Green pesticides, derived from natural sources, have gained wider attention as an alternative approach to synthetic pesticides in managing polyphagous pests like Spodoptera litura. In this study, the methanolic flower extract of Nyctanthes arbor-tristis (Mx-Na-t) was subjected to chemical screening, and major peak area derivatives 3-Hydroxy-1,2-dimethyl-4(1H)-pyridone (3H-dp) and Tyrosol (Ty-ol) were identified. The toxicity against S. litura larvae of Mx-Na-t (at 500 ppm) was highest in third instars (96.4%), and for 3H-dp and Ty-ol (at 5 ppm) in II instars (76.5% and 81.4%, respectively). The growth and development of S. litura larvae and pupae were significantly reduced by all three extract and phytochemical treatments. Fecundity rates also declined with the treatments, from 1,020 eggs (control) to 540 eggs (Mx-Na-t), 741 eggs (3H-dp), and 721 eggs (Ty-ol). The extract and its active constituents decreased adult emergence and slowed total larval development in a dosedependent manner. The major gut enzymes of S. litura decreased in young larvae (II instar) exposed to Mx-Na-t, 3H-dp, and Ty-ol. Fourth instar midgut tissues were severely damaged by Mx-Na-t (250 ppm), 3H-dp, and Ty-ol (2.5 ppm) treatments, which induced structural damage to the epithelial cells and gut lumen. The earthworm Eisenia foetida was used to test for non-target toxicity. Crude Mx-Na-t at 500 ppm (13% and 3%) and 3H-dp (9.3% and 2.1%) and Ty-ol (10.2% and 1.5%) at 5 ppm produced lower mortality than the synthetic chemical cypermethrin at 1.0 ppm (27% and 18%) in filter paper and artificial soil assays, respectively. In addition, there was no significant change in earthworm weights under all three phytochemical treatments compared to controls. Additionally, the in-silico predictions of BeeTox and ProTox II indicated little or no toxicity toward honey bees and other nontargets associated with 3H-dp and Ty-ol. Overall these phyto-chemicals offer an effective pest management strategy.

• Prabhakaran Vasantha-Srinivasan(Department of Applied Biology, Chonnam National University)
• Yeon Soo Han(Department of Applied Biology, Chonnam National University)