DISEASES OF THE CHESTNUT AND OTHER TREES 71 



newest branch of plant pathology. During the past few years we 

 have made in the Department of Agriculture a disease survey of 

 the national forests. Many fungi, such as Echinodontium tinc- 

 torium or Poh/ponis amnrus, which five years ago were mere myco- 

 logical curiosities or wholly unknown, have been discovered to be 

 serious enemies of forest trees (5, 6, 7). I may briefly indicate the 

 lines of attack upon some of these forest diseases, and first I may 

 speak of the diseases of reproduction. 



Forest Nursery Diseases. 



When a tree reproduces itself naturally in the forest the great 

 majority of 3'oung seedlings perish before they have " passed 

 the kid's lip, the stag's antler." It is therefore necessary that 

 in large reforestation operations the young trees be started in 

 nurseries, and so there has been built up a large forest nursery 

 practice, private, state, and national, which every year is enor- 

 mously increasing. Now every person present who has attempted 

 to grow even a few forest tree seedlings, particularly conifers, 

 knows how they suffer from damping-off and related diseases of in- 

 fancy. We have set ourselves to no less a task than the over- 

 coming of these damping-off diseases by the use of soil fungicides, 

 and have so far met with very good success. If damping-off and 

 related nursery diseases can be overcome in a practical way, one of 

 the greatest factors in the way of artificial reforestation will be 

 removed. This problem is so closely related to soil and weather 

 conditions that it will probably have to be worked out variously 

 for different sections of the country. For conifer seedlings sul- 

 phuric acid is the most hopeful soil fungicide, according to the 

 researches of Spaulding (8) and Hartley (9). This has the advan- 

 tage of killing weeds and stimulating germination of the conifer seeds, 

 in addition to preventing damiDing-off. It has been successfully 

 applied by Spaulding in New York and Vermont, and by Hartley 

 in the sandhill section of Nebraska: it is yet to be tested in other 

 parts of the country. Another destructive disease " blight " 

 affecting yearling or two-year-old conifer seedlings, has in Nebraska 

 and Colorado yielded readily to a modified system of watering 

 and shading. 



