No abstract

In recent years, essential oils (EOs) as alternatives to synthetic pesticides in managing pests have been assessed. The use of bioinsecticide in pest management is encouraged in agroecology for a sustainable agricultural system. Essential oils of Lantana camara L. leaves from different climatic zones of Kenya were extracted by steam distillation and analyzed through GC-MS to identify the compounds. The contact toxicity and repellent activity of EOs against the invasive tomato pest, Tuta absoluta, were tested. The toxicological assays were performed following the leaf-dip bioassay protocol, while the repellency activity was performed using the repellent response method for phytophagous pests and the data analyzed using the ANOVA test. It was found that L. camara EO has a good insecticidal activity with higher mortality (89%) on the 2 nd instar larvae with a higher dosage (0.01 µl/µl). The repellence test also showed a higher average repellence (93.44%) effect with a higher dosage (0.01 µl/µl) of the EOs. According to these results, the EO of L. camara may well be a sustainable, eco-friendly alternative for synthetic insecticide in the T. absoluta management program.

Studies examining the variability in wild plant metabolic expression propose that environmental factors significantly influence the essential oil (EO) quality and quantity in a plant. Lantana camara is a widely distributed invasive plant species worldwide. However, its immense metabolites can become a source of novel compounds to produce biopesticides in the agricultural industry. Although, the quality aspect has to be considered due to the environmental influence on the metabolites synthesised. Therefore, this research aimed to understand the influence of environmental factors and how it shapes the plant’s metabolite profile in multiple populations of L. camara. Leaf samples were collected from six different geographic regions of Kenya and the corresponding monthly climatic data and soil samples. GC-MS data from leaf EO were analysed with environmental variables (climate and soil data) using unimodally unconstrained and constrained ordination methods for untargeted metabolomics analysis. Partial Least Squares-Discriminant Analysis (PLS-DA) and Random Forests (RF) were used to confirm the variability further. Seasonal and regional variability was observed for secondary metabolites (SMs) in the leaf EO, which correlated to climatic factors and soil attributes. We highlight the season-al-geographic metabolism relationship for L. camara and the combined analytical approach to obtain data that contributes to understanding the influence of environmental factors on the synthesis and accumulation of SMs. This research will have all-embracing implications for maximising phytochemical uniformity.