icipe – 50 years of plant health research
The United Nations has designated 2020 as the International Year of Plant Health (IYPH), as an opportunity to raise global awareness on how keeping plants healthy can help end hunger, reduce poverty, protect the environment and boost economic development.
At the International Centre of Insect Physiology and Ecology (icipe), we use this occasion to reflect on our plant health research over the past 50 years. At the heart of all our activites is the wellbeing of smallholder farmers, aiming to provide them with yield-improving, integrated pest management (IPM) strategies that are environmentally safe, as well as economically and technically feasible.
The core of icipe plant health research is biological control, around three thrusts. First is conservation biological control, includes habitat management and behavioural manipulation based on intricate knowledge of chemical ecology and insect-plant tri-trophic interactions. The most outstanding example in this regard is the push-pull technology (http://www.push-pull.net/). Climate-smart technologies and adaptation strategies have been designed, including a climate-smart version of push-pull technology.
Second, classical biological control (the introduction of a natural enemy of exotic origin to control a pest) activities has become a powerful tool to address invasive pests like: the notorious fruit fly species Bactrocera dorsalis; Tuta absoluta, a highly destructive pest of tomato plants and fruit; Chilo partellus, a damaging stemborer of cereals; the diamondback moth, Plutella xylostella, a pest of all brassica crops; and Liriomyza leafminers, pests of many vegetable and flower crops.
Third is icipe’s efforts in augmentative biological control that have concentrated on the formulation of microbes, mainly fungi, into powerful biopesticides against numerous horticultural and staple crop pests.
In-depth knowledge of the biology and taxonomy of pests has also been generated as a vital foundation for IPM programmes, especially for species complexes such as tephritid fruit flies, cryptic species such as thrips and vector-borne diseases such as citrus greening. Through careful morphometrics, molecular biology, chemo-taxonomy and physiology, the identities of a diverse array of pests are revealed.
Commercialisation of several tools and strategies has been undertaken successfully, through public-private partnerships, reaching millions of farmers. For example, a range biopesticides developed from icipe’s fungal isolates have been commercialised and are being used on more than 130,000 hectares across Africa.
In capacity building, more than 49 MSc and 25 PhD students were trained last year. The vast majority of these students are from Africa and more than 40% of them are women. Thousands of farmers and partners are trained each year.
- The main focus was on the management of major insect pests of maize (stemborers – Chilo partellus, Busseola fusca, Sesamia calamistis and Eldana saccharina); sorghum shoot fly (Atherigona soccata); cowpea pod borer (Maruca vitrata); bean flower thrips (Megalurothrips sjostedti); banana weevil (Cosmopolites sordidus); nematodes (Pratylenchus sp.); cassava green spider mite (Mononychellus sp.); and rice pests.
- A major biological control initiative of the highly destructive stemborer Chilo partellus, commenced with the introduction of a wasp, Cotesia flavipes.
- Insect pathogens like bacteria, fungi, nematodes and protozoans were also tested and found to be efficient against stemborers.
- Control of thrips in cowpea using neem seed extract was effectively tested.
- Sorghum and maize lines and hybrids with improved grain yields and resistance to stemborers were developed, as well as banana cultivars resistant to the banana weevil and root lesion nematodes.
- Studies were initiated to understand the potential of intercropping as a strategy for insect suppression. Intercropping of sorghum-cowpea was found effective in managing stemborer and thrips populations, backed by exploitation of behaviour-affecting chemicals produced by plants and insects.
- Building on earlier studies on intercropping to control stemborers, icipe made one of its greatest breakthroughs to improve cereal production in Africa, through the launch of push-pull technology. The technology is based on a ‘stimulo-deterrent’ approach using rigorously selected companion crops planted around and among maize plants to attract crop pests to a highly susceptible trap plant (the ‘pull’) and to drive them away from the main crop using a repellent plant as an intercrop (the ‘push’). Napier grass, an important cattle fodder, was selected as the ‘pull’ plant. Silverleaf desmodium (Desmodium uncinatum) was selected as the ‘push’ crop.
