Pleasant Talk About Fruits, Flowers and Farming

by Henry Ward Beecher

II. Theories.—A variety of theories exist as to the causes of this disease. Some are mere imaginations; some are only ingenious; and some so near to what I suppose to be the truth, that it is hardly possible to imagine how the discovery was not made.

The injury is done in the fall, but is not seen till spring or summer, or even the next fall. Thus, six months or a year intervene between the cause and the effect—a sufficient reason for the difficulty of detecting the origin of the evil.

1. Some have alleged that the rays of the sun, passing through vapors which arise about the trees, concentrate upon the branches, and destroy them by the literal energy of fire. Were this true, the young and tender shoots would suffer first and most; all pear-trees would suffer alike; moist and hot summers would be affected with blight; herbaceous plants would suffer more than ligneous: all of which results are contrary to facts.

2. