| Summary: | 博士 === 國立中興大學 === 昆蟲學系所 === 94 === The life history of Bemisia argentifolii Bellows & Perring (Homoptera: Aleyrodidae) on tomato was studied based on the age-stage, two-sex life table at 15, 20, 25, 28, 30, and 35℃. The intrinsic rate of increase (r) at these temperatures is -0.0176, 0.0667, 0.1469, 0.1611, 0.1745, and 0.0989 d-1, respectively. The relationship among the gross reproductive rate (GRR), the net reproductive rate (R0) and the preadult survivorship (la) is consistent with for all results at different temperatures. The mean generation time is 81.9, 48.6, 28.4, 25.3, 22.1, and 18.2 days, respectively. The developmental rate of the egg stage at different temperatures fit a linear equation with a thermal summation 89.2 degree-day and a developmental threshold of 11.4℃. The developmental rates of the nymph stage fit Stinner et al.’s model and the parameters of C, Rmax, k1, k2 were 0.085, 0.0833, 5.298, and -0.263, respectively. To reveal the differences among the life tables under laboratory, screen house and field conditions, life history data of B. argentifolii on tomato were collected in a screen house and in the field. In the screen house, the intrinsic rate of increase was 0.1171 d-1, the net reproductive rate (R0) was 11.1 offspring/individual, the mean generation time (T) was 20.8 d, and the life expectancy of newborn was 22.4 d. Population parameters were also obtained for B. argentifolii kept in cages in two fields. The intrinsic rates of increase were 0.0769 and 0.1024 day-1, the net reproductive rates were 5 and 9.8 offspring/individual, and the mean generation times were 21.8 and 22.6 d. Significant differences were found for the life tables generated under screen house, field, and laboratory conditions. In the dispersal experiment, adults of B. argentifolii were found to be capable of dispersing at least 3 m within a 24 h period. Immediately after dispersal, adults are able to oviposit on the new host plant. The population growth initialized with 20 eggs showed similar stage structure to the simulation based on the age-stage, two-sex life table at 25℃. Results of computer simulation showed that a single treatment on the 54th day after the first adult was detected would keep the pest population below the economic threshold (20 adults/plant) at 20℃for a period of 60 days. At 25℃, however, three treatments, i.e., on the 26th, 43rd and 58th day, would be necessary to keep the pest population below the same economic threshold. At 28℃, three treatments on the 26th, 42nd and 56th day are sufficient for control. In pesticide-treated fields, eggs, nymphs and adults showed an aggregated distribution with a variance/mean ratio up to 5.5. In untreated fields, all developmental stages showed significant aggregated distribution with the highest variance/mean ratio of 11.3. In untreated screen houses, the highest density was only 0.1 adult/plant, and the infection rate of TYLCV (tomato yellow leaf curl virus) was only 5%. However, in untreated fields, the highest density of developmental stages was 9.3 eggs/plant, 12.3 nymphs and 3.5 adults respectively, and, by the end of the experiment, the infection rate of TYLCV was 90%. The LC50 of abamectin to the nymphal stage of B. argentifolii is 3.88 mg (AI)/liter, and the LC90 is 15.4 mg (AI)/liter. The LC50 of imidacloprid to nymphal stage is 3.6 mg (AI)/liter. The adult stage is more susceptible to both insecticides, while the egg stage is non-susceptible to all tested concentrations. The economic threshold (ET) equation based on the growth of tomato is described as a function of time: ET = 24.0307 + 100.7306/(1 + 32.2155 e -0.0962 t). The control strategy based on ET and computer simulation shows that a single application of imidacloprid is sufficient to control B. argentifolii in screen house. It increases a profit of 24,545 NT/ha in comparison with routine weekly control practiced by most farmers. Computer simulation of population growth based on life tables incorporating ET provides the efficient timing of control; it reduces the cost of control and increases the profit of farming.
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