Analyses of Numerical Responses and Main Life Parameters for Determining the Suppression of Amblyseius cucumeris on Panonychus citri

In this paper, the numeral response and main parameters of experimental population life table were analyzed for determining the suppressing ability of Amblyseius cucumeris on Panonychus citri. The result showed that: (1) Under 21-31°C and 1 - 9 prey densities/leaf fragment condition, the prey consumptions of A. cucumeris increased with the temperature or prey density; (2) In 1:3 predator-prey ratio treatment, the suppression of P. citri (Ro=34.0053; T=19.4369; t=3.8204) was rather weak, it was enhanced as the ratio over 5:30, and the populations of P. citri in these treatments can be fully controlled within 4-5 days; (3) Under 25±1°C, 80-85% RH and 15L: 9D illumination conditions, the net reproductive rate, mean generation duration and the time for population double increase of P. citri (Ro=34.0053; T=19.4369; t=3.8204) were higher than those of A. cucumeris (Ro=21.8750; T=16.8943; t=3.7954). While the intrinsic rate of increase and finite rate of increase of the former (rm=0.1814; λ=1.1989) were lower than those of the latter (rm=0.1826; λ=1.2004). These results indicated that A. cucumeris is a desirable bio-control agent to suppress P. citri at lower population stage in citrus orchard.

Sublethal Effects of Metaflumizone on Plutella xylostella (Lepidoptera: Plutellidae)

Metaflumizone is a novel sodium channel blocker insecticide, which has been registered for controling the diamondback moth （DBM）, Plutella xylostella （Lepidoptera： Plutellidae） in China. It is unavoidable for DBMs to be exposed to sublethal dose of metaflumizone in brassicaceous vegetable field. Sublethal effects of metaflumizone at LC15 （1.06 mg L-1） and LCz5 （2.03 mg L-1） on the biological characteristics were investigated. Pupation rate, pupal period and pupal weight were significantly declined comparing with the control （P=0.05） when third instar larvae were exposed to LC15 and LC25 of metaflumizone. Comparing the control group to LC15 and LC25 treatment groups, there were significant differences in the development periods of eggs, first instar larvae, pupae and total preoviposition period. The peak of age-specific fecundity in LC15 and LC25 treatment groups was lagged behind control group. Mean values of intrinsic rate of increase （rm）, net reproductive rate （R0） and finite rate of increase （λ） observed from the LCl5 and LC25 treatment groups were lower than those from the control group. But mean values of gross reproduction rate （GRR） was not different. The mean generation time （T） of the treatment groups was prolonged. Whether sublethal doses of metaflumizone could stimulate reproduction in the long term needs further investigation on continuous generations.

Comparative life table analysis of Tetranychus urticae （Acari Tetranychidae） on 14 soybean genotypes

The life table parameters of two-spotted spider mite （TSSM）, Tetranychus urticae Koch, on 14 soybean genotypes （Sari, Sahar, Tellar, Zane, Ks3494, LI7, Dpx, 032, 033, Clark, Hill, 127, Tms and Williams） were evaluated at 28 ±1℃, 65% ± 5% RH and a photoperiod of 16 ： 8 h L ： D. The survivorship data （lx） of adult females were fitted to the Weibull frequency distribution model in all genotypes tested. Based on the Weibull parameters, the survival curve was type I on all genotypes, which indicated that the mortality mostly occurred in old individuals. Furthermore, two mathematical models （Analytis and Enkegaard） were fitted to age-specific fecundity data （mx）. The highest intrinsic rate of increase （rm） was recorded on L17 （0.392） and the lowest values of this parameter were obtained on Tms （0.233）, Hill （0.236）, 032 （0.236）, 127 （0.237） and Clark （0.240）. In addition, net reproductive rate （R0） and finite rate of increase （λ） of the TSSM had the highest value on L17 as 45.521 and 1.475, respectively. The lowest values of these parameters were recorded on Tms as 12.149 and 1.258, respectively. Doubling time （DT） varied significantly on different genotypes and the shortest and longest values of this period were obtained on L17 and 032, respectively. Our findings revealed that Tms, Hill, 032, 127 and Clark were less suitable genotypes, suggesting that they are more resistant to the TSSM than the other genotypes.

Multiaxial fatigue life prediction of composite materials

In order to analyze the stress and strain fields in the fibers and the matrix in composite materials,a fiber-scale unit cell model is established and the corresponding periodical boundary conditions are introduced.Assuming matrix cracking as the failure mode of composite materials,an energy-based fatigue damage parameter and a multiaxial fatigue life prediction method are established.This method only needs the material properties of the fibers and the matrix to be known.After the relationship between the fatigue damage parameter and the fatigue life under any arbitrary test condition is established,the multiaxial fatigue life under any other load condition can be predicted.The proposed method has been verified using two different kinds of load forms.One is unidirectional laminates subjected to cyclic off-axis loading,and the other is filament wound composites subjected to cyclic tension-torsion loading.The fatigue lives predicted using the proposed model are in good agreements with the experimental results for both kinds of load forms.