Efficacy of Precocene I from Desmosstachya bipinnata as an Effective Bioactive Molecules against the Spodoptera litura Fab. and Its Impact on Eisenia fetida Savigny

Abstract

The sustainability of agroecosystems are maintained with agro-chemicals. However, after more than 80 years of intensive use, many pests and pathogens have developed resistance to the currently used chemistries. Thus, we explored the isolation and bioactivity of a chemical compound, Precocene I, isolated from the perennial grass, Desmosstachya bipinnata (L.) Stapf. Fractions produced from chloroform extractions showed suppressive activity on larvae of Spodoptera litura (Lepidoptera: Noctuidae), the Oriental armyworm. Column chromatography analyses identified Precocene I confirmed using FTIR, HPLC and NMR techniques. The bioactivity of the plant-extracted Dp-Precocene I was compared to a commercially produced Precocene I standard. The percentage of mortality observed in insects fed on plant tissue treated with 60 ppm Db-Precocene I was 97, 87 and 81, respectively, for the second, third and fourth instar larvae. The LC50 value of third instars was 23.2 ppm. The percentages of survival, pupation, fecundity and egg hatch were altered at sub-lethal concentrations of Db-Precocene I (2, 4, 6 and 8 ppm, sprays on castor leaves). The observed effects were negatively correlated with concentration, with a decrease in effects as concentrations increased. Distinct changes in feeding activity and damage to gut tissues were observed upon histological examination of S. litura larvae after the ingestion of Db-Precocene I treatments. Comparative analyses of mortality on a non-target organism, the earthworm, Eisenia fetida, at equal concentrations of Precocene I and two chemical pesticides (cypermethrin and monocrotophos) produced mortality only with the chemical pesticide treatments. These results of Db-Precocene I as a highly active bioactive compound support further research to develop production from the grass D. bipinnata as an affordable resource for Precocene-I-based insecticides.

Insecticidal activities of two fig tree leaf extracts against the cotton pest Spodoptera litura (Fab.) and their impact on the non‐target red worm Eisenia foetida (Savigny)

“…In addition, the sub-lethal impact of herbal toxins can have implications beyond developmental duration in insect pests ( Benelli & Maggi 2022). Biological extracts or essential oils have been found to impact the fitness and reproductive capacity of surviving insects, affecting population growth and long-term pest management (Chanthini et al 2021;Ponsankar et al 2020;Sundar et al 2021;Vasantha-Srinivasan et al 2021). The ongoing studies support the present findings wherein sub-lethal doses of Ex-Fl and Ex-Fa significantly reduced pupal weight and decreased the reproduction rate (fecundity) of S. litura.…”

“…The tobacco pest Spodoptera litura (Fab. ), also known as the tobacco cutworm or cotton leafworm, holds significance owing to its ecological implications by damaging agriculture crops (Murfadunnisa et al 2019;Ponsankar et al 2016;Sundar et al 2021). This tobacco pest has a relatively short life cycle and can complete multiple generations in a year.…”

“…Its presence or absence can serve as an indicator of soil conditions. Monitoring this species potentially assists in assessing ecosystem health and the impact of environmental changes on soil quality (Shyam- Sundar et al 2021). Further, E. foetida is often used in eco-toxicological studies to assess soil contaminants (Ye, Xiong, & Liu 2016).…”

“…2016; Sundar et al . 2021). This tobacco pest has a relatively short life cycle and can complete multiple generations in a year.…”

Soil macrofauna diversity and weed dynamics in response to different methods of weed control in smallholder rubber farming

“…Weed control that resulted in changes in the vegetation height might have altered the feeding habits of the soil macrofauna (Rebrina et al 2022). The variation of macrofauna in response to herbicide application highlighted their movement to a different location where the feed is available, so that some macrofauna might decrease (Sundar et al 2021). The applied herbicide has changed the vegetation and directly affected the number and diversity of soil macrofauna.…”