potential of the bioherbicide seed treatment technology across major Striga-infested agroecological zones and maize-based farming systems, while also confirming the biosafety and developing molecular detection tools. Here are the highlights of the results:

Technology validation: Several multilocation trials were conducted under natural and artificial Striga infestation across two agroecological zones in northern Nigeria to evaluate the efficacy of Striga bioherbicide (F. oxysporum f. sp. strigae). The inoculum produced by UH and SUET seed company was delivered as a film-coat on maize seeds (see below).The application of the bioherbicide technology in combination with Striga resistant maize reduced Striga emergence by 73% and 39%, compared to the susceptible and resistant controls, respectively, and prevented 81% and 58% of emerged Striga plants from reaching flowering and 56% and 42% of the maize plants from attack by Striga (see next page). The combination of bioherbicide with Striga susceptible variety significantly reduced Striga emergence by 53%, resulting in 42% reduction in number of flowering plants and in 21% increase in grain yield compared to the susceptible control.

In addition, disease symptoms were recorded on emerged Striga plants parasitizing maize plants coated by the bioherbicide. The reduction in Striga emergence across maize varieties indicates the effectiveness of the bioherbicide to attack seeds under the soil surface. The synergistic effect of the bioherbicide technology combined with the Striga resistant maize is expected to reduce the Striga seedbank and thus the impact of Striga on subsequent maize crops.

Biosafety: To further ensure the safety of Striga BCA and to demonstrate and increase awareness among farmers, regulatory authorities, and stakeholders, a wide host range study was carried out using 25 crops in collaboration with IAR-ABU and the Nigerian Plant Quarantine Service (NPQS)  under field and screenhouse conditions in Nigeria. Results revealed that none of the test plants showed any infection by the biocontrol agent both in the field and screenhouse, and no detrimental growth effects were measured or visual losses to plant health recorded in any of the inoculated crops tested, i.e., inoculation with the Striga BCA did not cause any delay in emergence, and a decrease in plant height, plant vigor, chlorophyll content per leaf, shoot fresh and dry weight. Hence, the Nigerian regulatory authorities (NPQS, NAFDAC) and other stakeholders were satisfied and confident that no disease was produced on plants other than Striga by the BCAs and that it is safe to use. In addition, a mycotoxin produced by Striga bioherbicide  F. oxysporum f. sp. strigae was analyzed and evaluated by our project partner, the University of Stellenbosch in South Africa. An evaluation of existing isolates of F. oxysporum f. sp. strigae does not produce well-known mycotoxins (e.g., Fumonisin and Moniliformin) that pose a threat to animal or human health. This finding further confirms the safety of this bioherbicide.

Molecular detection tools: Development of a monitoring tool specific to the Striga bioherbicide is important to certify inoculum quality, monitor the presence and persistence of the BCA in soils, and validate its environmental biosafety. UH is developing a monitoring tool.

The AFLP fingerprinting technique was successfully used in developing a primer pair capable of differentiating the F. oxysporum f. sp. strigae group from other Fusarium species. In addition, the monitoring tool has shown a high specificity for isolate Foxy2 and was used to monitor its spread and persistence in rhizobox experiments under different management practices using Kenyan soils. This promising result provides a proper baseline to further the existing primer set.

Bioherbicide + pesticide technology: The novel combination and integration of the bioherbicide technology plus imazapyr herbicide for Striga control with pesticides in a single-dose seed treatment to control fungal pests offers farmers with maize seed that is able to achieve its yield potential. The use of each technology (BCA or imazapyr) has been shown to be effective when applied independently using seed coating techniques, but have not been integrated.

The compatibility of Striga BCAs with different pesticides (herbicides and fungicides with insecticide components) was studied in vitro in the laboratory. Striga BCAs showed excellent compatibility with imazapyr (a herbicide seed coating used in combination with IR maize to control Striga), Metsulfuron Methyl (MSM) (a herbicide seed coating developed by DuPont to control Striga in sorghum), and glyphosate (an intensively used herbicide). A similar result was also achieved with the commonly used seed treatment fungicides at the recommended application doses.

