Sublethal effects of cyflumetofen and clofentezine on life table parameters of Tetranychus urticae Khoch (Prostigmata: Tetranychidae
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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
Two-spotted spider mite, Tetranychus urticae Koch, is one of the economically most important pests on a wide range of crops in fields, greenhouses and orchards worldwide. Its management has been largely based on the use of acaricides. The pest has developed considerable resistance to many chemical compounds due to short life cycle and high reproductive potential. In this research, the effect of a low lethal concentration (LC25) was studied on life table parameters of T. urticae. Fresh bean leaf discs (2 cm in diameter) were placed individually on wet cotton in Petri dishes. Three pairs of males and females of T. urticae were transferred to each leaf disc and were incubated at 25 ± 1 ͦC, 60 ± 10% RH and 16:8 h L:D. The females were allowed to lay eggs for 24 h; then, the adults were removed from each experimental unit. The leaf discs with eggs laid by females were dipped into the LC25 concentration of either cyflumetofen or clofentezine acaricide for 5 second. Cyflumetofen and clofentezine LC25 values were 0.45 and 0.20 µg a.i/ml, respectively. About 70-60 treated eggs were randomly selected and transferred individually into fresh leaf discs and reared to adult stage at above mentioned conditions. After adults’ emergence and mating, female mites were transferred onto fresh leaf discs and the number of eggs laid by females was recorded daily. The procedure was continued until the last mite died. The development time of subsequent stages, the number of eggs per female, and the sex ratio of offspring provided the basic elements for construction of life table and calculation of life-table parameters. Results showed that adult pre-oviposition period (APOP) and total pre-oviposition period (TPOP) in cyflumetofen and clofentezine treatments were 0.2 day and 10.24 days, and 0.37 day and 10.14 days, respectively. The mentioned parameters were significantly different compared to those of control (0.1 day and 7.77 days, respectively). The fecundity was obtained as 2.7, 4.22 and 15.31 eggs / female for mites treated with cyflumetofen, clofentezine and control, respectively. The LC25 of cyflumetofen and clofentezine significantly reduced T. urticae intrinsic rate of increase (r), net reproductive rate (R0) and finite rate of increase () (r=0.012 d-1, R0=1.16, 1.01d-1 and r=0.041 d-1, R0=1.61,=1.04 d-1, respectively), compared with those in control (r=0.202 d-1, R0=8.12 and 1.42 d-1). The results showed that low-lethal concentrations of tested acaricides has a strong potential for affecting life characteristics of two-spotted spider mite and reducing mite population in subsequent generations of the pest.
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