No. 1. 



Blight-beetle. 



15 



From the Massachusetts Ploughman. 

 Blight-beetle. 



Cambridge, June 1st, 1843. 



Wm. Buckminstek, Esq., — Dear sir: The 

 insects contained in the branch of the apple- 

 tree, which you submitted to my examina- 

 tion, are the same as those which produce 

 the sudden withering- of the leaves and the 

 death of the limbs of the pear-tree, an aflec- 

 tion commonly called fire-blight. The dis- 

 covery of the blight-beetle in the limbs of 

 the apple-tree, is a new fact in natural his- 

 tory, but it is easily accounted for, because 

 this tree belongs not only to the same natu- 

 ral group, but also to the same genus as the 

 pear-tree : it is not, therefore, surprising that 

 both the pear and the apple-tree should, 

 occasionally, be attacked by the same in- 

 sects. 



The piece of the apple-tree branch now 

 efore rne, measures twenty-eight inches in 

 length, and is three-quarters of an inch in 

 diameter at the lower end. Its surface bore 

 the marks of twenty buds, thirteen of which 

 were perforated by the insects above named ; 

 and from the burrows, I took twelve of the 

 blight-beetles in a living state, the thirteenth 

 having previously been cut out. This goes 

 far towards confirming my remarks on these 

 insects, published in the fifth volume of the 

 " New England Farmer," page 171, where 

 you will find the following statement : " A 

 whole limb may swarm with them; every 

 bud may conceal the place of their opera- 

 tions, without e.xciting a suspicion of their 

 presence." For their history, I might have 

 referred you to the various published com- 

 munications of Mr. Lowell and Professor 

 Peck, who have described the agency of 

 these insects in producing the " disease in 

 pear-trees," or, to my own remarks on the 

 same subject, in the " N. E. Farmer," and 

 in the " Treatise on Insects injurious to Ve- 

 getation," a book that has been more praised 

 than read; but experience has taught me 

 that line upon line and precept upon pre- 

 cept, are needed to keep the attention of the 

 public directed to the depredations of insects. 

 Allow me, therefore, to extract for you, the 

 following passages from the last named work. 



"The grub or larva of the insect, eats its 

 way inward through the alburnum or sap- 

 wood, into the hardest part of the wood, be- 

 ginning at the root of a bud, behind which 

 probably the egg was deposited, following 

 the course of the eye of the bud towards 

 the pith, around which it passes, and part of 

 which it also consumes ; thus forming, after 

 penetrating through the alburnum, a circular 

 burrow or passage in the heart-wood, con- 

 tiguous to the pith which it surrounds. By 



this means the central vessels, or those 

 which convey the ascending sap, are divided, 

 and the circulation is cut off. This takea 

 place when the increasing heat of the at- 

 mosphere, producing a greater transpiration 

 from the leaves, renders a large and con- 

 tinued flow of sap necessary to supply the 

 evaporation. For the want of this, or from 

 some other unexplained cause, the whole of 

 the limb above the seat of the insect's ope- 

 rations, suddenly withers and perishes, du- 

 ring the intense heat of midsummer. The 

 larva is changed to a pupa, and subsequently 

 to a little beetle in the bottom of its burrow; 

 makes its escape from the tree in the latter 

 part of June, or beginning of July, and pro- 

 bably deposits its eggs before August haa 

 passed. This little beetle is only one-tenth 

 of an inch in length ; it is of a deep brown 

 colour, with the antennse and legs rather 

 paler, or of the colour of iron-rust. The 

 thorax is short, very convex, rounded and 

 rough before; the wing covers are minutely 

 punctured in rows, and slope off very sud- 

 denly and obliquely behind ; the shanks are 

 widened and flattened towards the end, beset 

 with a few little teeth externally, and end 

 with a short hook; and the joints of the feet 

 are slender and entire." 



" The minuteness of the insect, the diffi- 

 culty attending the discovery of the precise 

 seat of its operations before it has left the 

 tree, and the small size of the aperture 

 through which it makes its escape from the 

 limb, are probably the reasons why it has 

 eluded the researches of those persons who 

 disbelieve in its existence as the cause of 

 the blasting of the limbs of the pear-tree. 

 It is to be sought for at or near the lowest 

 part of the diseased limbs, and in the imme- 

 diate vicinity of the buds situated about that 

 part." 



" The remedy suggested by Mr. Lowell 

 and Professor Peck, to prevent other limbs 

 and trees from being subsequently attacked 

 in the same way, consists in cutting off the 

 blasted limb below the seat of injury, and 

 burning it before the perfect insect has 

 made its escape. It will therefore be ne- 

 cessary, carefully to examine our pear-trees 

 daily, during the month of June, and watch 

 for the first hidication of disease, or the 

 remedy may be applied too late to prevent 

 the dispersion of the insects among other 

 trees." 



We are now to look for the disease aflfl 

 its cause in the apple, as well as in the pear- 

 tree, and should not delay to cut off" and burn 

 the infected limbs, as soon as the leaves be- 

 gin to wither. 



Yours respectfully, 



T. W. Harris. 