Accordingly, doses and complementary seed coating protocols for the three compatible technologies (BCA, herbicide, and fungicides) have been developed and IR maize seeds were successfully coated with a single-dose seed treatment of BCA inoculums and imazapyr. The results showed that imazapyr did not interfere with the BCA during seed coating, with BCA growth and sporulation after coating, and with IR maize seed germination. Seeds of IR maize varieties can thus be coated with the herbicide and the BCA and then fungicide and delivered to farmers using the same input pathway. Screenhouse and field trials are being carried out to generate data on the combined efficacy of the applied technologies. The demonstrated compatibility of Striga BCA with the different pesticides that contain a wide range of active ingredients indicate that the combination and delivery of the Striga bioherbicide technology with a large number of pesticide products is possible. These findings are expected to provide a triple action seed coating package for direct control of Striga and fungal diseases of maize in sub-Saharan Africa.

Suitability to African farming systems
Our strategy for scaling-up the bioherbicide innovation is based on using technology appropriate to Africa to ensure that sustained production of the bioherbicide is feasible at a cost affordable to African small-scale farmers. The seed-coating treatment requires significantly less inoculums, establishes the BCA in the cereal rhizosphere, i.e., the infection site of Striga, and provides a simple, practical, cost-effective delivery system for adoption by input suppliers to subsistence farmers. Arabic gum as a coating material has been shown to increase the rate of mycelia development and enhance BCA sporulation. Its availability in sub-Saharan Africa at a low price is an additional economic advantage. A commercial seed coating process, developed and optimized at UH with SUET Seed Company in Germany, is being transferred and adapted at IITA, Ibadan, to be used as an experimental production unit for capacity building and as a model for eventual transfer of seed treatment technology to the private sector after validation.

One unique advantage of this bioherbicide is that the ability of Striga to become resistant to it is virtually unknown as a consequence of the suite of enzymes and secondary metabolites that the BCA produce to become pathogenic and virulent against the target (Striga). Hence after validation, delivering the bioherbicide technology in combination with resistant maize or with the herbicide imazapyr is expected to increase efficacy in controlling Striga. Bioherbicide and other compatible technologies have different modes and sites of action against Striga, and in a combination they will have a much greater chance of reducing the potential risk of development of resistance to a single technology (resistant varieties or herbicides) used separately and repeatedly.
The potential delivery of coated seeds of resistant maize with bioherbicide in one package to farmers using the same input pathway will reduce transaction and application costs and enhances the economic feasibility and adoptability of the technologies. Similarly, compatibility of BCA with imazapyr and fungicides allow seed coating of IR-maize with bioherbicide, imazapyr, and fungicides with a single-dose seed coating application.

Future plans
Currently, large-scale field testing is ongoing and is being implemented to further validate bioherbicidal efficacy across two agroecological zones where the common scenarios for maize infestation by Striga in northern Nigeria are represented. For understanding of farmers’ preferences and perceptions, socioeconomic analysis and cost-benefit analysis of bioherbicidal technology based on field data/surveys and interviews, current market information, and links with other Striga control strategies will be undertaken. After validation, dissemination and commercialization will be promoted through private sector partnerships and integrated with other control options such as resistant varieties, IR varieties combined with seed treatment with imazapayr, crop rotation with legumes, and soil fertility management practices, to achieve sustainable management of Striga.

IITA (Dr F. Beed, Dr A. Elzein & Dr A. Menkir), Institute for Agricultural Research – Ahmadu Bello University (Dr A. Zarafi), Nigeria; University of Hohenheim (Prof G. Cadisch, Dr F. Rasche & Prof J. Kroschel), Germany; The Real-IPM Company Ltd (Dr H. Wainwright), Kenya; University of Stellenbosch (Prof A. Vilioen), South Africa; and McGill University (Prof A. Watson), Canada.

Beed F.D., S.G. Hallet, J. Venne, and A. Watson. 2007. Biocontrol using Fusarium oxysporum; a Critical Component of Integrated Striga Management. Chapter 21 in Integrating New Technologies for Striga control: Towards ending the Witch-hunt (Ejeta, G. and J. Gressel, eds). World Scientific Publishing Co. Pte. Ltd. pp 283-301.

Ciotola, M., A. DiTommaso, and A. Watson. 2000. Chlamydospore production, inoculation methods and pathogenicity of Fusarium oxysporum M12-4A, a biocontrol for Striga hermonthica. Biocontrol Science and Technology 10: 129-145.

