| Aleurodicus dispersus Russell is a dangerous pest widely watched in the world, they invaded Hainan Island in2006, Its wide host range and rapid spread, which posed a serious threat to the production and development of the agriculture and forestry in Hainan Province. Biocontrol is the ideal approach to combat the spread of the pest. Encarsia guadeloupae Viggianis is a major parasitic natural enemy for A.dispersus. This study focused on E. guadeloupae, exploring the effects of five different temperatures (16℃,20℃,24℃,28℃,32℃) on the tested.population of E. guadeloupae and the activity of protective enzyme. The main results were as follows:1. Effects of temperature on the development and reproduction of E.guadeloupae(1) Developmental duration and survival rateThe influence of temperature on growth and development of E. guadeloupae was consistent with the general biological principles. Within a certain temperature range, the faster developmental rate is, the shorter developmental duration is. At16-32℃, E. guadeloupae could complete generation development. The development duration was range of14.90-54.41d. At28℃, the cumulative survival rate of E. guadeloupae immatures was the highest,63.82%.(2) Adult longevity and body sizeTemperature and nutrient have influence on adult longevity. The adult longevity was negtively correlated with the temperature. Adult longevity under different feeding conditions was in descending order:20%honey water solution>20%glucose>20%sucrose>20%fructose> clear water> nothing. Adult hind-tibia length varies from temperature to temperature, more obvious at less than20℃.(3) FecundityThe number of eggs was increased with the temperature range of16-28℃. At32℃, fecundity waned and the amount of oviposition reduced.Within the test temperature range, fecundity per female ranged from2to141eggs. The average of fecundity per female reached the maximum at28℃,85eggs/♀. The maximum daily fecundity was up to17eggs. The above results suggested that28℃was the optimal temperature for reproduction of E. guadeloupae. (4) Developmental threshold and effective accumulative temperatureThe threshold temperature for the development and the effective accumulative temperature for E. guadeloupae were11.33℃and495.72day-degrees. The developmental threshold temperature of the pupae was the highest,11.33℃, compared with that of the nymphs,9.11℃. It was concluded that E. guadeloupae could have9to10generations one year in Hainan Island.(5) Tested populationLife table parameters varied with temperature. The maximum intrinsic rate of increase (rm=0.18), index of population trend (1=54.25) and finite rate of increase (λ=1.21) were observed at28℃respectively. Average generation period was the shortest at32℃(T=18.08), the longest at16℃(T=60.63). Time for doubling population was the shortest at28℃(t=3.79), the longest at16℃(t=20.57). Net reproduction was the highest at28℃,54.25/♀. Various life parameters suggested that28℃is the optimal temperature for growth, development and reproduction of E. guadeloupae.2. Effects of temperature on the activity of protective enzymeThe activity of three kinds of protective enzyme on adult of E. guadeloupae was determined at different temperatures with spectrophotometric method. The result showed that, under different temperature regimes, there was different change in the activity of three kinds of protective enzyme. Among them, the activity of catalase (CAT) and superoxide dismutas (SOD) was merely sensitive to the relatively high temperature and low temperature,24℃was the most suitable temperature at which H2O2was scavenged by CAT and SOD. The activity of the CAT and SOD increased significantly at16℃and32℃, while POD showed a contrary tendency.3. Control efficiency of E. guadeloupae on A. dispersusThe functional response of E. guadeloupae on A. dispersus was consistent with Holling-Ⅱ&Holling-Ⅲ formulas at the range of tested temperatures. At the same temperature, with the increasing density of A. dispersus, the parasitic capacity of E. guadeloupae was increased, and then the searching rate was weakened. The parasitic efficiency reached the maximum at28℃, whose value of a’/Th was18.77. There was a stronger interference effects between the individual which were parasitizing, the interference effects was increase with the increasing density of E. guadeloupae. At16℃-32℃, Hassell equation (E=QP-m) could reflect the parasitic changes in different parasitoid density. At16-28℃, with the rise in temperature, searching rate and mutual interference increased, dropping at32℃. |
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