and improvement in the sustainable use of natural resources.
The strategy provides several benefits, directly or indirectly
contributing to the livelihoods of rural families. Such
opportunities include:
Improving food security
Push-Pull has increased maize yields of farmers in Kenya by
an average of 20 - 30 percent in areas with only stemborers
(Trans Nzoia district), and by more than 100 percent in areas
with both stemborers and Striga (e.g. Vihiga, Siaya, Suba and
Migori districts). This has been a key incentive for its increased
adoption.
Reduced soil erosion and increased soil fertility
By providing a good ground cover, the strategy improves
soil conservation. Through nitrogen fixation, the strategy
reduces the required amount of nitrogen fertilizers, which are
unaffordable by most smallholder farmers. A long-term study at
ICIPE’s on-station fields in Mbita, western Kenya, has shown a
significant increase in total nitrogen on field plots under maize-
Desmodium intercropping for three years, especially when
compared to maize fields intercropped with other legumes.
Enhanced biodiversity
The Push-Pull strategy promotes and conserves biodiversity by
maintaining species diversity. This, in turn, improves natural
and agricultural ecosystems by contributing to ecosystem
services such as nutrient cycling and decomposition. This helps
in developing sustainable crop protection systems which rely
less on pesticides. A study conducted in Lambwe Valley (Suba
district, Kenya) shows that the strategy is associated with an
overall enhancement of beneficial predators, which is important
in agricultural systems.
Livestock production and human health
Unstable availability and seasonality of livestock feed have
been major constraints to improving dairy livestock in Eastern
Africa. Push-Pull provides quality fodder for livestock. On
small farms where land pressure is high, this is likely to
improve the health of farming families, especially children.
Improved dairy cows and goats are emerging as important
income alternatives for smallholder farmers.
Protecting fragile environments
Higher crop yields and improved livestock production, resulting
from habitat management strategies, have the potential to
support rural households under existing circumstances. This can
slow the migration of rural populations to areas designated for
protection. Moreover, farmers using such strategies have less
reason to use pesticides that could affect flora and fauna in the
agro-ecosystem.
Income generation and gender empowerment
Push-Pull has shown promising impacts of not only enhancing
farm incomes but also empowering rural women. It provides
alternative income sources, as surplus grain, fodder and
Desmodium seed can be sold. It also has potential for
improving the quality of rural life as more partners interact with
farmers to disseminate it to other farmers.
Push-Pull dissemination to smallholder farmers
The Push-Pull strategy has been adopted by more than 10 000
households in 19 districts in Kenya, five districts in Uganda,
David Amudavi, Zeyaur Khan and John Pickett
Millions of rural people in Eastern Africa depend on maize
and sorghum for food security and cash income. Despite this,
production of these crops is seriously affected by constraints such
as stemborers, the parasitic weed Striga hermonthica, low and
declining soil fertility, lack of knowledge on how to manage these
pests and weaknesses in the extension system. Stemborers lead
to yield losses of 30 - 40 percent, while Striga infestation causes
a loss of 30 - 50 percent to Africa’s agricultural economy on 40
percent of its arable land. Although chemical control is usually
recommended, it is uneconomical and impractical for many small-
scale farmers, and has negative impacts on the environment and
human health. On the other hand, the commonly used cultural
method of uprooting Striga is labour-intensive and less effective.
Adoption of effective control methods is limited due to lack of
labour, little knowledge about the pest problems, and lack of other
resources needed to make the necessary investments.
Affordable alternative strategies are needed to combat the
growing threats to the smallholders’ livelihoods. One such
method is the “Push-Pull” strategy. This combines knowledge of
the chemical ecology and agro-biodiversity of the stemborer, with
Striga management. This strategy 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 research organisations in
Eastern Africa. A first article about Push-Pull in LEISA Magazine
(Vol.17 No.4, December 2001) presents it as a viable “organic”
alternative to genetically modified maize (Bt maize). This article
explains how the Push-Pull strategy has been adopted by farmers
in Kenya since then.
How does the Push-Pull strategy work?
Push-Pull uses a combination of legume repellent plants to deter
the pest from the main crop (“push”) and trap crops to attract
the repelled pest (“pull”). Molasses grass (Melinis minutiflora)
and Desmodium (Desmodium uncinatum) are the common
repellents, whereas Napier grass (Pennisetum purpureum) and
Sudan grass (Sorghum vulgare var. sudanense) are the common
trap plants. Research has shown that the repellent plants produce
chemical compounds, some of which repel the stemborer pests.
On the other hand, during dusk Napier grass produces other
chemical substances that evaporate easily, some of which are good
attractants for stemborers to lay eggs. Fortunately, Napier grass
produces a gummy substance which traps the resulting stemborer
larvae, and only few survive to adulthood, thus reducing their
population.
Push-Pull also suppresses and eliminates the Striga weed through
several mechanisms, including nitrogen fixation, soil shading and
allelopathy. Allelopathy is where one plant harms another with
chemical substances: Desmodium roots produce such chemical
compounds. Some of these compounds stimulate Striga seeds to
germinate but others inhibit lateral growth and the attachment of
the Striga roots on to maize roots. The Striga dies, and eventually
the number of Striga seeds in the soil decreases. As Desmodium is
a perennial crop, it controls Striga even when the host crop is out
of season, making it a better repellent than other legumes.
Opportunities for diversifying livelihoods
The Push-Pull strategy is a good case of how basic research
can contribute to the enhancement of agricultural productivity
Enhancing the Push-Pull strategy
LEISA MAGAZINE 23.4 DECEMBER 2007
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