Investigations on the using potential of essential oil components the control of insects and mites

ABSTRACT INVESTIGATIONS ON THE USING POTENTIAL OF ESSENTIAL OIL COMPONENTS IN THE CONTROL OF INSECTS AND MITES Fedai ERLER Ph.D. Thesis in Department of Plant Protection Adviser: Prof. Dr. İrfan TUNÇ June, 2000, 120 pages In this study, the fumigant toxicity of 8 essential oil components were assessed against different developmental stages (eggs, larvae and adults) of 3 stored-product insects (Tribolium confusum du Val., Ephestia kuehniella Zeller and Sitophilus oryzae L.). Of the eight components tested, four showed higher activity against stored product insects than the others. These four were anethole, carvacrol, thymol and y-terpinene. Menthol and 1,8-cineole were found to have low activity against all stages tested. In general, while the adults of S. oryzae and the eggs of E. kuehniella were more susceptible than the other stages, the larvae of E kuehniella were the least sensitive to all components tested. Based on the LT5o values, the efficacy of essential oil components against stored product insects was ordered as following: anethole> carvacrol>thymol>y-terpinene>/?-cymene>terpinen-4-ol> 1,8-cineole>menthol. With another study, the repellency properties of essential oil components were evaluated using Y-tube olfactometer against the adult females of T. confusum. In Y-tube olfactometer bioassays, anethole showed higher repellency against T. confusum compared to others at all doses tested. 1,8-cineole, carvacrol, thymol and terpinen-4-ol were also found the most efficient components. P-cymene, menthol and y-terpinene showed moderate repellent properties. While repellency increased with increasing concentrations of the components, it significantly decreased by the time elapsed. A parallel study was also done to evaluated the fumigant activity of components for the control of different stages of greenhouse pests {Aphis gossypii Glov., Frankliniella occidentalis Pergande and Tetranychus cinnabarinus Boisd.). According to the results obtained from the fumigant tests conducted to greenhouse pests, it was found that anethole, carvacrol and thymol were very toxic to all stages tested (the adults of A. gossypii and T. cinnabarinus and the eggs of T. cinnabarinus), except for the larvae of F. occidentalis. Menthol showed minimum fumigant property against the all stages tested. None of the components, however, could show significant fumigant toxicity to last instar larvae of F. occidentalis. In the fumigant tests conducted to both stored product insects and greenhouse pests, the effectiveness of components significantly increased by length of exposure time. There was also a highly significant increase of toxicity by increasing dose. The oviposition deterrent effects of essential oil components were tested against T. cinnabarinus. The percentage of hatchability of the resulting eggs were also calculated. iiiThe results obtained showed clearly that the fecundity of the females of T. cirmabarinus influenced more or less by the components. A strong inhibition of oviposition was produced by anethole. O.D.I, (oviposition deterrent index) in treatment with anethole was higher than those with others. Anethole proved to be more effective than the others as the percentage of reduction in the total number of eggs laid per female during the oviposition stage was 90.4% in comparison with control. Also the hatchability of the resulting eggs was greatly reduced (26.7%). Thymol and carvacrol were also the most effective components with 68.7 and 66.8% O.D.I., respectively. Terpinen-4-ol, y- terpinene and/?-cymene (55.4, 49.5 and 44.7% O.D.I., respectively) showed moderate effect. Menthol and 1,8-cineole were found to be having the lowest activity. To determine the retardant effect of essential oil components on durations of the developmental stages, newly emerged larvae of the mites T. cinnabarinus were used in the tests. In conclusion, it was clearly shown that the durations of the immature stages and the adult were slightly affected or unaffected. In terms of phytotoxicity, menthol, terpinen-4-ol and thymol appeared to be the most toxic components tested, followed by 1,8-cineole, carvacrol and y-terpinene in that order. Certain symptoms of phytotoxicity were observed which included withering as if it was frozen, discoloration and eventually drying of all plants. KEY WORDS: essential oil components, fumigant, repellent, retardant, toxicity, stored product insects, Tribolium confusion, Sitophilus oryzae, Ephestia kuehniella, greenhouse pests, Aphis gossypii, Frankliniella occidentalis, Tetranychus cinnabarinus. COMMITTEE: Prof. Dr. İrfan TUNÇ Assoc. Prof. Dr. Hüseyin GÖÇMEN Prof. Dr. Özdemir ALAO?LU IV