| Greenhouse whitefly, Trialeurodes vaporariorum(Westwood) is an important pest. it has serious overlapping generations, and the host is very extensive.Due to its fast population development and reproductive rate, low mortality and high diffusion. capacity, this whitefly has brought huge economic losses to agricultural production. Reports of greenhouse whitefly at home and abroad has many, but because China’s vast territory, different geographical environment and the stress of cropping systems can form different populations, only some research was mainly focused on the greenhouse whitefly biology ecology, monitoring and prevention in northern region. In recent years, the pest causing widespread harm in tobacco fields of Chongqing area, while the research of biology,ecology and population are deficiency. Therefore we focused on the research of Tobacco T. vaporariorum population in Fengjie County of Chongqing,this paper mainly discussed the effects of the growth and development of T. vaporariorum in different temperature, humidity, photoperiod, and host environmental conditions and the population dynamics in the field to provide the theoretical basis for the prevention and control of T. vaporariorum.The main research results are as follows:1. The influence of temperature on the T. vaporariorum experimental population reproductionThe effects of the growth and reproduction of T. vaporariorum were researched at the range of 20 to 35 °C. The results show that, within the temperature range of 20-26 °C, the population in all instars developmental duration was shortened with the increasing of temperature. A completed generation need 35.72 d under 20 °C, whereas 22.95 d under 26 °C,under 29 °C – 35 °C its condition developmental duration extended another trend, namely 23.15 d, 23.3 d and 26.83 d. Initial temperature of the greenhouse whitefly population development required to be 7.54 °C, effective accumulated temperature was 389.86 day-degrees. In addition, the survival rates of all the T. vaporariorum instars at different temperatures also have significant difference. Eggs, third instar, fourth instar nymphs have no significant difference at 20, 23 and 32 °C conditions, but the survival rate at 35 °C was significantly lower, respectively, 61.62%, 46.16% and 35.22%. At 26 °C condition, the survival rates of T. vaporariorum instars are higher, followed by 94.66%, 88.87%, 93.33%, 92.24% and 95.92%. Also longevity and fecundity were significantly different at different temperatures, At 20 °C,average life expectancy was 38.6 d, but only 8.3 d at 35°C, which showed the average female life expectancy was gradually shortened with the increase of temperature. In the test temperature range, with increasing temperature, total egg production decreased, the fecundity at 20 °C is more than three times as the amount of eggs at 35 °C. Highest single female fecundity occurred at 20 °C. the most suitable temperature of Integrated development, survival and reproduction parameters, population growth and development is about 26 °C.2. The influence of humidity and photoperiod on T. vaporariorum experimental population reproductionThe effects of the growth and development of T. vaporariorum on different relative humidity(40%, 55%, 70%, 85%) and photoperiod(16L: 8D, 14L: 10 D, 12L: 12D) were researched. The results showed that the development duration of T. vaporariorum within 40% to 55% relative humidity has no significant difference. When the relative humidity was 70%, the development duration of T. vaporariorum was shortest about 22.35 d, when relative humidity rised to 80%, the development duration was extended about 22.87 d. Under the condition of relative humidity of 70%, 1st and 2nd instar nymphs development time is significantly shorter than the other conditions, but the eggs and 3rd instar nymphs have a longer development time. In the pseudopupa stage the development under the condition of 85% RH need a long time, with no significant difference with other relative humidity conditions.. The influence of the survival of the population on relative humidity showed pseudopupa survival rate had no significant difference in different relative humidity conditions, and higher at around 90%. Instars survival rates were higher at 70%, respectively 89.82%, 84.48%, 87.44%, 84.29%, 94.27%. In addition, under the condition of relative humidity of 70%, T. vaporariorum adult’s longevity and fecundity were the highest with 30.1 d, 148.3 respectively.The above data show that the T. vaporariorum population growth optimum relative humidity is 70%.At the same teperature and relative humidity conditions, the longer the exposure time, the shorter the duration of the development of T. vaporariorum, the faster the rate of development, the longer the adult longevity, and the fecundity is also higher. And the average survival rates of instars were higher. All the results indicated that long-day occurrence was good to the growth and fecundity of T. vaporariorum.3. The influence of different host plants on T. vaporariorum experimental population reproductionThe results show that, there are significant differences(P < 0.05) in the five varieties of development period. The results showed that the growth of greenhouse whitefly calendar period in the order: NC55, YUN97, Hongda, MSK326, KRK26. Each period have different developmental duration on different tobacco varieties.The developmental duration of 1st instar nymphs about 2.3 d on KRK26 tobacco..The developmental duration of 2nd instar nymphs was shortest on MSK326 and longest in YUN97. The developmental duration of 3rd instar nymphs was shortest on YUN97. The developmental duration of pseudopupa periods was shortest in KRK26, longest in MSK326 and YUN97.The survival rate of the eggs was highest in MSK326 about 94.87%, and the survival rates in the other four kinds of tobacco were all more than 90%, of which the tobacco variety YUN97 eggs lowest survival rate, 90.74%. The survival rate of 1st instar nymphs on the NC55 was the highest, followed by YUN97. The survival rate of 2nd instar nymphs on the NC55 was the highest which was 92.21%. And the lowest was in YUN97 for 70.91%. The survival rates of 3rd instar nymphs in five tobacco have no significant difference(P > 0.05), and the survival rate is relatively high, more than 90%. Psuedopupal survival on HD is the lowest, about 72.58%, the survival rate was 85.69% on YUN97.The average longevity of T. vaporariorum adults on YUN97 were longest, about 30.1 d, and the average fecundity was 148.3. The average fecundity on HD was highest with 163.3, but the adult longevity was shortest, only 19.6 d.4. The preliminary study on occurrence dynamic T. vaporariorum of tobacco field in Fengjie of ChongqingThe results show that the T. vaporariorum populations in the field occurred unimodal growth. Adults began to appear in late May in the field, and from July to August the T. vaporariorum occurrence amount reached a peak, to the end of September,as the temperature drops, the amount of T. vaporariorum occurrence in the field is gradually reduced. T. vaporariorum had certain dispersal ability, located in the field along with changes in environmental conditions and made the appropriate dispersal. At low temperatures in late May, T. vaporariorum main infested in the tobacco fields at lower elevations. As temperatures rising high, the temperature of low elevation areas are not suitable for the T. vaporariorum growth and reproduction. So the population is gradually transferred to the high altitude tobacco field to make damage. When the temperature gradually became cooler, the population has shifted to the low altitude tobacco field again. In addition, the survey also found that the T. vaporariorum population prefers to damage in the shade. |
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