Mortality of Rachiplusia nu (Guenée, 1852) (Lepidoptera: Noctuidae) Caused by Sophora flavescens Bioinsecticide and Its Selectivity to Trichogramma pretiosum (Riley, 1879) (Hymenoptera: Trichogrammatidae)

There is a global demand for reducing the adoption of traditional chemical insecticides in agriculture. Among the most promising alternatives, botanical insecticides have gained increasingly attention due to their efficacy combined with a more environmentally safe impact. Among the different botanical insecticides commercially available, oxymatrine is 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 to 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 hours after spraying (close 100% mortality) associated with low impact on the egg parasitoid. The botanical insecticide was classified as harmless to the pupae and slightly harmful to the adults of T. pretiosum accordingly to the International Organization for Biological Control (IOBC) protocols. Therefore, the slower rates of 0.6 to 1.4 (range also registered and recommended for other caterpillar in soybean – Anticarsia gemmatalis) should be tested in field conditions to evaluate possible extension of the botanical insecticide registration and recommendations to be also used to control R. nu in the field.