man in field

Thomas Odhiambo, push-pull and an African approach to science and farming

In 1967, a young Kenyan scientist called Thomas Odhiambo wrote a paper for the journal Science [1] in which he set out his hopes for East Africa as it moved out of the colonial era. With a doctorate from Cambridge University in the reproductive physiology of the desert locust, he saw science as key to that. And no wonder: it was a time when science seemed invincible, in agriculture as in every other area of life. Grain yields were increasing rapidly in Mexico, Pakistan and India due to a combination of new crop varieties, pesticides and fertilizers, the original Green Revolution. Hunger would be defeated by technology, and anyone who suggested otherwise was standing in the way of progress.

Odhiambo however saw things differently. Science for him was not a neutral modernizing tool, to be valued simply for its technological gains. It was not enough for him that Africans should pick up a scientific training and become competent surgeons, for instance; he wanted them to have full mastery of the subject and to integrate it with their cultural frameworks on their own terms. What really mattered was human knowledge.

A different world view

It was in his view vital to understand the African mind. The West and the East had developed knowledge systems which relied on a distinction between subjective and objective reality, allowing one to produce science, while the other developed mysticism. The African, however, had ‘concentrated his intellectual powers in devising a vastly intricate and communalistic social system.’ He does not explain further, but the African concept of ubuntu, which sees society as the source of humanity, comes to mind. Proverbs like ‘if you want to travel fast, go alone. If you want to travel far, go together,’ and ‘I am because we are’ indicate a mindset very different from the individualistic West.

This meant that Africa needed new institutions that would integrate the scientific method with indigenous cultural frameworks. The result was the foundation in 1970 of ICIPE, the International Centre of Insect Physiology and Ecology, of which he was the first director. Based in Nairobi, it recently celebrated its Golden Jubilee and its website announces that it now works in 41 countries, published 143 articles in 2019 and has so far trained 1058 postgraduate students. So what came of the meeting between Western science and African communalism?

Things did not go quite to plan. ICIPE never became the university that Odhiambo wanted it to be, and as a result of conflicts with the governing body he was even removed as Director in 1994. As his Guardian obituary notes, this ‘was a massive blow; his reputation had been built in the cause of self-reliance for Africa, yet his fate was being decided by foreign governments and donor agencies.’ Nevertheless, the work he began at ICIPE lives on, and is worth a closer look.

One of ICIPE’s flagship projects, a method of crop protection known as push-pull, shows what can happen when science is put in service to traditional practice, as he recommended. The story begins around 1993, when staff at ICIPE turned their attention to a destructive caterpillar, the maize stem-borer. Rejecting the use of pesticides, which farmers in any case could not afford, Odhiambo encouraged his staff to observe the life cycle of the insect and look for a biological method of controlling it. The result was the discovery that some plants, grown alongside the maize, are able to produce volatile chemicals that will ‘push’ the moth out of the crop and ‘pull’ it to the margins.

The push-pull method

In the classic form of push-pull, maize alternates with rows of a legume called Desmodium, and the plot is surrounded by a strip of Napier grass. The Desmodium repels the stem-borer and additionally suppresses a parasitic weed called striga, besides fixing nitrogen. The Napier grass attracts the stem-borer but also attracts its natural predators and secretes a glue that traps the caterpillars. Free of striga and the stem-borer, maize yields double or triple. Meanwhile both the legume and the grass are cut regularly, producing an abundance of protein-rich forage which is fed to cows, goats, poultry or pigs.

Maize, desmodium and grass
Maize and desmodium (rear), grass (foreground)

There are many other benefits. Being perennials, these forage crops help to hold soil in place and protect the crop against wind and flooding. Each time they are cut, their roots die back and add organic matter in the soil, just as happens when sheep and cows graze pasture. Soil fertility therefore increases, moisture retention improves, and the family enjoys a good supply of nutrient-dense milk and meat. Women in particular benefit because they no longer have to spend long hours weeding the striga and collecting forage from the bush. Instead, many run small businesses selling their surplus produce, and are able to pay school fees.