Ejeta, G. 2007. The Striga scourge in Africa: A growing pandemic In: Ejeta, G. and J. Gressel, eds. Integrating New Technology for Striga Control: Towards Ending the Witchhunt. World Scientific Publishing Co. Pte. Ltd., UK. pp. 3-16.

Elzein, A.E.M. 2003. Development of a granular mycoherbicidal formulation of Fusarium oxysporum “Foxy 2” for the biological control of Striga hermonthica. In: “Tropical Agriculture 12– Advances in Crop Research (2)” (J. Kroschel, ed.). Margraf Verlag, Weikersheim, Germany, 190 pp, ISBN 3-8236-1405-3.

Elzein, A., J. Kroschel, and V. Leth. 2006. Seed treatment technology: an attractive delivery system for controlling root parasitic weed Striga with mycoherbicide. Biocontrol Science and Technology, 16(1) 3-26.

Elzein, A., F. Beed, and J. Kroschel. 2012. Mycoherbicide: innovative approach to Striga management. SP-IPM Technical Innovations Brief, No. 16, March 2012.

Kroschel, J. and D. Müller-Stöver. 2004. Biological control of root parasitic weeds with plant pathogens. In: Inderjit, K. (ed.), Weed biology and management. Kluwer Academic Publishers, Dordrecht, The Netherlands, pp. 423–438.

Kroschel, J., A. Hundt, A.A. Abbasher, J. Sauerborn. 1996. Pathogenicity of fungi collected in northern Ghana to Striga hermonthica. Weed Research 36 (6), 515–520.

Marley, P.S., S.M. Ahmed, J.A.Y. Shebayan, and S.T.O. Lagoke. 1999. Isolation of Fusarium oxysporum with potential for biocontrol of the witchweed Striga hermonthica in the Nigerian Savanna. Biocontrol Science and Technology 9: 159–163.

Venne J., F. Beed, A. Avocanh, and A. Watson. 2009. Integrating Fusarium oxysporum f. sp. strigae into cereal cropping systems in Africa. Pest Management Science 65: 572–580.

Ken Neethling: Biocontrol champion

Ken Neethling, CEO, BCP
Ken Neethling, CEO, BCP

Ken Neethling is the chief executive officer of Biocontrol Products (BCP) based in South Africa. An engineer by training, he started working for BCP 13 years ago. Commercial biocontrol was a relatively new concept then, he says. Along the way, he became exposed to commercial fermentation and the world of microbes. Today, he manages the business and works with a “very competent team”.

BCP started as a biocontrol company, initially producing a fungal nematicide (egg stage) to work alongside those targeted at adult nematodes in an IPM program. In 1997, the Biological Control of Locusts and Grasshoppers (LUBILOSA) project approached BCP to commercially produce Green Muscle®, a flagship product, for the control of locusts, relates Ken. BCP has subsequently used its platforms of research, registrations, and production to bring other microbes to a commercial level. BCP’s range today includes many bacteria, fungi and plant extracts—for a diversity of uses in agriculture, including growth promotion, insecticides, nematicides, fungicides, and nutrition.

What are the prospects of biological control products in Africa?
BCP’s corporate slogan is “restoring nature’s balance”. In many respects this sums up the case for biocontrol products: They’re natural, generally safe to nontargets and already found in nature; they have a smaller environmental footprint and work in harmony with nature; they restore balance; this recognizes that the way we have historically treated our environment was out of balance. Restoring balance also implies sustainability and “subeconomic threshold” control strategies.

Biocontrol products are not a silver bullet—they’re part of a solution. When considering the growing global population that needs to be fed, the fertile soils of Africa are also part of the solution.

If Africa’s decision makers are receptive, then I believe biological control has a bright future in this continent.

IITA was part of the team that developed Green Muscle® years ago. The technology is one product of research that has proved quite successful. Tell us more about Green Muscle®.
I have a very high regard for IITA’s researchers…The development of Green Muscle® was truly a multidisciplinary, multicultural and multinational success story. BCP’s contribution to the development of Green Muscle® was in the areas of production, stability, formulation, costing, packaging, and providing product for trials. Over the years, BCP has also provided training on aspects of quality control and standard operating procedures. We advise on storage and provide analytical services to our Green Muscle® customers. BCP has also contributed to the registration process in some of the affected countries.

