ARTICLE IN PRESS Journal of Stored Products Research 43 (2007) 349–355 www.elsevier.com/locate/jspr Toxicity of naturally occurring compounds of Lamiaceae and Lauraceae to three stored-product insects V. Rozmana,Ã, I. Kalinovica, Z. Korunicb aFaculty of Agriculture in Osijek, University of J. J. Strossmayer in Osijek, Trg Sv. Trojstva 3, 31000 Osijek, Croatia bDiatom Research and Consulting Inc., 14 Greenwich Dr., Guelph, Ont., Canada N1H 8B8 Accepted 18 September 2006 Abstract The compounds 1,8-cineole, camphor, eugenol, linalool, carvacrol, thymol, borneol, bornyl acetate and linalyl acetate occur naturally in the essential oils of the aromatic plants Lavandula angustifolia, Rosmarinus officinalis, Thymus vulgaris and Laurus nobilis. These compounds were evaluated for fumigant activity against adults of Sitophilus oryzae, Rhyzopertha dominica and Tribolium castaneum. The insecticidal activities varied with insect species, compound and the exposure time. The most sensitive species was S. oryzae, followed by Rhyzopertha dominica. Tribolium castaneum was highly tolerant of the tested compounds. 1,8-Cineole, borneol and thymol were highly effective against S. oryzae when applied for 24 h at the lowest dose (0.1 ml/720 ml volume). For Rhyzopertha dominica camphor and linalool were highly effective and produced 100% mortality in the same conditions. Against Tribolium castaneum no oil compounds achieved more than 20% mortality after exposure for 24 h, even with the highest dose (100 ml/720 ml volume). However, after 7 days exposure 1,8-cineole produced 92.5% mortality, followed by camphor (77.5%) and linalool (70.0%). These compounds may be suitable as fumigants because of their high volatility, effectiveness, and their safety. r 2006 Elsevier Ltd. All rights reserved. Keywords: 1; 8-cineole; Camphor; Eugenol; Linalool; Carvacrol; Thymol; Borneol; Bornyl acetate; Linalyl acetate; Fumigant toxicity; Sitophilus oryzae; Rhyzopertha dominica; Tribolium castaneum; Wheat 1. Introduction organisms. Botanicals with low human toxicity currently available include rotenone and pyrethrum. Others now During the past few decades, application of synthetic available include neem, used as insect repellent, feeding pesticides to control agricultural pests has been a standard deterrent and growth regulator; eugenol, the component of practice. However, with growing evidence that many clover oil that is applied to cockroaches, ants, dust mites, conventional pesticides can adversely affect the environ- flies, wasp, spiders, crickets and fleas; and D-limonene ment, requirements for safer means of pest management isolated from citrus oils and citrus fruit peel and used as a have become crucial. Therefore, the use of safe, low- contact insecticide against ants, roaches, fleas, silverfish toxicity botanical pesticides is now emerging as one of the and palmetto bugs. prime means to protect crops, their products and the The insecticidal activity of a large number of essential environment from pesticide pollution, a global problem oils and other plant extracts has been assessed against (Prakash and Rao, 1997). Generally, they should cause less several major agricultural pests (Regnault-Roger et al., damage to human and environmental health than conven- 1993; Regnault-Roger and Hamraoui, 1993; Golob et al., tional insecticides. Many of them degrade rapidly and do 1999; Weaver and Subramanyam, 2000; Ke´ita et al., 2001; not accumulate in the body and environment while some Lee et al., 2001; Andronikashvili, and Reichmuth, 2002; are very pest specific and do little or no damage to other Kalinovic et al., 2002; Papachristos and Stamopoulos, 2002; Kim et al., 2003; Park I.K. et al., 2003). Prakash and ÃCorresponding author. Tel.: +385 31 224 244; fax: +385 31 207 017. Rao (1997) described 866 different plant species that E-mail address: [email protected] (V. Rozman). produce chemicals useful against insects and listed their 0022-474X/$ - see front matter r 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.jspr.2006.09.001 ARTICLE IN PRESS 350 V. Rozman et al. / Journal of Stored Products Research 43 (2007) 349–355 256 biologically active chemical components. However, in 2.2. Chemicals (compounds) spite of the wide recognition that many plants possess insecticidal properties, only a handful of pest control The main compounds present in oils of the aromatic products directly obtained from plants are presently in use plants (Table 1) were purchased from ‘‘Sigma-Aldrich’’ because the commercialization of new botanicals can be (Export Division Gru¨nwalder Weg 30 D-82041 Deisenho- hindered by a number of issues (Isman, 1997). Botanicals fen, Germany) and ‘‘Fluka’’ (Industriestrasse 25, CH-9471 used as insecticides presently constitute 1% of the world Buchs, SG Switzerland). These compounds were tested by insecticide market. bioassay. The focus over the last few years has been on the determination of the insecticidal activity of isolated 2.3. Insects chemical compounds from plant extracts in order to find out the most biologically active chemical