INTRODUCTION AND HISTORY 



Rhabdocline pseudotsugae Syd., the cause of a serious needle cast 

 disease, is threatening Douglas-fir [Pseudotsuga menziesii (Mirb.) 



Franco] in plantations in New York and other parts of the North- 

 east. The fungus infects the newly-developing needles in the spring 

 and earl) summer and, usually within a year, causes severe damage 

 through excessive needle discoloration and tasting. Diseased trees are 

 undesirable as Christmas trees because of sparse, discolored foliage 

 and decreased needle retention. In addition, the growth of severely 

 diseased trees is sharply reduced and death frequently results. 



The production of high quality Douglas-fir Christmas trees will 

 require the use of good cultural methods. Foremost among these 

 may be the control of the Rhabdocline needle cast disease. A better 

 understanding of the life history of R. pseudotsugae, as it occurs in 

 New York, is needed for successful control. With these thoughts in 

 mind, the general objectives of the present study were: (1) to deter- 

 mine the range of the disease in New York including number of 

 plantations infected and severity of the infections; (2) to determine 

 the life cycle of R. pseudotsugae in New York, with particular 

 emphasis on the factors affecting spore release; (3) to investigate 

 the role of late (lammas) shoot development in the spread of the 

 disease; (4) to determine the rate of spread of the disease in 

 plantations in central New York; and (5) to evaluate the effec- 

 tiveness of various fungicides for the control of the disease. 



The Rhabdocline needle cast disease was first observed by Weil 

 in Montana and Idaho in 1911. The first published account (66) 

 was given by him in 1917 at which time he indicated its prevalence, 

 and described the symptoms and causal fungus. He tentatively 

 referred the fungus to the family Stictidaceae of the class Ascomy- 

 cetes, but did not name it. 



An examination of the specimens from Weir's collection by Sydow 

 (58) revealed the fungus to be an undescribed species in the Phaci- 

 diaceae, close to the genus Stegopeziza of von Hoehnel. Sydow 

 proposed the new genus Rhabdocline based on the single species 

 Rhabdocline pseudotsugae. From the same needles Sydow described 

 Rhabdogloeum pseudotsugae Syd. as a new conidial stage of the 

 fungus. The- relationship of Rhabdogloeum to Rhabdocline has 



