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Essential oils of four aromatic plants, Artemisia monosperma Del., Callistemon viminals (Sol.ex Gaertn.) G. Don, Citrus aurantifolia (Christm.) Swingle and Cupressus macrocarpa Hartw. ex Gordon, were evaluated for their anti-nutritional, antifeedant, growth inhibitory and insecticidal activities against Sopdoptera littoralis (Boisduval) (Lepidoptera: Noctuidae). The essential oils of A. monosperma and C. aurantifolia caused the highest reduction in relative growth rate (RGR) at the tested concentrations (125, 250, 500, 1000 and 2000mg/l). The RGR values ranged between 8.63 and 3.05 mg/day for A. monosperma, and between 10.74 and 2.89 mg/day for C. aurantifolia compared with 14.89 mg/day for control after 72 h of treatment. In general, the results showed that the values of relative growth rate (RGR) decreased with increasing the concentration of the tested oils. In addition, the tested oils significantly reduced efficiency of conversion of ingested food (ECI) and efficiency of conversion of digested food (ECD) values, particularly at the higher concentrations of 500, 1000 and 2000mg/l. On the other hand, the tested oils showed antifeedant activity against the larvae of S. littoralis with A. monosperma and C. aurantifolia oils being more active than C. viminals and C. macrocarpa oils. The tested oils showed remarkable growth inhibition effect as the growth inhibition index values were increased from 37.63 to 79.80% for A. monosperma, from 21.69 to 52.12% for C. viminals, from 16.55 to 28.59% for C. aurantifolia and from 37.64 to 52.32% for C. macrocarpa when the concentration increased from 125 to 2000mg/l. Based on chitin formation ratio values, the tested essential oils induced reduction in chitin formation. A. monosperma and C. macrocarpa essential oils revealed the highest insecticidal activity on 4^th instar larvae of S. littoralis. Examination of reproductive tracts of adult females emerged from treated larvae indicated that the tested oils caused undifferentiated ovarioles.

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In the present study, the toxicity of three oxygenated monoterpenes, viz., (R)-carvone, (R)-camphor and (1R, 2S, 5R)-menthol was evaluated against the adults of the peach fruit fly, Bactrocera zonata (Saunders). Effects of these monoterpenes on oviposition, adult longevity and ovarian development have also been studied. The tested compounds revealed strong toxic effect against the adults of B. zonata. Nevertheless, (-)-carvone showed higher insecticidal activity than (1R, 2S, 5R)-menthol and (R)-camphor. Moreover, the tested monoterpenes induced significant reduction in female longevity at 20 and 50 mg/kg compared with control, with (-)-carvone being the most effective monoterpene. In addition, egg deposition was completely inhibited when the adults were treated with (-)-carvone at 20 and 50 mg/kg, and (1R, 2S, 5R)-menthol and (R)-camphor at 50 mg/kg. Histological studies indicated that monoterpenes induced delay in the development of ovarioles of females that fed on artificial diet treated with 20 and 50 mg/kg of compounds. Changes, such as empty egg chambers; constricted germarium, vacant spaces between ovarioles and failure of oocyte formation were observed.

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The use of adjuvants enhances the insecticide efficiency and increases the persistence of insecticides. In this study, the effect of adjuvants on the toxicity of chlorpyrifos and cyhalothrin formulations were investigated under laboratory and field conditions. The comparative toxicity of two chlorpyrifos [(48% Emulsifiable concentrate (EC)] formulations (Dursban and Pyrifos El Nasr), two cyhalothrin (5% EC) formulations (Halothrin Gold El Nasr and Lambada Mox) and two adjuvants (Top Film and Tritone K) were examined against the second and the fourth larval stages of Spodoptera littoralis. The effect of adjuvants on the toxicity of chlorpyrifos and cyhalothrin formulations were investigated under laboratory and field conditions. The results showed that Dursban exhibited the highest toxicity against the second and fourth larval stages of S. littoralis with LC₅₀ values of 0.2 and 1.11 mg L^-1, respectively. In contrast, Pyrifos El Nasr had the lowest toxicity against both larval stages. The results of joint toxic effect between adjuvants and insecticides indicated that adjuvants revealed potentiating effect on the toxicity of four insecticide formulations as co-toxicity factor values were greater than +20. Mixing the adjuvants with chlorpyrifos and cyhalothrin formulations in spraying tank before application of insecticides in field strongly increased the toxicity and the persistence of insecticides. Cyhalothrin formulations mixed with adjuvants gave continued significant mortality through 21 days, while chlorpyrifos gave continued significant mortality through 15 days of treatment. However, chlorpyrifos and cyhalothrin formulations without mixing with adjuvants gave significant mortality through 3 to 4 days of treatments. These results indicated that adjuvants increased efficiency and residual effect of chlorpyrifos and cyhalothrin commercial formulations. Therefore, the adjuvants can be used for reducing the number of applications in the season and the application rates of insecticides.

