Insecticidal Activity of Some Aromatic Plants from Croatia Against Granary Weevil (Sitophilus

INSECTICIDAL ACTIVITY OF SOME AROMATIC PLANTS FROM CROATIA AGAINST GRANARY WEEVIL (SITOPHILUS GRANARIUS L.) ON STORED WHEAT

Vlatka ROZMAN1, Irma KALINOVIC1, Anita LISKA1

1 University J. J. Strossmayer in Osijek, Faculty of Agriculture, Trg Sv. Trojstva 3, HR-31000 Osijek, Croatia, e-mail: [email protected]

Abstract

These investigations proved that aromatic plants from Croatia like lavander, laurel, rosemary and thymus, had insecticidal activity against Sitophilus granarius L on stored wheat.

Key words: stored wheat, Sitophilus granarius, aromatic plants, lavender, laurel, rosemary, thyme.

Introduction

Conventional control measures in Croatia against granary weevil, Sitophilus granarius L. have been carried out by using insecticides applied directly on grain, or by gas fumigation. One of the alternatives is application of natural products derived from aromatic plants with potential repellent and insecticidal effect and no harmful effect on human environment. The focus over the last few years has been on the determination of the insecticidal activity of isolated chemical compounds from plant extracts in order to find out the most biologically active chemical components (Huang et al., 2002; Lee et al., 2003; Regnault-Roger et al., 2004). First studies of aromatic plants from Croatian mediterranean area show that plant species of Laurus nobilis L., Lavandula angustifolia Ch., Rosmarinus officinalis L., Thymus vulgaris L. have insecticidal effect on S. granarius if applied in the form of dry ground leaves, stem and flower or as essential oils (Kalinović et al., 1997). The purpose of the present study was to investigate the insecticidal activity of naturally occurring compounds 1.8-cineole, camphor, eugenol, linalool, carvacrol, thymol, borneol, bornyl-acetate and linalyl-acetate isolated from essential oils of lavender, rosemary, thyme and laurel against granary weevil.

Material and methods

Essential oils, compounds, gas chromatography The essential oils of L. angustifolia, R. officinalis, T. vulgaris and L. nobilis were purchased from "Ireks aroma", Zagreb, Croatia. Oils were analyzed by gas chromatography, using a “Perkin-Elmer” (USA) GC – type 8700, fitted with a “Supelco” (USA) SP-2380 capillary column 30m, i.d. 0.32mm, 0.20 μm film thickness, and the main compounds were determined. The main compounds - 1,8-cineole, camphor, eugenol, linalool, carvacrol, thymol, borneol, bornyl-acetate and linalyl-acetate discovered in oils of the aromatic plants analyzed were purchased from “Sigma-Aldrich” and “Fluka”.

1 Insects S. granarius, was collected from the granaries in the eastern part of Croatia. Adults used in the experiments were 1 to 3 weeks old and of mixed sex. S. granarius was reared on whole wheat grain in glass containers containing 0.5 kg of clean wheat with 13% moisture content (m.c.) at 29 ± 1 oC and 70 ± 5% relative humidity (r.h.) in darkness.

Method of insecticidal (fumigant) activity The method was a modified procedure described by Prates et all. 1998. Ten adults of S. granarius species were placed in silk mesh cages wich were put into glass jars of 720 ml capacity containing 250 g of wheat of 12% m.c. 1,8-cineole, camphor, eugenol, linalool, carvacrol, thymol, borneol, bornyl-acetate and linalyl-acetate were tested at dose rate 0.1µl/720 ml volume and over exposure periods of 7 days. The substances were applied with a “Hirschman” digital micropipette on filter paper attached to the lids of the glass, which were then containers tightly sealed. Each sample was set up in 4 replications and maintained under controlled conditions (temperature 29±1 oC, humidity 70±5%, in darkness). Insecticidal (fumigant) activity was determined by test insect mortality over the exposure periods of 1-7 days and compared to the untreated control samples. Mortality data were subjected to analysis of variance (ANOVA) for each day over the exposure period according to the GLM (general linear model). Significant differences were shown by LSD test (least significant difference) and entered in the tables. Data processing was conducted by the SAS System for Windows 98 and SPSS 11.0 for Windows.

