Antifeedant Activity of Artemisia Plant Extracts Against the Cotton Leafworm (Spodoptera littoralis) in Ornamental Plant Nurseries

Abstract

The cotton leafworm, Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae), is a highly polyphagous pest that poses a significant threat to ornamental plant nurseries, causing extensive defoliation and economic losses. The overreliance on synthetic chemical insecticides for its control has led to the development of insecticide resistance, environmental contamination, and risks to human health. Consequently, there is an urgent need to develop environmentally friendly and sustainable alternatives. This study investigates the antifeedant activity of crude ethanolic extracts from three Artemisia species, namely A. herba-alba, A. absinthium, and A. vulgaris, against the fourth instar larvae of S. littoralis under controlled laboratory conditions (26±1°C, 65±5% RH, 16:8 L:D). The antifeedant index was calculated using the leaf disc bioassay method at five different concentrations (0.5, 1, 2, 4, and 8 mg/mL) over 24 and 48-hour exposure periods. The results demonstrated a concentration- and time-dependent antifeedant effect for all tested extracts. A. absinthium exhibited the highest antifeedant activity, achieving an 86.4% feeding inhibition at the highest concentration (8 mg/mL) after 48 hours, followed by A. herba-alba (79.2%) and A. vulgaris (71.5%). The calculated median effective concentrations (EC₅₀) for antifeedant activity were 1.92, 2.48, and 3.15 mg/mL for A. absinthium, A. herba-alba, and A. vulgaris, respectively. Gas chromatography-mass spectrometry (GC-MS) analysis of the most active extract (A. absinthium) identified major terpenoid compounds, including camphor, 1,8-cineole, β-thujone, and artemisia ketone, which are known to disrupt insect chemoreception and feeding behavior. These findings highlight the potential of Artemisia extracts, particularly A. absinthium, as effective botanical antifeedants for the management of S. littoralis in ornamental nurseries. The integration of these plant-based extracts into integrated pest management (IPM) programs could reduce the reliance on synthetic insecticides, thereby mitigating environmental and health risks while preserving natural enemy populations.