Bioactivity of flours of seeds of leguminous crops Pisum sativum, Phaseolus vulgaris and Glycine max used as botanical insecticides against Sitophilus oryzae Linnaeus (Coleoptera: Curculionidae) on sorghum grains
Cereals occupy an important place in the solving of food insecurity problems in the northern Cameroon. Chemicals continue to be the main tools to protect cereals during storage in spite of the deleterious effects due to their current usage. Nowadays, entomotoxic proteins of seeds of leguminous are more and more considered as alternative insecticides. Efficacy of crude flours of four legumes seeds, applied to the sorghum grains, was evaluated against Sitophilus oryzae L. (Coleoptrea: Curculionidae) by contact-ingestion. This research revealed that flours of bean and pea are very active on S. oryzae. The lethal dose 100 (LD100) and the lethal times 100 (LT100) are respectively 5 g and 20 days for pea’s flour and 10 g and 50 days for bean’s flour. The toxicity of flours’ seeds increased with the dose and the duration of application (F=169.734***, Df =6; 28). During a period of 90 days, the flours of P. sativum and P. vulgaris keep their insecticidal activities, showing constant mortality rates for bean (F= 2.325ns, Df =6; 28) and for pea (F=1,91ns, df= 34). The flours of seeds of P. sativum and P. vulgaris at the weight ratio of 5 % and 10 % respectively can provide protection of sorghum grains against the attack of S. oryzae. The legumes seeds are the alternative active ingredients to hazardous conventional insecticides.
Keywords: Cereals; leguminous plants; entomotoxic proteins; persistence; Sitophilus oryzae.