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Toxicity and biological effects of essential oil from Cupressus arizonica against cotton bollworm, Helicoverpa armigera Lep.; Noctuidae

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عنوان دوره: سومین کنگره بین المللی حشره شناسی ایران
نویسندگان
Department Of Plant Protection, Faculty of Agriculture, University of Tabriz, Tabriz, Iran,
چکیده
Cotton bollworm, Helicoverpa armigera Hub., is one of the serious pests of the several agricultural crops. Essential oils are known for insect control properties. In this study, lethal and sublethal effects of essential oil from Cupressus arizonica were evaluated on the 3rd instar larvae of the insect by fumigant method. The insect was reared on artificial diet at laboratory. Bioassays were carried out at 25 ± 2 °C, 60 ± 5% RH and 16:8 (L: D) h. Young (24 h < old) 3rd instar larvae of the pest were exposed to determined concentrations of essential oil by fumigant method in 40 ml glass vials. The numbers of dead and alive insects were recorded 24 h after initial exposure. The LC50 and LC30 values were 32.65 and 27.68 µl / L air. In sublethal effects study, the third larvae were individually exposed to LC30 of the essential oil for 24 h and then biological parameters of survivors were evaluated. The means of larval and pupal weight at LC30 were 0.3 and 0.2 g, respectively that had a reduction compared to control with 0.4 and 0.3 g, respectively. The mean larval period was 16 and 21 days, and pupal period was 15 and 10 days in control and essential oil treatment, respectively. Mean number of eggs per female were 176 and 232 eggs and percentage of eggs hatching were 96 and 60 in control and treatment, respectively. Longevity of adults was 9 days in control; however, it reduced to 4 days in LC30 concentration of treatment. Eventually, 76 percent of larvae treated with LC30 pupated compared with that in control (100%). Finally, the results of this study showed that C. arizonica essential oil has a sufficient potential for controlling the pest and semi-field and field studies are recommended for applicable use of the oil.
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