Efforts by national and international research systems during the last two decades have contributed to nearly doubling the production of major staple foods including cassava, maize, yam, and banana in Africa. Most of these gains, however, have come about as a result of an expansion of the planted area, but crop production per unit area of the land is lower than anywhere else in the world.
Yet the continent is expected to improve food production dramatically, doubling or tripling the existing capacity, to feed over 200 million undernourished people1. Although new varieties have contributed to improve crop production, productivity, and quality, their performance has been constrained by suboptimal conditions, such as declining soil fertility, drought, attacks by pests and diseases, and lack of good quality planting material.
The current approachâ€”expanding the area under agriculture to increase food productionâ€”is unsustainable and results in significant ecological damage. This realization worldwide is driving the search for newer options to intensify agriculture within the existing area.
We believe that ensuring plant health is pivotal to increase productivity and the strategy of intensifying sustainable agriculture2. The compelling reason for this is that biological threats, such as diseases, pests, and weeds are directly responsible for reducing crop yields by at least one-third3, and at least half of these losses could easily be averted using simple and affordable technologies and practices that prevent diseases and pests from affecting plants and produce. Ensuring plant health, therefore, is one of IITAâ€™s most important R4D strategies to improve agricultural productivity and food security and reduce poverty.
This issue highlights some of the technologies and strategies developed and promoted by IITA and its partners for plant health protection.
The value of plant health management cannot be underestimated given the precarious nature of agricultural systems in Africa with the evolution, establishment, and quick spread of pests and diseases, such as fruit flies, cassava brown streak and banana bacterial wilt.
Although plant health protection measures are relatively easy to adopt, considerable training, awareness creation, and financial support are required to improve skills and infrastructure in national systems to foster the technology transfer to farms where plant health matters.
True national defense is a huge offensive force against biological threats to food systems.
1 FAO. 2010. The State of Food Insecurity in the World 2010. FAO, Rome.
3 Oerke EC. 2006. J. Ag. Sci. 144: 31â€“43.
Cassava brown streak disease (CBSD) is a virus disease that has emerged as a serious threat to production in Eastern and Southern Africa.
Two virus species, Cassava brown streak virus and Cassava brown streak Uganda virus, the cassava brown streak viruses or CBSVs, have been recognized to cause CBSD. The infection results in mosaic symptoms on leaves, brown streaks on stems, and a corky necrosis in tuberous roots.
Root necrosis has the most damaging effects on the use and marketability of the tubers and thus affects the livelihoods of cassava farmers. It can make susceptible varieties unusable if the roots are left in the ground for over 9 months.
CBSVs are spread through the planting of infected stem cuttings and also by a vector, a whitefly, Bemisia tabaci. The foliar symptoms of CBSD are less conspicuous and farmers are often unaware of the problem until they harvest the roots and the corky, yellow-brown necrotic rot becomes evident.
There is no cure for the disease. Once plants become infected, the only option for growers is to uproot and destroy them. The use of virus-free planting material and the cultivation of resistant varieties are the only options for the control of CBSD.
Where is it and where is it heading?
CBSD is endemic in Kenya, Malawi, Mozambique, Tanzania, and Uganda and its occurrence is suspected in Burundi, Gabon, Madagascar, DRC, and Rwanda. Available evidence suggests a westward spread of the disease.
What is IITA doing about it?
IITA has adopted a multipronged strategy to tackle CBSD, to reduce the effects on cassava in epidemic areas, and prevent a further spread of the disease. Its efforts begin with informing governments about the threat. The four technical pillars of this strategy are as follows.
-Monitor disease spread and assess its impact: Key outputs include (a) the development of disease distribution maps, (b) estimates of yield loss, and (c) identification of targets for development.
-Understand disease etiology and epidemiology; develop tools for monitoring and forewarning: Key outputs include (a) understanding the effects of the viruses in cassava, (b) examining the characteristics of virus spread, (c) creating diagnostic tools for CBSVs, and (d) using digital-enabled field surveillance tools for real time reporting and a monitoring network.
