BLIGHT AND INSECTS.Inan article on employing suckers of fruit-trees for stocks, which we shall copy, Dr. Kirtland says:“The practice of grafting and budding pears upon this quality of stocks has extended a diseased action, a kind of canker among our pear orchards, that has, in some instances, been mistaken forblight, a disease that has its origin in the depredations of a minute coleopterous insect, which has been satisfactorily described in all its stages of transformation by Dr. Harris, and other Massachusetts entomologists.”That the fire-blight is, to any considerable extent anywhere, but especially at the West, occasioned by an insect, is an idea, we believe, totally unsupported by facts. That some injury has been done by thescolytus pyri, the investigations of Mr. Lowell and Professor Peck leave no room to doubt. But we are not satisfied that, even in these cases, they were the cause of theblight, but only an accidental concomitant. Did Mr. Lowell or Professor Peckalwaysfind this beetle upon blighted trees? Was it found ineveryblighted limb? Did not blight occur without these insects? Has any one of New Englandsincefound the blight to proceed from the gnawings of this beetle?Has any one found this beetlebeforethe blight occurred at its mischievous work, or is it onlyafterthe blight is seen that the beetle is found? If thescolytus pyrihas beenfoundonly after the tree is thoroughly affected, there is reason to suppose that it did notcomeuntil after the disease had prepared the way for it.We are seriously skeptical of this alleged cause. Whatever may be true of the blight at the East, the blight in the West is unquestionably not an effect of thescolytus pyri. We have examined with the utmost pains, multitudes of trees in all soils—several of our shrewdest nurserymen have searched year by year, and we have, unfortunately, had too much opportunity and too many subjects, and yet no insector insect-track has been detected, except those which have attacked the tree inconsequenceof the blight.To be sure, we can find bugs, black, brown, green and grey, but the mere presence of an insect is nothing, though with many, it seems enough, when a tree is blighted, if a bug is found on it, to determine the parentage of the mischief. Nor do the published accounts of insects, found on blighted trees, increase our respect for this theory. The observations seem to have been not thorough enough, and not carefully made, and the reasonings even less philosophical. Men have searched for a theory rather than for the mere facts in the case. But by far the greatest number of those who write, give no evidence of relying upon any observations which they have themselves made, but go back perpetually to the old precedents, Mr. Lowell and Professor Peck, without being at any pains to verify them, Has Dr. Kirtland ever found thescolytus pyri? Has he ever, in time of extensive blight, found it under such circumstances as to satisfy his mind that it was the real cause of fire-blight? or does he rest satisfied that blight is occasioned by an insect simply because so it is set down in good books? The canker may be mistaken for blight by those who have not been acquainted with either; but surely, no one who has ever attentively examined one real case of fire-blight, would ever mistake it for anything else, or anything else for it.The insect theory we regard as wholly untenable except for special, local, peculiar ravages which are not properlyblights. The blight is a disease of thecirculation. It affects every tissue of the plant. It is not a disease from exhaustion of sap by the suction of aphides, as Dr. Mosher, of Cincinnati, supposed, for the trees have a plethora rather than scarcity of sap; it lacerates the sap-vessels, bursts the bark, flows down the branches, and dries in globules upon the trunk. On cutting the tree, if the blight is yet new, the texture of the alburnum will be found to resemble whatis called awater-corein the apple, its color is of a dirty greenish hue, soon changing by exposure to brown and black. But if the blight is old, the wood is of a dingy white, the alburnum colored like iron rust, and the bark of a brownish black. These appearances are incompatible with any idea of exhaustion by the gnawing of thescolytus pyri, or the suction of aphides, which would result in mere shrinking of parts, dryness and death. If insects have a hand in the mischief, it is by the secretion of poison, of which fact, we have never seen the trace of proof, although it has often been suggested, and is by some empyrically asserted. To our minds the insect-poison-theory is imaginary. It is entirely convenient to refer every excrescence, or shrinking of parts, every watery suffusion, wart, discoloration, crumpling leaf, wilting, etc., to poison, and still more convenient to find the insect so atomic