Ken Neethling, CEO of Biocontrol Products, South Africa. Photo from K. Neethling.
Ken Neethling with colleague Sifiso showing off one of BCP's industrial fermenters. Photo from K. Neethling.

Why did it take Green Muscle® almost 10 years from development to deployment to get into the market when it was so obviously a very effective product?
BCP is but one of the many champions of Green Muscle®. We worked tirelessly over the last 10 years. There were, and still are, many challenges.

The technology had to break new ground. For example, biocontrol has a completely different mode of action to the commonly used synthetic chemicals—it is slower acting on the knockdown, but with a longer residual and less environmental effect. In the case of Green Muscle®, the locusts stop feeding after 2 days. They become lethargic and, due to predation (they’re safe for birds and mammals to eat) they are quickly picked off. So the challenge was to show that not having hundreds of poisoned locust cadavers lying around was a good result!

The other challenge was cost—I’m sure many can appreciate that a biocontrol product, produced initially in small quantities, would have a very hard time competing in terms of price or cost against chemicals churned out in massive factories. Make no mistake, cost is important and especially in locust control, every dollar needs to be stretched to extract maximum benefit.

However, cost is a much bigger picture than simply the price of the active ingredient per hectare. Recent studies have indicated that the lifecycle cost of chemical control (including disposal of obsolete stock, soil decontamination, loss of pollination services, etc.), is higher than that of biocontrol.

I believe that there is still scope for even wider deployment—for example, preventative treatment campaigns in eco-sensitive breeding grounds that could prove more cost-effective than an emergency response to an outbreak.

What have been your challenges and opportunities in marketing Green Muscle®?
Our main marketing challenge is that we have so many different “customers” to consider.

First and most importantly the general population, who risk losing their food and livelihood to locust swarms of sometimes biblical proportions; the governmental plant protection departments of the various countries, who manage smaller campaigns within their borders; regional (i.e., cross border) emergency outbreak management bodies that largely depend on external funding; the United Nations, which coordinate and disperse donor funding for locust control; and the donor community, who ultimately hold the purse strings that need to be opened in large emergency campaigns.

How much is the demand for Green Muscle® in Africa?
Demand is obviously directly linked to locust outbreaks and contingent donor funding. To be honest, it has been frustratingly sporadic. This is not ideal from a production perspective, as it is more cost-effective to run continuously, with regular planned off-takes. To date, supply has been able to keep up, but we have also had to burn the midnight oil a few times in an emergency.

Is there any interest in the product outside Africa?
Yes there is interest outside Africa. My interpretation of this is that “good news travels fast”. But finding the right partners, doing trials, establishing market potential, drawing up agreements, licensing and all the other factors mean that this type of product can never be expected to be an “overnight success”.

What is the outlook of biocontrol, in general, in Africa? The world?
In summary, I would say the outlook is good, but this needs work and commitment from all stakeholders before it can have a meaningful impact on Africa. The same would apply to the rest of the world, except that consumer awareness (and hence demand) is higher in the developed world.

Do you think biocontrol would become competitive enough against chemical-based control measures?
Historically it can be argued that biocontrol hasn’t challenged chemical-based control measures, but that was partly due to the way we viewed this notion of control. What we have seen is that novel strains and human ingenuity are helping to make biocontrol a worthy alternative to chemicals. We’ve experienced this first hand with Green Muscle® in large-scale control operations, where we have had control comparable to that of the chemicals. In some extreme situations, such as in Algeria, we saw exceptional control, a level greater than 90%.

What would help to popularize the adoption of biocontrol technologies?
This challenge requires total commitment from many diverse stakeholders. But the basic principle, “Use it or lose it,” applies. Biocontrol technologies must be used and must make a difference in areas that count; otherwise they will forever remain in the research domain.

Green Muscle has gone the way of traditional R&D (i.e., research/science -> product development -> commercialization). When should the private sector come in?
Necessity is the mother of invention, so while I lean towards the commercial sector as being more in touch with the needs of the market, there is nothing to say that scientists can’t also fulfill this role. What is important is that there is a clear path to market, with early involvement of a commercial partner and good communication among all stakeholders during the development cycle.

