DANGEROUS INTERNATIONAL FOREST TREE DISEASES 105 



Cedar Blight 



G. TV. Peterson 

 Forest Service, U.S. Department of Agriculture, Lincoln, Nebraska 



Phomopsis juniperovora Hahn, cedar blight, is a devastating disease 

 of juvenile Juniperus virginiana L., ./. scopulorum Sarg., and several 

 other Cupressaceae species in the United States. Infected terminals 

 and laterals of •/. virginiana seedlings and transplants become light in 

 color, then brown, and finally gray. Lesions on stems and branches 

 frequently develop into cankers, which may result in girdling if stems 

 and branches are of small diameter (one-half inch or less) . 



Black pycnidia develop on infected stems, branches, and leaves. 

 Pycnidia are embedded at first, later becoming erumpent. Spores are 

 extruded in tendrils. A-spores are hyaline, unicellular, ellipsoid, bi- 

 guttulate. and commonly 7.5-10 X 2.2-2.8^: B-spores are hyaline, uni- 

 cellular, filamentous, slightly curved, and commonly 20.2-26.9 X 1/x. 

 Intermediate type spores occur infrequently. A- and B-spores are 

 produced in the same or different pycnidia. Perfect stage is unknown. 



Infection is by A-spores. which presumably are distributed by water, 

 wind, and insects. Infection in nursery stock occurs throughout the 

 growing season. Infected seedlings and transplants (1 to 4 years old) 

 of Juniperus virginiana and •/. scopulorum are killed by girdling. 

 Epidemics in the Great Plains have resulted in total losses in seedling 

 and transplant beds of these two species. Pathogen has been iso- 

 lated from 2- to 20-year-old natural reproduction of •/. virginiana. 

 Cankers seldom develop on such trees, thus mortality is negligible. 

 Infected Cupressaceae species used as ornamentals appear unsightly 

 because of numerous dead twigs; however, such trees are usuallv not 

 killed. 



Intercontinental spread could result from shipment of infected 

 trees, seed lots containing plant debris, or logs and lumber with bark 

 attached. 



Range: In the United States it is common in the Great Plains and 



eastward to the Atlantic coast. 

 Hosts: Cupressaceae — 



Chamaecyparis lawsoniana (A. Murr.) Pari. 



<7.tfZ>zW(Sieb.&Zucc.) Endl. (Planted in U.S.) 



C. phifera (Sieb. & Zucc.) Endl. (Planted in U.S.) 



Cupressu-s arizonica Greene 



C. goveniana Gord. 



C. Jusitanica Mill. 



C. macrocarpa Hartw. 



C. sempervirens L. (Planted in U.S.) 



Juniperus chinensis L. ( Planted in U.S. ) 



J. communis Li. 



J. exceha Bieb. (Planted in U.S.) 



./. horizontalis Moench 



J . lucayana Britt, 



J. ashei Buchh. 



J. pachyphloea Torr. 



J. procumbent (Endl.) Sieb. & Zucc. (Planted in U.S.) 



J.sabinaL,. (Planted in U.S.) 