- The benefits of the push-pull technology were quickly evident: in addition to controlling stemborers, researchers also demonstrated that push-pull could manage the parasitic weed Striga sp., improve soil health and provide high-quality fodder for livestock.
- By the end of 2005, 10,000 farmers in Kenya were using the push-pull technology. They had at least doubled their maize yields and increased milk production by 50%. The additional income had enabled more than 300 farmers to send at least one child to secondary school.
- After success in Kenya, biological control of stemborers using the previously introduced C. flavipes parasitoid, and a second wasp Xanthopimpla stemmator introduced later, was upscaled in Ethiopia, Malawi, Mozambique, Somalia, Tanzania, Uganda, Zambia, Tanzania (mainland and Zanzibar) and Zimbabwe. An economic impact study in Kenya calculated a benefit:cost ratio of 19:1, amounting to US$183 million following the first release of the natural enemy.
- In partnership with the French Institut de recherche pour le développement (IRD), research was started to evaluate the diversity, abundance and distribution of stemborers and their natural enemies, particularly parasitoids, in wild habitats around cultivated grasses.
- icipe initiated efforts to develop fruit fly IPM, using mango as a model crop and focusing on the plethora of indigenous African fruit flies, the most notorious being the Ceratitis cosyra species complex. Achievements included development of effective and affordable fruit fly lures from locally available materials, a control package for C. cosyra based on baiting and trapping techniques, the use of insect-killing fungi, and sanitation of orchards to rid them of fallen fruits. The IPM package was successfully applied in selected sites in Kenya.
- In October 2003, the oriental fruit fly Bactrocera dorsalis, a notorious pest that ranks high on quarantine lists, invaded and spread fast across Africa. icipe incorporated the pest into ongoing fruit fly management activities, expanding studies beyond Kenya to Benin, Tanzania and Uganda, and assessed abundance, distribution, pest status, seasonality and host plants.
- In 2000, icipe embarked on biological control of the diamond backmoth. The Centre imported and released the parasitic wasp Diadegma semiclausum in Eastern Africa, which provided phenomenal control in Cameroon, Ethiopia, Kenya, Tanzania and Uganda.
- In view of the European Union maximum residue limit (MRLs) guidance on fresh agricultural produce, icipe started efforts to support Africa’s export industry to balance compliance on safe plant protection measures with profitability. IPM packages for pests of French bean and tomato and pests (leafminers, aphids and whiteflies) were developed, consisting of the use of parasitic wasps, Bacillus thuringiensis (Bt), fungi and neem.
- A breakthrough was made in icipe’s 18-year-long locust research, with the discovery of a novel way of disrupting the social structure of the insects, reverting them to harmless solitarious individuals. icipe researchers identified the pheromone phenylacetonitrile (PAN), which governs the swarming behaviour of adult locusts. Studies established that PAN blocks communication between young (nymphal) locusts, resulting in total loss of communication between them. Field trials showed that even minute doses of a commercially available synthetic equivalent of PAN were effective in breaking up the social groups, or bands, of young locusts. As a locust control agent, PAN is environmentally friendly and less costly to develop, and it can be used either on its own or alongside other control measures like synthetic insecticides or biopesticides, but at largely reduced concentrations.
- Push-pull technology was initiated leading to the development and commercialization of Campaign, a biopesticide based on Metarhizium anisopliae strain ICIPE 69.
- Push-pull technology was scaled further, including addressing challenges towards its advancement. Particularly in view of climate change, the Centre commenced development of a climate-smart push-pull technology, by selecting crops against the basic principles employed in the original design of the technology.
- icipe identified the cause of the Napier stunt disease to be a phytoplasma and the leafhopper Recilia banda as one of its vectors in Kenya. The Centre also created a more superior and affordable molecular diagnostic tool for screening the phytoplasma, facilitating the discovery of genotypes of Napier grass that are resistant to the stunt disease, which were recommended to farmers.
- Towards biological control of indigenous African stemborers, the most important being Busseola fusca, icipe imported and released the parasitoid Cotesia sesamiae in West Africa in 2006.