What is needed to push agricultural technologies, such as biocontrol, from the research shelves to the market and eventually to the intended end-users?
A lot of money, for starters! Much more than I think anyone ever estimated. And a lot of time too. It needs product champions across the board: in government, in research, in the media, and in the procurement and purchasing channels.

What would you tell scientists or research organizations, such as IITA, working on biocontrol development?
There is a lot of good work being done by scientists around the world—biocontrol technology development is one of the many exciting and challenging areas with so much potential. The aim of science is to increase knowledge for the purposes of serving humanity and protecting our planet—whatever we research, develop, and commercialize must have these values as their foundation.

The power of biocontrol

Farmers and scientists have, time and time again, turned back to nature to find solutions to pest problems in crop fields.

Variegated grasshopper (<em srcset=Zonocerus variegatus). Photo from Wikimedia commons ” width=”250″ height=”188″ />
Variegated grasshopper (Zonocerus variegatus). Photo from Wikimedia commons

When several exotic pests were accidentally introduced into Africa from South America through infected planting materials in the early 1970s, ravaging economically important crops, such as cassava, scientists turned to the origins of the pests to solve the problem.

A lot has been said about the benefits of biological control or biocontrol. It is natural and safe to the environment and humans, and rigorous tests ensure that it is effective only on the target pests.

And almost three decades of research and development at IITA have shown the continuing effectiveness and sustainability of biological control in combination with other approaches for managing insect pests.

These biocontrol practices and technologies provide the subsistence farmers in sub-Saharan Africa with solutions that are sometimes their only safety net.

This issue on biocontrol celebrates the success of solutions to problems in tropical agriculture that IITA and its partners have developed for millions of African farmers.

Safeguarding against locust invasion

Nomadacris septemfasciata hopper band
Nomadacris septemfasciata hopper band. Photo from Wikimedia Commons

Fourteen years after the introduction of the fungal biopesticide—Green Muscle®—developed by IITA’s scientists with their partners, the product is gaining more prominence as a control option against invasive locusts that threaten African farmlands.

Recently, the biopesticide, which had been picked up by a South African firm for commercialization, averted the devastation of farmlands from an invasion of red locusts in Tanzania.

The rapid intervention by the Food and Agriculture Organization (FAO) using the biopesticide drastically reduced locust infestations in Tanzania and prevented a full-blown invasion that could have affected the food crops of around 15 million people in the region.

Ignace Godonou, entomologist based in IITA-Bénin, was part of the team that developed the biopesticide more than a decade ago. He said that, if left uncontrolled, a full-blown invasion would have caused a major setback to food security in the region.

“We are happy that Green Muscle® has proved effective in controlling locusts and is now widely used.”

Green Muscle® is a fungal biopesticide that was developed in response to a locust plague in the 1980s. It is effective against most locust and grasshopper species; it is safe, does not affect other species, and can be sprayed in the same way as chemical pesticides. A fungus, Metarhizium anisopliae, which is common in the tropics and subtropics, is used to kill the pests.

Top: Healthy hopper; Bottom: Hopper infested with Metarhizium
Top: Healthy hopper; Bottom: Hopper infested with Metarhizium. Photo by IITA

If not restrained, large swarms of red locusts will fly over vast areas of farmland, traveling daily more than 20 or 30 km and feeding on cereals, sugarcane, citrus and other fruit trees, cotton, legumes, and vegetables cultivated by poor farmers. A red locust adult consumes roughly its own weight in fresh food, about 2 g, in 24 hours. A very small part of an average swarm (about 1 t of locusts) eats the same amount of food in one day as around 2,500 people.

The biopesticide was developed by an IITA technical team under the LUBILOSA project (LUtte BIologique contre les LOcustes et les SAuteriaux – Biological Control of Locusts and Grasshoppers). It has proved effective in controlling locusts in the Sahelian region, including the Republic of Niger and Mauritania.

Godonou said that initial field trials of the product were conducted in the Republic of Bénin under the close watch of IITA scientists, based in Cotonou. The subsequent large-scale field trials were held in Niger and Mauritania.

“Mass production of the fungus for small- to large-scale field trials also started at IITA-Bénin,” he added.

“Moreover, it can persist in the ground for several weeks or for up to a year after spraying, continuing to attack and kill healthy locusts and grasshoppers. The fungus is very safe and has a narrow range of hosts,” said Godonou.

