Study On Resistance Mechanisms Of Tetranychus Urticae Koch To Fenpropathin And Spirodiclofen And Sublethal Effects Of Two Acaricides

Tetranychus urticae Koch is one of important of worldwide pest mites,and caused seriously damage in many countries and the resistance was caused the plant protection scholar's attention.The fenpropathrin was high efficiency and low toxicity, better contact action and safety to environment, so it was widly used to control for a long time in the orchard. However, With higher frequency and large amount use the T.urticae have had resistance to fenpropathrin.The spirodiclofen was a new acaricides which was invent by Bayer, but the resistance will be arise soon. Through study on the resistance mechanisms of T.urticae to fenpropathrin and spirodiclofen and sublethal effects of two acaricides to delay the occurrence of resistance and prolong the useful time of them.The main results are the following:1. The resistance selection of T.urticae Koch to fenpropathin and spirodicofen and the synergistic action of the synergists to the resistance populationThrough the indoor bioassay and reared the S strain of T.urticae Koch which were collected from XingLong Mountain in LanZhou.The R strain of T. urticae Koch to fenpropathrin(R-fen) and spirodiclofen (R-spi)were selected 45 generation and 30generation, respectively and the resistance index (RI) of R-fen and R-spi were 314.50 and 77.92 folds.The synergistic action of PBO, DEM, TPP, Organosilicone and Thiazone on the R-fen and R-spi were tested.The result showed that the synergism ratios(SR) between R and S strain of TPP, PBO, DEM to the R-fen were 12.15,7.78 and 3.09 folds. It is indicated that the MFOs and CarE were involved in the resistance mechanisms of T.urticae Koch to fenpropathrin. The SR of DEM to R-spi was higher than TPP, PBO and the value were 4.87, 3.67 and 1.91 folds. It showed that the resistance mechanisms to spirodicofen were related to the increasement of activities of GSTs and CarE.The resistance of R-fen and R-spi were not close with the alteration of cuticle permeability, because the SR between R and S strain of organosilicone and thiazone to R-fen and R-sp were 1.38, 1.42 and 1.18, 0.92 folds.2.The analysis of the activities of detoxifying enzymes in R-fen and R-spiThrough the test of the activities of detoxifying enzymes in R-fen and R-spi,the result showed that the activities of detoxifying enzymes in resistance population were higher than sensitive population. The activities of CarE, GSTs and MFOs in R-fen and R-spi were 5.43, 3.71, 12.79 and 1.55, 1.91, 1.21folds of the sensitive population separately.That means the resistance of T.urticae Koch to fenpropathrin were connect with CarE and MFOs and the CarE and GSTs were interrelate with the resistance to spirodicofen.3.The sublethal effects of fenpropathrin and spirodiclofen on T.urticae KochThe sublethal effects of fenpropathrin and spirodiclofen to T.urticae Koch were studied indoor. The result showed that: under the treatment of sublethal dosage of fenpropathrin, the longevity of F0 generation shortens 1.52d and the there was a decrease in hatchablity, longevity and fecundity; as for the population of F1 generation shorten developmental duration and the rm increased, so the low concentration fenpropathrin have a stimulatory effect on T.urticae Koch . The activity of sublethal dosage of fenpropathrin to CarE, GSTs were higher than CK. The influence of sublethal dosage to MFOs was inhibition at the 6h and 48h .At the peak period induction the activity of enzymes were obvious higher than CK and the value were 2.03, 1.91and 1.38.The longevity of F0 generation was shortens 3.03d and the hatchablity, longevity and fecundity were all decreased to some extent under the treatment of sublethal dosage of spirodiclofen, as for the population of F1 generation, prolonged developmental duration and reduced rm. So the spirodiclofen had obviouse inhibition effects on T.urticae Koch. The activity of GSTs and CarE were higher than CK after treated , and the activity of enzymes were obvious higher than CK and the value were1.41 and 1.31 at the peak period induction. The markedness inhibition of spirodiclofen on MFOs at 24h .4. Allied toxicity measurement of spirodiclofen and avermectin or flufenoxuron to T.urticae kochThe allied toxicity of spirodiclofen and avermectin or flufenoxuron to T.urticae were tested in laboratory by slide slip method.The results shows that the mixtures of avermectin and spirodiclofen at any ratio all have significant synergistic effects on T.urticae,in which the CTC of the mixture at the ratio of 1:5 was the highest one and the value was 154.28.The mixtures of flufenoxuron and spirodiclofen at any ratio also have synergistic effect on T.urticae,in which the mixture at the ratio of 1:4 is the highest and the CTC was 168.31.