16 BULLETIN 44, U. S. DEPARTMENT OF AGRICULTURE. 



turing, or heating, or both. Viable spores from pure cultures re- 

 cently isolated from arbor vitse were used. No results were ob- 

 tained. While the fungus is presumably parasitic in nurseries under 

 some conditions, the amount of damage it has caused is unknown. 

 Spraying with fungicides before infection takes place should pre- 

 vent damage by it. 



OTHER NEEDLE DISEASES. 



Various fungi which have been very little studied in this country 

 cause needle diseases in American forests. Though none have yet 

 been reported as causing disease in our nurseries, there can be little 

 doubt that some of them have made, or at least will soon make, trouble 

 in nurseries in this country. Much of the comparative freedom from 

 needle diseases of American nurseries, even those in the more moist 

 regions, has probably been due to the fact that most of our nurseries 

 are not in forests. So far as needle diseases are concerned, it will be 

 best to avoid forests of the same species as will be grown in the 

 nursery in choosing sites for new nurseries. Of the fungi mentioned 

 in the literature on needle diseases, which is mainly European, the 

 following species will especially bear watching: Lophodermiwm 

 macrosporum R. Hrtg. on spruces, Lophodermium nervisequium 

 D. C. on firs, Lophodermium laricinum Duby on larches, and Lopho- 

 dermium hrachysporum Rostr. on white pine. Lophodermiwm 

 orachysporum has been reported by Spaulding 1 as parasitic on 

 needles of young white pines in Maine. Other species of this genus 

 and species of Hypoderma and Sphaerella are also likely to prove 

 more or less parasitic. It is probable that there are parasitic strains 

 of needle fungi in foreign countries which if brought into this coun- 

 try will damage our nursery stock more than any of the fungi we 

 now have. No practicable quarantine or inspection system will be 

 able to keep out these diseases entirely. Nurserymen should avoid 

 bringing in foreign pests by using home-grown stock as far as pos- 

 sible. So far as is now known seed may safely be imported, but 

 bringing in growing stock should -be discouraged. 



The Atlantic seaboard and portions of the extreme western and 

 northwestern sections of the country, where the climate is especially 

 moist during parts of the year, are the most likely to suffer from 

 needle diseases. In the Middle West, where atmospheric conditions 

 are relatively dry, past experience indicates little trouble with needle 

 parasites in unmulched beds. It is presumable that other needle para- 

 sites, like the one causing needle-cast, will be found to be preventable 

 by spraying before infection takes place" 



1 Spaulding, Perley. The present status of the white-pine blights. U. S. Department 

 of Agriculture, Bureau of Plant Industry, Circular 85, p. 10, 1909. 



