Essential oils of aromatic plants with insecticidal properties are nowadays considered as alternative insecticides to protect stored products from attack by insect pests. A combination of some of these plants in the granaries is a current practice in certain localities of northern Cameroon. The aim of the present work was to analyze the impact of the combinations of the essential oils of Vepris heterophylla (Rutaceae), Ocimum canum, and Hyptis spicigera (both Lamiaceae), the three most used local aromatic plants because of their insecticidal activity and their repellent effect on Sitophilus oryzae. The present work revealed that these plants are rich in monoterpenoids. The GC/MS analyses have shown that monoterpenoids represented 65.5% for H. spicigera, 92.1% for O. canum and 47.0% for V. heterophylla. The crude essential oil of O. canum was the most insecticidal with a LD 50 of 42.9 ppm. The most repellent effect was obtained by a combination of the essential oils of H. spicigera and O. canum, with a repellent percentage at 77.5%. These results suggest a suitable strategy for pest management of stored products.
The warehouse pirate bug Xylocoris flavipes is an opportunist predator of many stored product insect pests. Its functional response in relationship with variable densities of prey appears as the Holling's type II model. The predator X. flavipes, collected within small holder granaries in Mayo Danay division in the far North province of Cameroon, feeds on Tribolium castaneum (Herbst) and could perform a good biological control of this pest.
To sustain agricultural production, pesticides are highly recommanded. In sub-Saharan Africa, two regulatory bodies are in charge of pesticide registration, for more than 10 years of duty, the impact of their activity has not yet best carried out. The present investigation aimed to evaluate the evolution in the quality of pesticides in agriculture in sub-Saharan Africa. Registration of pesticides began in Cameroon in 1996. There, less than 5% of pesticides used in 2004 were registered and more than 80% of producers were not aware of this legal process. In 2014, 85% of pesticides used are registered. In sub-Saharan Africa, Highly Hazardous Pesticides (HHPs) registered are rondenticides, insecticides and nematocides. They are frequently used for the protection of stored products. Ilicit Persistent Organic Pollutants (POPs) (heptachlore, chlorobenzene) and HHP (alluminium phosphide, terbufos, abamectine, ethropophos, etc.) are frequently used to protect stored grains. And 40% are registered for use in intensive bananas production (28% for nematodes control alone and 10% for control of both insects and nematodes). Moreover, 20% of HHPs registered are for the control of rondents.
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