Swiss scientist 's insect-control innovation prevents cassava disease

by Isobel Leybold

Insect expert Hans Rudolf Herren’s work in tackling the devastating cassava mealybug crop pest in Africa saved millions of lives and won him the 1995 World Food Prize.

Herren, the subject of a new biography, tells swissinfo.ch how he managed to naturally control the bug using a method that involved shooting the insect’s natural enemy, a type of wasp, from aeroplanes across huge swathes of Africa.

The scientist was only 31 when he took a job in the middle of a crisis: the mealybug was decimating Africa’s staple crop, cassava. After ten years, his radical, non-chemical solution had turned the situation around and averted a famine. He is so far the only Swiss to receive the World Food Prize.

Herren has since continued his research into insects and natural pest control in plants, animals and humans.

In 1998 he set up the Zurich-based Biovision foundation with friends, using money from his various prizes, to promote sustainable organic agriculture in Africa. He is also president of the non-profit Millennium Institute in Washington, which promotes sustainable development.

swissinfo.ch: The biography’s title is: How Hans Rudolf Herren saved 20 million people. How did you do this?

Hans Rudolf Herren: We knew that the mealybug was not of African origin. That’s actually one of the reasons it spread like wildfire after its introduction, because it had no natural enemies. Specialists decided it was a species from the New World and also from somewhere where cassava or any of its wild relatives would occur.

Cassava comes from the Amazon region so it was quite clear that somebody must have transported cuttings or plant material to Africa and brought the pest in. So the plan was to find where this mealybug had come from, check if there was anything useful you could connect to it and then bring this information back to Africa.

swissinfo.ch: So it was a lot of detective work.


H.R.H.: It was. What was interesting was that in all the many years scientists had studied cassava in Latin America, no one had seen the mealybug.

This seemed very strange to me. I thought it may actually be on one of the wild relatives of the crop. Eventually it was found in the border area of Brazil, Paraguay, and Bolivia, interestingly on cultivated cassava.




But no one had seen it there because it was a very low population. In the Americas there are very few mealybugs which meant something was keeping it under control.

swissinfo.ch: You found out that it was a type of wasp.

H.R.H.: Yes, it was a parasitoid wasp [which lays eggs into the bug, eventually killing it]. We had a big factory to produce hundreds and thousands of them and they were packaged in a way that they could be shot out of an airplane travelling at 300 kilometres per hour or more across Africa, from Senegal on one side to Mozambique on the other.

We were careful that it was specific to the cassava mealybug. Thirty years later, no problem has been created and the mealybug is still under control.

swissinfo.ch: Agriculture today still involves the use of many chemicals and even genetic technology. How does your vision of using nature’s tools fit in?


H.R.H.: The International Assessment of Agricultural Science and Technology for Development IAASTD report [published in 2008], of which I was co-chair, made clear that we needed a radical change to agriculture for both developed and developing countries.

The authors decided that we needed to change from this industrial, energy intensive agriculture and from the very traditional agriculture that has a low input and productivity towards a multifunctional, agro-ecological, organic type of agriculture which is self-regenerating.

Biovision was almost ahead of that report by promoting an ecologically-based agriculture, which is in harmony with the system, which doesn’t fight the environment but works with it, and which will produce enough to nourish everybody by 2050. I’m convinced we can do it. The question is can we actually implement it now?

Swiss Info