Achieving food security for one million sub-Saharan African poor through push-pull innovation by 2020

Abstract

Food insecurity is a chronic problem in Africa and is likely to worsen with climate change and population growth. It is largely due to poor yields of the cereal crops caused by factors including stemborer pests, striga weeds and degraded soils. A platform technology, 'push-pull', based on locally available companion plants, effectively addresses these constraints resulting in substantial grain yield increases. It involves intercropping cereal crops with a forage legume, desmodium, and planting Napier grass as a border crop. Desmodium repels stemborer moths (push), and attracts their natural enemies, while Napier grass attracts them (pull). Desmodium is very effective in suppressing striga weed while improving soil fertility through nitrogen fixation and improved organic matter content. Both companion plants provide high-value animal fodder, facilitating milk production and diversifying farmers' income sources. To extend these benefits to drier areas and ensure long-term sustainability of the technology in view of climate change, drought-tolerant trap and intercrop plants are being identified. Studies show that the locally commercial brachiaria cv mulato (trap crop) and greenleaf desmodium (intercrop) can tolerate long droughts. New on-farm field trials show that using these two companion crops in adapted push-pull technology provides effective control of stemborers and striga weeds, resulting in significant grain yield increases. Effective multi-level partnerships have been established with national agricultural research and extension systems, non-governmental organizations and other stakeholders to enhance dissemination of the technology with a goal of reaching one million farm households in the region by 2020. These will be supported by an efficient desmodium seed production and distribution system in eastern Africa, relevant policies and stakeholder training and capacity development.

Keywords: climate change; food security; pests; push–pull technology; sub-Saharan Africa.

Figure 1.

How the push–pull system works: stemborer moths are repelled by intercrop volatiles while attracted to trap crop volatiles. Root exudates from the desmodium intercrop cause suicidal germination of striga and inhibits attachment to maize roots. 1, (E)-β-ocimene; 2, α-terpinolene; 3, β-caryophyllene; 4, humulene; 5, (E)-4,8-dimethyl-1,3,7-nonatriene; 6, α-cedrene; 7, hexanal; 8, (E)-2-hexenal; 9, (Z)-3-hexen-1-ol; 10, (Z)-3-hexen-1-yl acetate; 11, 5,7,2′,4′-tetrahydroxy-6-(3-methylbut-2-enyl)isoflavanone (uncinanone A); 12, 4′,5″-dihydro-5,2′,4′-trihydroxy-5″-isopropenylfurano-(2″,3″;7,6)-isoflavanone (uncinanone B); 13, 4″,5″-dihydro-2’-methoxy-5,4′-dihydroxy-5″-isopropenylfurano-(2″,3″;7,6)-isoflavanone (uncinanone C) and 14, di-C-glycosylflavone 6-C-α-l-arabinopyranosyl-8-C-β-d-glucopyranosylapigenin. Adapted with permission from Khan et al. [59]

Figure 2.

Push–pull technology adoption has significantly increased because of its multiple benefits. (Online version in colour.)

Figure 3.

Mean (±s.e.) % stemborer-damaged plants, emerged S. hermonthica per 50 maize plants in each plot and grain yields (t ha⁻¹) of sorghum and maize planted within a climate-adapted push–pull plot or a sole stand in Bondo and Siaya districts of western Kenya. Means represent data averages of 10 farmers’ fields. In both crops and districts mean % stemborer-damaged plants and emerged S. hermonthica were significantly higher in the monocrop than in the push–pull plots. Grain yields were however significantly higher in the push–pull than in the monocrop plots in both crops and districts.