-Develop and disseminate durable CBSD-resistant cassava cultivars: Key outputs include (a) screening and selecting over 40 elite cassava cultivars with dual resistance/tolerance to CBSD and cassava mosaic disease (CMD) appropriate for various countries, (b) deploying tolerant varieties for farmers to cultivate in East Africa, (c) developing molecular markers and modern molecular breeding tools for the accelerated development of CBSD-resistant varieties, (d) pre-breeding in areas currently not affected by the viruses, and (e) developing clean seed systems for the multiplication and dissemination of virus-free planting material.
-Capacity building through the transfer of knowledge, technology, and products to stakeholders: IITA has (a) built a coalition of international teams to combat CBSD, (b) trained scientists, extension workers, and plant quarantine officials in disease recognition, monitoring, and diagnostics, (c) established regional diagnostic labs, (d) created awareness through the use of the mass media, and (e) provided technical backstopping to national efforts in combating CBSD.
A suite of knowledge, technologies, and products derived so far from IITAâ€™s R4D efforts is playing a vital role in checking the spread of the disease and has contributed to reviving cassava production in areas affected by the epidemic. However, complete recovery and the prevention of any further spread of CBSD are still a long way off. They require a strong commitment from national and international communities to sustain the ongoing and emerging research and development efforts that are devising effective and eco-friendly technologies for sub-Saharan Africa.
Advice to stakeholders
In countries where CBSD is already established, IITA recommends that governments require the use of available CBSD control programs, including the adoption of promising CBSD-resistant cultivars, and the production and distribution of clean cassava planting material.
Countries not yet affected need to increase their vigilance and develop the capacity to recognize CBSD and deploy eradication programs; establish plans for preemptive action to reduce the risk of CBSD spreading from affected regions; and put in place programs to produce and distribute clean planting material.
All the cassava-producing countries in Africa should:
-Organize large-scale awareness creation programs to inform farmers, extension workers, CSOs, and national research entities about CBSD, the eradication of infected plants, and the steps for disease control.
-Strengthen the monitoring capacity of the national quarantine authorities and other relevant bodies including the establishment of communication systems for a rapid response to prevent disease and eradicate infections where they are identified.
-Develop resistant varieties most urgently, through breeding, using both conventional and transgenic approaches.
-Put in place a strategy for the production and distribution of clean cassava planting material, and adopt improved varieties with resistance to CBSD and CMD.
-Affirm financial and political support for collaboration, cooperation, and coordination to prevent the further spread of CBSD in tropical Africa.
The publication consists of 33 chapters written by about 40 scientists and conservationists that cover an evaluation of 550 species based on the IUCN (International Union for Conservation of Nature, http://www.iucn.org/) criteria.
The book is of interest to those working in nature conservation, including schools, NGOs, government agencies, policymakers, as well as tourists.
The book was produced with the generous support of the following partners: Swiss Agency for Development and Cooperation (SDC), Leventis Foundation, Netherlands Embassy (Benin), and Helvetas (Switzerland).
Copies are available for sale from IITA. To get a copy, please contact Peter Neuenschwander, IITA-Benin, at email@example.com or Katherine Lopez, IITA, Ibadan, Nigeria, at firstname.lastname@example.org.
Irmgard Hoeschle-Zeledon*, email@example.com or firstname.lastname@example.org *Coordinator of the CGIAR Systemwide Program on Integrated Pest Management (SP-IPM) convened by IITA
The discussion on the impact of climate change (CC) on agriculture has often focused on how changes in temperature, rainfall, and CO2 concentrations will affect the suitability of temperate regions for crop production and how crops will react in terms of yields. The effects of climate change on biotic factors in the tropics, such as weeds, pests, and pathogens (hereafter referred to as pests), have not received much attention.
Empirical data exist, however, to show that these biotic factors have major effects in determining productivity in the tropics. For instance, during the 1997 El NiÃ±o phenomenon, the mean temperature on the Peruvian coast increased by about 5 Â°C above the annual average, causing a decrease in potato infestation by the leafminer fly Liriomyza hydobrensis, which otherwise was a major pest. However, the abundance and infestation severity of all other pests increased in all crops, including potato (Kroschel et al. 2010). The complex consequences of CC particularly on pests and pathogens are still only imperfectly understood (Gregory et al. 2009).
