Earth at Risk by Claude Henry

Author:Claude Henry
Language: eng
Format: epub
Tags: POL044000, Political Science/Public Policy/Environmental Policy, BUS068000, Business & Economics/Development/Economic Development
Publisher: Columbia University Press
Published: 2017-12-19T05:00:00+00:00

PUSH-PULL SYSTEMS: PROTECTING CROPS IN KENYA

A push-pull system is a biology-based method of protecting crops. In the example here, this system is used to protect maize in East Africa (the region’s main crop). It is the product of a joint project at the International Centre of Insect Physiology and Ecology (ICIPE, Kenya) and Rothamsted Research (UK), one of the longest running and most productive agricultural research stations in the world.14 The targets of the system are maize stem borers—the larvae of various moths that attack maize from within the stems. If left unchecked, stem borers can reduce yields by 20–40 percent and sometimes up to 80 percent. As research into the system progressed, a second target popped up by chance—or, more accurately, by recognition of an unexpected side effect. Striga hermonthica is a weed that is extremely difficult to eradicate by conventional methods, as it parasitizes the maize; the yield losses range from 30 to 100 percent in infested fields.

Pesticides are not very effective at reaching larvae inside stems. Thus, an all too common reaction is for farmers to increase the quantities applied, which results in more harm to soil biodiversity than to pests. Yet, the stakes are high; according to ICIPE (2015), “Preventing crop losses from stemborers could increase maize harvests by enough to feed an additional 27 million people in the region” (3). This was a strong motivation to try to find effective ways to at least keep the stem borer populations within limits so they cause little harm, while minimizing negative effects to soil and environment.

Researchers considered a few candidates for the push and a stunning 400 varieties of grass for the pull. Their research led to identification of a tree (a tree that also fixes nitrogen from the air as a bonus), called silverleaf desmodium, for the push, and two varieties of grass (Napier grass and Sudan grass) for the pull. These plants were selected for several interrelated reasons:

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