- To manage the larger grain borer, Prostephanus truncatus, an invasive beetle that causes 30-90% losses in stored grain, better adapted races of a predator beetle, Teretrius nigrescens, were introduced in several regions in Africa.
- The Centre contributed to mitigating postharvest losses of cereals and other crops by investigating better storage strategies, while also providing systematic evidence to assist decision makers in optimising post-production policies and strategies.
- IRD team discovered a considerable number of previously unreported species of stemborers and their parasitoids. A new wasp species, Cotesia typhae, was found in Kenya, as a biological control agent against Sesamia nonagrioides stemborers in France. The studies also showed that due to destruction and fragmentation of wild habitats, some current and future stemborer pests of grasses will originate from wild host plants.
- The fruit fly IPM focused on completing knowledge on the invasive B. dorsalis. The Centre continued monitoring of B. dorsalis, which showed its predominance and displacement of indigenous fruit flies. Research focused on population dynamics studies, identification of the pest’s host plants and testing of various IPM strategies for its management. Two effective natural enemies, Fopius arisanus and Diachasmimorpha longicaudata, were imported and pilot releases conducted in Benin, Kenya, Mozambique and Tanzania.
- Thrips management progressed with production of occurrence maps of over 60 species and some of their natural enemies. In partnership with Martin Luther University, Germany, the Centre developed user-friendly software that greatly enhanced identification and monitoring of thrips and their natural enemies in the region. An agreement was signed with Real IPM, a Kenya based commercial biopesticide producer, for the commercialisation of ICIPE 69, a thrips-effective isolate developed by the Centre from Metarhizium anisopliae. The biopesticide was registered in several countries in Africa, under the brand name ‘Campaign’. A proof-of-concept for a ‘lure-and-kill’ strategy combining Campaign with LUREM, a thrips attractant developed by Plant Research International, Netherlands and Plant & Food Research, New Zealand, was completed.
- Hundreds of farmers and staff of agricultural ministries in East Africa were trained in good agricultural practices (GAP) and IPM techniques for Liriomyza leafminer management to enhance compliance to international export markets. icipe imported and released the effective parasitoid Phaedrotoma scabriventris from Peru into Kenya, and studied its interactions with the indigenous parasitoid Diglyphus isaea. Scientists at the Centre also found neem and pyrethrum botanicals to be effective in controlling leafminers.
- An isolate of Metarhizium anisopliae, ICIPE 78, in combination with the predatory mite Phytoseiulus longipes imported from Brazil, was found effective in the control of the red spider mite Tetranychus evansi, an invasive pest of tomatoes. Eco-friendly nets for protecting tomatoes from the pest were also tested with commendable success in collaboration with the Centre de Coopération Internationale en Recherche Agronomique pour le Développement (CIRAD).
- To develop an IPM programme for cashew, a key cash crop in Africa, icipe conducted bioecology studies of the crop’s key insect pest complex and their natural enemies in diverse habitats and landscapes. Control options identified include: the weaver ant as a natural enemy, entomopathogenic fungi and fungal antagonists. New knowledge was generated on chemical and sex attractants of coreid and mirid bugs, pests of cashew. Chemical signals were identified, to monitor and lure pests on cashew and other crops (coconut, cocoa and macadamia nuts).
- Basic research on the biology and the chemical ecology of the coffee berry borer, Hypothenemus hampei, the most important biotic constraint of commercial coffee production worldwide, unveiled major attractants and repellents of the pest. Studies were also conducted on the potential effect of climate change on the coffee berry borer, with research on thermal tolerance and development of models of the pest’s distribution in East Africa under current and future climate change scenarios.
2013 – present
- icipe made a breathrough in development of climate-smart push-pull when it identified greenleaf desmodium (Desmodium intortum) and Brachiaria cv Mulato as the ideal intercrop and border crop, respectively.
- By the end of 2019, push-pull technology had been introduced in 17 African countries: Benin, Burkina Faso, Burundi, Cameroon, Democratic Republic of Congo, Ethiopia, Ghana, Kenya, Malawi, Mozambique, Rwanda, Senegal, Tanzania, Togo, Uganda, Zambia and Zimbabwe. A cumulative 241,040 farmers had adopted push-pull, with 55% of them female farmers, directly benefiting ~1,500,000 people (assuming a household size of six people).