CGIARâ€™s work on climate change
What are IITA and the other centers of the Consultative Group on International Agricultural Research (CGIAR) doing to mitigate the impacts and adapt to the effects of CC on pests? Historically, CGIAR centers have a broad R4D focus; centers have been developing knowledge (e.g., pest profiles), products (e.g., new crop varieties, biocontrol agents against invasive pests), and technologies (e.g., predictive models, diagnostic tools) that are suitable for diverse agroecologies including the tropics, wet, humid, semiarid, and dry, and to some extent the temperate zones as well. The broad knowledge and experience of centers provide an unprecedented advantage to assess the products and technologies in different agroecologies and weather settings and to determine their resilience and ability to cope in altered climatic situations.
Several programs directly focus on managing pests. For instance, the breeding of crop varieties for resistance to pests and pathogens has always been a focus of the CGIAR. With the uncertainties of CC, this work has become more relevant. Breeding for resistance to drought and waterlogging, although not the primary objectives, also aim at making varieties better able to tolerate biotic threats, since drought and excess water in the soil both increase the plantsâ€™ vulnerability to these factors.
A good example is the effort to develop drought-resistant maize cultivars by CIMMYT and IITA. These will not only allow the expansion of maize production into areas with less reliable rainfalls but also ensure the continued production in regions that are prone to future water scarcity. Drought- tolerant cultivars also reduce the risk of aflatoxin contamination in the field. Additional characters are incorporated into the drought-tolerant maize, such as resistance to maize streak disease which is endemic in Africa. Similar programs are ongoing to develop drought-resilient cassava and cowpea, and yam with tolerance for major pests.
The CGIAR centers are also working towards the development of cropping systems with greater intra- and interspecific diversity to increase resilience to CC-induced threats from biotic factors. For example, IITA is promoting maizeâ€“cowpea intercropping to reduce the pest pressure on cowpea.
Bioversity International is exploring how intra-specific crop genetic diversity on-farm not only reduces current crop losses to pests and pathogens, but also decreases the risk of genetic vulnerability and the potential of future crop damage, thus enhancing the impact of other IPM strategies and providing farmers with increased adaptive capacity to buffer against climatic changes.
CIP developed a temperature-driven phenology model for the potato tuber moth, Phthorimaea operculella that provides good predictions for the population in areas where the pest exists at present (Kroschel et al. 2010). Linked with geographic information systems (GIS) and atmospheric temperature, the model allows the simulation of risk indices on a worldwide scale to predict future changes in the distribution of the species due to increasing temperatures. The approach can also be used for other insect species. Hence, CIP created the Insect Life Cycle Modeling software (ILCYM) to facilitate the development of other insect phenology models. With its support, the phenology model can be implemented and allows for spatial simulation of insect activities.
Many centers support the collection and conservation of plant genetic diversity that can be built into new cultivars to enhance their resistance to biotic stresses. Diagnostics capacity is continuously augmented for the accurate and timely recognition of endemic pests, new variants, and invasive pests. Crop biodiversityâ€”landraces and wild relatives that are the reservoirs of genes for abiotic and biotic factorsâ€”is conserved ex situ to protect the species from erosion by CC-induced changes.
In a collaborative effort, CIP, IITA, icipe, and partners in Germany and Africa are implementing a project to understand the effects of rising temperatures on the distribution and severity of major insect pests on main food crops. ILCYM will be further improved and adapted to cover a wide range of insect species. The results will contribute to filling the knowledge gap about CC effects on economically important insect herbivores and their natural enemies.
IITA is planning to research the effect of changes in temperature on the invasion potential of major biotic threats in the Great Lakes region of East Africa and elsewhere: Banana bunchy top virus (BBTV), Banana Xanthomonas Wilt (BXW), and Panama Diseaseâ€“Tropical Race 4, cassava brown streak virus disease, cassava mosaic disease, maize streak, soybean rust, and pod borer pests, among others.
As whiteflies and aphids are considered to become more problematic with increased temperatures, IITA is also preparing research on the biocontrol of different whitefly and aphid species in vegetables and staple crops.
