322 THE PEAR. 



In orchard culture, the pear is usually planted about thirty 

 feet distant each way in fruit gardens, where the heads are 

 somewhat kept in by pruning, 20 feet is considered sufficient by 

 many. 



Pear trees in a bearing state, where the growth is no longer 

 luxuriant, should have, every autumn, a moderate top dressing 

 of manure, to keep them in good condition. This, as it promotes 

 steady and regular growth, is far preferable to occasional heavy 

 manuring, which, as will presently be shown, has a tendency to 

 induce the worst form of blight to which this tree is subject. 



DISEASES. As a drawback to the, otherwise, easy cultivation 

 of this fine fruit, the pear tree is, unfortunately, liable to a very 

 serious disease, called the pear tree Might, orjire blight, appear- 

 ing irregularly, and in all parts of the country ; sometimes in 

 succeeding seasons, and, again, only after a lapse of several 

 years ; attacking, sometimes, only the extremities of the limbs, 

 and, at other times, destroying the whole tree ; producing, occa- 

 sionally, little damage to a few branches, but often, also destroy- 

 ing, in a day or two, an entire large tree ; this disease has been, 

 at different times, the terror and despair of pear growers. Some 

 parts of the country have been nearly free from it, while 

 others have suffered so much as almost to deter persons from ex- 

 tending the cultivation of this fine fruit. For nearly an hun- 

 dred years, its existence has been remarked in this country, and, 

 until very lately, all notions of its character and origin have 

 been so vague, as to lead to little practical assistance in removing 

 or remedying the evil. 



Careful observation for several years past, and repeated com- 

 parison of facts with accurate observers, in various parts of the 

 country, have led us to the following conclusions : 



1st, That what is popularly called the pear blight, is, in fact, 

 two distinct diseases. 2nd, that one of these is caused by an 

 insect, and the other by sudden freezing and thawing of the sap 

 in unfavourable autumns. The first, we shall therefore call the 

 insect blight, and the second, the frozen-sap blight. 



1. THE INSECT BLIGHT. The symptoms of the insect blight 

 are as follows : In the month of June or July, when the tree is 

 in full luxuriance or growth, shoots at the extremities of the 

 branches, and often extending down two seasons' growth, 

 are observed suddenly to turn brown. In two or three days the 

 leaves become quite black and dry, and the wood so shrivelled 

 and hard as to be cut with difficulty with a knife. If the branch 

 is allowed to remain, the disease sometimes extends a short dis- 

 tance further down the stem, but, usually, not much further than 

 the point where the insect had made his lodgment. The insect 

 which causes this blight, was first discovered by the Hon. John 

 Lowell, of Boston, in 1816, and was described by Professor Peck, 

 under the name of Scolytus pyri. It is very minute, being 



