Journal of Plant Diseases and Protection, 119 (2), 59–67, 2012, ISSN 1861-3829. © Eugen Ulmer KG, Stuttgart J.Plant Dis.Protect. 2/2012 Chemical analysis of three herbal extracts and observation of their activity against adults of Acanthoscelides obtectus and Leptinotarsa decemlineata using a video tracking system Helena Rojht 1,* , Iztok Jože Košir 2 & Stanislav Trdan 1 1 University of Ljubljana, Biotechnical Faculty, Dept. of Agronomy, Jamnikarjeva 101, SI 1111 Ljubljana, Slovenia 2 Slovenian Institute of Hop Research and Brewing, Cesta Žalskega tabora 2, SI 3310 Žalec, Slovenia * Corresponding author: e-mail: Helena.Rojht@bf.uni-lj.si Received 31 January 2012, accepted 5 May 2012 Abstract Ethanol extracts of Rosmarinus officinalis, Lavandula angus- tifolia and Ruta graveolens were tested against adults of Acan- thoscelides obtectus and Leptinotarsa decemlineata. Using a newly developed computer tracking system, a choice test revealed that all of the extracts have a repellent action. The highest repellent activity against the bean weevils adults was the ethanol extract of rue, whereas the highest repellent activity against the Colorado potato beetle adults was the lavender extract. We suggest that a cocktail of volatile com- ponents in the ethanol extracts was responsible for the observed repellent action. All three of the extracts have insec- ticidal effects on bean weevils, reducing F1 adult emergence, with no side effects on the germination of the bean plants. In contrast, the extracts did not demonstrate an insecticidal effect on Colorado potato beetles. Key words: insect movement, insecticidal effect, ethanol extract, GC-MS, HPLC, repellent action Introduction Insect pests of stored products are a problem worldwide because these pests reduce the quantity and quality of stored grains. The damage may reach 5–10% in temperate zones, 20–30% in tropical zones (Nakakita 1998) and 40% in coun- tries in which modern storage technologies have not yet been introduced (Shaaya et al. 1997). Since the domestication and diffusion of beans, the bean weevil (Acanthoscelides obtectus, Coleoptera, Chrysomelidae) has become dispersed via human- mediated migrations and is now a major pest in bean grana- ries (Alvarez et al. 2005). The Colorado potato beetle (Lepti- notarsa decemlineata, Coleoptera, Chrysomelidae) is one of the most important pests of both potato and eggplant in America and Europe. Because of the rapid development of resistance to every insecticide used against it, it is necessarily to develop new insecticides or new alternative methods for the suppression of pest activity (Mota-Sanchez et al. 2006). There are many plant extracts and essential oils, compris- ing a rich source of bioactive chemicals that can be used for stored-product insect control (Papachristos & Stamopolus 2003, Adedire et al. 2011). Ruta is a genus of the Rutaceae family, which are mainly shrubby plants with bluish-green leaves that emit a powerful odour and have a bitter taste. Ruta spp. is native to the Mediterranean region and has been present in traditional medicine, folk life and the eco- nomic botany of this region since ancient times (San Miguel 2003). The aerial parts of common rue (Ruta graveolens) contain more than 120 compounds of different classes of natural products, such as acridone alkaloids, coumarines, essential oils, flavonoids and furoquinoline (Oliva et al. 2003). In addition, rue has fungicidal (Oliva et al. 2003) properties as a deterrent (Landolt et al. 1999) and insecti- cidal activity (Guarrera 1999) against some insects. Rosmarinus officinalis and Lavandula angustifolia belongs to the Labiatae (Lamiaceae) family, which consists of approxi- mately 3500 species centred chiefly in the Mediterranean area, although some small groups have local distributions in Australia, South-west Asia and South America (Kokkini et al. 2003). The essential oil of rosemary has been widely studied, showing repellent (JiSen & ErrLieh 2005) and toxic or contact insecticidal properties on insects (Papachristos & Stamopoulos 2003). It has been reported that the essential oil of common lavender repels some insects (Mauchline et al. 2005) and has an insecticidal effect (Regnault-Roger & Hamraoui 1993). The aim of the present study was to determine whether ethanol extracts have any effect on two Chrysomelidae spe- cies. We also wanted to evaluate the nature of the activity (repellent or insecticidal) and to define the active ingredi- ents that are responsible for the mode of action. The Colorado potato beetle was chosen as the target organisms because of its wide distribution and economic importance; we also tested the bean weevil, which has proven to be more sensitive to treatments than certain other pests (Leon et al. 2000). Material and methods Preparation of the crude extracts Aerial parts of three plants, Rosmarinus officinalis, Ruta gra- veolens and Lavandula angustifolia, were collected during the flowering period of 2008 in Slovenia. The plant material was ground using an electrical grinder (M 20, IKA®-Werke GmbH & Co. KG, Germany) after air-drying in the shade for several days at room temperature. The extraction was per- formed using 96% ethanol at a mass ratio of 1:5 (dried plant : ethanol) at room temperature. The mixture was periodically shaken for 7 days, filtered and stored in a refrigerator at 6°C.