Comparative Study of the Efficacy of Two Biological Insecticides (Azadirachta indica and Bacillus thuringiensis) and a Chemical insecticide (Diflubenzuron WP) against Fall Armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae) in Maize Crop, Western Bur

Abstract

Aims: This study aimed at comparing the biological efficacy of Diflubenzuron WP, a chemical insecticide, and two biopesticides, one based on neem oil (Azadirachta indica) and an entomopathogen (Bacillus thuringiensis) against the fall armyworm on maize. Place and Duration of Study: The work was carried out on the irrigated scheme of Bama, western Burkina Faso during the 2022 and 2023 wet seasons. Methodology: The experimental design was a Fisher block with 4 treatments: T0: untreated or control; T1: Bacillus thuringiensis; T2: neem oil; T3: Diflubenzuron WP, in 4 replications. Entomological observations focused on the score and severity of attacks, as well as the pest's infestations rate. Results: The results showed that the different insecticides tested over the two wet seasons of 2022 and 2023 induced better control of S. frugiperda populations, with larval density being kept lower with the treatment of Diflubenzuron WP (4.25±1.2%), neem oil (14.28±1.6%) and Bacillus thuringiensis (24.5±3.2%). The insect damage severity rates and scores of damaged ears were also low for the three treatments respectively (1.09±0.2, 0.9±0.26 and 0.27±0.71) over the two cropping seasons. Diflubenzuron WP insecticide treatment not only reduced pest pressure, but also significantly improved maize yield.  No surprisingly the highest yield (5.14 t/ha) was recorded with Diflubenzuron WP, followed by neem oil (4.62kg/ha) and finally Bacillus thuringiensis (3.92kg/ha). Conclusion: Further studies are needed to determine the optimal doses of neem oil and Bt for the control of Fall Armyworm. Neem oil can be considered as a good alternative to a chemical insecticide like Diflubenzuron WP.