Food for All - Agri-culture: Reconnecting People, Land and Nature - page 94

as he says: 'We do not know how much this has spread to other farmers.' I asked him
what he thought was the most significant element of success, and it is clear
again that farmers have crossed a frontier:
CARE was able to change the behaviour of participating farmers with regard to
irrational use of fertilizers and unwise use of insecticides, and they now have an
improved understanding of ecology. They now take decisions based on careful study
of their farms.
Once we start with the idea that diverse systems can provide enough food,
particularly for farmers with few resources, then whole new fields of
scientific endeavour can emerge. One of these is the science of semio-
chemicals , aromatic compounds given off by plants. In East Africa, Hans
Herren, winner of the World Food Prize for work on a parasite to control
the cassava mealybug, is director of the International Centre for Insect
Physiology and Ecology. He believes that minimum- to zero-pesticide
farming systems are possible throughout the tropics, and his centre is
researching sustainable pest management through biological control, using
one organism to control another, botanical agents for natural pest-control
compounds derived from plants, habitat management, and pest-tolerant
varieties of food crops.
In Kenya, researchers from the International Centre for Insect Physiology
and Ecology (ICIPE) and Rothamsted in the UK found that maize
produces semiochemicals when fed upon by the stem borer ( Chilo spp.).
They also found that these same chemicals increase foraging and attack
by parasitic wasps, and are fortuitously also released by a variety of local
grasses used for livestock fodder and soil erosion control. 26 The inter-
actions are complex. Napier and sudan grass attract stem borers to lay their
eggs on the grass instead of the maize. Another grass, molasses grass, and
a legume, Desmodium , repel stem borers. Both napier and molasses grass
emit another chemical that summons the borers' natural enemies, so that
pest meets predator. There is yet more, as Desmodium not only fixes nitrogen
but is allelopathic (toxic) to the parasitic witchweed Striga hermonthica .
Researchers call their redesigned and diverse maize fields vutu sukumu :
push-pull in Swahili. They clearly work, as more than 2000 farmers in
western Kenya have adopted maize, grass-strip and legume-intercropping
systems, and have at the same time increased maize yields by 60 to 70 cent.
The sad truth is that for 30 years, the official advice to maize growers in
the tropics has been to create monocultures for modern varieties of maize,
and then apply pesticide and fertilizers to make them productive. Yet, this
agricultural simplification eliminated vital and free pest management
services produced by the grasses and legumes. Vutu sukumu systems are