Studies On The Population Ecology Of Tetranychus Cinnabarinus On Manihot Esculenta

Studies on the population ecology of Tetranychus cinnabarinus on Manihot esculenta were systematically carried out. The main content and results were as follows:1. Effect of temperature on development of T. cinnabarinus:Within the temperature rang from16to32℃, the development duration of different immature stages decreased with the increasing temperature except larva. Temperature had a significant effect on the development of T. cinnabarinus.2. The experimental population life tables of T. cinnabarinus were constructed at16,20,24,28and32℃. The result showed that T. cinnabarinus had the longest female longevity (53.500d) at16℃, but little eggs were laid at the temperature. At16,2032,28,24℃, mated females laid on average0.973,2.907,4.576,4.769,4.859eggs per day, and the average eggs that mated females laid per day at28℃was almost the same as24℃. The highest intrinsic rate of increase (rm=0.2626) of T. cinnabarinus were obtained at32℃and increased as temperature increased.3.The spatial distribution type of T. cinnabarinus was assembly distribution. The population dynamics of T. cinnabarinus had two peak, the damage time of the insect were from October to November and August. Several aggregation indices、 Taylor power law and m*-x liner regression equation of Iwao were used to determine the spatial distribution type of T. cinnabarinus, and the spatial distribution type was assembly distribution. Based on these analyses, the optimum sampling number was established as followed:N=27.7+86.95√x4. The predation of female Neoseiulus barkeri on T. cinnabarinus was examined at five constant temperatures (16,20,24,28℃and32℃) under the laboratory condition RH85%. The results showed that functional responses of predator to prey density at the five temperatures approximated Holling type Ⅱ. Over the full rang of temperature tested, the predation of N. barkeri on T. cinnabarinus increased with increasing temperature, and peaked at28℃, the handling time is also the shortest. But the a’/Th value of female N. barkeri vary from different temperature. The a’/Th value increased with increasing temperature, and was significantly higher at28℃and32℃.