Qualitative analyses of tested mercantile wheat Analysis of tested mercantile wheat was carried out in the laboratory for flour quality at IPK “Croatia”d.o.o. Silos i Mlin, Osijek according to the standard technological methods by using farinograph, ekstenzograph, with determination scent. Reological tests were done on 60% laboratory flour (after purification, wheat samples were prepared for grinding by soaking in two phases: I – soaking in 13,5% m.c. and growing stale for 24 h; II phase – soaking in 14% m.c. ½ h before grinding). The reological tests were carried out after 5 days. Dough properties were determined by farinograph from flour obtained over the grinding proces. Dough properties over the elasticity process were determined by ekstenzograph. Samples of tested wheat (cca 100) broken in laboratory mixer, and poured with heated water were prepared for organoleptic analysis for scent.

Results and discussion

Chemical compounds of the essential oils The majority of the compounds identified by GC in the essential oil of lavender, rosemary, thyme and laurel are presented in Table 1. Table 1. L. angustifolia R. officinalis T. vulgaris L. nobilis Compounds lavender rosemary thyme laurel 1,8-cineole + + + + camphor + + eugenol + + + linalool + + + carvacrol + thymol + borneol + + + bornyl-acetate + + + linalyl-acetate +

2 Insecticidal (fumigant) activity At the end of the 7-day test in untreated grain was not mortality of S. granarius. This species showed very high susceptibility to all compounds after 24 hours at the dose 0.1 μl/720 ml volume with average mortalities of 96.5 – 100% (Table 2).

Table 2. Insecticidal (fumigant) activity compounds to 7-day test on S. granarius (P>0,05)

% mortality of S. granarius Compounds exposure time in dose 1. day 2. day 3.day 4. day 5. day 6. dan 7. day 0.1μl/720ml X  Std.E. X  Std.E. X  Std.E. X  Std.E. X  Std.E. X  Std.E. X  Std.E. eugenol 97.0±2.0a 98.0±1.5a 100.0±0.0a 100.0±0.0a 100.0±0.0a 100.0±0.0a 100.0±0.0a linalyl acet. 96.5±2.6b 96.5±2.6b 98.5±1.5a 99.0±1.0a 99.0±1.0a 99.5±0.5a 99.5±0.5a 1.8-cineole 99.0±1.0a 99.0±1.0a 99.0±1.0a 99.0±1.0a 100.0±0.0a 100.0±0.0a 100.0±0.0a carvacrol 98.5±1.5a 99.0±1.0a 100.0±0.0a 100.0±0.0a 100.0±0.0a 100.0±0.0a 100.0±0.0a camphor 100.0±0.0a 100.0±0.0a 100.0±0.0a 100.0±0.0a 100.0±0.0a 100.0±0.0a 100.0±0.0a linalool 100.0±0.0a 100.0±0.0a 100.0±0.0a 100.0±0.0a 100.0±0.0a 100.0±0.0a 100.0±0.0a bornyl acet. 100.0±0.0a 100.0±0.0a 100.0±0.0a 100.0±0.0a 100.0±0.0a 100.0±0.0a 100.0±0.0a borneol 100.0±0.0a 100.0±0.0a 100.0±0.0a 100.0±0.0a 100.0±0.0a 100.0±0.0a 100.0±0.0a thymol 100.0±0.0a 100.0±0.0a 100.0±0.0a 100.0±0.0a 100.0±0.0a 100.0±0.0a 100.0±0.0a untreated 0.0±0.0c 0.0±0.0c 0.0±0.0c 0.0±0.0c 0.0±0.0c 0.0±0.0c 0.0±0.0c * means in the same column followed by the same letters are not significantly (P>0.05) different as determined by the LSD-test.

Aromatic plants contain essential oils only in concentrations of 1 – 3%. Large quantities of plant material would need to be processed to gain enough essential oil for commercial-scale tests. These results proved that lavender, laurel, rosemary and thyme from Croatia had some active ingredients and may be suitable as fumigants because of their high volatility, effectiveness, and their safety. The results of our study are mostly in the agreement with the results of other investigators (Obeng-ofori et al., 1997.; Obeng-Ofori and Reichmuth, 1999.)