A project has been proposed on the bio-enhancement of seeds and seedlings of cereals and vegetables for East Africa to stimulate the plantsâ€™ defense mechanisms against pests and pathogens expected to increase in number, frequency, and severity. This project also addresses the registration of biopesticides and the availability of endophytes to the tissue culture industry.
CGIAR research programs
Under the new CGIAR Research Programs (CRPs), centers are addressing CC-induced crop health issues in various ways. Breeding for resistance to predicted biotic stresses continues to be a major focus in CRP3 (roots, tubers, banana) and its subcomponents. This component, coordinated by CIP, specifically recognizes CC and agricultural intensification as drivers for higher pressure from pests. Hence, this program aims at developing management strategies for priority biotic threats to these crops. These include the development of improved detection and monitoring tools, and surveillance methods for detecting and mapping existing, emerging, and resurgent molecular pests and pathogens. It will look into increasing general plant and root health through the enhancement of the natural disease suppressing potential of soils, and the antagonistic pest and disease potential of the aboveground agroecosystems.
The CRP on Integrated Systems for the Humid Tropics, led by IITA, will have a substantial focus on CC, its impact on pests, and plans for mitigation. For example, research will establish the relationship between CC and key cassava pests to develop integrated pest management (IPM) strategies including those for whitefly, African root and tuber scale, termite, green mite, aphid, and mealybug.
Phenology models for insect and mite pests and their antagonists on several crops will be developed and validated and their potential for changes in warming will be determined.
In collaboration with CABI, community surveillance for pests and diseases will take place through the expansion of the mobile plant clinic network.
Knowledge and decision support tools for the management of potato and sweetpotato pests (diseases and insects) will be developed and assessed in relation to the expected intensification of the agroecosystems in the humid and subhumid tropics.
Sustainable management of cassava virus disease in the cassava-based system will also be studied, and the vulnerabilities of these systems to CC- induced pest and disease problems will be determined.
The CIAT-coordinated CRP on CC, Agriculture, and Food Security began operations this year. It will continue the activities initiated by the CGIAR Challenge Program on CC. This CRP aims at mainstreaming strategies that address the management of CC- induced pest and disease threats among international and national agencies. It will identify and test innovations that enable communities to better manage and adapt to climate-related risks from biotic factors.
A lot of surprise shifts in ecosystems could come. It is therefore important that research capacity and knowledge bases are maintained to understand and rapidly react to mitigate any debilitating impacts (Shaw and Osborne 2011).
To accomplish this, it is necessary to establish good baseline data on current pest status in agroecosystems. This knowledge base will serve as a reference point to measure the fluctuations and the effectiveness of interventions.
It is important to determine the key weather variables that could change as a consequence of CC and their influence on agroecosystems and pests, and establish preemptive coping strategies. Available CC models could be handy for predicting CC factors.
A diverse scientific base including specialists in pathology, entomology, ecology, taxonomy, and epidemiology is required. They should work together to ensure that the outcomes of their research are linked to existing knowledge, economic forces, and common understanding (Shaw and Osborne 2011).
As it generally takes more than 10 years to breed a new resistant cultivar of a crop, breeding programs must start well in advance of the serious risk of a biotic threat Breeders need to be informed on the problems which might become important in the future (Chakraborty et al. 1998 in Juroszek and Tiedemann 2011).
Crops being bred for abiotic threats such as drought, waterlogging, and salinity should be prepared for the pests that could flourish under these conditions and select varieties that can tolerate pests as well.
Changes in occurrence, prevalence, and severity of infections and infestations will also affect crop health management (CHM) practices. There is a need to effectively disseminate and use those techniques that are currently underused (Juroszek and Tiedemann 2011).
Significant contributions could be made in improved field monitoring of pests and diseases, and better delivery systems for pest control products (Strand 2000 in Juroszek and Tiedemann 2011). Preventive crop protection measures may become more relevant under CC to reduce the risks (Juroszek and Tiedemann 2011).
CC is a global problem that affects all countries. Hence, global cooperation is required. However, given the nature of plant pests and pathogens, more local or regional strategies need to be put in place that define potential risks and measures to tackle expected threats. Investments in early detection systems, including border controls to monitor the migration of pests through plants, plant products, and other goods, will be the key to avoid the spread of invasive pests and reduce high management and eradication costs (FAO).