that it cannotbefound, and thus to heap the multiform sins of the orchard on the scape-goat of a hypothetical insect.As to electricity, as no one knows anything about this elemental sprite, his out-goings or in-comings, we are like to have acted over again all the caprices of witch-times, when elves and gnomes cut up every prank imaginable, and when any prank, which was cut up, of course was performed by them. Everybody is agog about electricity. But we respectfully suggest that it is one thing to ascertain facts by cautious, guarded experiments or careful observation, and quite another to set down everything, which one does not know what else to do with, to electricity, simply becauseit may be so for aught that we know to the contrary. People reason somewhat in this wise; electricity performs a vast number of very mysterious operations, therefore, every operation which is mysterious is performed by electricity. We believe electricity to have something to do with it, only because it seems to have concern with every living, growing thing.We believe that the blight is, in all cases, the effect offrost upon the sap. We have, until recently, supposed it to arise from autumnal freezing, while the tree is in full growth. We are now inclined to suppose that severe freezing and sudden thawing at any time, autumn, winter or spring,when the sap is in motion, will result in blight. The blight of 1844 was from the freezing of growing trees in the autumn of 1843, and the premonitory stages were clearly discernible in the tree during the whole winter months before it broke out in its last malignant form.When a warm winter allows continuous motion of sap, and sudden, severe freezing with rapid thawing occurs, wesupposeit to cause a variety of blight. We are making investigations on this head, but are not yet prepared to speak with certainty.When a sudden violent freezing overtakes growing trees in spring, with rapid thaws, it, we suppose, results in a blight resembling the autumn-caused blight.We are diligently searching into this whole matter, and hope to throw some light upon it.But now comesthequestion. What is it that makes some trees so obnoxious to this evil while others escape? Why are some orchards generally affected, and contiguous orchards entirely saved?It is very plain that the blight occurs, as a general disease, in some seasons more than in others, because it depends upon the peculiar condition of the season, the time and degree of frosts. But it does not seem so clear why, when these conditions are favorable to blight, one tree should suffer, and the next in the row should not; why one orchard should be depopulated, and another in the same town not touched.We think that light will be afforded on this point by a consideration of thetextureof trees.When trees are rapidly grown by stimulating manures, or upon strong clay loams, or from any other cause, the wood is coarse, the passages enlarged, the tissue loose and spongy. The tree passes a great volume of sap—it is but imperfectly elaborated (as is seen by the late period towhich such trees defer the bearing of fruit), and the tissues formed by it are correspondingly imperfect in wholesomeness, compactness, and solidity of parts. The tree is bloated—is dropsical.On gravelly soils, or loams with a gravelly subsoil, or on any kind of soil, which gives a slow and thorough growth, the wood is fine, close and perfect; the vessels are not expanded, their sides are firmer, less sensitive to sudden changes of temperature, and when exposed to them better able to resist them.Whatever soil produces rank or coarse wood, a flabby tissue will be subject to blights. Whatever soil induces a fine-grained, compact fibre, and vigorous tissue, will be free from blight. The same is true of the various methods of cultivation; those who drive their trees, who aim chiefly at a rapid and strong growth, will give their trees a condition requisite for blight. Those who pursue a more cautious, a slower method, and look to thequalityrather than thequantityof their wood, will be comparatively free from blight.To be sure, there may be seasons so extreme that blight will occur in the most healthy tree; so disease will occur in the most temperate men; yet temperance, conformity to the laws of nature, is the rule of health, and nonconformity the preparation for disease.Meanwhile, will those who are unfortunate enough to have a good opportunity for observing, examine—1. The soil and subsoil of blighted trees?2. The habit of the tree, as to rankness of growth?3. The character of the cultivation which has been employed?4. In short, the relative condition of orchards and trees which have escaped or been blighted, as to fineness and closeness, and health of texture. It is high time that this matter should be minutely investigated. It is theopprobrium cultorum.
