PLANT DISEASES IN I908. 2/ 



bringing about a condition in the plant tissues comparable to 

 drouth in summer. Leaves on conifers remaining on throughout 

 the year remove more or less water from the tissues all 

 winter by transpiration. In the case of young, shallow- 

 rooted trees the ground may be frozen to the depth and often 

 below where the roots extend, thus effectually cutting off the 

 upward current of water to the branches. Now if the tree is 

 exposed to severe and long continued dry winds, particularly if 

 accompanied by bright sunlight during a part of the day, the 

 tissues may become sufficiently dried out in this manner as to 

 injure them beyond recovery. The fact that the larger trees are 

 deeper rooted, and their trunks much better protected against 

 the radiation of heat and the consequent stoppage of the upward 

 current in them doubtless explains in a measure why the large 

 pines suffered only slightly as compared with younger trees. 



As has already been stated there is another well marked pine 

 leaf trouble in Maine. The writer has seen a few trees showing 

 this disease in Brunswick, Winthrop and Orono, and has 

 received specimens of the same thing from Lewiston. The 

 Orono trees have been under observation for two years. The 

 disease appeared on the young needles the second year much the 

 same as when first observed, and in this respect as well as the 

 general aspect of the diseased trees the trouble is decidedl}'- dif- 

 fernt from the winter injury. At Orono branches of healthy 

 trees, interlocking with those of aflFected trees did not develop 

 the disease either season. This disease is very well described 

 in a circular issued in May 1908 by the United States Forest 

 Service and entitled "Extent and Importance of White Pine 

 Blight." 



"Trees affected by the blight may readily be recognized from 

 the characteristic reddish-brown color assumed by the newest 

 needles. The- tip of the needle is always affected first and 

 needles with the base or middle turned brown but the tip green 

 are practically never seen. The extent of the decoloration varies 

 greatly in the different nedles, and in different trees ; sometimes 

 only the tip is affected, sometimes the whole needle. Attacked 

 trees look as if they had been scorched by fire, or as if the tips 

 of the needles had been dipped in reddish-brown ^jye. ******** 

 A tree which is attacked nut vear appears rarelv to escape the 

 next." 



