Effects of hexaflumuron at 10% lethal concentration （LC10） and LC25 on development and reproduction parameters of the diamondback moth, Plutella xylostella （Linnaeus, 1753） （Lep.： Yponomeutidae） were investigat...Effects of hexaflumuron at 10% lethal concentration （LC10） and LC25 on development and reproduction parameters of the diamondback moth, Plutella xylostella （Linnaeus, 1753） （Lep.： Yponomeutidae） were investigated. Estimated LC50, LC10 and LC25 values of leaf dip bioassay of hexaflumuron on the third instar larvae of the P xylostella were 1.48, 0.59 and 0.91 mg/L, respectively. Hexaflumuron decreased pupal weight in the parent generation at sublethal concentrations but in the offspring generation, this effect was not observed. Sublethal concentrations increased egg, first and second larval instar and pupa developmental time and shortened life span of adults, but did not change the third and fourth larval instars and pre-pupa developmental period. Also fecundity of females reduced significantly but hatchability of treatments and control were similar. Survival rate of pre-adult stages declined significantly at LC25 concentration. Reproduction parameters such as reproductive rate （R0） and intrinsic rate of increase in sublethal concentrations were significantly lower compared with control, but gross reproduction rate （GRR） at the LC10 concentration was increased and it could be hormoligosis. Also hexaflumuron significantly increased doubling time （Dt）. We conclude that the sublethal effects of hexaflumuron might exhibit significant effects on the population dynamics of P xylostella.展开更多
The effect of temperature on the development of the Plutella xylostella （Linnaeus） （Lepidoptera： PluteUidae）, was evaluated at eight constant temperatures （10, 15, 20, 25, 28, 30, 32.5 and 35~C）, with relative ...The effect of temperature on the development of the Plutella xylostella （Linnaeus） （Lepidoptera： PluteUidae）, was evaluated at eight constant temperatures （10, 15, 20, 25, 28, 30, 32.5 and 35~C）, with relative humidity of 65% and a photoperiod of 14：10 （L： D） hours on two host plants, cauliflower, Brassica oleracea var. botrytis and cabbage, Brassica oleracea var. capitata. The low temperature threshold was estimated to be 7.06℃ and 7.84℃ and the thermal constant was 263.74 and 261.58 degree-days for P. xylostella on cauliflower and cabbage, respectively, using the linear model. Data were fitted to various nonlinear temperature-dependent models, and the low and high temperature thresholds, as well as the optimum temperature for development, has been estimated. Criteria of choice from the literature were used to evaluate models and to select the most suitable equation for P. xylostella development on each host plant. Conclusively, linear and Briere-2 models are recommended for the description of temperature-dependent development of P. xylostella on two host plants.展开更多
文摘Effects of hexaflumuron at 10% lethal concentration （LC10） and LC25 on development and reproduction parameters of the diamondback moth, Plutella xylostella （Linnaeus, 1753） （Lep.： Yponomeutidae） were investigated. Estimated LC50, LC10 and LC25 values of leaf dip bioassay of hexaflumuron on the third instar larvae of the P xylostella were 1.48, 0.59 and 0.91 mg/L, respectively. Hexaflumuron decreased pupal weight in the parent generation at sublethal concentrations but in the offspring generation, this effect was not observed. Sublethal concentrations increased egg, first and second larval instar and pupa developmental time and shortened life span of adults, but did not change the third and fourth larval instars and pre-pupa developmental period. Also fecundity of females reduced significantly but hatchability of treatments and control were similar. Survival rate of pre-adult stages declined significantly at LC25 concentration. Reproduction parameters such as reproductive rate （R0） and intrinsic rate of increase in sublethal concentrations were significantly lower compared with control, but gross reproduction rate （GRR） at the LC10 concentration was increased and it could be hormoligosis. Also hexaflumuron significantly increased doubling time （Dt）. We conclude that the sublethal effects of hexaflumuron might exhibit significant effects on the population dynamics of P xylostella.
文摘The effect of temperature on the development of the Plutella xylostella （Linnaeus） （Lepidoptera： PluteUidae）, was evaluated at eight constant temperatures （10, 15, 20, 25, 28, 30, 32.5 and 35~C）, with relative humidity of 65% and a photoperiod of 14：10 （L： D） hours on two host plants, cauliflower, Brassica oleracea var. botrytis and cabbage, Brassica oleracea var. capitata. The low temperature threshold was estimated to be 7.06℃ and 7.84℃ and the thermal constant was 263.74 and 261.58 degree-days for P. xylostella on cauliflower and cabbage, respectively, using the linear model. Data were fitted to various nonlinear temperature-dependent models, and the low and high temperature thresholds, as well as the optimum temperature for development, has been estimated. Criteria of choice from the literature were used to evaluate models and to select the most suitable equation for P. xylostella development on each host plant. Conclusively, linear and Briere-2 models are recommended for the description of temperature-dependent development of P. xylostella on two host plants.