This environment-friendly alternative to synthetic chemical pesticides weakens and kills the locusts in 10 to 14 days, continuing to attack and kill the grasshoppers. It remains effective under prolonged dry conditions and is therefore more effective as a control agent. The fungal spores are suspended in an oil solution, giving the product its green color.

Apart from IITA, other leading institutions in the LUBILOSA project were the Commonwealth Agricultural Bureau International in the UK, and the Département de Formation en Protection des Végétaux in Niger, with many partners drawn from donors, several research institutes, national agricultural research and extension systems, nongovernmental organizations, FAO, private sector companies, and farmers.

Recipe for African farmlands

Damage by cassava green mite
Damage by cassava green mite. Photo by IITA

A natural enemy, capable of tackling the green mite menace, has been helping millions of Africans whose livelihoods depend on cassava.

The natural enemy, Typhlodromalus aripo, has proven to be an ideal candidate in controlling the cassava green mite (Mononychellus tanajoa) after 7 years of studies, says Dr Alexis Onzo, IITA entomologist based in Cotonou.

Back in the 1970s when the pest entered Africa, cassava green mite wreaked havoc on African cassava farms, depleting yields, in some cases, up to 80%.

Onzo says the neotropical spider mite attacks cassava—a major crop in Africa—by damaging the photosynthetically active leaf surface area of the plant.

The good news, however, is that the biocontrol option which saw the introduction of T. aripo in Africa has substantially reduced the population of green mites, as evident in studies carried out by scientists in southwestern Bénin and in many other countries in the African cassava belt. The results indicate that the introduction of T. aripo has helped in ensuring farms with healthier cassava plantations in Africa.

The predatory mite, T. aripo, was introduced by IITA and partners from Brazil, South America for the control of the cassava green mite. It resides primarily in the apices of the cassava plant, feeding on and reducing the populations of green mites not only in the apices but also in the upper part of cassava foliage.

Alexis Onzo inspects cassava leaves for pests
Alexis Onzo inspects cassava leaves for pests. Photo by IITA

Onzo says T. aripo was released in Africa by IITA and partners in the 1990s to contain the devastation caused by green mites. Since then the natural enemy has, on its own, been spreading to different parts of the continent, playing its role as a natural control agent against that cassava pest.

Unlike chemical control which wipes out the pests and other benevolent species, the biocontrol option reduces the population of the pest to a level that makes the pest’s impact on the crop economically insignificant. Besides, the pollution associated with chemical control is also avoided.

Onzo described the continuing success of green mite control in Africa as a welcome development and a victory for resource-poor farmers who will have the opportunity of cultivating healthier cassava farms.

With the prevention of the devastation by green mites and other pests, cassava has now become a cash crop in Africa, generating wealth and improving the food security of many Africans.

“Today we see cassava serving as a raw material in the flour, ethanol, and glucose industries. Even the governments are benefiting from these benefits,” he says.

As cassava green mite becomes less of a problem, Onzo says he intends to take up the fight against mites that are ravaging and depleting the production of coconuts and vegetables in Africa.

Biocontrol: saving the environment, saving farmers’ incomes

Water hyacinth grows fast and can clog water bodies
Water hyacinth grows fast and can clog water bodies. Photo by IITA

Biological control of water hyacinth is not only restoring the balance of nature in Africa but also putting savings in the pockets of resource-poor farmers whose livelihoods depend on fishing, thanks to IITA.

Using natural enemies, scientists have been able to control the purple-flowered water weed in southern Bénin, for instance, showing that annual incomes in that region increased by US$30.5 million.

The result of the studies, which was published in the Journal of Agriculture, Ecosystems & Environment, estimated the total cost of the biocontrol program at $2.09 million.

“Assuming that the benefits are to stay constant over the next 20 years—a most conservative assumption—the accumulated present value would be $260 million, yielding a respectable benefit-cost ratio of 124:1,” say Drs Hugo de Groote and Peter Neuenschwander.

Water bodies, such as lakes, rivers, and dams are important for agriculture and as water sources for domestic needs.

However, floating aquatic weed species mostly originating from South America, such as water hyacinth (Eichhorniae crassipes), water lettuce (Pistia stratiotes), giant salvinia (Salvinia molesta), and the red water fern (Azolla filiculoides) were deliberately or accidentally introduced from their native home into these water bodies as ornamental plants or for use in the aquarium trade. Because of their rapid reproduction by vegetative means and through seeds, these plants have attained a pest status.

