It is within this context that recent efforts have been made by many governments to promote research focussing more on the promotion of food crops. This involves a more radical focus on alternative methods to the use of pesticides. These methods are more natural and better thought out, being based on a greater respect for nature and farmers’ knowledge of traditional farming methods. Given the fact that the use of pesticides cannot be abandoned overnight, the focus here is on “integrated” crop management. However, the long-term objective is to bring about an end to the use of pesticides wherever possible, thus reducing not only public health risks and environment damage, but also agricultural costs.
Given his intimate knowledge of Senegalese agriculture and his keen interest in observing traditional farming practices in that country, Dr Guèye has examined the possibility of using local plants for the purposes of crop protection. During an initial experiment conducted in the laboratory, he demonstrated that maize harvests, traditionally stored in granaries in rural areas (generally made from bamboo poles, branches and cow dung), can be effectively protected against pests – especially the maize weevil – through the use of a powder made by crushing empty plant husks (cobs). There is nothing revolutionary in this as the practice is well known to farmers, in certain regions at least. The real innovation here is the fact that the conditions for ensuring the maximum efficacy of this method have been achieved, and that this method may be almost as effective as the most commonly used chemical pesticide (Actellic).
“When the grains are left without any protection, we can, on average, expect damage to the crops to be as high as 40% after four months of storage (in the case of infestation by the maize weevil alone)”, Dr Guèye explains. “But if you store the grains with maize cobs, the situation changes radically. If the weight of the cobs incorporated into the harvest is limited to 0.8% of the total weight of the stored foodstuffs, 15% of the harvest will be damaged and the farmer can expect losses of 5%. On the other hand, if the proportion of cobs is increased to 4% of the total weight of the harvest, the damage level will drop to 1% and losses will be reduced to 0,3%. The use of a natural product therefore ensures protection for almost the total harvest, thus matching the chemical pesticide in terms of damage reduction, but without the associated disadvantages! These results have been confirmed outside the laboratory, in real conditions, through observations made both in traditional farmers’ granaries and in granaries that were built for specific experimental purposes (in the Kédougou region, east of the country).”
Then Dr Guèye examined the role played by Boscia Senegalensis in crop protection. Capable of reaching heights of up to two or three metres, this shrub is very widespread in the dry areas of Senegal. The plant is widely used for medicinal purposes or as a foodstuff. “Previous work – carried out by Dogo Seck (2) – has demonstrated the role played by the release of methyl isothiocyanate from the enzymatic breakdown of a precursor (glucocapparin) in pest poisoning: when Boscia senegalensis is damaged by an insect sting, for example, methyl isothiocyanate (a secondary metabolite serving to defend the plant) is emitted into the atmosphere. When the insect inhales this compound, it becomes poisoned. As Boscia is known to provide effective protection for cowpea and peanut crops against pea weevils (a family of beetles that is particularly damaging to the crops), the testing of the efficacy of this plant against other pests that cause damage to seed stocks is recommended. It would also be advisable to investigate variability in efficacy of Boscia according to its geographical origin, physiological specificities and the harvest period.”
