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

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

Impact of Soil Fertility Management Practices on Insect Pests and Diseases of Maize in Southwest Cote d’Ivoire

Objectives: Integrated soil fertility management (ISFM) is essential for sustainable management of tropical soils. However, soil fertility management is able to affect plant susceptibility to pests and diseases. The study investigated impact of soil fertilization practices on maize pests and diseases during two identical and simultaneous trials setup in South-West Cote d'Ivoire.Methodology and Results: Experiments were laid out using complete randomized block designs with three replicates and four treatments: (1) control; (2) chemical fertilization; (3) fertilization with cattle manure; (4) association “maize + legume” combined with chemical fertilization. Overall, 22 insect species collected and two diseases (maize streak disease and curvularia leaf spots) observed at both sites. Only cattle manure clearly increased pest and disease damages. The use of cattle manure significantly increased leaf infestation rate and maize streak disease frequency at both sites. Similar impact of NPK and cattle manure was obtained on maize yields either in monocropping or in mix cropping.Conclusions and application of findings: This study clearly confirmed that ISFM is able to affect plant susceptibility to pests and diseases. Cattle manure attracted a diversity of insects of diverse functional groups such as air-borne pests. These latter affected some plant parts; in this case, maize leaves which infestation rate significantly increased. This attraction for multitude insects may increase vector-borne diseases such as maize streak which frequency significantly increased at both sites. Consequently, despite the potential of cattle manure to increase maize yield, their use as organic fertilizer requires to take some precautions. So, the promotion of cattle manure as organic fertilizer in substitution of chemical fertilizer in tropical regions where it is available is encouraged. However, it should be converted into compost or pre-treated for optimal use in agriculture. Finally, mix cropping could be suggested for optimization of economic profit.Keywords: Maize, leaf infestation, maize streak disease, soil fertility management, cattle manur

A native arbuscular mycorrhizal fungus inoculant outcompetes an exotic commercial species under two contrasting yam field conditions

This study aimed to assess the performance of an indigenous arbuscular mycorrhizal fungus (AMF) inoculant isolated from yam rhizosphere on yam (Dioscorea rotundata Poir.) growth and yield in field conditions. For this purpose, a factorial experiment was carried out in two contrasting agricultural soils located in Duokro and INPHB in Yamoussoukro, Côte d’Ivoire. The Duokro soil was neutral sandy loam with high nutrient content and an established AMF community dominated by Glomeraceae whereas the INP-HB soil was acidic sand with low nutrient content and codominance of Glomeraceae and Paraglomeraceae. The inoculation treatments were two native AMF species, namely Rhizophagus irregularis (Blaszk., Wubet, Renker & Buscot) isolated from yam rhizosphere and Acaulospora colombiana (Spain & N.C. Schenck) isolated from cassava rhizosphere, applied singly or together, and Rhizophagus intraradices (N.C. Schenck & G.S. Sm.), an exotic commercial species. Mycorrhizal colonization frequencies of inoculated yam plants were substantially higher at Duokro than INP-HB. As consequence, all the growth and yield parameters measured were higher at Duokro than at INP-HB. Plants inoculated with the native inoculant R. irregularis had the highest mycorrhizal frequencies, the best growth and tuber production at both sites. Moreover, the exotic commercial inoculant was outcompeted by the native inoculants. R. irregularis appeared therefore to be a good candidate for commercialization as an inoculant for yam crops

Mutualism between euryhaline tilapia Sarotherodon melanotheron heudelotii and Chlorella sp. – implications for nano-algal production in warmwater phytoplankton-based recirculating systems

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