Potential Benefits and Side Effects of Sophora flavescens to Control Rachiplusia nu

There is a global demand for reducing the adoption of traditional chemical insecticides in agriculture. Among the most promising alternatives, botanical insecticides have been increasingly gaining attention due to their efficacy combined with a more environmentally safe impact. Among the different botanical insecticides commercially available, oxymatrine is an alkaloid found in the roots of Sophora flavescens which exhibits wide insecticide activity. However, their side-effects on non-target organisms have not been extensively evaluated. Therefore, this study aimed to investigate in laboratory conditions the insecticidal potential of a commercial botanical insecticide (Matrine®) based on ethanolic extract of S. flavescens roots at 0.2; 0.6; 1.0; 1.4; 1.8; and 2.2 L of commercial product per hectare to control third-instar larvae of Rachiplusia nu and its selectivity in the egg parasitoid Trichogramma pretiosum. Overall, our results showed that the ethanolic extract of S. flavescens is an efficient tool to control R. nu from 0.6 to 2.2 L/ha, with similar R. nu mortality at 48 and 72 h after spraying (close to 100% mortality) associated with no impact to pupae and minimum impact to adults (slightly harmful) of the egg parasitoid. The botanical insecticide was classified as harmless to the pupae and slightly harmful to the adults of T. pretiosum according to the International Organization for Biological Control (IOBC) protocols. Thus, the use of the ethanolic extract of S. flavescens emerges as a relevant alternative to control R. nu, which needs to be confirmed in future field trials.