Heliyon (Oct 2024)
Determination of insecticidal potential of selected plant extracts against fall armyworm (Spodoptera frugiperda) larvae
Abstract
The fall armyworm, Spodoptera frugiperda (J.E. Smith), is a devastating pest that attacks a wide range of crops, including sugarcane, rice, and maize. The purpose of this study is to evaluate the toxicity potential of native plant extracts (Azadirachta indica, Eucalyptus globulus, Parthenium hysterophorus, Cannabis sativa, Citrullus colocynthis, Nicotiana tabacum) against S. frugiperda. Four different concentrations (50, 100, 200, and 400 ppm) of the ethanolic plant extracts was evaluated against S. frugiperda third-instar larvae to determine their median lethal concentration (LC50). After 72 h of exposure, the LC50 values of A. indica, E. globulus, P. hysterophorus, C. sativa, C. colocynthis, N. tabacum, and positive control (Spinetoram) were 186.104, 518.438, 320.027, 334.259, 252.651, 720.980 and 189.369 ppm respectively. The maximum percent mortality was caused by the highest concentration (400 ppm) of A. indica (64 ± 0.18), E. globulus (48 ± 0.22), P. hysterophorus (56 ± 0.18), C. sativa (56 ± 0.18), C. colocynthis (60 ± 0.00), and N. tabacum (40 ± 0.28), after 72 h of treatment while Spinetoram induced 100 ± 0.00 percent mortality of S. frugiperda and only 4 ± 0.18 percent mortality was recorded in a control group. Results showed that all plant extracts were found to be effective against S. frugiperda. The compounds from the two most effective ethanolic plant extracts were identified by using Gas chromatography-mass spectrometry analysis (GC-MS). The key compounds identified in neem leaf extract and kortuma fruit extract are predominantly biologically active molecules. Many of them were volatile compounds that belonged to different chemical categories, such as fatty acids, hydrocarbons, esters, terpenoids, phenolic compounds, and amines. Terpenes exhibited a wide range of different biological activities, such as serving as insecticides and antifeedant. The presence of various functional groups in the plant extract was determined by conducting a Fourier Transform Infrared Spectroscopy (FTIR). Farmers should employ these kinds of environmental friendly insecticides to lessen the impact of fall armyworm because these products are cheaper to use and better for the economy and the environment.