Obinna Ajuono explains how water hyacinth invasion was brought under control using a weevil
Obinna Ajuono explains how water hyacinth invasion was brought under control using a weevil. Photo by IITA

Obinna Ajuonu, IITA entomologist, says the damage caused by water hyacinth, for instance, on the fishing community alone was devastating.

“It accumulates a large biomass that enables the plants to block waterways,” he explains, “thus impeding fishing and transport by boat or canoe, leading to increased transport costs and loss of revenue. They can also increase the incidence of diseases, such as bilharzia, and provide refuge for reptiles, such as snakes.”

A survey by IITA in southern Republic of Bénin in 1999 revealed that at the peak of the infestation, water hyacinth had reduced the yearly income of a community of about 200,000 people by approximately $84 million. Men lost revenue mostly in fishing, while women experienced loss of income in trade, primarily in food crops and fish.

The intervention by IITA and partners through the release of three natural enemies, two weevil species and one moth that feed exclusively on water hyacinth, however, brought succor to the West African region where the devastation was most extensive.

Neochetina eichhorniae, the weevil that brought water hyacinth under control
Neochetina eichhorniae, the weevil that brought water hyacinth under control

IITA implemented the first biological control of floating weed in West Africa (Bénin) way back in 1991 with the release of the weevil Neochetina eichhorniae that ate nothing but the water hyacinth at immature and adult stages. Biological control of water lettuce, giant salvinia, and the red water fern using their specific agents, followed thereafter.

From IITA-Bénin, a starter colony of biocontrol agents against aquatic weeds and expertise in implementing weed biological control were provided to other countries, such as Burkina Faso, Côte d’Ivoire, Ghana, Kenya, Nigeria, Republic of Congo, Senegal, Tanzania, Uganda, and Zimbabwe.

Other benefits brought by IITA’s intervention included an improvement in water quality and human health. Before the biological option was used, national governments in the subregion applied herbicides and mechanical/manual removal to control water hyacinth—options that were neither environmentally friendly nor cost-effective.

Ajuonu says an additional biological control agent for the water hyacinth is being planned. “The new ideal candidate is the mite Orthogalumna terebranti,” he explains. This has been discussed in several Economic Community of West African States (ECOWAS) meetings on aquatic weed control, where IITA was represented.

He explained that IITA provided many of the ECOWAS countries with starter colonies of agents and would continue to do so by importing the mite in 2009/2010 and maintaining a laboratory culture for supply to individual countries.

O.A. Adenola: More awareness needed on the dangers of aflatoxins

Pastor O.A. Adenola
Pastor O.A. Adenola. Photo by IITA

The president of one of the strongest crop networks in Nigeria, Pastor O.A. Adenola, talks about the need for stakeholders to join forces against aflatoxin spread and other issues. This is an excerpt from his interview with Godwin Atser.

Do farmers understand what aflatoxins are?
They may see the fungus on the maize cob but really many Nigerian farmers do not know the danger in what they see: what it is… what effects it has on people as a result of eating grain that is already contaminated… I think we need a lot of awareness, a lot of teaching to get our farmers to know the dangers of aflatoxins in our foods. The problem is that you don’t see them and their effect physically. If you look at the cassava mealybug, for instance, the farmer sees the plant die. In the case of aflatoxins, you don’t see them causing anything bad to maize; it is the after-effect that damages people’s health.

What can be done to bring the message to the people?
It has to involve a collective effort from all of us: the research institutes, the Agricultural Development Programs, the Maize Association of Nigeria, and the media. We won’t make any progress if we don’t collaborate to get the farmers to know the importance of the effect of aflatoxins on human beings and on animals.

You participated in the Doubling Maize Project. What were your observations?
At the time the project was initiated in 2006, the maize production level on average was 1.5 t/ha. The project target was to double production—from 1.5 to 3 t/ha. A farmer who could not combine production inputs to give us 3 t/ha was not qualified to be involved in the scheme because we did not want to increase the area planted. We wanted to increase production per unit area. The intention was to intensify production so that we could double what was on the ground.

So what happened?
I tell you, farmers made more than 3 t/ha! Also if the technology is properly applied, Nigeria can easily double maize production.