New farming practices, different crops, and IPM technologies must be developed to control the established pests and prevent the spread of new ones (FAO).
Governments should consider developing country-specific strategies to cope with CC-induced changes and put in place favorable policies for the introduction and promotion of new technologies for CHM.
It is also crucial to create and augment awareness about the effects of CC among policymakers and other officials involved in developing agricultural strategies.
Chakraborty S and Newton AC. 2011. Plant Pathology 60: 2-14.
Climate change (CC) is a long-term change in the statistical distribution of global weather patterns over periods of time that range from decades to millions of years. Several factors, known as climate forcers, usually natural events such as volcanic eruptions, earthquakes, solar radiation, and ocean currents shape climate change.
However, the climate forcer of the 21st century CCâ€”carbon dioxide (CO2)â€”is mainly human-induced and attributed to the burning of fossil fuels and tropical deforestation. The property of CO2 to trap heat within the earthâ€™s atmosphere is contributing to global warming. Thus, a rise in CO2 levels increases the warming effect. Trapped heat in the atmosphere warms oceans, melts ice caps, raises sea levels, and increases average surface temperature, all of which are affecting normal weather patterns.
Some of the abnormal changes experienced over the last two decades include severe and prolonged droughts, extreme storms and prolonged rainfall pattern, high temperatures, and heat waves. These sudden and extreme variations in weather patterns due to â€˜global warmingâ€™ have profound effects on living organisms on earth. The altered conditions create risks as well as opportunities favoring certain living beings over others and contribute to shifts in niches. In addition, it could lead to long-term variations in climate (e.g., permanent increase in average temperature) that might irreversibly affect biodiversity in a given region.
In the context of agriculture, sudden and abnormal changes in weather could change the suitability of a given environment for cultivation of crops. This could be due to abiotic factors such as drought, heat (cold), or excessive water directly linked to weather or simply due to increased pests and diseases that would severely impede performance of the crops. Since crops, diseases (pathogens), and pests (including vectors) are intimately associated and influenced by the environment, any shift in these factors will alter the balance, and could have a positive impact (e.g., decreased pest pressure) or negative impact (e.g., increased pest pressure) on overall crop performance.
Using simulation models, attempts the world over are being made to determine the impact of CC on agroecosystems to establish appropriate coping strategies, particularly for the negative impacts. Although this appears simple, it is the most complex issue confronting researchers, policymakers, governments, and entrepreneurs worldwide.
Communities are working together to bridge the gaps and establish global coordination networks to mitigate the impact of CC. IITA and other CGIAR centers, together with national and international organizations, are contributing to these endeavors with a primary focus on conserving biodiversity and improving the resilience of smallholder agriculture in the developing countries in Africa, Asia, and Latin America.
The governments of Ghana and the Republic of Liberia have officially agreed to jointly develop, promote, and implement research activities to improve their agricultural sectors.
A memorandum of understanding was signed by representatives of Ghana and Liberia, with the assistance of IITAâ€™s Sustainable Tree Crops Program (STCP), in collaboration with the Ghana Cocoa Board. IITA/STCP works in both countries.
The agreement was signed by the Minister of Finance and Economic Planning, Kwabena Duffuor, and the Chief Executive of COCOBOD, Anthony Fofie, for Ghana, and by the Minister of Agriculture, Florence Chenoweth, and the Deputy Director General of the Central Agricultural Research Institute (CARI), Abugarshall Kai on behalf of Liberia.
Under the MoU, the Cocoa Research Institute of Ghana and Liberiaâ€™s CARI will exchange expertise, knowledge, and genetic resources (seeds and nursery development) to develop and improve the tree crops sector in Liberia. Specifically, the national research institutions of both countries will facilitate the provision of planting material as requested by either countries, make available research and training facilities and materials to visiting scientists from either institution, and provide technical expertise for the successful implementation of mutually-agreed projects.
Cassava value addition is helping African farmers increase their income, and improve livelihoods and food security through a USAID-funded project called Unleashing the Power of Cassava (UPoCA).
