THE CAUSE OF PEAR BLIGHT. 



MICROSCOPIC INSECTS THE CAUSE OF PEAR BLIGHT. 



BY PROFESSOR TURNER, JACKSONVILLE, ILL. 



Mr. Downing — Dear Sir: I am more and more convinced of the utter uselessnes3 of 

 talking about " blight." fVhat is hlightl Simply the death of certain portions of a tree, 

 in the only way they can die of any sort of sudden disease, while in full sap in warm 

 weather. Any poison or affection that kills in hot weather, will of course, produce blight. 

 However different the fatal cause, the sequali, from the laws of vegetation, must be the 

 same. There may be minute differences, but the general phenomena must be similar; and 

 whether the cause is in the root, trunk, or branches, the tree will attempt to throw it off 

 through the externals and extremities, and there, to the careless observer, the disease and 

 the death, (or blight, as it is called,) will first appear, though it may have existed for 

 months, or even years, in other parts of the tree, unobserved. 



Again, allow me to say, that in our present state of knowledge, the world is but illy pre- 

 pared to talk or to hear about, either the infinitely small, or infinitely great. We shall hard- 

 ly be prepared to contemplate the created universe as it is, till we begin to regard with 

 more attention, the infinite above and below us — and to deem it possible that even man 

 may crush microcosms of worlds beneath his puny tread, as the footsteps of Deity scat- 

 ter stars and suns above and around us. 



I have made these remarks with reference to that form of Pear, Quince, and Apple 

 blight, which so fearfully appeared in this state last season for the first time, and to which 

 I alluded in my last paper, as probably caused by a microscopic insect. I am now both 

 sad and rejoiced, to inform you that this is no longer a probability, but a certainty. Re- 

 joiced at the fact of knowing it — but sad at the appalling nature of the fact itself, as you 

 will see as I progress in my statement — which I hasten to communicate to the public — 

 knowing how important it is that all eyes should at once be turned to the true cause, as 

 the only hope of any relief — at least so far as our pears are concerned. I shall present, 

 at first, no theory, but simply state facts which any one can verify at his leisure. 



1. Examine the trunks and branches of apples, pears, and quinces. There will be seen 

 little holes in the bark, sometimes two or three together, which look like the pick of an 

 awl. These will more usually be found near the origin of a branch or sprout — and much 

 more frequently to be seen on the apple than the pear, for reasons which will be stated. 



Take a knife and cut into these perforations, and you will find the bark dead to the 

 wood, and giving evident signs of poison, or other influence, differing from a similar wound 

 with an awl or simple puncture, as you may learn by making the latter side by side with 

 the former. 



2. Sometime in the month of August, take out one of these pieces of punctured bark, 

 in which the puncture has been rccenthj mad?, (as the old ones were used and abondoned 

 the year before,) and lay it in a bright sun-light, under a powerful compound solar micro- 

 scope, and you will not cut many before you will discover an infinitessimal insect, some- 

 what resembling in legs, shape, and color, a common " sow-bu^^-," as they are here called, 

 running about between the fibies of the bark, much as a pig runs from side to side through 

 the fence, to avoid the scorching heat of the sun. This discoverj"- I made last August, as 

 stated in a former paper, but was still not quite cert liii whether tliis animalcula; was a 

 cause or consequence of the blight. But the discoveries of this month, I think, fully 

 cide that question. 