compo- Cultures of the rice weevil—Sitophilus oryzae, the lesser nents (Regnault-Roger and Hamraoui, 1995; Clemente grain borer—Rhyzopertha dominica and the red flour et al., 2000; Huang et al., 2002; Lee et al., 2003; Park I.K. beetle—Tribolium castaneum (Herbst), were collected from et al., 2003; Park C. et al., 2003; Regnault-Roger et al., granaries in the eastern part of Croatia. They were reared 2004). in the laboratory to obtain the first generation (F1) for use The purpose of the present study was to investigate the in bioassays. Adults used in the experiments were 1–3 fumigant activity of naturally occurring compounds 1,8- weeks old and of mixed sex. Sitophilus oryzae and cineole, camphor, eugenol, linalool, carvacrol, thymol, Rhyzopertha dominica were reared on whole wheat grain borneol, bornyl acetate and linalyl acetate of the essential in glass containers containing 0.5 kg of clean wheat with oils of Lavandula angustifolia Chaix, Rosmarinus officinalis 13% moisture content (m.c.) while Tribolium castaneum L., Thymus vulgaris L. and Laurus nobilis L. against three was reared on a mixture of whole wheat flour and maize stored-product beetles. This paper describes for the first flour at the ratio of 1:1 in glass containers containing 0.5 kg time the fumigation activity of thymol, borneol, eugenol of the mixture with 12% m.c. All species were reared at and linalyl acetate against Sitophilus oryzae (L.) and 2971 1Cand7075% relative humidity (r.h.) in darkness. eugenol, borneole, bornyl acetate, carvacrol, linalool and linalyl acetate against Rhyzopertha dominica (F.). 2.4. Fumigant activity 2. Materials and methods The method used to determine the fumigant activity of tested compounds was based on that described by Prates et 2.1. Essential oils, compounds, gas chromatography al. (1998a). Four replicates of 10 adults of each of the three test insect species were placed in silk mesh cages that were The essential oils of Lavandula angustifolia (cultivar from put into separate glass jars of 720 ml capacity containing island Hvar, common name ‘‘budrika’’), Rosmarinus 250 g of wheat of 12% m.c. Nine compounds identified by officinalis (‘‘Miss Jessopp’s Upright’’ cultivar), Thymus analyzing the essential oils of Lavandula angustifolia, vulgaris (‘‘Argenteus’’ cultivar) and Laurus nobilis (‘‘Angu- Rosmarinus officinalis, Thymus vulgaris and Laurus nobilis stifolia’’ cultivar) were purchased from ‘‘Ireks aroma’’, and purchased from ‘‘Sigma’’, ‘‘Aldrich’’ and ‘‘Fluka’’ Zagreb, Croatia. Oils were analyzed by gas chromatogra- were tested at 5 dose rates (0.1, 1, 10, 50 and 100 ml/720 ml phy, using a ‘‘Perkin-Elmer’’ (USA) GC—type 8700, fitted volume) and over exposure periods of 1, 2, 3, 4, 5, 6 and 7 with a ‘‘Supelco’’ (USA) SP-2380 capillary column 30 m, days under controlled conditions (2971 1C, 7075% r.h., i.d. 0.32 mm, 0.20 mm film thickness. A similar method is in darkness). The substances were applied with a ‘‘Hirsch- described by Andronikashvili and Reichmuth (2002) and man’’ digital micropipette on to filter paper attached to the Regnault-Roger et al. (2004). lids of the glass containers, which were then tightly sealed. Table 1 List of the compounds purchased from Sigma, Aldrich and Fluka Compounds EC number Produced by 1,8-cineole ( ¼ eucalyptol) 207-431-5 Sigma Camphor (1R)-(+) camphor 99% 207-355-2 Sigma Eugenol (2-methoxy-4-[2-prophenyl]phenol) 202-589-1 Sigma Linalool 97% linalool 201-134-4 Aldrich Carvacrol 98% 5-isopropyl-2-methylphenol 207-889-6 Aldrich Thymol 99.5% 5-methyl-2-isopropylphenol 201-944-8 Sigma Borneol 87% borneol, 12% isoborneol 208-080-0 Sigma Bornyl acetate (-)-bornyl acetate, 97% — Aldrich Linalyl acetate linalyl acetate 95% — Fluka ARTICLE IN PRESS V. Rozman et al. / Journal of Stored Products Research 43 (2007) 349–355 351 All the samples for determination of fumigant activity were 100% mortality was obtained with the highest dose of observed daily over the exposure period of 1–7 days, or 100 ml/720 ml volume after 2 days exposure. After 7 days until 100% mortality of the test insects, and compared to exposure only with the lowest dose of linalyl acetate (0.1 ml/ the untreated control samples. 720 ml volume) was there any survival of S. oryzae (mortality 97.5%). 2.5. Statistical analysis For Rhyzopertha dominica (Table 4), besides camphor and linalool, eugenol, linalyl acetate, 1,8-cineole, bornyl Mortality data were subjected to a multi-factorial acetate, borneol and thymol all gave complete control at analysis of variance (ANOVA) for each day of the the dose rates of 1 ml/720 ml volume and above within 24 h. exposure period according to the general linear model For carvacrol, the highest doses (50 and 100 ml/720 ml (GLM). Significant differences were identified by least volume) were required for 100% mortality after 24 h. After significant difference (LSD) tests and entered in the tables. 7-days exposure survival occurred only at the lowest Data processing was conducted by the SAS System for dose (0.1 ml/720 ml volume), mortality with carvacrol or Windows 98 and SPSS 11.0 for Windows.