::'PUSH-PULL':: A Platform Technology for Improving Livelihoods of Resource Poor Farmers

Healthier maize crop in a push-pull farm

A Platform Technology for Improving Livelihoods of Resource Poor Farmers in Africa

Stemborers, striga weeds and poor soil fertility are the main constraints to efficient production of cereals in sub-Saharan Africa (SSA). Losses caused by stemborers can reach as high as 80% in some areas and an average of about 15-40% in others. Losses attributed to striga weeds range between 30 and 100% in most areas, and are often exacerbated by the low soil fertility prevalent in the region. When the two pests occur together, farmers often lose their entire crop. Spraying with pesticides is not only expensive and harmful to the environment, but usually ineffective as the chemicals cannot reach deep inside the plant stems where stemborer larvae reside. Crop losses caused by stemborers and striga weeds amount to about US $ 7 billion annually, affecting mostly the resource poor subsistence farmers. Preventing crop losses from stemborers and striga weeds, and improving soil fertility in eastern Africa could increase cereal harvests enough to feed an additional 27 million people in the region.

A conservation agricultural approach known as `push-pull' technology has been developed for integrated management of stemborers, striga weed and soil fertility. Push-pull was developed by scientists at the International Centre of Insect Physiology and Ecology (icipe), in Kenya and Rothamsted Research, in the United Kingdom, in collaboration with other national partners. The technology involves intercropping maize with a repellent plant, such as desmodium, and planting an attractive trap plant, such as Napier grass, as a border crop around this intercrop. Gravid stemborer females are repelled or deterred away from the target crop (push) by stimuli that mask host apparency while they are simultaneously attracted (pull) to the trap crop, leaving the target crop protected. Desmodium produces root exudates some of which stimulate the germination of striga seeds and others inhibit their growth after germination. This combination provides a novel means of in situ reduction of the striga seed bank in the soil through efficient suicidal germination even in the presence of graminaceous host plants. Desmodium is a perennial cover crop (live mulch) which is able to exert its striga control effect even when the host crop is out of season, and together with Napier grass protect fragile soils from erosion. It also fixes nitrogen, conserves soil moisture, enhances arthropod abundance and diversity and improves soil organic matter, thereby enabling cereal cropping systems to be more resilient and adaptable to climate change while providing essential environmental services, and making farming systems more robust and sustainable.

The technology is appropriate and economical to the resource-poor smallholder farmers in the region as it is based on locally available plants, not expensive external inputs, and fits well with traditional mixed cropping systems in Africa. To date it has been adopted by over 25,000 smallholder farmers in East Africa where maize yields have increased from about 1 t/ha to 3.5 t/ha, achieved with minimal inputs.