Predation Ability Of Amblyseius Eharai(Acari: Phytoseiidae)on Tetranychus Piercei(Acari: Tetranychidae)

Overuse of chemical pesticides aggravates the problem of pest resistance to pesticides,and suppressing the population of natural enemies,and causing serious environmental pollution and food safety problems.Biological control as a long-term,environmentally friendly and self-sustaining way has received an increasing amount of attention.Predatory mites particularly are among the key components in the integrated pest management.The objective of this study was to investigate the control efficiency of Amblyseius eharai（Acari:Phytoseiidae）,a widely distributed predatory natural enemy of pest mites and small insects,on Tetranychus piercei,a key agricultural pest mite.A laboratory population of A.eharai fed on T.piercei was established,and the age-stage,two-sex life tables of individually-reared or group-reared A.eharai on T.piercei were constructed.The prey preference of A.eharai on egg,larva and nymph of T.piercei on different sizes of leaf surfaces were investigated.The functional response of A.eharai on egg,larva and nymph of T.piercei were evaluated.The results showed that A.eharai has great potential to prevent and control T.piercei.The main results of this research are as follows:The experiment on the age-stage,two-sex life tables of A.eharai individually-or group-reared on T.piercei were carried out under laboratory conditions of 25±2°C,80±5%RH and 16L:8D photoperiod.The intrinsic rate of increase（r）,finite rate of increase（λ）,net reproductive rate（R₀）,mean generation time（T）,and doubling time（DT）of the individually-and group-reared predators were 0.20±0.01/d,1.22±0.01/d,17.69±2.49 offspring/individual,14.31±0.30 d,3.45±0.22 d and 0.21±0.01/d,1.24±0.01/d,21.40±2.45offspring/individual,14.34±0.17 d,3.24±0.15 d,respectively.The population dynamic parameters of the group-reared A.eharai showed no significant difference from those of the individually-reared group.The prey preference of female adult A.eharai on T.piercei was tested on three different sizes of leaf areas（d=2,4,and 6 cm）.The results showed that the size of leaf areas didn’t affect the preference of A.eharai,which preferred to feed on nymphs,followed by larvae and eggs.However,the leaf size affected the predation efficiency.When the density of prey was constant,the number of nymphs of T.piercei fed by female adult A.eharai decreased accordingly as the increase of leaf area.Within a same leaf area,the number of T.piercei nymphs fed by female adult A.eharai increased.This indicated that the size of the leaf area didn’t affect the feeding preference of A.eharai to the immature stages of T.piercei.The predation of A.eharai on eggs and larvae of T.piercei was significantly greater than that on nymphs.The daily maximum consumption of A.eharai on eggs,larvae and nymphs of T.piercei were57.00±2.35,58.60±1.86,27.60±1.21,respectively.The predation rate demonstrated the same trend and fitted with a cubic curve within 24 hours.The predation rate reached the maximum within the first 3 hours,then decreased,but slightly increased after 18 hours.The predation rate of female adult A.eharai on eggs of T.piercei was basically stable in the first 12 hours,then gradually decreased from 12 hours to 21 hours,and slightly increased in the last 3 hours.The predation functional response of A.eharai on T.piercei eggs,larvae and nymphs all fell in Holling type II,that was the predation increased with the density.However,when the density of the prey reached a certain level,the predation stabilized after reaching the maximum value.The predation ability of A.eharai on T.piercei larvae was the largest.The searching efficiency of A.eharai on eggs,larvae and nymphs of T.piercei all increased with the density of prey.To sum up,A.eharai exhibited a strong predation efficiency against T.piercei,and implied a great potentiality for prevention and control of T.piercei.This research provided a theoretical basis for the mass breeding and field application of A.eharai in biological control of pest mites.