Push-pull cropping: fool the pests to feed the people

Crop yields have tripled in Africa with push-pull cropping, a simple system grown from complex science

Smallholder farmers in sub-Saharan Africa feed around 80% of a population that is approaching 1 billion people. And yet Striga weed and stemborer pests (caterpillars/moths) regularly threaten to wipe out their entire cereal crops at an estimated cost to the region of $7billion/year.

“Push-pull” is a simple but powerful response that relies on chemical signals to fool the invaders. The signals are produced naturally by two different plants that are sown among or around the crops of maize, sorghum and rice.

The “push” plant, grown among the crop, repels the stemborer and inhibits Striga; the “pull” plant, grown as a 2m-wide border around the crop, attracts and traps the stemborer. Desmodium, of which there is now a drought-tolerant variety, is the pusher; Napier grass or drought-tolerant Brachiaria grass is the puller.

Furthermore, these two companion plants provide nutritious animal fodder, for use on the farm or for sale; and the intercrop “push” plant, often Desmodium, enhances fertility and reduces degradation of the soil.

Appropriate and economical

The system, derived from work in chemical ecology, agrobiodiversity, plant-plant and insect-plant interactions, has been developed by Kenya’s International Centre of Insect Physiology and Ecology and Rothamsted Research. Smallholders, working up to 10 hectares of land, have seen yields rise from 1t/ha to 3.5t/ha.

Push-pull is appropriate and economical; it sits well with Africa’s mixed cropping systems and it is based on locally available plants. By 2017, more than 130,000 smallholders in Kenya, Uganda, Tanzania and Ethiopia had adopted the system, after a slow start in the late 1990s.

Climate-smart companions

Uptake has escalated since 2012 following development of climate-smart (drought-tolerant) companion plants, which more than 54,000 farms have adopted. They are mostly run by women, who traditionally do most of the manual labour and welcome the labour-saving system.

For more information
Contact: Michael Birkett
Read: Pickett & Khan 2016. New Phytologist 212: 856–870

Date: May 2017