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



damage. An early growing season or one with limited rainfall re- 

 sults in less disease buildup. 



The earliest symptoms appear on needles of the current season's 

 growth when the bud scales begin to slough off. Yellowish-pink spots 

 show on the needle tissue uncovered by the loosening bud scales. The 

 young, developing twig, bearing these needles, usually continues to 

 grow for a time, but before reaching maturity may turn dark brown 

 or black and become shriveled, slightly curved, and brittle. Needles 

 on such twigs change in color from light green to yellowish pink, then 

 to dark reddish brown, and finally to gray. As these color changes 

 occur, the needles dry out and their margins roll backward toward 

 the lower surface, thus appearing narrower than healthy needles. 

 They also frequently curve or bend. Adventitious buds may develop 

 below the dead tips and produce weak, stunted needles late in the sea- 

 son. Infected needles are very brittle, but most of them overwinter 

 on the twigs for one season and sometimes two. 



The fungus may enter the twig tissue from an infected needle on 

 Abies concolor, producing small cankers around leaf scars. Such 

 cankers have not been observed on other species of fir. 



About a month or 6 weeks after the first evidence of the disease, 

 small, black fruiting bodies of the fungus appear in the tissue of the 

 upper leaf surface. These develop slowly during the summer and 

 reach maturity the following spring. The fruiting bodies also de- 

 velop on shriveled twigs and on the small cankers at the base of in- 

 fected needles. Ascospores are dispersed at the time new needles are 

 being produced. 



The fir tip blight in North America is very similar to the blight 

 previously known in Europe. The causal organism is a distinct species 

 from the European Rehmiellopsis abietis (E. Rostr.) O. Rostr. (Syn: 

 R. bohemica Bub. & Kab.) with which it was once confused. The 

 ascomata, asci, and ascospores of the American species are larger than 

 the European. The ascomata of R. balsameat are 200-250/a in diam- 

 eter. The asci are conspicuously thickened at the apex, being 5 to 8/a 

 at the thickest point. The 16-spored asci are 81-141 X 33^1/a. The 

 fusiform-elliptic ascospores are hyaline, 1-septate, cells unequal, some- 

 times slightly constricted at the septum, densely granular, straight or 

 curved, and 31.5-49.9 X 6.3-12.6/x. A conidial stage has not been 

 observed. 



Hosts and Range : Pinaceae — 



Abies concolor (Gord. & Glend.) Lindl. in Maine, New Hamp- 

 shire, Massachusetts, Rhode Island, and New York. 

 A. balsamea (L.) Mill. New England States and New York. 

 A. cephalonica Loud. Rhode Island. 

 A . procera Rehd. Massachusetts. 

 A.fraseri (Pursh.) Poir. Massachusetts. 

 Literature: 



Waterman, Alma M. New hosts and distribution of Rehmiellopsis 

 bohemica. Phytopath. 27 : 734-736. 1937. 



. Tip blight of species of Abies caused by a new species of 



Rehmiellopsis. Jour. Agr. Res. 70 (10) : 315-337. 1945. 



, and Aldrich, Kenneth F. Rehmiellopsis needle blight of 





balsam fir in Maine. Plant Dis. Rptr. 24 : 201-205. 1940 



-, and McKenzie, M. A. A disease of Colorado fir. Phyto 



pathology 23 : 108-109. 1933. 



