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Exploiting phytochemicals for developing a 'push-pull' crop protection strategy for cereal farmers in Africa.

Authors
  • Khan, Zeyaur R1
  • Midega, Charles A O
  • Bruce, Toby J A
  • Hooper, Antony M
  • Pickett, John A
  • 1 International Centre of Insect Physiology and Ecology, PO Box 30772, Nairobi, Kenya. , (Kenya)
Type
Published Article
Journal
Journal of Experimental Botany
Publisher
Oxford University Press
Publication Date
Oct 01, 2010
Volume
61
Issue
15
Pages
4185–4196
Identifiers
DOI: 10.1093/jxb/erq229
PMID: 20670998
Source
Medline
License
Unknown

Abstract

Lepidopteran stemborers and parasitic weeds in the genus Striga are major constraints to efficient production of cereals, the most important staple food crops in Africa. Smallholder farmers are resource constrained and unable to afford expensive chemicals for crop protection. Development of a push-pull approach for integrated pest and weed management is reviewed here. Appropriate plants were discovered that naturally emit signalling chemicals (semiochemicals). Plants highly attractive for egg laying by stemborer pests were selected and employed as trap crops (pull), to draw pests away from the main crop. Of these, Napier grass, Pennisetum purpureum (Schumach), despite its attractiveness, supported minimal survival of the pests' immature stages. Plants that repelled stemborer pests, notably molasses grass, Melinis minutiflora P. Beauv., and forage legumes in the genus Desmodium, were selected as intercrops (push). Desmodium intercrops suppress Striga hermonthica (Del.) Benth. through an allelopathic mechanism. Their root exudates contain novel flavonoid compounds, which stimulate suicidal germination of S. hermonthica seeds and dramatically inhibit its attachment to host roots. The companion crops provide valuable forage for farm animals while the leguminous intercrops also improve soil fertility and moisture retention. The system is appropriate 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 more than 30,000 smallholder farmers in East Africa where maize yields have increased from ∼1 t ha(-1) to 3.5 t ha(-1). Future directions for semiochemical delivery by plants including biotechnological opportunities are discussed.

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