INJURIOUS INSECTS, FUNGOUS DISEASES, ETC. 201 



Ulcers can be treated by making vertical incisions in 

 the bark near the wound to allow the liquid to flow off as 

 rapidly as possible and, when the current stops, cutting 

 away the diseased bark and painting with coal-tar. 



Drying Out and Leaf Scorch. — ^Young leaves and some- 

 times tender shoots which have pushed out during a spell of 

 cold or cloudy weather frequently wither and die, when ex- 

 posed to bright, hot sun. The trouble usually occurs when 

 a rather moist spring, favorable to growth, is followed by 

 dry and very hot weather. 



Remedial measures are not always easy to carry out, but 

 the harm may be lessened by any treatment that keeps the 

 soil moist and aerated, so that the foliage may have an am- 

 ple supply of water to draw upon. 



Frequently there is much complaint of the leaves of 

 many trees, especially sugar maples, being affected with 

 an apparent disease that causes a loss of green in those 

 parts most distant from the main veins. The trouble 

 has been studied at several experiment stations, and the 

 consensus of opinion is that it is of physiological origin. 

 A lack of water-supply to the leaf tissue causes the death 

 of the least resistant portions of the leaf during a hot and 

 dry spell. 



The writer has found that such a condition can generally 

 be remedied by the mulching of trees in the fall, keeping the 

 soil loose and watering freely. 



Frost. — The injuries from freezing are of a nature simi- 

 lar to drying. Freezing of the plant tissues in fact is the 

 drying out of the water which they contain. If the tissues 

 are dried beyond the point where they are able to take up 

 water again, they are killed. In general, trees native to a 

 given section resist injuries of this sort. In the case of trees 



