Field Control of Maize Borers Using Aqueous Seed Extracts of Thevetia Peruviana (Pers.) K. Schum

Aims: In order to find an alternative to chemical control, the insecticidal potential of aqueous extracts of Thevetia peruviana seeds formulated at 16.66 g/l were tested in the field on the maize stalk borer species.

Study Design: The factorial design in subdivided plots or "split-plot" with four replicates and two factors studies was used on an area of 250 m2.

Place and Duration of Study: The experiment was carried out in a field located in the city of Yaounde, Cameroon where cassava was grown beforehand, between July and October 2021.

Methodology: The extracts at 250 g per 15 l of water were tested against a synthetic insecticide Cypercal at 37.5 ml per 5 l of water and an absolute control (untreated) in a four replicate split-plot device. Two maize varieties (V1: CMS 8704; V2: local) and three treatments (T1: control; T2: T. peruviana seed extract; T3: Cypercal 12 EC) were used. The aqueous extract of T. peruviana was applied by spraying on stems, leaves and leaf cones from 5th to 9th weeks after sowing (SAS). Data were recorded on growth parameters, stem borer density, and maize grain yield.

Results: The results show that the application of the treatments resulted in a good development of the growth parameters in the two maize varieties used. Two species of borer Busseola fusca and Sesamia calamistis belonging to the order Lepidoptera were identified. The density of maize stalk borers was significantly reduced (T2: 3 borers) in the subplots treated with aqueous extracts compared to the control (T1: 10 borers). Treatment T2 (2.05 t/ha) gave higher grain yield than the control (1.41 t/ha).

Conclusion: The aqueous extracts of T. peruviana seeds having thus shown a strong insect repellent potential in the field can therefore be integrated into the framework of biological control that protects the environment and human health.