| To study the retention effect of LdNPV in the natural environment and the influencing factors of LdNPV in the natural environment,and to increase the practical application effect.Spray LdNPV onto soil and leaves,Bioassay of LdNPV 2nd instar larvae was carried out by feeding methodto study the appropriate residence time.The results are as follows:1.The concentration of LdNPV was 5×106OBs/mL in the soils of Larix gmelinii Kuze.,Pinus tabuliformis Carr,and Populus cathayana Rehd.After 0d,14d and 28d,the mortality of the 2nd instar larvae feeding on unsterilized soil was higher.The mortality rate was higher at 14d,and the soil depth was 5cm and 15cm.When the soil depth is 5cm,the mortality of Larix gmelinii Kuze.,Pinus tabuliformis Carr,and Populus cathayana Rehd.euphratica forests is 96.67%,96.67%,92.22%,LT50 is 8.3d,7.5d,9d respectively;when the soil depth is 15cm The mortality rates were 95.56%,96.67%,and 98.89%,and the LT50 was 8d,8d,and 8.1d.As the residence time increases,the pathogenicity of LdNPV decreases.2.When the concentration of LdNPV is 5×106OBs/mL in the soils of Larix gmelinii Kuze.,Pinus tabuliformis Carr,and Populus cathayana Rehd.,the mortality of the 2nd instar larvae feeding on unsterilized soil is higher,and the soil depth is 5cm.At the time of feeding,the mortality rate of the soil in the forest was higher.The mortality rates at Od and 14d were 98.87%and 92.22%respectively.The LT50 was 8.4d and 9d.The mortality of the soil in the three forests was similar at 28d;At a depth of 15 cm,the difference in the mortality of the three forest soils was not significant.3.The concentration of LdNPV was 2.25×105OBs/mL.After staying on Larix gmelinii Kuze.,Pinus tabuliformis Carr,and Populus cathayana Rehd.leaves for 0d,2d,4d,8d and 16d,the mortality of Od was the highest when feeding the same host plants.The LT50 of Larix gmelinii Kuze.,Pinus tabuliformis Carr,and Populus cathayana Rehd.leaves were 4.5d,3.5d and 2.9d,The mortality of 16d was the smallest,which was 27.95%,24.95%and 23.97%,and LT50 was greater than 20d.As the residence time increases,the activity of LdNPV on the leaves decreases.4.When the host plant staying time was Od,the mortality rate of the 2nd instar larvae feeding on Larix gmelinii Kuze.,Pinus tabidiformis Can.and Populus cathayana Rehd.was 100%.When the residence time was 16d,the mortality rate was less than 30%;when the residence time was 2d,4d and 8d,there was no difference in mortality between the 2nd instar larvae feeding on Pinus tabuliformis Carr,and Populus cathayana Rehd.The mortality rates of 2nd instar larvae feeding Larix gmelinii Kuze.were lower at 87.99%,77.95%and 72.02%.11.2d,14.7d,16.7d are relatively lagging.It is indicated that the effect of spraying LdNPV on Larix gmelinii Kuze.for controlling Lymanteia dispar is worse than that of Pinus tabuliformis Carr.and Populus cathayana Rehd. |
