44 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



in most states carry on a large amount of educational work 

 looking toward the more careful use of fire in woodlands. 



The more serious diseases and insect enemies of forest trees 

 are now subject to control measures by the states and Federal 

 Government. Until recently the United States has had very 

 inadequate plant quarantine laws, with the result that many 

 serious insect pests have been introduced from abroad. Such 

 an insect as the gypsy moth, brought into Massachusetts some 

 twenty years ago, has done tremendous damage, cost millions 

 of dollars of public money to combat, and at present is 

 still increasing its area, although under partial control in the 

 older infested regions. Recently the rapid spread of the white 

 pine blister rust, introduced some fifteen years ago on German 

 nursery stock, has become so serious as to threaten the com- 

 mercial future of the best forest tree in the north-eastern states. 

 Such pests may change the silvicultural practice in different 

 regions from time to time, and ultimately eliminate trees of 

 great commercial value. Experiments are already under way 

 to determine the best substitutions which might be made from 

 among European trees. The control of most tree diseases and 

 insect enemies is handled by the scientific branches of the 

 Federal Government and by the State Agricultural Experiment 

 Stations. When a disease or insect becomes so bad that 

 extensive restrictive measures involving police power become 

 necessary, the work of control is often taken over by the State 

 Department of Forestry, the research and scientific work being 

 continued by the Experiment Station. In such cases a co- 

 operative agreement is drawn up between the two departments, 

 the Federal Government generally furnishing part of the necessary 

 funds and outlining the general control policy. 



Afforestation. 



In spite of good natural reproduction of forests, the continued 

 extensive and unregulated cuttings, together with fire, insects, 

 and disease, have reduced markedly the areas of valuable timber 

 in the older settled states. In the western states, where virgin 

 timber is still abundant, the time has hardly arrived for strong 

 public support of afforestation, but in the eastern and lake 

 states, it has been realised for many years that timber was being 

 removed much faster than nature reproduced it. Nearly all of 

 these states contain large areas of non-agricultural land, most 



