Plant-based extracts for cotton pest management in Sub-Saharan Africa: a review

Cotton crops are hampered by a complex of arthropod species, insects and mites that attack all plant organs. In sub-Saharan Africa, crop pest control mainly involves synthetic pesticide applications based on a treatment calendar consisting of 5–6 applications at 14-day intervals. Organic cotton production chains have however been set up to supply a niche market, with botanical extracts used for crop protection. This review presents published results of experiments conducted in sub-Saharan African countries. A total of 37 plant species were laboratory tested in research stations (24 trials) and village fields in Central and West African countries. Neem (Azadirachta indica) was the plant most commonly used in the form of seed-pressed oil. In Mali, this compound was combined with Carapa procera oil in organic cotton cropping conditions. Cassia nigricans is another species reported to be used in Mali, Burkina Faso and Benin. Aromatic species such as Ocimum gratissimum, Cymbopogon citratus, Citrus sp. were also tested. Further research could focus on species such as Anacardium occidentale and Hyptis suaveolens, which seem to be locally available. The use of essential oils does not appear to take priority over aqueous extracts, which could be tested in crop protection programmes involving partial substitution of synthetic insecticides.