122 EEPOET OF THE No. 3 



been destroyed. Therefore, it comes about that when there is a sudden increase 

 in the water requirements of the plant, as at the time of leafing, the absorbing 

 organs are unable to supply the demand; the succulent young needles are the 

 first organs of the crown to exhibit the resulting distress. It also seems apparently 

 sound to assume that young trees are able the more quickly to repair the damage 

 done; and under favourable weather conditions, as in the summer of 1918, to 

 produce new roots in sufficient amount to provide an increased, if not fully 

 sufficient, flow of water for the growing leaves and tissues of the next season. 

 The older, more nearly mature, trees, and especially as is so often the case if 

 handicapped by a certain amount of butt rot, are incapable of recovery, or if so, 

 must recuperate more slowly. It will be necessary to follow our trees of this 

 group for a few years, and incidentally in the case of recovery to note the effect 

 on wood accretion. 



The cause of the disturbance to the root system remains undemonstrated. 

 Drought seems the most reasonable explanation. It may be possible to test this 

 theory out by a simulation of drought conditions and by a study of the course 

 of these outbreaks in connection with the rainfall and temperature reports for 

 affected districts. That severest blight occurs on shallow and on sandy soil 

 appears significant in this connection. A more detailed account of needle blight 

 will l)e prepared after the completion of the present investigation. 



The following conclusions may be tentatively offered: 



1. " Needle blight '' is at present the most serious of the needle troubles of 

 our white pine. 



2. In some localities it will kill a good many trees and seriously retard the 

 growch of others- — to such an extent as to be reckoned with in determining the 

 time at which a stand has attained maximum productivity. 



8. It is at least a menace to young stands. 



4. Young trees recover, older trees may recover though more slowly ; a variable 

 percentage of old trees die — according to observations so far, up to 5 per cent. 



5. It is now possible to distinguish between sulphur fume injury, or winter 

 injury on the one hand, and needle blight on the other, 



6. The blight is not of biotic origin. 



7. The blight is not a communicable physiological disease. 



8. The blight is not contagious. 



9. The blight is related to root injury — possibly due to drought. 



« 



Survey of Diseases of Timber Trees in Ontario. 



A more extended survey was made of the diseases of the timber trees in 

 Ontario, especially in the Timagami Forest Reserve. At least two new to science 

 were discovered, and many not before reported for Ontario were found. Eesearches 

 on some of those are now in progress. A first contribution to the list follows 

 under the technical names of the causal agents. Collections were made of the 

 various forms, both of the fungi and of the diseased hosts, and they have be6n 

 catalogued and stored for future reference. 



In addition, valuable collections have been received from the United States 

 laboratories of plant pathology, from agents of the Canadian Conservation Com- 

 mission, and the Forest Products Laboratory, Montreal, including a collection of 

 fungi on diseased spruce pulpwood from Thorold, Ontario, and individual con- 

 tributions from various other sources. Exchanges in some cases have been effected. 