Inan article on employing suckers of fruit-trees for stocks, which we shall copy, Dr. Kirtland says:
“The practice of grafting and budding pears upon this quality of stocks has extended a diseased action, a kind of canker among our pear orchards, that has, in some instances, been mistaken forblight, a disease that has its origin in the depredations of a minute coleopterous insect, which has been satisfactorily described in all its stages of transformation by Dr. Harris, and other Massachusetts entomologists.”
That the fire-blight is, to any considerable extent anywhere, but especially at the West, occasioned by an insect, is an idea, we believe, totally unsupported by facts. That some injury has been done by thescolytus pyri, the investigations of Mr. Lowell and Professor Peck leave no room to doubt. But we are not satisfied that, even in these cases, they were the cause of theblight, but only an accidental concomitant. Did Mr. Lowell or Professor Peckalwaysfind this beetle upon blighted trees? Was it found ineveryblighted limb? Did not blight occur without these insects? Has any one of New Englandsincefound the blight to proceed from the gnawings of this beetle?
Has any one found this beetlebeforethe blight occurred at its mischievous work, or is it onlyafterthe blight is seen that the beetle is found? If thescolytus pyrihas beenfoundonly after the tree is thoroughly affected, there is reason to suppose that it did notcomeuntil after the disease had prepared the way for it.
We are seriously skeptical of this alleged cause. Whatever may be true of the blight at the East, the blight in the West is unquestionably not an effect of thescolytus pyri. We have examined with the utmost pains, multitudes of trees in all soils—several of our shrewdest nurserymen have searched year by year, and we have, unfortunately, had too much opportunity and too many subjects, and yet no insector insect-track has been detected, except those which have attacked the tree inconsequenceof the blight.
To be sure, we can find bugs, black, brown, green and grey, but the mere presence of an insect is nothing, though with many, it seems enough, when a tree is blighted, if a bug is found on it, to determine the parentage of the mischief. Nor do the published accounts of insects, found on blighted trees, increase our respect for this theory. The observations seem to have been not thorough enough, and not carefully made, and the reasonings even less philosophical. Men have searched for a theory rather than for the mere facts in the case. But by far the greatest number of those who write, give no evidence of relying upon any observations which they have themselves made, but go back perpetually to the old precedents, Mr. Lowell and Professor Peck, without being at any pains to verify them, Has Dr. Kirtland ever found thescolytus pyri? Has he ever, in time of extensive blight, found it under such circumstances as to satisfy his mind that it was the real cause of fire-blight? or does he rest satisfied that blight is occasioned by an insect simply because so it is set down in good books? The canker may be mistaken for blight by those who have not been acquainted with either; but surely, no one who has ever attentively examined one real case of fire-blight, would ever mistake it for anything else, or anything else for it.
The insect theory we regard as wholly untenable except for special, local, peculiar ravages which are not properlyblights. The blight is a disease of thecirculation. It affects every tissue of the plant. It is not a disease from exhaustion of sap by the suction of aphides, as Dr. Mosher, of Cincinnati, supposed, for the trees have a plethora rather than scarcity of sap; it lacerates the sap-vessels, bursts the bark, flows down the branches, and dries in globules upon the trunk. On cutting the tree, if the blight is yet new, the texture of the alburnum will be found to resemble whatis called awater-corein the apple, its color is of a dirty greenish hue, soon changing by exposure to brown and black. But if the blight is old, the wood is of a dingy white, the alburnum colored like iron rust, and the bark of a brownish black. These appearances are incompatible with any idea of exhaustion by the gnawing of thescolytus pyri, or the suction of aphides, which would result in mere shrinking of parts, dryness and death. If insects have a hand in the mischief, it is by the secretion of poison, of which fact, we have never seen the trace of proof, although it has often been suggested, and is by some empyrically asserted. To our minds the insect-poison-theory is imaginary. It is entirely convenient to refer every excrescence, or shrinking of parts, every watery suffusion, wart, discoloration, crumpling leaf, wilting, etc., to poison, and still more convenient to find the insect so atomic that it cannotbefound, and thus to heap the multiform sins of the orchard on the scape-goat of a hypothetical insect.
