REPORT OF THE SOCIETY 17 



The most striking of the symptoms of bhght consist of a yellowing or 

 reddening of the new partly-grown needles very shortly following their emer- 

 gence from the buds, an event that occurs in late June or the first part of July. 

 The discoloration continues progressively from the tips of aifected needles 

 downwards over an interval of about two weeks. The upper part of the tree 

 is usually most severely affected although all parts are commonly involved. 

 The extent of the blighting is most frequently uniform for all needles of any 

 sirigle fascicle, and shows itself in varying degrees up to totality. 



It was soon ascertained that the injury was not a winter killing of the 

 foliage, an enzymatic disease, or due to fungi or insects, nor could it be induced 

 in healthy branches by fusing them at freshly abraded spots with diseased 

 branches of affected trees. It was discovered in 1919 that the trouble la}' in the 

 roots, that the absorbing roots were largely dead in blighted trees, as a result 

 of which, at the time the new needless are expanding there is a sudden demand 

 for a greatly increased supply of water which cannot be delivered. Consequently 

 the young needles turn pale and then redden from the tips downwards. The 

 foliage of trees recovering from blight in later years may be short, tufted and 

 pale, but there are other factors to be considered in that connection. The 

 cause of the killing of the absorbing roots has not been fully demonstrated, 

 but there is evidence to show that it ma}' be brought about by a drying out 

 that takes place in periods cf drought in shallow or leachy soils. Owing to the 

 dry weather experienced in the summer of 1921, the blight, while not as abun- 

 dant in Timagami as in 1918, was more sharph- defined than in 1920. 



But white pine (Pinus stroLus) is not the only tree affected in the blight 

 areas, although it probably suffers much more severely than other types; proof 

 is accumulating that shows that other timber species are involved to a greater 

 or less extent, depending on their relative susceptibilities. 



The question of needle blight has come into consideration in relation to 

 anotber problem, namely, the possibilit}' of distinguishing between needle 

 blight and discolorations due to sulphur fumes in areas within the possible 

 range of sulphur dioxide emanations. They can be differentiated during the 

 growing season, but probably not at any other time. Observations on both 

 phenomena have shown that burning of the leaves from sulphur fumes takes 

 place rapidly and v.'henever conditions of temperature and humidity are favor- 

 able, and the injuries are not necessarily restricted to the needles of the current 

 season, although these are the ones that are most susceptible. As has been seen, 

 needle blight occurs at a definite period in relation to the emergence of the 

 needles from the buds. In the early spring, that is, before the l)uds break, it is 

 doubtful if it be always possible to distinguish with certaintj' needle blight 

 from winter browning or from injuries due to sulphur fumes. 



Observations on the needle })light have now been carried on for four years, 

 and the status of 633 white pine trees whose histories have been followed since 

 1918 is simimarized in the table that follows. 



