6 



is a class of injuries which no one can be accused of en- 

 couraging, and which it is very desirable to control if 

 possible. Sudden frosts after the sap begins to flow in 

 spring may result in injuries not in themselves very 

 serious, but which open the way to attacks by insects. 

 Sleet and wind storms may occasion injuries which in the 

 nature of things cannot be avoided. Droughts when 

 prolonged often weaken trees which are not very vigor- 

 ous, or are badly situated, and then insects when encour- 

 aged by very favorable weather, will overrun a place in 

 spite of all the ordinary precautions that may be taken, 

 attacking in sucli cases the more thrifty trees, as well as 

 the enfeebled ones. 



Svinstroke of Trees. 



In considering the nature of injuries suffered by shade 

 and ornamental trees we must not omit mention of an 

 injury which is very common in Kentucky, and often 

 very destructive. I refer to that sudden blighting of 

 trees with rather succulent foliage, which occurs in hot 

 weather in July. Trees seemingly in perfect health, with 

 splendid growtlis of leaves, receive a check which in its 

 suddeness and effects can only be likened to sunstroke. 

 The crisp green leaves wither on most of the branches in 

 a day, and ultimately blacken and dry up as if tlie tree 

 were utterly killed. After a time such trees partially or 

 .wholly recover and put out a new growth of leaves before 

 fall, still, however, by their enfeebled condition showing 

 that the shock was a severe one. When I first observed 

 this trouble among trees, I supposed it miglit be due to 

 attacks from some one of those minute organisms known 

 as bacteria. The dying leaves show no trace of ordinary 

 parasitic fungi such as occasion the mildew of grape 

 vines and the scab of apple. But careful examination of 

 the tissues when first affected shows no bacterial or other 