As to electricity, as no one knows anything about this elemental sprite, his out-goings or in-comings, we are like to have acted over again all the caprices of witch-times, when elves and gnomes cut up every prank imaginable, and when any prank, which was cut up, of course was performed by them. Everybody is agog about electricity. But we respectfully suggest that it is one thing to ascertain facts by cautious, guarded experiments or careful observation, and quite another to set down everything, which one does not know what else to do with, to electricity, simply becauseit may be so for aught that we know to the contrary. People reason somewhat in this wise; electricity performs a vast number of very mysterious operations, therefore, every operation which is mysterious is performed by electricity. We believe electricity to have something to do with it, only because it seems to have concern with every living, growing thing.
We believe that the blight is, in all cases, the effect offrost upon the sap. We have, until recently, supposed it to arise from autumnal freezing, while the tree is in full growth. We are now inclined to suppose that severe freezing and sudden thawing at any time, autumn, winter or spring,when the sap is in motion, will result in blight. The blight of 1844 was from the freezing of growing trees in the autumn of 1843, and the premonitory stages were clearly discernible in the tree during the whole winter months before it broke out in its last malignant form.
When a warm winter allows continuous motion of sap, and sudden, severe freezing with rapid thawing occurs, wesupposeit to cause a variety of blight. We are making investigations on this head, but are not yet prepared to speak with certainty.
When a sudden violent freezing overtakes growing trees in spring, with rapid thaws, it, we suppose, results in a blight resembling the autumn-caused blight.
We are diligently searching into this whole matter, and hope to throw some light upon it.
But now comesthequestion. What is it that makes some trees so obnoxious to this evil while others escape? Why are some orchards generally affected, and contiguous orchards entirely saved?
It is very plain that the blight occurs, as a general disease, in some seasons more than in others, because it depends upon the peculiar condition of the season, the time and degree of frosts. But it does not seem so clear why, when these conditions are favorable to blight, one tree should suffer, and the next in the row should not; why one orchard should be depopulated, and another in the same town not touched.
We think that light will be afforded on this point by a consideration of thetextureof trees.
When trees are rapidly grown by stimulating manures, or upon strong clay loams, or from any other cause, the wood is coarse, the passages enlarged, the tissue loose and spongy. The tree passes a great volume of sap—it is but imperfectly elaborated (as is seen by the late period towhich such trees defer the bearing of fruit), and the tissues formed by it are correspondingly imperfect in wholesomeness, compactness, and solidity of parts. The tree is bloated—is dropsical.
On gravelly soils, or loams with a gravelly subsoil, or on any kind of soil, which gives a slow and thorough growth, the wood is fine, close and perfect; the vessels are not expanded, their sides are firmer, less sensitive to sudden changes of temperature, and when exposed to them better able to resist them.
Whatever soil produces rank or coarse wood, a flabby tissue will be subject to blights. Whatever soil induces a fine-grained, compact fibre, and vigorous tissue, will be free from blight. The same is true of the various methods of cultivation; those who drive their trees, who aim chiefly at a rapid and strong growth, will give their trees a condition requisite for blight. Those who pursue a more cautious, a slower method, and look to thequalityrather than thequantityof their wood, will be comparatively free from blight.
To be sure, there may be seasons so extreme that blight will occur in the most healthy tree; so disease will occur in the most temperate men; yet temperance, conformity to the laws of nature, is the rule of health, and nonconformity the preparation for disease.
Meanwhile, will those who are unfortunate enough to have a good opportunity for observing, examine—
1. The soil and subsoil of blighted trees?
2. The habit of the tree, as to rankness of growth?
3. The character of the cultivation which has been employed?
4. In short, the relative condition of orchards and trees which have escaped or been blighted, as to fineness and closeness, and health of texture. It is high time that this matter should be minutely investigated. It is theopprobrium cultorum.