What effort is your association making to disseminate some of the findings of that research to increase maize production?
The maize network is stronger than the networks of other crops in Nigeria, maybe, because of the facilities we have at IITA that are linking us up properly with research and also with Ministries of Agriculture all over the country. And since we were the beneficiaries of the research findings, it was easier for us and for our members to adopt the improved technologies.

All that the researchers were telling us was “You can be better farmers if you take the technology.” I must tell you that every farmer is out there in the field because he wants to make more money. So the benefit is good enough to propel the technology.

How is the collaboration between MAAN and IITA?
Excellent! I have been relating with IITA since 1984 and when this Association was formed in 1992, it was formed in IITA. Since then we have had very good collaboration.

What can IITA do to make this partnership grow?
Whenever there is a need and we call on IITA, they have always answered. The Director General and the maize “chief”, Dr Sam Ajala and his team, have been very cooperative. That collaboration is what is important. If you have a problem and you call your friend and he answers, then you are okay.

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!

Peter Neuenschwander: How Africa can control invasive pests

P Neuenschwander
P Neuenschwander
The “father of biocontrol”, Peter Neuenschwander, joined IITA’s biocontrol project against the cassava mealybug in 1983. The project was later expanded to include biological control and integrated pest management of mango mealybug, spiraling whitefly, and floating water weeds. He retired in 2003. Last year, the International Organization for Biological Control recognized his life-long contributions to biological control by giving him Honorary Membership. In this interview with Godwin Atser, he bares his mind on the contribution of biocontrol and strategies on how Africa can check invasive pests.

Please explain the concept of biocontrol.
Biological control is a technique whereby we use natural enemies to combat pests. The pests can be insects, mites, pathogens, or even plants. Most times we apply biocontrol against invading pests. The beauty is that once something works, it spreads on its own and it carries on its business without difficulties.

Please give an overview of your work on biocontrol in Africa.
The cassava mealybug was actually one of the things that brought me to Africa. The mealybug was introduced in Africa in the 1970s. Eventually parasitoids were found in South America and transported here. With national partners, we made about 150 releases in most sub-Saharan African countries. From there we went on to other projects such as the mango mealybug, and water hyacinth control.

How can biocontrol check the spread of invasive pests in Africa?
Biocontrol is good; it slows the pests but it would have been best not to have introduced those exotic organisms in the first place. So, we need to strengthen and train the quarantine people.

We also need to tighten quarantine services in all African countries, not just on land borders but also the seaports and the airports so such invasions which cost so much can be reduced.

What has been the impact of biocontrol?
For the cassava mealybug alone, the project resulted in money directly going to the farmers with the entire cassava improvement project in Africa.

What are the challenges you faced in the biocontrol projects?
Our main challenge is the uptake or adoption by the countries. Countries are autonomous in their decisions to import or not to import.

So, we have to convince some 30 quarantine authorities that they should give us quarantine permits, that they should help us, and that they should allow the insect to come in, and so on.

The challenges also include unsatisfied expectations from colleagues from different disciplines who expect us to extinguish the pest. We don’t really extinguish anything.

What is the perception of people towards biocontrol?
The public in most cases is more afraid of biocontrol (insects) than the invasion itself. This is because they don’t understand how it works.

Does biocontrol break down?
In technical terms, yes, it can break down—when biocontrol is working and you forget about it and suddenly start spraying the field with pesticides. That is, you kill the natural enemies and the pest.

What is the future of biocontrol?
The demand for biocontrol is already there and there will always be invasive pests. We also have to maintain the human capital in biocontrol. Unfortunately, the capacity in biocontrol worldwide is declining, not only in IITA.

Your colleague referred to you as the father of biocontrol. Can you comment on this.
I am the last surviving biocontrol specialist at IITA. That was what was written about me when I retired 6 years ago. I am still helping out.

What were the most exciting moments in your work on biocontrol?
The excitement was going out in the field and also the fact that I had a “privileged” job. It also includes getting recognition. In the scientific world, the cassava mealybug project was seen as a success.

You have been retired for several years now. What’s next?
I have a request to go to Asia, because after 20–30 years, the cassava mealy bug turned up in Asia, and it is spreading. They want us to introduce biocontrol to curtail the spread.