Toxicity of essential oils from Baccharis species on Spodoptera frugiperda and their selectivity to the parasitoid Telenomus remus

The lepidopteran Spodoptera frugiperda, a key pest in maize production, has developed resistance to various active ingredients. In this context, botanical insecticides such as essential oils (EOs) offer promising alternative, particularly when integrated with biological control strategies. Baccharis EOs demonstrates to be a promising botanical insecticide for the control of agricultural pests. This study aimed to evaluate the bioactivity of EOs from Baccharis articulata, Baccharis calvescens, Baccharis dracunculifolia, Baccharis milleflora, and Baccharis uncinella and its effects in biomarkers against S. frugiperda, as well as their effects on the parasitoid Telenomus remus. The chemical composition of the EOs was identified through gas chromatography–mass spectrometry. Insecticidal activity was assessed via contact and ingestion assays, with toxicity evaluated using biochemical markers. Additionally, the impact of the EOs on different developmental stages of T. remus was investigated. The number of compounds identified in the EOs ranged from seven in B. articulata to 27 in B. milleflora. Toxicity levels varied across Baccharis species, with B. articulata exhibiting the lowest LC₅₀ value (0.67%) and B. calvescens exhibiting the highest LC₉₀ value (2.05%). Baccharis EOs showed evidence of neurotoxicity and lipid peroxidation damage in S. frugiperda. Notably, B. calvescens and B. milleflora caused no mortality in T. remus eggs and pupae but exhibited repellency rates of 40–55%. Baccharis species have significant insecticidal activity against S. frugiperda, with neurotoxic effects, while demonstrating selectivity for T. remus. These findings highlight Baccharis EOs as promising botanical insecticides that align with sustainable agricultural production models, offering an alternative to synthetic insecticides.