PREFACE 



A message from George M. Jemison, President, IUFRO, states-- 



"Around the world today is a steadily growing pressure on forest 

 resources—pressure to produce the many goods and services that such lands 

 provide. Highly developed countries and those striving for greater 

 social and economic gains, botn look to forests for the material v,ealtli 

 and environment to satisfy human needs. 



' ; But as efforts increase to manipulate natural forests to better 



serve mankind, we find that many new problems arise and oid ones intensify, 



Forestry scientists have responded by bringing their skills to focus more 

 effectively on a iarge array of critical problems. 



"Forest geneticists and pathologists have sought for a long time to 

 comprehend, to utilize, and to stabilize genetic resistance to rust dis- 

 eases of forest trees. Rust diseases are known to be a major cause of 

 huge timber losses in many parts of the world. Faced with substantial 

 gaps in knowledge and problem solutions of great technical difficulty, 

 the small band of dedicated forest biologists has made steady progress 

 in understanding the biology of rust resistance in forest trees." 



Amplifying the comments of Dr. Jemison, the significance of these 

 problems is illustrated by the fact that in the U.S.A. two tree rusts, 

 one introduced and one indigenous, in a single year accounted for losses 

 of pine growing stock and sawtimber equivalent to 375 million cubic feet 

 of wood.* And in Europe, a glacially impoverished pine flora is sus- 

 taining increasing rust losses in the altered environments of forest 

 plantations, while substitution of promising pine introductions often is 

 stymied either by indigenous or introduced rusts. 



Two very challenging problems face biologists concerned with tree 

 rust resistance. These biologists are forced to proceed with mere than 

 the usual quota of ignorance. Nearly complete voids exist in their 

 knowledge of sexuality and pathogenic variability in the tree rusts, and 

 in their knowledge of the mechanisms and genetics of host resistance. 

 Second, economic hosts for which they seek resistance are perennial, long- 

 lived gymno- or angiosperms . Reproductive cycles in these trees may range 

 from 5 to 25 or more years while the rust may be cycling 10 to more than 

 100 times. 



Hopefully the small band of biologists can expect greater public 

 support for attacking these problems, now that crowded humanity is more 

 vociferously demanding increased productivity of clean air and water, of 

 recreational and aesthetic opportunity, and of wood, fiber, fuel and other 



1 U. S. Dep. Agr. 3 Forest Service. 1958. Timber resources for 



America's future. Forest Resource Rept. 14. 713 p. (bd. ft. data con- 

 verted using 7 bd. ft. = 1 au. ft.). 



Ill 



