JWSS - Journal of Water and Soil Science

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  In order to evaluate insecticidal potential of some botanical extracts, a factorial experiment of complete randomized design with three replications on Callosobruchus maculatus was adopted for a pilot experiment in the laboratory. Plant extracts were prepared from 22 plants with three solvents (Methanol, Acetone and N-Hexane) with 30% concentration. Experiments were carried out at 25˚C and 70 ± 5% RH under 16: 8 (D: L) conditions. Each unit of experiment was a petri dish covered with a filter paper and 1.5 ml of each treatment solution was poured in it and 25 insects were released. Mortality was recorded after 36 hours. In this experiment, each plant extract with more than 50% mortality on C. maculaus was selected for further laboratory screening. In this stage of experiment methanolic leaf extract of Teucrium polium (with 55.04 percent mortality), hexane extract of Sonchus oleraceus (with 54.64 percent mortality), acetonic leaf extract of Calotropis procera (with 53.6 percent mortality), methanolic extract of Fumaria parviflora (with 52.7 percent mortality), methanolic extract of Capsicum annuum (with 50.04 percent mortality), and acetonic extract of Thymus vulgaris (with 50 percent mortality) were selected. After carring out the pilot experiment, the effective extracts with five concentrations of 15, 22.4, 33.5, 50.2 and 75% and one control were evaluated on the C. maculaus. This experiment also was designed in the laboratory as a factorial experiment of complete randomized design with three replications and mortality was recorded after 36 hours. In the highest concentration (75%), extract of Fumaria parviflora and extract of Thymus vulgaris (with 88.3% mortality) and extract of Sonchus oleraceus (with 78.3%) had higher and lower percentage of mortality resectively. The LC₅₀ values of effective extracts were calculated for C. maculaus after 36 hours of treatment with plant extracts. The results showed that C. maculatus with LC₅₀ = 126.27 µl/ml has highest sensitivity against extract of Fumaria parviflora and has lower sensitivity against extract of Sonchus oleraceus with LC₅₀ = 370.09 µl/ml in comparison to other extracts. Amongst the tested concentrations of plant extracts, 5 plant extracts with the concentrations that had the higher mortality on C. maculaus, were selected for experiment on Laphigma exigua in greenhouse. This experiment was carried out with complete randomized design with four replications. The acetonic leaf extract of Calotropis procera (with 57.5 %) caused the highest mortality and acetonic extract of Thymus vulgaris (with 27.5 %) caused the lowest mortality on L. exigua in comparison to other extracts.

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In this study diflubenzuron as a chitin synthesis inhibitor with a dosage of 25 mg A.I/L, and Pyriproxyfen as a juvenile hormone analogue with a dosage of 0.4 mgA.I/L were incorporated in the wax diets of young and last instar larvae of greater wax moth and reared at different temperatures (25, 30, 35°C). Results showed that these compounds in comparison with control increased larval mortality. Diflubenzuron and pyriproxyfen caused 33.9% and 24.1% mortality respectively. The young larvae showed higher mortality with the mean of 57.8% in diflubenzuron and 31.5% in pyriproxyfen. In evaluation of pupation and emergence of adults, no significant differences were observed between diflubenzuron and control. Pyriproxyfen induced reduction in pupation about 48.4% and adult emergence about 44.8% and caused some abnormalities of pupae. Last larval instar was more sensitive to JHA in this respect. Maximum pupation disruption occurred at 25ºC and 30ºC in comparison with 35ºC which reduced abnormal pupae up to 19.7%. IGRs were effective in last larval instar at 35 ºC and increased abnormality of adult up to 49.4%. Reproductive potential (egg viability, hatchability) of adults reduced in F1 generation and was 70-90 percent. IGRs have unfavorable effects on biological aspects of larvae therefore, it is possible to use IGRs alone or in conjunction with other pesticides (Fumigants) in integrated control of these pests.

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Various effects of methanolic extract of neem seed kernel on larvae of cotton boll worm, Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae) were studied and compared with those of Neem Azal T/S and Neem Plus, two commercial formulations. The pest was collected from Gorgan (Golestan Province, Iran) and reared on a bean based artificial diet. The neem seed was collected from Bandar-Abbas (Hormozgan Province) and extracted in laboratory. Growth inhibitory and antifeedant assays were carried out on larvae treated with seed kernel extracts in 3 concentrations,1, 2.5 and 5%, under choice and no-choice conditions. The neem extract had a significant antifeedancy effects on larvae. Neem Plus and 5% extract had the least and most antifeedancy effects, respectively. The most and least feeding rates belonged to Neem Plus and Neem Azal treatments, respectively, which differed significantly (P<0.05). Feeding deterrence index (FDI) was highest in 5% extract which also differed significantly from Neem Plus treatment. Larvae treated with extract led to malformation and prevented formation of pupa and ultimately caused death. The LT50 values with confidence limit (CL) of 95% were 3.84 and 4.13 d, for Neem Azal and 5% extract respectively. DC50 and EC50 of extract were 4.73% and 2.73% at similar CL, respectively.