I48 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



The method and time of attack are not yet fully known. 

 Ripe spores capable of germination have been collected in April 

 and October, and it is probable that infection takes place during 

 the summer. In all probability the species is a wound parasite ; 

 this must certainly be the case where the main stem of plants, 

 4-8 years old, is directly attacked not much above ground-level, 

 although it is possible that young uninjured shoots may become 

 infected. 



The narrowing of the stem in the infected portion is the result 

 of the death of the cambium and consequent stoppage of 

 secondary thickening. Probably some considerable time elapses 

 between infection and death of the cambium. In the case of a 

 tree 6-8 years old infected near the base, secondary thickening 

 of the infected portion probably ceases about a year after 

 infection when the leaves begin to turn yellow ; death probably 

 takes place during the following winter. In a tree in which the 

 leading shoot is infected near the apex, growth continues during 

 the following summer and death of the shoot takes place in the 

 winter. Fructifications of the fungus are often found all over 

 the dead trees, and it is evident that the fungus can live on as 

 a saprophyte after the death of the tree. 



From the above observations it may be concluded that 

 Phomopsis Psendotsugae is widespread in Scotland, and is 

 probably increasing in abundance; it is doing very considerable 

 damage to young plantations of the Douglas fir. At the present 

 stage of our knowledge of the fungus little can be said as to 

 prevention, but it is especially necessary to emphasise one point 

 in this connection. Owing to the long period which elapses 

 between infection and the first obvious signs of the disease, it is 

 possible that nursery stock which is apparently healthy, although 

 really diseased, may be planted out, and in this way the disease 

 may be widely distributed. The following general precautions 

 should be taken : — 



(1) Young plantations should be carefully examined for trees 

 showing the early signs of the disease, and these should be 

 removed and burnt. All trees killed by the disease should be 

 at once removed and burnt. 



(2) Plantations, and especially nurseries, should not be 

 established in areas known to be infected. 



In conclusion, I wish to thank Miss L. Snelling for the draw- 

 ing shown in Fig. 4, and Mr R. M. Adam for Photos 1, 2 and 3. 



