surface and never through stoniata as suggested by Hubert (23). 

 The present study indicated that all trees, except for a few appar- 

 ently resistant individuals, can be completely infected if conditions 

 are favorable For the fungus. The disease was found to have a short- 

 distance spread of from 100 to 250 feet per year. Spores are dissem- 

 inated b\ moisture-laden winds as was suggested by Weir (66). 



The role of lammas shoots, in relation to the Rhabdocline needle 

 cast disease was investigated. They have been reported to develop 

 too late to become infected (29) but were commonly infected in New 

 York. The extension of the spore dispersal period for R. pseudot- 

 sugar answers four pertinent questions on the activities of the causal 

 fungus. One, the apparent duplicity in appearance of symptoms is 

 explained by the parallel, but distinctly separate, development of 

 two groups of infected needles. The spring needles were heavily 

 infected, whereas needles of late or lammas shoots produced typically 

 weak, slow-developing infections. Two, the reported (5) retention 

 of infected needles for two years before apothecial development is 

 found to be directly related to the fact that although many infected 

 lammas needles develop minute apothecia by the following spring, 

 most of these infections are so weak, and develop so slowly that two 

 years are needed for the fungus to fruit. Three, lammas infection, 

 which may have failed to develop at the end of one year, might 

 easilv be mistaken for infection of two-year-old needles, especially 

 if it was uncertain whether lammas growth had occurred. Lastly, if 

 lammas branches were not infected, some of them would retain 

 needles entirely free from the disease. In central New York, even 

 though lammas branching occurred during the summers of 1955, 

 1956, and 1957, the twigs of infected trees were entirely defoliated. 



The formation of lammas shoots makes it difficult to develop 

 an adequate spray program. The late development of apothecia on 

 lammas needles could maintain or even increase the disease in an 

 area where successful control was achieved on spring needles. 



Histopathological studies substantiate the previous suggestion 

 that penetration by R. pscudot.su gae may occur on either surface of 

 the needle. There is much evidence to suggest that the upper surface 

 is by far the most commonly penetrated. The development of two 

 kinds of hyphae within the needle is in agreement with the findings 

 of previous workers (7, 29, 63). Concentrations of hyphae were 

 closelv appressed against the endodermal cells but failed to pene- 

 trate bevond. Arrangement of hyphae to form the hymen ium was 



59 



