Ovicide and Larvicide Activities of the Essential Oils Extracted from Polyalthia longifolia and Clausena anisata on Sitotroga cerealella

This work has objectives to study the chemical composition of volatile extracts obtained from leaves of Polyalthia longifolia and Clausena anisata and to evaluate their ovicide and larvicide effects by fumigation against Sitotroga cerealella, as alternative to the pesticides of synthesis. The analyses of the extracts by GC-MS showed that the essential oil of P. longifolia contains 57 compounds representing 86.1% of oil and 26 compounds corresponding to 97.3% of the essential oil of C. anisata. The main compounds identified for the extract of P. longifolia are the β-Caryophyllene (24.5%), Allo-Aromadendrene (13.5%), the α-Zingiberene (9.4%), the α-Humulene (8.5%) and the α-Selinene (2.6%). The extract of C. anisata mainly composed of methyl chavicol (69.9%) is characterized by the presence of oxygenated monoterpens (1.4%), hydrogenated monoterpens (7.8%), hydrogenated sesquiterpens (16.2%), oxygenated sesquiterpens (1.7%) and of aromatic compounds (69.9%). The biological test results showed that the treatments by fumigation done with the essential oils reduce meaningfully (p<0.001) the bursting of the ovums on the paddy rice. The essential oil of C. anisata has completely inhibited the viability of the larvas and the emergence of adult butterflies from the dose 0.5 µl mL^-1 contrary to P. longifolia that recorded respectively 10.0±0.3% and 50.0±0.2% at the strong dose 3 µl mL^-1. The study has, otherwise, shown that the essential oils delayed the cycle of development “ovums to adult” of S. cerealella (29.0±0.4 to 35.4±0.5 days) in relation to the witness (25±0.1 days). The essential oil of C. anisata proved to be more poisonous for the juvenile stages of S. cerealella. These results provide the scientific basis for potential alternatives to the synthetic fumigants in subsistence and commercial agriculture.