May,i 9 i6 Hypoderma Deformans 287 



by other observers. 1 The writer has observed and collected H. de- 

 jormans in the National Forests of the Northwest as follows: Sioux, 

 Helena, Deerlodge, Jefferson, Missoula, Coeur d'Alene, St. Joe, Clear- 

 water, Selway, Bitterroot, Pend Oreille, Kaniksu, Nez Perce, Lolo, 

 Cabinet, Flathead, Kootenai, and Whitman. The late J. F. Pernot, 

 forest examiner, supplied specimens from the Deschutes, Wallowa, 

 Malheur, Crater, Colville, and Wenatchee National Forests. Along 

 the Thompson River in British Columbia the fungus was occasionally 

 found by the writer in the summer of 1913. 



CONCLUSIONS AND RECOMMENDATIONS 



A very conspicuous disease on yellow-pine needles in many parts 

 of the Northwest, the cause of which has for several seasons remained 

 unknown, is found to be caused by a fungus which is described as a new 

 species under the name "Hypoderma deformans." 



H. deformans is a true parasite and attacks the foliage of all age 

 classes; and in some of the more exposed sites of the typical yellow- 

 pine belt of Montana, Oregon, Washington, and Idaho, young seed, 

 lings at first suffer great suppression and are finally killecl. 



The first sign of infection of the needles is usually a slight browning 

 of the tips; or in the regions of heavy infection the entire needle may 

 gradually assume a straw-yellow color, deepening to a brown on the 

 first appearance of the apothecia. 



Because of the destruction of the youngest needles and the penetra- 

 tion of the mycelium of the fungus in the tissues of the stems of the 

 host, the terminal shoots do not attain their proper development, but 

 become stunted and deformed, eventually producing a witches' broom. 

 These witches' brooms on young yellow-pine saplings or older trees are 

 often very conspicuous and often occur in such numbers as to make 

 either an individual tree or an entire stand look very ragged and un- 

 sightly. 



Up to the present time the disease has not been found in the forest 

 nursery, but it may be regarded as a possible nursery disease. Since the 

 vegetative mycelium of the fungus may hibernate in the shoots of seed- 

 lings after the infected needles have fallen, the fungus may make its 

 appearance in the forest nursery and may be unknowingly transferred 

 to the planting areas. 



The presence of the fungus on mature forest trees is very readily recog- 

 nized by the foliage browning up in patches or by the formation of 

 brooms. Since the fungus does not affect the merchantability of the 

 tree, except by influencing the increment in cases of very severe infec- 

 tion, all trees of the regulation diameter classes should be marked for 



1 Meinecke describes a very destructive needle fungus, under the name "Hypoderma," on yellow and 

 Jeffrey pines, which apparently is the same fungus as the one described in these pages. (Meinecke, E. P. M. 

 Forest Tree Diseases Common in California and Nevada, p. 34. Washington, 1914. Pub. by U. S. Dept. 

 Agr. Forest Serv.) 



