The Relationship Between Euseius Finlandicus And Tetranychus Truncates And Their Susceptibility To Different Acaricides

As an important member of Tetranychus （Tetranychidae）, Tetranychus truncatesis a worldwide pest mites and widely distributed in the cotton, maize, vegetable andflower growing regions in China. Due to its strong ability to adapt to the environment,Propagation speed and other features, Tetranychus truncates has become importantfactors affecting agricultural production in China. Euseius finlandicus belongs toAmblyseius （Acari: Phytoseiidae） and act a important role of advantage naturalenemies to pest mites, thrips and other small insects. Euseius finlandicus was used asmaterial for study the control potential to Tetranychus truncates, as well as theprotection and utilization of natural enemies, this paper systematically studied thesearching and predation ability of Euseius finlandicus against to Tetranychustruncates. Besides, we did the toxicity test of common acaricides to Euseiusfinlandicus and Tetranychus truncates, the main results are as follows:1. Arrestment Response of the Predatory Mite Euseius finlandicus toTetranychus truncates.The attract effect of Tetranychus truncates to Euseius finlandicus was studied indoors. The result showed that every mite-state of Tetranychus truncates could attractEuseius finlandicus obviously, especially the web-nets under the simulative naturalcondition. However, the excreta and feeding spot of Tetranychus truncates were failedto attract Euseius finlandicus. During the experiment, Euseius finlandicus appearedmost at the second hour; only42.50%did not reach the significant level. Theattraction of Tetranychus truncates to Euseius finlandicus showed than Euseiusfinlandicus can search Tetranychus truncates spontaneous, is a kind of bio-controlagents to control Tetranychus truncates effectively.2. Predatory function of Euseius finlandicus to Tetranychus truncates.The predation of Euseius finlandicus on at three stages （adult females, nymphsand eggs）was examined at five constant temperatures （16,20,24,28and32℃） underthe laboratory condition RH80%±5%.The results showed that Euseius finlandicus preferred eggs and nymphs rather to adult females of T.truncatus. Predatory functionto prey density in above temperatures can be imitated by Holling type Ⅱ. At the rangeof16～28℃temperatures: attack index, the a/Thvalue and the maximum predatorynumber are increased with increasing temperature, while average treatment time isreduced. When the temperatures passed28℃, the result of a/Thof adult females,nymphs and eggs was4.9232、29.2088and47.0022. As temperature rise, thepredation capacity began reducing gradually, to32℃, the a/Thwas just3.0988、18.9295and30.6014. With a fixed number of prey available, predation rate perpredatory decreased with the increase of predator density due to mutual competitionand interference.3. Toxicity and selective of eight kinds of acaricides to Euseius finlandicus andTetranychus truncates.The effect evaluation of eight kinds of acaricides against to Euseius finlandicusand Tetranychus truncatus indoors was studied, as well as the selective action to them.The acaricides Avermectins showed a strong inhibition effect on Euseius finlandicus.The LC50was3.0279mg·L^-1. Beta-cyfluthrin, Cyenopyrafen, Hexythiazox andAzocyclotin took second place. The LC50were10.1046mg·L^-1,12.0767mg·L^-1,27.3072mg·L^-1and36.2061mg·L^-1. For Tetranychus truncates, the effect ofAvermectins, Fenpropathrin, Fenpyroximate and Cypermethrin were better thanothers The LC50were0.2931mg·L^-1,2.1778mg·L^-1,5.2479mg·L^-1and6.3217mg·L^-1. Besides, with the LC50just86.5314mg L^-1, Pyranica showed the lowestsensibility. The Hexythiazox and Avermectins had strangest selectivity to Tetranychustruncates and Euseius finlandicus, as well as Ave·Clofentezine, the selectivity ratio ofeach acaricide was12.5389,10.3306and14.2136. On the contrary, the selectivity ofBeta-cyfluthrin and Azocyclotin were poor, the selectivity ratio of each of them wasjust0.6401and0.5319。...