The effect of Stemona tuberosa root extract on preventing diamondback moths (Plutella xylostella) from infesting cruciferous vegetables (Brassicaceae) in the winter-spring season of 2020-2021, Thai Nguyen

Abstract

This study examined the function and efficiency of Stemona tuberosa root extract as an organic pesticide against the diamondback moth on cruciferous vegetables. The 100% root extract, which was obtained via extraction by ethanol, was diluted with water in different ratios and resulted in various efficiency on eliminating diamondback larvae. Particularly, the extract diluted in ratio 1:0 was most efficient with 79.26% diamondback larvae eliminated after 4 days of application. This was closely followed by 77.04% and 76.30% from ratios 1:1 and 1:5, proving that dilution was feasible in terms of maintaining efficiency and reducing economic costs. Those results were much more prominent compared to the effect of other pesticides, which included Padan 95SP 0.01% (44.44% efficient after 4 days spraying), 1% Sapindus saponaria extract (24.44%), and 0.1% soap powder (22.22%). This study also showed that combined usage with those other pesticides enhanced the effect of S. tuberosa. The combination of S. tuberosa root extract (diluted with water in a ratio of 1:5) and 1% S. saponaria extract resulted in excellent effect with 19.61% diamondback moths eliminated after 1 day spraying and 90.18% eliminated after 7 days spraying. Although it was negligibly lower than S. tuberosa + Padan 95SP, this combination is completely organic and eco-friendly. In addition, S. tuberosa extract-based pesticides in this study were tested in cabbage fields. At the 95% confidence interval of Duncan testing, the productivity of CT7 cabbages (34.53 tons/hectar), which were treated with Stemona tuberosa root extract (diluted with water in a ratio of 1:5) mixed with 1% Sapindus saponaria extract, and CT6 cabbages (35.89 tons/hectar), which were treated with Stemona tuberosa root extract and 0.1% soap powder, was homogeneous but slightly lower than the yield of CT8 (chemical pesticides + 0.01% Padan 95SP) with 35.75 tons/hectar.