- An economic assessment study showed that climate smart push-pull technology increases yields by between 2.5 and 3.8 tonnes per hectare. Push-pull technology has the potential to lead to an additional total income (economic surplus) of US$ 72-73 million in Western Kenya under the current technology adoption level (14.4%). Further findings suggest that the technology is gender-neutral, as there are no differences in its adoption between men and women. Also, push-pull technology adoption reduces labour requirements during ploughing, weeding and threshing. In comparison to men, women save more labour hours during weeding and threshing periods but less during ploughing. Adoption of push-pull technology increases child education investment and shifts household expenditures towards goods associated with female consumption preferences. Moreover, push-pull technology enhances women and household dietary diversity scores.
- icipe has taken a leadership role in the control of the invasive fall armyworm, Spodoptera frugiperda, which arrived in Africa in January 2016 and as of 2020, has spread to 48 countries across the continent.
- In 2017, participatory studies established that climate-smart push–pull is effective in controlling the fall armyworm, providing a suitable, accessible, environmentally-friendly and cost-effective strategy for management of the pest. These findings represented the first documented report of a readily available technology that could be immediately deployed in Africa.
- icipe developed a number of newly discovered fungal biopesticides, providing farmers in Africa with effective and environmentally safe alternatives for the management of the invasive and highly destructive fall armyworm. Significantly, with the support of development partners, government and regulatory authorities, as well as private sector actors in East Africa, the Centre has undertaken label extension of two of its commercially available biopesticides, Mazao Achieve based on M. anisopliae strain ICIPE 78 and Mazao TickOff based on M. anisopliae ICIPE 7, which are now being upscaled for fall armyworm control.
- icipe and partners identified indigenous natural enemies for fall armyworm in Ethiopia, Kenya and Tanzania. Among these, Cotesia icipe was the most widely distributed.
- In 2020, as East Africa experienced the worst desert locust outbreak in decades, icipe contributed to the management of the crisis by using machine learning techniques and environmental variables in predicting the potential breeding areas of desert locust in East Africa. This study demonstrated that large areas of Kenya, Northwestern and Northeastern Uganda, and middle and central regions of South Sudan have the highest potential in providing conducive breeding for the pests. Such specific knowledge will enable optimal action and efficient use of resources.
- icipe research revealed the superiority of the innate defence mechanism of maize landraces, the so-called ‘smart maize’, to stemborers in comparison to some commercial hybrid maize varieties.
- Upscaling of the icipe fruit fly IPM tools, technologies and strategies was intensified. The identity of B. dorsalis was resolved. First recorded in Kenya in 2003, the fruit fly was initially inaccurately described as a new pest to science and accorded the name Bactrocera invadens in 2005. icipe established the pest to be synonymous to B. dorsalis, already present in many countries worldwide. The settlement of the pest’s identity enables adaptation of control tools developed for species in other regions.
- icipe researchers discovered host-marking pheromones that enable certain fruit fly species to deposit a pheromone to indicate fruits where they have already laid eggs, thereby preventing repeated egg-laying on the same fruit. These ‘host-marking pheromones’ provide a novel and exciting tool in the IPM package against Ceratitis spp. fruit flies.
- In a global first, icipe designed novel primers to identify endosymbionts in African fruit flies. Of particular interest was the discovery of Spiroplasma species that are new to science in both native and exotic species. The Centre has also increased knowledge in the underresearched area of the gut microbiome of fruit flies.
- Five new fruit fly species in the genus Ceratitis were identified and genetic barcode libraries constructed for easier identification. Employment of integrative taxonomy, molecular and morphological tools determined the highland and lowland populations of Ceratitis rosa to be separate sibling species designated as Ceratitis rosa sensu stricto and the newly described Ceratitis quilicii. The Centre also identified potential natural gut microbes and hosts transcriptional profiles that could be used to define and differentiate the two fruit fly sibling species.
- Protocols for postharvest disinfestation of B. dorsalis in mango were developed to facilitate access to lucrative export markets. These protocols are being translated into technologies and commercial set-ups that will benefit mango growers in the region, in partnership with private sector partners in Kenya and Uganda.
