134 DDT— Killer of Killers 



forests are the spruce bud worm; the gypsy, brown-tail, and 

 pine-tip moths; the hemlock looper; the Saratoga spittle bug; 

 the red-headed pine sawfly; and the white pine weevil. Of 

 course there are many others, but that gives you some idea 

 of what our forest trees have to contend with. 



The Agricultural Research Administration of the U. S. 

 Department of Agriculture, in cooperation with several other 

 organizations, has carried out a number of investigations on 

 the control of forests insects by the use of DDT. Although 

 much still remains to be learned, there is no question about 

 the effectiveness of this new insecticide. In general, no more 

 than a pound of DDT per acre is required, and this amount 

 will not kill birds or animals. In fact, with proper methods 

 of application, /4 pound per acre, or even less, is sufficient, 

 and where there are fishing streams to be considered, not 

 more than /4 pound should be used. DDT emulsions, and 

 even suspensions, have given good results when applied by 

 aircraft, but most of the work has been done with rather con- 

 centrated solutions of DDT in oil. The DDT is first dis- 

 solved in xylene or some other excellent solvent, and then 

 this solution is diluted with fuel oil to a concentration of 

 about 10 or 12 % DDT. Only a gallon per acre, or less, of 

 the finished solution is required. The oil solution forms a 

 tacky deposit of DDT on the trees, and this tacky deposit 

 seems more effective than the deposit left by powder disper- 

 sions. On the other hand, suspensions form larger droplets 

 and less material is carried away by the wind, and suspen- 

 sions are less toxic to fish. There is still much to be learned, 

 but a lot has already been found out in the short time since 

 the use of DDT against forest insect pests was first started. 



