Abstract: The control effects of mixed and single insecticides against Hemiberlesia pitysophi la in woods were tested. The best proportion of mixture with tree-trunk injection and lacquer hy Orthogonal design was found. At the same time, the change of population by spray, trunk injection, trunk lacquer was investigated respectively. The results showed that the best mixing proportions with trunk injection and lacquer were the same as 40% methidathion EC (1 : 5)+40% chlorpyriphos EC (1 : 5)+40% omethoate EC(1 : 2.5). The control effects wit h tree-trunk injection and lacquer were 98%,81% respectively, which both had remarkable synergisms. The observation of the population growth showed that the rates of population reducing of tree-trunk injection and lacquer were more steady than that of leaf-spray.