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The insecticidal and antifungal activities of Curcuma longa L. rhizome extracts and two isolated compounds, namely, ar-turmerone and curcumin, were evaluated. Rhizomes of C. longa were extracted with n-hexane, methylene chloride, methanol and water, successively. Hexane, methylene chloride, and methanol extracts exhibited remarkable insecticidal activity against the larvae of Culex pipiens. The LC₅₀ values were 5.28, 5.82, and 6.44 mg L^-1, respectively, after 48 h. In contrary, the extracts exhibited weak toxic effect on the third instar larvae of Spodoptera littoralis. The LC₅₀ values of water, methylene chloride, and hexane extracts were 495.9, 565.7 and 709.7 mg L^-1, respectively after 48 hours. On the other hand, the extracts showed variable antifungal activity against plant pathogenic fungi, Fusarium oxysporum, Pythium debaryanum, Phytophthora infestans, Fusarium solani and Alternaria alternata. Methanol extract had the highest antifungal activity among the tested extracts with EC₅₀ values of 159.8, 242.7, and 322.2 mg L^-1 on P. infestans, F. solani and A. alternata, respectively. Two compounds, namely, ar-turmerone and curcumin were isolated from methylene chloride/methanol (1:1) extract of C. longa rhizomes and their chemical structures were identified by using spectroscopic analysis. Ar-Turmerone had moderate toxicity against C. pipiens larvae. The LC₅₀ values were 158.5 and 117.6 mg L^-1 after 24 and 48 hours, respectively. In addition, ar-turmerone showed moderate antifungal activity against P. infestans (EC₅₀= 588.9 mg L^-1) and weak activity against F. solani (EC₅₀= 820.6 mg L^-1). Curcumin caused 51.1 and 54.32% growth inhibition of F. oxysporum and P. infestans at 250 mg L^-1, respectively.
 

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The control of different agricultural insect pests still relies mainly on the use of synthetic insecticides. However, excessive use of these chemicals cause many problems, including high residue levels, harmful effects on the environment and human health, and development of insect resistance. Therefore, new strategies for the management of agricultural insects are urgently needed. Plant-based natural products are promising alternatives to be applied for pest control, with remarkable and broad-spectrum biological activities. Among the plant secondary metabolites, essential oils, and their major constituents, mainly monoterpenes, have been widely studied for their application in insect control, food additives, perfumes and cosmetics. In this review, we focus on the studies describing the toxic effects of monoterpenes, including fumigant, contact and residual toxicities against insect pests attacking economic crops in fields. Furthermore, the effects of monoterpenes on insect behaviors (antifeedant and repellent activities) and insect growth regulation are also discussed.

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Fungi are a good source for lead molecules in drug discovery and development. However, many compounds derived from fungi were not evaluated for their bioactivity against economic, agricultural, and public health pests. Twelve fungal secondary metabolites (1-12) were evaluated for herbicidal activity against Silybum marianum and insecticidal activity against Culex pipiens larvae. Among the tested metabolites, brefeldin A (6) and 6-eopxy-4-hydroxy-3-methoxy-5-methyl-cyclohex-2-en-1-one (11) showed potent herbicidal activity against S. marianum with complete inhibition of seed germination at 500 mg L⁻¹. Compound 6 revealed an exceptional herbicidal activity as it caused complete inhibition of root growth and strong reduction in shoot growth (I = 74.5%) and germination (10.0%) at 25 mg L⁻¹. In addition, dehydroaustin (9), phomaxanthone A (4) and deacetylphomaxanthone A (5) displayed a potent toxicity against fourth larval instar of C. pipiens with LC₅₀ values of 3.27, 57.03 and 63.50 mg L⁻¹, respectively. Based on the results of this study, compounds 4-6, 9 and 11 should be developed as natural pesticides.