Implemented in seven African countriesâ€”Nigeria, DR Congo, Ghana, Malawi, Mozambique, Tanzania, and Sierra Leoneâ€”by IITA, the project has benefited thousands of farmers in these countries.
In Sierra Leone, the Tongea Women farmers in Sandeyalu community formed the Tongea women’s development association comprised of 54 women and 4 men.
Through the IITA-UPoCA project, a cassava microprocessing center was subsequently inaugurated, providing farmers with a financial window of opportunity. Incomes from USAID projects such as UPoCA have helped the people of Sandeyalu in rebuilding their community after years of civil unrest.
This success story echoes across other countries such as Nigeria, DR Congo, Ghana, Malawi, Mozambique, and Tanzania where UPoCA is being implemented.
In Malawi, UPoCA helped revive a moribund starch factoryâ€”the first in that country. Thousands of farmers benefited from improved cassava cuttings, training, and capacity building for processors.
In Nigeria the project linked up processors to farmers for steady production/supply of cassava roots, provided improved cuttings and training, and also helped build the capacities of farmers and processors.
Farmers in Ido community, Oyo State, Nigeria, have more than doubled the yield of cassava from an average of 10 t/ha to more than 20 t/ha. Other states that benefited from the UPoCA project were Osun, Ondo, Ekiti, Kogi, Nasarawa, and Benue states.
Farmers say the project has increased the production of cassava with the availability of improved cassava stems, making food more secure and generating wealth.
Apart from boosting the productivity of cassava in the project areas and maximizing the use of the root crop, the project is also promoting food security and improving the incomes of women farmers and processors in particular, and African farmers in general.
The Consortium for Improving Agriculture-based Livelihoods in Central Africa (CIALCA) and the CGIAR Consortium Research Program (CRP) on the Humid Tropics led by IITA will convene an international conference on ‘Challenges and Opportunities for Agricultural Intensification of the Humid-Highland Systems of sub-Saharan Africa’, in Kigali, Rwanda, on 24-27 October 2011.
The humid highlands in sub-Saharan Africa are characterized by high population densities and require intensification. Unfortunately, many communities lack easy access to the means to achieve this.
The conference aims to take stock of the state-of the art in agricultural intensification in the highlands of sub-Sahraran Africa, and to chart the way forward for agricultural research for development in the humid highlands, through keynote presentations, oral and poster presentations, and strategic panel discussions.
Two African nationsâ€”Malawi and Nigeriaâ€”have released three improved soybean varieties that can enhance the productivity of the crop and offer farmers better opportunities.
The varieties are TGx1740-2F, TGx1987-10F, and TGx1987-62F. TGx1740-2F was developed by IITA in collaboration with the Department of Agricultural Research Services (DARS) in Malawi. Varieties TGx1987-10F and TGx1987-62F were developed by IITA in collaboration with Nigeriaâ€™s NCRI.
The Malawi Agricultural Technology Clearing Committee officially approved the release of TGx1740-2F in January 2011 while the Nigeria Varietal Release Committee released TGx1987-10F and TGx1987-62F in December 2010.
The varieties outperformed the standard and local checks grown in the two countries, with high grain yield in multiple locations under on-station and on-farm trials.
Many farmers preferred the varieties because they smother weeds and reduce the cost of weeding. Farmers that participated in the on-farm trials of the varieties last year said they preferred them especially for their golden color at maturity.
In Malawi, TGx1740-2F gave the highest mean grain yield of 2.5 t/ha. It exceeded the yield of checks, grain variety Nasoko by 10% and the widely grown promiscuous variety Magoye by 32% during the two-year multilocation on-station trials.
The variety performed equally well during on-farm participatory variety selection trials in four districts of central Malawi. In the 2009/10 season, it outyielded all the new types of soybean varieties under testing with 2.2 t/ha. It also surpassed Nasoko by 15% and Magoye by 38%.
High in nutritive value, soybean is fast gaining appeal in Africa, offering a cheap source of protein. The crop is also emerging as an important feed, food, and raw material for producing high-quality protein products. For smallholder farmers it is an important cash crop and also improves soil fertility because of its ability to fix high amounts of atmospheric nitrogen.