Once a farmer has invested labour in establishing a push-pull plot – and so far nearly a quarter of a million in East Africa and elsewhere have done so – it needs little maintenance. The method is also adaptable. A variant has been developed that is more tolerant of drought, using different species of grass and legume, and it has been shown to work with other cereal crops and pests, notably the fall armyworm. With support from partner organizations and government extension services, it has spread widely in Kenya and elsewhere in Africa, including Ethiopia and Rwanda

Science meets practice

Science was key to this story. A partnership between ICIPE and Rothamsted Research in the UK meant that researchers could identify the volatile chemicals that directed the moths’ flight and attracted their natural enemies. This allowed them to screen large numbers of companion plants to identify the most effective varieties. This in turn was possible because of funding from the Gatsby Foundation which allowed the researchers the scope to follow their own interests, so that what was ‘little more than a promising idea in the minds of an informal global network of chemical ecologists’ became a practical reality. [2]

Just as important though was the knowledge that was embedded in African farming practice. Push-pull developed from the interaction of modern science with traditional methods, notably mixed cropping, and in a context of collaboration and trust. As the project proceeded, farmers have been drawn in as experimenters, trainers and popularizers of push-pull, with demonstration plots and field schools. They have even become co-researchers and owners of the method, testing and adapting it to new settings. This has been possible because the technology was designed to fit with, and so empower, existing practice.

Push-pull works on many levels. It is a model for controlling pests without using pesticides, and has for instance inspired scientists at Rothamsted to experiment with companion cropping to control the pollen beetle that is a serious pest of oilseed rape. But it is much more than that. It is a mixed farming approach which balances food production with nutrition, builds soil fertility and maintains biodiversity, all while supporting the prosperity and self-reliance of farmers. This is in stark contrast to the UK, where farmers face uncertainty over subsidies and global trade, are dependent on fossil fuels, synthetic fertilizers and expensive machinery, and all too often vilified for the damage that farming has done – on behalf of us all – to biodiversity and soil health. So what are the lessons for us?

Lessons for the UK

We won’t get very far with maize, Napier grass and Desmodium in the UK, but many of the elements of push-pull can be discerned here, ripe for amplification. These include companion planting for pest control, the use of perennial intercrops (for instance, undersowing wheat with clover, as well as agroforestry), mixed farming (the integration of livestock and arable crops, now increasingly rare), and on-farm research, or ‘field labs’ in which farmers are investigators, not merely the consumers of technology. We also have a strong movement of small-scale farmers, growers and food activists, exemplified by the Permaculture Association, the Land Workers’ Alliance, and the Oxford Real Farming Conference. What might we achieve if we directed agricultural research towards this network of practice?

This brings us back to the relationship between science and society, which was Odhiambo’s concern. The science behind push-pull is orthodox enough: mass spectrometry and field trials, not Kirlian photography. What is significant is the context in which it is used. It is as if the head-based knowledge of science has been sensitively joined to the embodied wisdom of generations of farmers, transcending the artificial distinction between tradition and innovation. Science is thus employed at a human scale.

Odhiambo wanted to improve the lives of his fellow Africans, but his global connections allowed him to conduct an experiment with much wider significance. As Hans Herren, director of ICIPE from 1994 to 2005, said of push-pull: “there was an opportunity here in Africa to implement knowledge on biological control…in a very sustainable way when nobody talked about sustainability”. [3]

Now that we really are talking about sustainability, it’s time to learn from this visionary project.

[1] Odhiambo, T.R. Science, New Series, Vol. 158, No. 3803 (Nov. 17, 1967), pp. 876-881. Published by: American Association for the Advancement of Science. Stable URL:

[2] Gatsby Charitable Foundation (2005) The quiet revolution: push–pull technology and the African farmer. Gatsby Occasional Paper, London, pp. 23-24.

[3] Holdrege, C. (2012) Context-sensitive action: The development of push-pull Farming in Africa.

Images courtesy of Rothamsted Research.