76 EXPERIMENT STATION. [Jan. 



some time would peel off in reddish flakes, finally crumbling 

 into dust. We have observed cases in which all the outer bark 

 of large sycamore trees extending to the cortex had peeled off 

 without causing any particular harm. 



Sun Scald. 



Sun scald is a quite common type of injury affecting various 

 maples and other trees, — the apple in particular, where it is 

 often associated with canker (Sphceropsis). White pines, also, 

 when thinned too freely, will sun scald severely on the trunk. 

 Many shade trees in our State show injury from this cause, the 

 trouble being more conmion in some localities than in others. 

 In one section of a city in the eastern part of the State we found 

 a short time ago more than 60 per cent, of the maples suffering 

 from sun scald. The scars were invariably on the sunny side of 

 the tree, and more commonly on the southwestern side, where 

 the maximum temperature was usually found. 



Sun scald does not usually involve the whole trunk of large 

 trees, but in many cases, particularly small maples, the whole 

 tree will suffer. A few years ago on one street in a compara- 

 tively short distance, sixteen maples might have been seen which 

 had died from sun scald, and at one time most of our wild 

 cornels {Cornus circinata) suffered severely from this trouble, 

 many of them never recovering. The moose maple, a shade 

 plant, seldom scalds in its native habitat but when timber 

 is removed and the sun allowed to enter, it is affected. This 

 tree is undoubtedly the most sensitive of any to sun scald. 



Most cases of sun scald are followed by an outbreak of 

 Nectria cinndbarina, as is often the case with winter killing, 

 and unripened wood is more susceptible to the trouble than 

 well-ripened wood. The under branches of unpruned apple 

 trees are especially susceptible to sun scald, while the upper 

 branches, which receive the light, are affected the least. 



Bleeding. 

 A great many trees suffer from bleeding from different types 

 of injury, such as borers, frost cracks, splitting of the trunk 

 and occasionally linemen's spurs. Often trees filled with cement 



