1420 A NATIONAL PLAN FOB AMERICAN FORESTRY 



set out and selection of planting sites adapted to the species are 

 essential for the development of satisfactory plantations. Experi- 

 ence shows that in large-scale planting operations this is not now 

 done consistently, with the result that trees from an improper source 

 of seed or on unfavorable sites suffer seriously from avoidable disease. 

 All this demands an increase in the study of nursery and plantation 

 diseases, and particularly of root diseases and their relation to soil 

 conditions, far beyond anything that has so far been done. 



Directly bearing on nurseries and plantations is an investigation 

 of the mycorrhizal relations of forest trees already begun in a small 

 way. Experience in other countries has indicated that the failure 

 of some plantations is directly connected with the failure of tree 

 roots to develop mycorrhiza. On the other hand, there is reason to 

 suppose that some kinds of mycorrhiza or any mycorrhiza under some 

 conditions are harmful. There is also need to study the correlation 

 of soil factors with disease on planting sites. 



Individual trees of the same species grown under the same condi- 

 tions vary greatly in their resistance to disease. The basis neither of 

 their resistance nor their immunity is known, nor to what extent this 

 character is transmitted through seed to their progeny. This is prob- 

 ably the most time-consuming problem in forest pathology, yet it is 

 of fundamental importance in reforestation because of its bearing on 

 the choice of seed for growing trees. It is already too late for this 

 line of attack to be of any value to reforestation work for the next 

 decade, but under a long-time program it should begin immediately. 

 The marked success attained with agricultural crops is all that is 

 needed to illustrate the far-reaching results to be expected. 



In the West the application of blister-rust control to 5-needle pine 

 stands and reduction of the damage to softwood stands caused by 

 dwarf mistletoes are outstanding problems. 



Decay in living trees in the future can be largely avoided by cutting 

 stands before they reach the age at which decay becomes extensive. 

 Investigations have determined this age for a few species, but it must 

 be obtained for all defective species and for each of them on different 

 sites before management can be placed on a sound basis. Further- 

 more, there still remain extensive stands of badly decayed timber 

 in which information on the rate of decay and the outward evidences 

 of decay are essential for intelligent utilization and salvage. Better 

 knowledge of the relation of decay to wounds is a primary need in 

 much of the eastern hardwood region. Investigations on the control 

 of decay must be carried on for years to come. 



The proper disposal of slash after logging is important to the de- 

 velopment of the new forest. Present slash-disposal methods in 

 managed forests are usually expensive. Investigations by patholo- 

 gists on the relation of decay to various methods of slash disposal 

 have already resulted in modifications of method in certain regions, 

 greatly reducing expense; further extension of these studies should 

 be made to all regions where slash disposal is a problem. 



The use of forests for recreation is increasing greatly. While study 

 of forest diseases in general will bring out results of value for recrea- 

 tional forests, yet control measures must differ markedly from those 

 applied to forests of which the primary purpose is timber production. 

 New factors will present themselves as investigations proceed; only 

 by the application of control measures based on fundamentally sound 



