THE PEAR. 645 



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. 



2d. That one of these is caused by an insect, and the other by sud- 

 den freezing and thawing of the sap in unfavorable 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 luxuri- 

 ance of 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 distance farther down the stem, but usually not much farther 

 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 scarcely one-tenth of an inch 

 long ; and it escapes from the branch almost as soon as, by the wither- 

 ing of the leaves, we are aware of its attack ; hence it is so rarely seen 

 by careless observers. In the perfect state it is a very small beetle, 

 deep brown, with legs of a paler color. Its thorax is short, convex, 

 rough in front, and studded with erect bristles. The wing-covers are 

 marked with rows of punctured points, between which are also rows of 

 bristles, and they appear cut off very obliquely behind. 



This insect deposits its egg some time in July or August, either be- 

 hind or below a bud. Whether the egg hatches at once, we are not 

 aware, but the following spring the small grub or larva bores through 

 the sap-wood or tender alburnum, beginning at the root of the bud, and 

 burrows toward the centre of the stem. Around this centre or pith it 

 forms a circular passage, sometimes devouring it altogether. By thus 

 perforating, sawing off, or girdling, internally, a considerable portion of 

 the vessels which convey the ascending sap, at the very period when the 

 rapid growth of the leaves calls for the largest supply of fluid from the 

 roots, the growth and the vitality of the branch are checked, and finally 

 extinguished. The larva about this time completes both its transforma- 

 tion and its passage out, and, in the beetle form, emerges, with wings, 

 into the air, to seek out new positions for laying its eggs and continuing 

 its species. The small passage where it makes its exit may now more 

 easily be discovered, below or by the side of the bud, resembling a hole 

 bored with a needle or pin. 



It is well to remark here that the attack of this blight insect is not 

 confined to the Pear, but in some parts of the country we have observed 

 it preying upon the Apple and the Quince in the same manner. In the 

 latter tree, the shoots that were girdled were shorter, and at the extremi- 

 ties of the branches only ; not leading, therefore, to such serious conse- 

 quences as in the Pear. 



The ravages of the insect blight, we are inclined to think, do not ex- 

 tend much below the point where the insect has deposited its egg, a 

 material point of difference from the frozen-sap blight, which often 

 poisons the system of the whole tree if allowed to remain, or if origin- 

 ally very extensive. 



