78 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 5 



this type of trouble than with those of other kinds of plants. The 

 horticultural inspector is especially interested in the field characters 

 of these various diseases. 



The chief field characters of the white pine blister rust are: 



(1) A swelling of the main stem usually where the first branches 

 are given off. This swelling usually begins very abruptly at the 

 point of insertion of the branches upon the main stem and tapers 

 gradually downward. It may also extend upwards in the stem and 

 also outwards in the lateral branches in very marked cases. This 

 disease is characterized by the swelling being almost exclusively in the 

 bark tissues, not in the wood of the stem; that is, if a sharp knife be 

 taken and a suspected tree which has this type of swelling is split 

 carefully down the middle through the swelling, it will be seen that the 

 bark in the swollen portion is from one to several times thicker than 

 the normal bark of the same tree, but the wood of the stem is not 

 swollen at all. 



(2) Trees three or four years of age are very apt to have a stunted 

 appearance. The tree very often consists of a bare stem bearing an 

 abnormally thick tuft of needles at the top and without lateral 

 branches. Oftentimes, too, the growth in height is decidedly less 

 than that of healthy trees. 



(3) A coarse yellow mottling of the bark of the stem and of young 

 needles is a rare but very characteristic symptom of this disease. It 

 has been found by the speaker but twice : once in a lot of trees set out 

 in the field and once in trees in the greenhouse. 



(4) Older trees, five to ten years or more of age, which have had 

 this disease and have borne fruiting bodies in preceding years have 

 an abnormally thick scaly bark upon the stem at the affected parts. 

 Healthy young trees never have scaly bark before they are from 15 to 

 20 years of age. The occurrence of scaly bark upon stems of less than 

 this age is a very good symptom of this disease. 



(5) Finally may be mentioned the actual presence of fruiting bodies 

 upon the affected stem. These fruiting bodies are so characteristic 

 that no one need to be confused by them. They are also so well 

 described in my publications that they will not be mentioned further. 



This disease is caused by a fungus which has an alternate stage of 

 growth upon the leaves of Ribes. The disease can not spread from pine 

 to pine, but is produced upon healthy pines only by the spreading of 

 the fungus from diseased Rihes leaves to the pines. This gives a very 

 fair chance for controlling the disease so far as it has yet been intro- 

 duced into this country. While the disease affects our eastern white 

 pine especially, it is not limited to that single species. It also is known 

 to attack two of the western white pines and it presumably may attack 



