| Field efficiency trials showed imidacloprid as a trunk-injectable insecticide was found to be effective in controlling a number of borers and suck insect pests of trees. However, there are fewer reports about the uptake, translocation, and distribution of imidacloprid with trunk injection at home and abroad. In order to use this trunk-injectable insecticide for controlling insect pests of trees effectively, uptake of imiacloprid liquid formulation by trees under several factors with auto flowing trunk injection, translocation, and distribution of imidacloprid in weeping willow, and efficiency of imidacloprid on adult Holotrichia oblita Fald. in vivo bioassay after injection was determined. The main results as follows:1. Effects of several factors on the uptake of 4% Imidacloprid Liquid Formulation (ILF) by trees was studied with auto flowing trunk injection in sunshine. The results showed injection hole-diameter and tree species had highest impact on the uptake of ILF, and the lowest in injector blowhole-diameter. 5 mm injection hole performed well; generally the uptake of ILF was 6-8 mL at 10 h after injection. Diameter of injector blowhole had less influence on the uptake of ILF. The absorbability to ILF was various in 9 tree species; Populus tomentosa had a most strong ability and the least in Albizia julibrissin. Effect of trunk basal diameter on the uptake to ILF was indefinite, depending on the species, in Sophora japonica the uptake ability to ILF was greater with bigger trunk basal diameter, but in Platycladus orientalis that was reverse, in Populus tomentosa it was not significantly different between trees with different trunk basal diameter. Uptake rates were lower during maturity period (September) than peak growth season (May). All these factors are to be taken into account in order to ensure the most efficient use of auto flowing trunk injection with chemicals in agriculture and forestry.2. Imidacloprid was transmitted well in the weeping willow after trunk injection. Imidacloprid concentration (IC) varied depending on the positions of leaves located. In the upper crown IC were more than those in the lower crown as a whole. 48 h after injection, the gap of IC between upper crown and lower crown reached the maximum. The IC of the leaves upon the injection spot were more than the others sides. The results about translocation of imidacloprid in the xylem and phloem of tree trunk as follow. Imidacloprid was transmitted much effectively in the vertical direction along the xylem. IC in the south xylem at trunk height 0.5～0.9 m was as much as 20.30μg?g-1 at one day after injection, which was almost 10 times more than the other three sides. And the gap of IC among different sides decreased gradually with the trunk height ascending. As the time passed by, the distribution center of IC moved up quickly. At 6 days after injection, IC reached the maximum in the top part of trunk xylem. In trunk phloem imidacloprid was only presented in the east side at 1 day after injection. And imidacloprid was detected in all trunk phloem samples at 3 days after injection. IC reached the maximum in trunk phloem at 13 days after injection as a whole. IC in trunk phloem was less than that in trunk xylem in 20 days after injcetion. In conclusion, Imidacloprid was able to transport in both xylem and phloem.3. The results showed concentration of total imidacloprid residues varied among different tissues of weeping willow after injection. Concentration of total imidacloprid residues in the leaves was the most, next were twig xylem, twig phloem and trunk xylem, and the least in trunk phloem. The trends of total imidacloprid residues concentration in several tissues were different. It decreased gradually in the trunk xylem from 5 days after injection. The total imidacloprid residues concentration in the leaves reached the maximum at 25 days after injection, and gradually declined after immediately rising. The tatoal imidacloprid residues concentration increased slowly in the twig phloem, and reached the maximum at 30 days after injection. In trunk phloem the total imidacloprid residues concentration varied smoothly during 110 days after injection. Since 70 days after injection the total imidacloprid residues concentrations among these five tissues become equal relatively and decreased at a lower level. Imidacloprid and its metabolites after trunk injection into weeping willow could last for 110 days, which is good for controlling insect pests of trees.4. The results showed imidacloprid had strong knock down action against adult Holotrichia oblita (Fald.) with trunk injection into weeping willow, and the persistence was sustained over 80 days. Efficacy of imidacloprid after injection had less lethal effect on test insect; however it took on well at knock down action, and knock down rates of all samples on test insect were all over 65%. LC50 of imidacloprid on adult Holotrichia oblita (Fald.) applied with foliar spray and trunk injection were 6.3368 and 3.6439μg?g-1 respectively, which indicated toxicity of imidacloprid against adult Holotrichia oblita (Fald.) was stronger with trunk injection.To sum up, 4% imidacloprid liquid formulation had better uptake, translocation property and the persistence effect could last for at least 3 months. It is a new kind of trunk-injectable liquid formulation with bright prospect of application.
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