Screening for anti-insect activity in Mediterranean plants

A screening of plant extracts from wild species for insecticidal activity could lead to the discovery of new agents for pest control. Aerial parts of a group of 50 plant species of south-eastern Spain, belonging to different botanical families, were harvested in 1995 and 1996. From each sample three extracts were obtained using organic solvents of increasing polarity. Activity was tested in bioassays using the stored grain pest Tribolium castaneum Herbst (Coleoptera: Tenebrionidae). Larval growth inhibition was significantly induced when extracts were incorporated into the diet at 0.05%. The most active plants were: Anabasis hispanica, Senecio lopezii, Bellardia trixago and Asphodelus fistulosus. However, only with Ajuga iva was 70% mortality obtained. Polar extracts of Cichorium intybus, Rieichardia tingitana, Mentha longifolia, Zygophillum fabago, Helleborus foetidus and Datura stramonium, and non-polar extracts of Chondrilla juncea and Ailanthus altissima gave 70-100% of mortality when applied topically at a dose of 3 mu g/larva. Repellency was detected when extracts of Pistacia lentiscus, Genista umbellata. and Cachrys sicula where mixed with the insect diet. (C) 1998 Elsevier Science B.V. All rights reserved.