Are bioinsecticides able to effectively substitute chemicals in the control of insect pests of okra (Abelmoschus esculentus L. Moench) in Cote d'Ivoire?

Abstract

Objective: Okra (Abelmoschus esculentus, Malavaceae) production faces pest and disease attacks that leads to use of chemical pesticides. This study was performed to compare effectiveness of the bioinsecticide Levo 2.4 SL (Oxymatrin 2% and Prosular 0.4%) to the chemical pesticides Abalone 18 EC (Abamectin 18g/l) and Viper 46 EC (Acetamiprid 16g/l and Indoxacarb 30g/l) against okra insect pests in Cote d'Ivoire. Methodology and Results: So a field experiment was carried out at Bonoua (05°16'17N; 03°35'40 W) in the South East of Cote d’Ivoire, in a Randomized Complete Block Design (RCBD) with four replications and four treatments; Levo 2.4 SL, Abalone 18 EC, Viper 46 EC and the Control. Insect communities, damages and yield profit rate were assessed and analyzed with Statistica 7.1 at 5%. The inventory of insect allowed the identification of 28 species distributed into 19 families and 10 orders. The main pest insects observed were Hemiptera; Aphis gossypii (41.59%), Bemisia tabaci (39.11%), Jacobiasca sp (1.26%) and Dysdercus wolkerii (1.44%), Coleoptera; Podagrica decolorata (9.03%) and caterpillars of Lepidoptera; Syllepte derogate (1.36%). Then control plots presented no healthy plants (0%), while the bioinsecticide (Levo 2.4 SL), and the chemical insecticides; Abalone 18 EC and Viper 46 EC presented respectively 60%, 77.5% and 90% of healthy plants (index 0). Overall, the effectiveness of the bioinsecticide to control insect pests appeared similar to those of the chemical pesticides. However, Levo 2.4 SL seems to be less effective against Aphis gossypii and Dysdercus wolkerii populations. Highest fruit yield of okra was recorded in treated plot with Viper 46 EC (12.55±0.98 t/ha), followed by Abalone 18 EC (12.2±0.8 t/ha) and Levo 2.4 SL (11.15±1.09 t/ha). Whereas, the lowest yield obtained from control plots was 6.84±0.15 t/ha. The yield profit rates were 62.82; 78.18 and 83.28% respectively for Levo 2.4 SL, Abalone 18 EC and Viper 46 EC when compared to the control. The control of insect pests by the bioinsecticide and the chemical insecticides increased significantly the okra yield. Conclusion and application of Results: Therefore, the bioinsecticide can be eco-friendly alternative to control insect pest of okra in Cote d’Ivoire. Then, the bioinsecticide Levo 2.4 SL can be proposed to limit damages caused by chemicals on the environment and human health.Keywords: Bioinsecticide, Levo 2.4 SL, Abelmoschus esculentus, insect pests, Cote d’Ivoire.