98 U.S. DEPT. OF AGRICULTURE MISC. PUB. 939 



Gray Blight of Hard Pines 



G. D. Darker 



Plant Research Institute, Canada Department of Agriculture, 

 Ottawa, Ontario 





Hypoderma lethale Dearness is a needle blight and cast of hard pines 

 in the eastern United States. The first symptoms occur on the youngest 

 needles as a rather sudden discoloration in late winter or early spring 

 before new needle growth begins. In early spring, the initial zones of 

 infection become reddish brown in color and are often separated by 

 greenish areas of the leaf or they may be terminal. About this time of 

 year the diseased portions may become slightly wrinkled and pycnidia, 

 concolorous with the needle, develop on them. In late spring the ini- 

 tial areas of infection usually become straw colored or grayish and 

 hysterothecia begin to appear within them. These areas often remain 

 bounded by darker orange-brown zones while the green portions be- 

 tween infected areas turn brown. 



The elliptical, shining black, flat, subepidermal hysterothecia 

 mature in late spring or early summer and are 0.4-1.4 mm. long, 0.18- 

 0.42 mm. wide, and 0.13-0.21 mm. deep. The hysterothecia open nar- 

 rowly by a longitudinal fissue exposing the concolorus hymenium com- 

 posed of narrow, filiform paraphyses and 8-spored asci, the latter 

 90-160 X 16-22/*. The ascospores are short, bacillar to fusiform, 

 hyaline, 24-40 X 3-6^, and are surrounded by a gelatinous sheath; 

 on germination they divide and there emerges from one cell a short 

 germ tube from which a terminal swollen portion is delimited by a 

 septum. Infection is by windborne ascospores and takes place during 

 the period of ascospore discharge and germination, principally during 

 June and July in the more southern States and perhaps extending into 

 Auffust in the more northern areas. 



This is one of the most serious and widespread needle diseases of 

 hard pines in the eastern United States. Trees ranging from seedlings 

 to sawlog size are infected. Destruction of 40 percent of the needle 

 tissue per tree has been reported although at present direct evidence 

 of significant reduction of the growth of infected trees is still lacking. 

 Intercontinental spread of the disease could most possibly come 

 about through shipment of seedlings, especially in the late fall when 

 the symptoms are latent. Rigorous inspection in the late spring prior 

 to needle emergence should reveal the presence of the fungus and pro- 

 vide a sounder basis for prevention of its spread into new areas. 

 Control of the disease by spraying, though possible, does not at present 

 appear to be feasible on a large scale. Pezizella minuta Dearness, a 

 secondary fungus, which fruits only on needles infected by Hypoderma 

 lethale and prevents the maturation of the latter, provides a limited 

 natural control and its importation into infected stands would no 

 doubt have some beneficial effect. 



Range: Entire eastern seaboard of the United States (except Dela- 

 ware) ; along the Gulf of Mexico west to Louisiana ; and scattered 

 stations in Tennessee, West Virginia, Ohio, Michigan ( ? ) , and 

 Missouri. Perhaps more widely spread throughout the eastern 

 United States and adjacent regions than present knowledge indi- 

 cates. 