- In partnership with Kenya Biologics, a fruit fly protein bait facility was established to enable local, commercial production of protein bait (Fruit Fly Mania), a product developed based on icipe research.
- Studies in Kenya in 2015 showed that the icipe fruit fly IPM package can reduce infestation in mango by more than 80%. Follow-up assessments between 2016 and 2018 showed that the use of fruit fly IPM technologies increases net income by 9-137% and decreases insecticide use by 74%. The estimated economic value of the fruit fly IPM package is US$ 19 million per year in Kenya with a benefit:cost ratio of 27:1 and with a potential to reduce the number of rural poor people by 72,642. The imported fruit fly parasitoids were released in several African countries including Benin, Botswana, Cameroun, Ghana, Kenya, Mozambique, Senegal and Tanzania, with several request from other African countries. Between 2015 and 2019, icipe‘s fruit fly IPM package was expanded to Arba Minch Region in Ethiopia, where fruit fly infestation has been reduced from about 70% to 10–13%. icipe is now upscaling its fruit fly IPM package in several African countries, and new sites in Kenya, Ethiopia Malawi, Mozambique, Tanzania, Uganda, Zambia and Zimbabwe.
- An IPM package against T. absoluta has been developed, consisting of biopesticides based on entomopathogenic fungi, the use of pheromone lures for monitoring and mass-trapping, classical biological control, garden sanitation and habitat management.
- The Centre developed the first-ever DNA barcode reference library of the African citrus psyllid, Trioza erytreae, presenting a basis for rapid and accurate identification of the pest to aid phytosanitary measures. In collaboration with relevant regulatory authorities, icipe made progress in the management of Diaphorina citri, the Asian citrus psyllid, including designing of methods, tools and technologies (traps, attractants, sampling design and methods) to monitor and detect the pest early to guide intervention and minimise spread.
- Thrips and tospovirus IPM strategies were scaled out in East Africa, through effective public-private partnerships, which resulted in the commercialisation of biopesticides, field demonstration of technologies, and building capacity among quarantine agencies and agricultural extension officers.
- The Centre discovered pheromones that could be exploited to develop technologies for trapping bean flower thrips (Megalurothrips sjostedti). This study provided the first information regarding the aggregation pheromone among thrips belonging to the Megalurothrips group in Africa.
- Eco-friendly management strategies were developed against pests of African traditional vegetables such as African nightshade, amaranth and cowpea. Strategies involve the use parasitoids, biopesticides, attractants, resistant varieties and cultural practices. The Centre discovered that a species of the African nightshade, a widely consumed traditional vegetable in Africa, has evolved a unique ability to defend itself against one of its major pests, the tomato red spider mite, by luring the pest to its ‘dead end’.
- The chemical signals involved in the interaction between the root-knot nematode Meloidogyne incognita (a highly damaging species) and a common sweet pepper cultivar grown in East Africa have been identified. This is the first time that the mediating chemicals provide the potential for breeding peppers that are resistant to root-knot nematodes.
- The Centre is significantly involved in the management of the potato cyst nematode (PCN), an invasive quarantine pest that was first reported in Kenya in 2014. Activities include training technicians to determine the prevalence, general severity, and species diversity of PCN nematodes across Kenya; generating knowledge on PCN biology under Kenyan conditions; identification of potential biological control agents and trap crops; evaluation of potato cultivars that are resistant to PCN; and awareness creation among farmers and plant health workers in the country. These efforts are being extended regionally.
- icipe is participating in a project led by North Carolina State University, USA, to develop a biodegradable matrix from banana fibre that acts as a carrier for effective application of micro-dosages of nematicides, for the management of PCN.
- The Centre’s studies have revealed that it may be possible to control PCN by inducing ‘suicidal hatching’ of the pests using naturally occurring chemicals in crop roots. Blends of the compounds obtained from crude material of such plants may be used to treat potato fields as organic soil amendments.
- Findings also indicate that certain crops act as dead-end PCN traps, presenting promising leads for PCN management.