Results of qualitative analyses of tested mercantile wheat

Results of the farinograph analyses show that compounds of essential oils did not have negative effect on dough properties (Table 3).

Table 3. Results of farinograph analyses FARINOGRAM water dough dough resistention Quality Quality compounds absorb progress stability min. soften level No. group % min. min. FJ thymol 63,2 1,6 0,2 1,8 107 48,1 B2 1.8-cineole 62,7 1,7 0,2 1,9 98 48,1 B2 carvacrol 63 1,8 0,3 2,1 86 50,9 B2 linalyl acetate 62,6 1,6 0,2 1,8 83 50,2 B2 linalool 63,1 1,6 0,5 2,1 84 53,3 B2 eugenol 62,7 1,7 0,2 1,9 80 51,8 B2 camphor 62,7 1,7 0,3 2 83 53,3 B2 bornyl acetate 62,8 1,6 0,3 1,9 78 55,3 B1 borneol 62,9 1,7 0,1 1,8 79 53,9 B2 control 62,7 1,7 0,3 1,9 80 51,6 B2 Results of the ekstenzograph analyses (Table 4) show that the treatments did not exhibit negative effect on the dough quality during the elasticity process.

3 Table 4. Results of ekstenzograph analyses

EKSTENZOGRAM compounds resistence relation energy cm2 EJ elasticity mm EJ/mm thymol 60,2 355 120 2,96 1.8-cineole 55,1 307 122 2,52 carvacrol 66,4 320 130 2,46 linalyl acetate 66,3 379 119 3,18 linalool 67,5 360 130 2,77 eugenol 66,1 325 134 2,43 camphor 61,4 324 128 2,53 bornyl acetate 68,5 370 124 2,98 borneol 64,1 348 123 2,83 control 61,5 325 135 2,44

Determintaion scent was conducted in the laboratory by organoleptic method on tested mercantile wheat mixed with water. The wheat samples with thymol and carvacrol application retained the scent of the compounds tested.

Conclusions

Such investigations offered new options in search for alternatives for fumigants currently in use. If the problem of cost/effective commercial production can be solwed, it is possible that some of the compounds tested could find a place in IPM strategies.

References Huang, Y., Ho, S. H., Lee, H. C., Yap, Y.L., 2002. Insecticidal properties of eugenol, isoeugenol and methyleugenol and their effect on nutrition of Sitophilus zeamais Motsch. (Coleoptera: Curculionidae) and Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae). Journal of Stored Products Research 38, 403-412. Kalinović, I., Martinčić, J., Rozman, V., Guberac, V. 1997. Insecticidal activity of substances of plant origin against stored product insects. Ochrana Rostlina, 33 (2): 135-142. Lee, S. E., Peterson, C. J., Coats, J. R., 2003. Fumigation toxicity of monoterpenoids to several stored product insects. Journal of Stored Products Research 39, 77-85. Obeng-Ofori, D., Reichmuth, C. H., Bekele, J., Hassanali A. 1997. Biological activity of 1,8- cineole, a mayor component of essential oil of Ocimum kenyense (Ayobangira) against stored product beetles. Journal of Applied Entomology, 121: 237-243. Obeng-Ofori, D., Reichmuth, C. 1999. Plant oils as potentiation agents of monoterpenes for protection of stored grains against damage by stored product beetles pests. International Journal of Pest Management, 45: 155-159. Prates, H. T., Santos, J. P., Waquil, J. M., Fabris, J. D., Oliveira, A. B., Foster, J. E., 1998. Insecticidal activity of monoterpenes against Rhyzopertha dominica (F.) and Tribolium castaneum (Herbst). Journal of Stored Products Research 34, 243-249. Regnault-Roger, C., Ribodeau, M., Hamraoui, A., Bareau, I., Blanchard, P., Gil-Munoz, M-I., Barberan, F. T., 2004. Polyphenolic compounds of Mediterranean Lamiaceae and investigation of orientational effects on Acanthoscelides obtectus (Say). Journal of Stored Products Research 40, 395-408.