342 VI. General Discussion 



as sudden widespread outbreaks of disease and these must be in- 

 vestigated by the Ministry's officers. There is also much research work 

 of a tedious routine nature which must be carried out, such as control 

 methods and spraying problems. The American Gooseberry Mildew 

 for example has been studied for nineteen years and its control is 

 still imperfect. In addition there are always special problems eluci- 

 dation of which is very desirable and these will not be neglected. To 

 appreciate these special points the workers need to possess the true 

 research spirit. 



Professor A. Henry {Royal College of Science, Dublin). 



I agree generally with Professor Somerville's remarks. I wish to 

 point out that attacks by fungi on trees in plantations twenty, thirty 

 or more years old may involve greater financial loss than is the 

 case in attacks of fungi on other cultivated plants. The accumulated 

 capital of many years growth of timber may be completely de- 

 stroyed. 



We know that Pinus stobus can no longer be cultivated in Europe 

 on account of the destructive effects of blister rust. This fungus, carried 

 into the United States by young trees from German nurseries a few years 

 ago, now threatens the existence of the extensive forests of this valuable 

 pine in the United States. Thuya gigantea, a tree hitherto regarded as 

 immune from disease and cultivated considerably in Britain and Ireland, 

 has recently been attacked by a fungus, Keithia Thujina, which may 

 spread and render valueless plantations of this species made in the last 

 twenty years. At present afforestation is carried out mainly with exotic 

 species; some Uke the European larch, hazardous to cultivate on account 

 of the canker which infests it in so many situations; other species, like 

 the Douglas fir and Sitka spruce, up to the present free from disease, 

 and forming the bulk of many new plantations. If disease of a similar 

 character to those first mentioned attacks the two last most valuable 

 trees, say in ten or twenty years time, enormous loss will be incurred by 

 the State and by private owners of woods. 



What is wanted is a number of workers in mycology, who will 

 tackle under field conditions the problem of the attacks of fungi on 

 our common forest trees, to refer both to old and well-known enemies 

 like larch canker and Agaricus melleus and to new diseases like Keithia 

 Thujina. 



Afforestation, without concurrent research into disease, may turn 

 out in many cases a disastrous failure. 



