Pesticidal plants for stored product pests on small-holder farms in Africa

Despite the near elimination of pests from food stores in industrialised nations, insects are still the most important challenge to food security for small-holder farmers in less developed nations. Losses are frequently as high as 20 %. Synthetic products provide effective control when used correctly but are not sustainable or universally appropriate and present many challenges for farmers, not least of all their cost. Pesticidal plants offer an economic, effective and often the only alternative. Much published research, however, overlooks critical knowledge gaps providing outputs that are unlikely to improve pesticidal plant use or improve food security. This chapter identifies opportunities for better targeted research and improvements for uptake and use of pesticidal plants. We also highlight how a deeper understanding of different morphs, gender and age of insect can influence experimental results and should be considered more carefully. To be effective plant materials need to show low animal and environmental toxicity at typical application levels but at the same time be effective against a wide range of target species, at low doses and with longevity. They must also be low cost, safe, compatible with other pest management technologies and stable and have no consequences for the stored products such as impairing flavour. Research should be targeted at optimising the efficacy of the pesticidal plants already known to have potential, and this should be supported by chemistry to fully understand spatial, temporal and phenotypic variability and nontarget impacts. Availability of plants is a limiting factor to uptake so propagation and cultivation of elite provenances would alleviate pressure on natural ecosystems and improve reliability of efficacy and supply when supported by improved harvesting techniques. The large-scale commercialisation of plants may not compete with synthetic products globally but local production may foster a mechanism to support and encourage uptake through local markets and value chains