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This paper describes the ‘push–pull’ or ‘stimulo-deterrent diversionary’ strategy in relation to current and potential examples from our own experiences. The push–pull effect is established by exploiting semiochemicals to repel insect pests from the crop (‘push’) and to attract them into trap crops (‘pull’). The systems exemplified here have been developed for subsistence farming in Africa and delivery of the semiochemicals is entirely by companion cropping, i.e. intercropping for the push and trap cropping for the pull. The main target was a series of lepidopterous pests attacking maize and other cereals. Although the area given to the cereal crop itself is reduced under the push–pull system, higher yields are produced per unit area. An important spin-off from the project is that the companion crops are valuable forage for farm animals. Leguminous intercrops also provide advantages with regard to plant nutrition and some of the trap crops help with water retention and in reducing land erosion. A major benefit is that certain intercrop plants provide dramatic control of the African witchweed (striga). Animal husbandry forms an essential part of intensive subsistence agriculture in Africa and developments using analogous push–pull control strategies for insect pests of cattle are exemplified. [ABSTRACT FROM AUTHOR]

The khat plant contains psychoactive alkaloids with psychostimulant properties, and has been used for centuries as a recreational and religious drug, mainly in some African and Middle Eastern countries. With changing migration patterns, epidemiological and clinical outcomes may have changed. The aim of this article is to review current knowledge on pharmacological, epidemiological and clinical aspects of khat use. Khat use is still highly prevalent in the countries mentioned, and in African and Yemeni emigrant groups. Preclinical and clinical data confirm its addictive potential as well as possible psychological, psychiatric and medical consequences related to stimulant use; however, existing epidemiological studies do not focus on the prevalence of problematic use or dependence. There are no indications of high prevalence of khat use in other cultural and ethnic groups. Data are lacking on possible increased psychotogenic risks when khat is used outside of the original cultural context. As with alcohol use in many countries, khat use can be considered as a lifestyle in some specific countries, covering the spectrum from nonproblematic use to problematic use and dependence. Khat dependence is associated with high morbidity and societal and economical costs.