Study On The Biology And Application Of Lasioseius Sp.

Lasioseius sp. (Acari: Mesostigmata: Ascidae) is a common predatory mite with potential economic value in pest control. In this these the development, reproduction and morphology of Lasioseius sp. fed on Tyrophagus putrescentiae as well as developmental duration of Lasioseius sp. fed on Bemisia tabaci were studied at five temperatures. To develop basic knowledge on the biological control of Bemisia tabaci, a series of experiments on interspecific predation between Lasioseius sp. and Lasioseius sugawarai, the influence of development and reproduction of pesticide to Lasioseius sp. and the early effect of releasing Lasioseius sp. to Bemisia tabaci in green houses were conducted. The major results are as follows:1 Effects of temperature on the development and reproduction of Lasioseius sp. fed on Tyrophagus putrescentiae1.1 Effect of temperature on development of Lasioseius sp.The temperature effects on the development and reproduction of Lasioseius sp. fed on larvae and nymphs of Tyrophagus putrescentiae at 16℃, 20℃, 24℃, 28℃and 32℃were observed. The results showed that the developmental durations of Lasioseius sp. were shortened when the temperature was increased from 16℃to 28℃. The generation time were 35.52±2.60, 17.76±1.54, 11.05±1.34, 7.64±0.48 and 9.14±1.66 days at 16℃, 20℃, 24℃, 28℃and 32℃, respectively. The lower threshold temperature of development for egg, larva, protonymph, deutonymph, pre-oviposition and generation were 10.70, 12.12, 11.12, 14.12, 16.01 and 16.80℃, respectively, and the corresponding effective accumulated temperature were 43.70, 21.52, 17.48, 18.31, 19.80, 121.45 degree day, respectively.1.2 Effect of temperature on survival and reproduction of Lasioseius sp.Within the range of 16~32℃, the hatching rate of eggs reached the highest values (97.5℅) at 32℃, the percentage of survival of larvae and nymphs reached the highest values of 100℅ at 28℃, the eggs hatching and the survival rates of larva and nymph were 96℅ and 98.23℅, respectively. Maximum value of the fecundity (82.05) was reached at 24℃and the maximum daily number of eggs (3.64) was reached at 28℃.1.3 The life tables of experimental population of Lasioseius sp. The life tables of Lasioseius sp. fed on Tyrophagus putrescentiae were constructed at 16℃, 20℃, 24℃, 28℃and 32℃. The results showed that the intrinsic rate of natural increase (rm) and finite rate of increase (λ) reached the highest values of 0.2408 and 1.272 at 28℃, respectively, higher than those, 0.1937 and 1.214, at 24℃,. The net reproductive rate (Ro) reached the highest value, 82.43, at 24℃, followed by 74.68 at 28℃. The population doubling time (t) was the shortest, 2.879 days, at 28℃. The above results revealed that 24~28℃was the optimum temperature scope for the development and reproduction of Lasioseius sp.2 Effect of prey at different temperatures and fed the development of Lasioseius sp.The developmental duration of Lasioseius sp. fed on Tyrophagus putrescentiae and Bemisia tabaci within the range of 16~32℃were studied. The developmental spans of a generation of Lasioseius sp. fed on Bemisia tabaci were 29.06±2.43, 23.26±1.36, 10.50±0.80, 9.03±0.72 and 11.81±1.57 days at 16℃, 20℃, 24℃, 28℃and 32℃, respectively. There were no significant differences on development of Lasioseius sp. on different foods, but it was significantly influenced by the cross effects of food and temperature.3 Interspecific predation between Lasioseius sp. and Lasioseius sugawaraiThe interspecific predation between Lasioseius sp. and Lasioseius sugawarai occurred frequently with or without prey, mainly occurred as the higher developmental stages preying on lower stages. The ability of Lasioseius sugawarai preying on Lasioseius sp. was stronger than Lasioseius sp. preying L. sugawarai. The interspecific predation between Lasioseius sp. and L. sugawarai could maintain its population development, but adult females of both predators preying on each other laid fewer eggs than those preying on Tyrophagus putrescentiae.4 Effect of pesticides on Lasioseius sp. and studies on Lasioseius sp. on controlling of Bemisia tabaci25% Thiamethoxam WG 7500 times and 10% Imidacloprid WP 1500 times had a certain impact on Lasioseius sp. without stimulation. Toxicity of the two pesticides against Lasioseius sp. was low toxic and no effect on the hatching rate of egg. Lasioseius sp. could effectively control Bemisia tabaci in net-houses, the control effect in 10 days reached 69.66 % after the release of Lasioseius sp. , and reached 80.84 % in 20 days.