Antifeedant and ovicidal activities of ginsenosides against Asian corn borer, Ostrinia furnacalis (Guenee)

Quillaja lancifolia Immunoadjuvant Saponins Show Toxicity to Herbivores and Pathogenic Fungi

Saponins from leaves of Quillaja lancifolia, a native species from southern Brazil, show potent immunoadjuvant activity in experimental vaccine formulations. The accumulation of the immunoadjuvant saponin fraction QB-90 is induced in cultured leaf disks and seedlings by several stresses and stress signaling molecules, such as osmotic agents, salicylic acid, jasmonic acid, mechanical damage, ultrasound, UV-C radiation, and high light irradiance. These observations suggest a role in plant defense. To further examine this possibility, an investigation of the potential inhibitory role of Q. lancifolia saponins on plant and human pathogenic fungi and two herbivore models was carried out. The screening tests showed that saponin-rich fractions, particularly QB-90, were able to significantly inhibit the growth of Bipolaris micropus, Curvularia inaequalis, Fusarium incarnatum, and Cryptococcus gattii R265. The same metabolites acted as deterrents against the generalist mollusk and insect herbivores Helix aspersa and Spodoptera frugiperda, respectively. Significant reductions in consumption of leaf area and larvae body weight were recorded. Taken together, these data indicate a role for Q. lancifolia saponins in plant defense against diverse herbivores and fungi, having potential as a natural pest control agent and/or as a molecular platform for the development of new environmentally friendly biocide molecules.

Ethanolic Botanical Extracts: A Bioinsecticide Approach to Controlling Epicauta atomaria (Coleoptera: Meloidae)

The blister beetle, Epicauta atomaria (Germar) (Coleoptera: Meloidae), is a Neotropical pest of various horticultural crops. This pest consume leaves causing significant reduction in the plant foliage. To develop sustainable tools for managing this insect species, we evaluated the repellent and insecticidal activity of ethanolic extracts from six plant species commonly found in Argentina: Artemisia annua (L.), Cantinoa mutabilis ((Rich.) Harley and J.F.B Pastore), Dysphania ambrosioides ((L.) Mosyakin and Clemants), Lantana camara (L.), Ricinus communis (L.), and Taraxacum officinale (F.H Wigg). The results showed that D. ambrosioides was the most active extract, with strong repellent activity at concentrations below 200 μg/μL (1.5 mg/cm2). Additionally, the extract caused a mortality rate of 78% at 10 μg/μL after 24 h, with an LC50 of 7.9 μg/μL against E. atomaria. The enzymatic activity of E. atomaria acetylcholinesterase was evaluated in vitro to reveal the mode of action, resulting in a 58% inhibition at 5.0 μg/μL. The main bioactive compounds in fractionated D. ambrosioides ethanolic extracts were identified by GC-MS. The extract contained high concentrations of thymol and carvacrol in the less polar fractions, which were the most active. The bioactivity of both compounds against E. atomaria was also tested, showing strong insecticidal activity with an LC50 of 1.6 and 1.4 μg/μL for thymol and carvacrol, respectively. Overall, our results highlight the potential of D. ambrosioides as a biopesticide for managing E. atomaria.

Botanical Antifeedants: An Alternative Approach to Pest Control

Plant protection against phytophagous pests still largely relies on the application of synthetic insecticides, which can lead to environmental and health risks that are further exacerbated by the development of resistant pest populations. These are the driving forces behind the current trend of research and the development of new ecological insecticides. The mode of action does not have to rely exclusively on acute or chronic toxicity. Another promising approach is the use of plant antifeedants, which can significantly reduce the food intake of phytophagous insects. However, the information on antifeedant substances has not yet been sufficiently evaluated. The aim of this review was to find the most promising plants that provide potent extracts, essential oils (EOs), or isolated compounds with antifeedant properties. The selection was based on a comparison of effective concentrations or doses. Effective extracts were obtained from 85 plant species belonging to 35 families and the EOs came from 38 aromatic plant species from 11 families. Based on the results, Angelica archangelica, Caesalpinia bonduc, Grindelia camporum, Inula auriculata, Lavandula luisieri, Mentha pulegium, Piper hispidinervum, and Vitis vinifera were selected as promising plants with antifeedant potential. These plants are potent antifeedants, and at the same time provide sufficient biomass for industrial use in the development and production of botanical antifeedants.