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Expanded web feature: Opinion: John Pickett
Pest management expert shares his experiences of working with subsistence farmers and policymakers in the developing world
In the early 1990s, we were working to find new ways to control pests relating to the natural defences of plants. In the department responsible for inventing pyrethroids, which are safe and effective pesticides, we had nonetheless seen criticism because these have a neurotoxic mode of action. We wanted to look at a non-toxic action, and the idea was to produce pest control with plant chemistry by getting the plant to do it, without using toxic mechanisms.
So, we and other groups started to join strategies together, such as the ‘push-pull’ or ‘stimulo-deterrent diversionary’ strategy – you divert (push) the pests from the crop and entice (pull) them into a trap crop and, at same time, you bring in beneficial organisms such as parasitoids and predators.
The push-pull system in action. Left-right: Owen Mugune, Christine Alokit, Dr Charles Midega, Prof John Pickett, Dr Zeyaur Khan
In 1993, we formed Rothamsted International and the idea was to use a proportion of our elite science to benefit really poor farmers in Africa. This coincided with the Gatsby Charitable Foundation wanting to fund research to reduce poverty in rural Africa.
Coincident with that, at the International Centre for Insect Physiology and Ecology in Nairobi, headed by Thomas Odhiambo, they were thinking about habitat management by surrounding or intercropping with plants that would bring more predators into the crops or interfere with pests. There’s a kiSwahili phrase, ‘kilimo cha mchanganyiko’, for this process of companion cropping. This is a cheap technology which does not require the purchase of external inputs and fits in with the culture the farmers already have.
Within a year or two, we were finding plants that were very attractive to the maize stem borer pests. We then found a plant with fantastic repellent properties called molasses grass, so we set up demonstrations in Kenya to bring farmers in to explain what to do. We were battling against the myth that the technology is already there and all you have to do is transfer it to the farmers. However, we were published in Nature proving that you can do top science relevant to subsistence farming (ref 1).
As the programme progressed, we had a lot of meetings with farmers. One idea persistently expressed was that they would like some edible beans as a companion crop. Molasses grass makes good goat and cattle feed, so we also looked at better animal fodders in a genus of legumes called Desmodium, which did quite a good job. It was not as good a repellent as molasses grass, which by this time was being grown in rows of 1:4 with maize. Desmodium had to be grown 1:1, didn’t attract the wasps as well and was not edible for people, but it did provide better cattle forage.
The nitrogen-fixing legume Desmodium can suppress germination of African Witchweed
Serendipity and Striga
In the farms around Lake Victoria, we had another problem: the African witchweed, Striga hermonthica, a bigger problem in some areas than stem borers and a very big problem Africa-wide. Where we had the Desmodium intercrop, to our great surprise we found massive suppression of the Striga weed.
We had a job selling this idea. I remember meetings with funding agencies where they would look at you with one eyebrow raised as if to say, “Pull the other one, there are lots of things that control Striga, such as cowpea or the forest legume lablab or sweet potato.” We said, “Desmodium is something different and gives a massive yield benefit, but with sweet potato or lablab, you get a yield loss.” Finally, we demonstrated these effects in the scientific literature (ref 2).
Advances and antagonism
By this time we were working with wider collaborators in Kenya, Uganda, Tanzania, and through the Sasakawa Foundation in Ethiopia, but the push-pull system can be viewed quite antagonistically by groups practising other technologies. One such technology is to rotate crops with something non-susceptible to Striga, but the problem is that poor farmers can’t afford to have a non-food crop. Another is herbicide-tolerant hybrid maize with a seed coating of herbicide. Although potentially valuable for higher input farming, this worked very badly for the farmers who were persuaded to buy or were given it. Indeed, they were very ill-disposed towards that project.
Farmers teach and learn each push-pull techniques through local networks
We currently have over 20,000 farmers doing push-pull, a drop in the ocean in some ways, but it shows that the system really is viable. When you try to persuade funding agencies and national programmes that there should be a big international roll out, they are driven by the idea that market forces should prevail, but we’re talking about farmers that aren’t part of the market force-driven economy. I learnt this from my colleagues and from working in Africa, and what these farmers can do is use the push-pull system really very well.
And you often find people know things that you don’t expect them to know. If it hadn’t been for farmers saying they wanted a legume as an intercrop, we wouldn’t now know that Desmodium can control Striga. Some farmers even went to vegetative propagation with Desmodium. They thought, because it looks like sweet potato, they could put cuttings straight into the ground. Well, I said “No, it’s not Convolvulaceae, this is Fabacae, they’re not similar”, but the farmers showed us that it worked, against my and the team’s expectations. If it hadn’t been for them, naively perhaps, trying to propagate Desmodium vegetatively, we wouldn’t know you could do this.
Policies and politicians
A lot of the NGOs and agencies fund projects that tend to cause farmers to move too quickly away from subsistence. If you cause farms to get bigger, which is the usual result if you put in new technology like growing soya, hybrid or high-protein maize or tomatoes, or if you irrigate, that coalescence of farms dispossesses people from this rural economy.
We need to keep these people on their land and allow them to use appropriate technology to improve their lot beyond subsistence – something I think the aid community is slow to appreciate. There was a wonderful speech by Akinwumi Adesina, head of the Gates Foundation agricultural programme, in which he emphasised the point that we must not encourage more displacement of poor rural communities by causing farms to get bigger by using conventional technology (ref 3).
Conventional technology is not sustainable globally and certainly not sustainable for Africa. We can’t just go forward, as Bob May said when he was president of the Royal Society, with the same technology that we have now. The hybrid seeds are great, fertilizers are great, pesticides are great, but we have to look at new technology and we have to deliver much more via locally propagated seed and plants generally.
Zeyaur Khan, left, has done much work to develop the push-pull system
There’s a misunderstanding of what these farmers are. People think they are like our farmers but just not very efficient, and so they should move on by buying hybrid seed, fertiliser and pesticides. But you are talking to what is, in economic terms, a peasant farmer – they don’t buy things because they don’t sell.
It’s quite a battle. I’m a part of it and my African colleagues are part of it. I have great hope that people will realise this push-pull approach, or ‘vuta sukuma’ (actually pull-push) in kiSwahili, embodies something that can be used by subsistence farmers but will move them to a higher level of production – without having to buy the farm next door and dispossess their neighbours.
Politicians around the world and many aid agencies would like all farmers to be like British farmers: producing lots of material, very cheaply, very cost effectively and where it’s needed, but that is not the formula for a very high rural population. Really, Africa needs a new paradigm – it has to be technology that relates to their needs.
The barrier is in convincing people that these subsistence farmers shouldn’t be dispensed with and packed off to town to become poor industrial workers. They do need to stay where they are and if they are going to do that, they need to get more out of the land, not less, and this will have to be dealt with by having the inputs being appropriate, locally produced, and not giving off a large carbon footprint.
Profile: John Pickett
Professor John Pickett is the Director of the Centre for Sustainable Pest and Disease Management, based at Rothamsted Research in Harpenden, UK, where he has worked since 1976. Following BSc and PhD degrees from the University of Surrey, his work has focused on characterising insect pheromones and how plant semiochemicals can influence insect behaviour.
John was awarded the 2008 Wolf Foundation Prize in Agriculture in 2008 and delivered the Royal Society Croonian Lecture in 2008. He was awarded a CBE in 2004 for services to biological chemistry.
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- Intercropping increases parasitism of pests (external link)
- http://www.push-pull.net/publications.shtml (external link)
- http://www.scienceforum2009.nl/Portals/11/Adesina-pres.pdf (external link, PDF)
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