A NATIONAL PLAtf FOR AMERICAN FORESTRY 721 



though hoth seeds and wood may sometime bring in destructive 

 foreign diseases or decay organisms. No provision exists for pre- 

 venting the spread of native forest diseases from East to West or 

 vice versa. 



One of the most useful methods in meeting diseases of crop plants 

 is the development of resistant or immune varieties. In a plant 

 with a reproductive period as long as that of a typical forest tree, 

 ordinary plant-breeding procedure is extremely slow. Nevertheless, 

 there is an excellent chance to get results in a reasonable length of 

 time in species which produce seed at an early age or in those in 

 which vegetative propagation can be done readily and cheaply. The 

 introduced willow scab mentioned earlier is a disease which perhaps 

 can be met best in this way. A beginning has been made along this 

 line with poplars for pulp production. Constructive activity against 

 the chestnut blight is also under way in an attempt to develop 

 resistant lines by selecting and hybridizing among the native chest- 

 nuts and a large number of Asiatic chestnut types which have been 

 assembled for the purpose. It is obvious that even when resistant 

 strains have been developed, they can be established only in situa- 

 tions where planting is economically practicable. 



The constantly increasing use of forests for recreational purposes 

 leads to new concepts of disease and its control. The difference 

 between recreational forest areas and timber-producing areas as to 

 standards for evaluating disease damage has already been discussed. 

 The two types of forest differ quite as much in the needs and possi- 

 bilities of control. Investigation of the needs and possibilities in 

 the recreational areas has been barely begun, and many of the state- 

 ments following are to be regarded as tentative. Virulent killing 

 diseases need control in such areas, and protection of the 5-needled 

 pines against the white-pine blister rust is going forward in much 

 the same way as in the commercial forests. For most other types of 

 disease, less attention need be paid to control in extensive stands 

 set aside purely for recreation than in commercial stands. The fact 

 that little or no cutting is done in recreational stands furthermore 

 removes one of the best opportunities for forest sanitation. However, 

 because of the unnatural conditions created by tourist use in the 

 neighborhood of camps, hotels, and scenic attractions, and the im- 

 portance of the trees in such places, there are unusual local needs for 

 protection, and over small areas methods of prevention or control 

 are justifiable that would be entirely too expensive to employ where 

 timber production is the only consideration. Despite the opinion of 

 some that the dwarf mistletoes add to the picturesqueness of the 

 trees, the owners of recreational areas in several places in the West 

 have undertaken special cutting-out campaigns against them. The 

 spraying or dusting methods developed in orchard work could be 

 employed against unsightly leaf diseases in such places. 



The greatest need is for measures that will protect the forest for the 

 campers and sightseers, against the injury that they themselves do 

 to it. Regulations against the careless use of fire and the concentra- 

 tion of trampling and automobile traffic that have partially devas- 

 tated some of the camping grounds and places of interest are not 

 enough. On the basis of preliminary study of the habits and needs 

 of the tourist, plans have been developed for the laying out of camp 

 sites and other areas where visitors concentrate, in such a wav that 



