A NURSERY BLIGHT OF CEDARS 



By Glenn G. Hahn, Scientific Assistant; Carl Hartley, Forest Pathologist; and 

 Roy G. Pierce, Forest Assistant, Investigations in Forest Pathology, Bureau of 

 Plant Industry, United States Department of Agriculture 



INTRODUCTION 



For at least 15 years nurserymen who raise red cedars (Juniperus vir- 

 giniana L. and /. scopulorum Sarg. and their horticultural varieties) have 

 lost large quantities of stock from a disease of unknown origin. As a 

 result, several of the largest growers have been forced to abandon the 

 raising of red cedar. While both of these cedars are undesirable for use 

 in regions where apples {Malus sylvestris) are grown, on account of their 

 ability to carry the very harmful rust of apples,^ they have proved very 

 desirable trees for planting in some of the drier regions where apples are 

 not grown. The demand for them is sufficient to make their propagation 

 of considerable importance in certain nurseries of the Middle West. 



HISTORY OF THE DISEASE 



In 1900 Dr. G. G. Hedgcock, of this Office, observed a Phoma sp. upon 

 the smaller terminal branchlets of large trees of Juniperus mrginiana in 

 the vicinity of Nora, Nebraska. Later, in 1904, he took notes upon a 

 serious disease of red-cedar nursery stock in Iowa and Minnesota, having 

 found on the diseased material a fungus which he again referred to 

 Phoma sp. and which he believed to be the cause of the condition. Speci- 

 mens gathered in 1900 by Dr. Hedgcock show pycnidia and spores of a 

 species of Phoma, but no nursery specimens observed in 1904 were pre- 

 served. In the spring of 19 16 the writers, in ignorance of Dr. Hedgcock's 

 observations, found a species of Phoma upon diseased /. virginiana 

 fruiting on so many and such recent lesions that its parasitism was 

 strongly indicated. Cultures were made by "taking, with aseptic precau- 

 tions, pieces of inner bark from recent lesions and planting them in agar. 

 The cultures most commonly obtained in this way were indistinguishable 

 on artificial media from the cultures made from spores of the fungus 

 under suspicion. Numerous controlled woimd inoculations were made, 

 both with cultures from single spores and from the tissue plantings. In 

 each series 50 to 100 per cent of the inoculations gave positive results. 

 Positive inoculations were also obtained on nine other species of the 



' /. scopulorum has not been previously reported as a host for the cedar-apple rust. In 1916, trees of 

 this cedar, raised in Illinois from seed obtained in the Dakota Black Hills, and differing decidedly in habit 

 and color from trees of /. virginiana of the same age, were found bearing niunerous rust galls. The spore 

 horns and teleutospores were identical with those described for Gymnosporangiuin juniperi-virginianae 

 Schw. The specimens are in the collections of the Office of Forest Pathology (F. P. 2500S) and in the 

 Pathological Collections, Bureau of Plant Industry. 



Journal of Agricultural Research, Vol. X, No. 10 



Washington, D. C. Sept. 3, 1917 



iq KeyNo. G— n8 



(533) 



