الفهرس 
Chemical composition of essential oilsOnly 14 pages are availabe for public view
 |  | from | 212 |  |  |
| | | from | 212 | | |
Abstract
objective of this study was to explore a novel, biodegradable, safe and environment friendly replacement of conventional synthetic insecticide to protect stored rice and cowpea commodities against two major and most common stored grain pests in storage facilities in Egypt; S. oryzae and C. maculatus. This study determines the major constituents present in the EOs. The contact, growth regulatory, antifeedant and repellent activities of four commercially available EOs (cumin, mandarin, marigold and better orange) and three EO monoterpenoid components (citronellol, geraniol and linalool) and one synthetic pyrethroid insecticide (Deltamethrin) were evaluated against S. oryzae and C. maculatus . In addition, the present study also aims to identify the type, number and distribution of sensilla on the antennae of S. oryzae and C. maculatus to understand these beetles species feeding behavior. VI.1. Chemical constituents of the essential oils. The essential oils were analyzed by Gas chromatography (GC) -mass spectrometry (MS). Analysis of bitter orange, C. aurantium peel EO revealed the presence of 48 compounds. The EO contained a significant amount of limonene (85.47%). α –terpineol, β- myrcene and α – pinene were present in small quantities (2.37, 1.67 and 1.01%), respectively. In mandarin, C. reticulata peel EO, a total of 53 components was detected. The main compound was tricarbonyl [methyl 6- vinylidenehepta 2,4-dien-1-oate]iron (52.8%) followed by dimethyl hexane (15.28%), limonene (5.45%) and1,3,6 octatriene (3.88%). Fifty compounds were identified in cumin, C. cyminum seed EO. The main components were propanal (26.07%) and ˠ- terpinene (15.78%) followed by Benzenemethanol (11.32%), isopropylidene (10.48%), β – pinene (10.37%) and p-cymene (7.45 %). A total of 50 components were identified in marigold, Tagetes erecta flower essential oil. The main constituents were α- terthienyl (8.79%), squalene (7.92%), 2-cyclohexen-1-one (2.83%), pyridine-3- carboxamide (2.44%), ˠ-tocopherol (2.27%) and β-amyrin (2.08%). VI.2. toxicity of essential oils alone and in mixtures, monoterpenoids and Deltamethrin against Sitophilus oryzae and Callosobruchus maculatus adults. Contact toxicity of chemicals to S. oryzae and C. maculatus adults was assayed by coating onto wheat grains or cowpea seeds. VI.2.1. toxicity of essential oils alone and Deltamethrin against Sitophilus oryzae adults. Two days post wheat grain treatment, Deltamethrin possessed the highest contact toxicity against S. oryzae when compared with the other EOs with LC50 value of 10.7 ppm followed by mandarin, cumin, bitter orange and marigold EOs with LC50 value of 8974, 18925, 46050 and 114938.6 ppm, respectively. Five days post exposure, Deltamethrin induced 100% mortality at the concentration of 60 ppm. Bitter orange EO was the most toxic to S. oryzae with LC50 value of 1752.7 ppm followed by mandarin, cumin and marigold EOs with LC50 values of 2090.8, 2210.9 and 3296.6 ppm, respectively. VI.2.2. toxicity of essential oils alone and Deltamethrin against Callosobruchus maculatus adults. Deltamethrin exhibited markedly the highest contact toxicity against C. maculatus as compared with the four EOs two days post exposure with LC50 value of 8.7 ppm. Meanwhile, bitter orange EO exhibited highest contact toxicity with LC50 value of 1138.5 ppm followed by cumin, marigold and mandarin EOs with LC50 values of 1626.2, 7601.0 and 8901.4 ppm, respectively. Five days post exposure, mandarin EO was the most toxic followed by cumin, bitter orange and marigold EOs with LC50 values of 14, 63.3, 362 and 437.9 ppm, respectively. Deltamethrin still possess the highest contact toxicity five days post exposure of C. maculatus to treated cowpea seeds. VI.2.3. Co-toxicity of essential oil mixtures against Sitophilus oryzae and Callosobruchus maculatus adults. Mixtures of EOs possess either antagonistic or synergistic toxic effects against S. oryzae and C. maculatus two days post exposure. Mixture of marigold plus mandarin wheat grain protectant exhibited the highest synergistic toxic effect against S. oryzae with calculated co-toxicity coefficient value of 17.4. In contrast, treatment of cowpea seeds with the combined mixtures of most EOs evoked a moderate synergistic toxic effect against C. maculatus. However, in case of combined mixtures of marigold plus cumin and bitter orange plus cumin antagonistic toxic effect against C. maculatus was observed with calculated co-toxicity coefficient values of 0.79 and 0.15, respectively. VI.2.4. toxicity of the monoterpenoids citronellol, geraniol and linalool against Sitophilus oryzae and Callosobruchus maculatus adults. Two days post exposure, only the higher concentration of monoterpenoids (20000 ppm) exhibited moderate toxic effect against S. oryzae. Five days post exposure, monoterpenoids induced higher mortality rates (60%, 63.3% and 53.3% at (20000 ppm), respectively of adults of S. oryzae. The monoterpenoids exhibited considerably high contact lethal effect against C. maculatus two days post exposure. According to the toxicity index, geraniol was the most toxic compared to either linalool or citronellol five days post exposure of C. maculatus to treated cowpea seeds. VI.3. Effect of essential oils, monoterpenoids and Deltamethrin on the biology of Sitophilus oryzae and Callosobruchus maculatus. The effects EOs, the monoterpenoids and Deltamethrin on S. oryzae and C. maculatus biology were evaluated in terms of adult emergence and reproductive potential. In addition, the effects of treatments on cowpea, V. unguiculata weight loss caused by C. maculatus were also investigated. VI.3.1. Effect of essential oils, monoterpenoids and Deltamethrin on the biology of Sitophilus oryzae. VI.3.1.1. Effect of essential oils on Sitophilus oryzae adult emergence. All EOs at all concentrations reduced the number of S. oryzae offspring as compared to control. Adult emergence from treated grains decreased with increase in concentration of EO. No insects emerged from grains treated with 10000 ppm and 5000 ppm of cumin, mandarin, marigold and bitter orange EOs. VI.3.1.2. Effect of monoterpenoids on Sitophilus oryzae adult emergence. All concentrations of citronellol, geraniol and linalool components significantly decreased the total number of emerged adults as compared to the control. At the higher concentrations of 20000, 15000, 10000 and 5000 ppm, the reduction of emerged adult ranged between 94.35 and 99.55%.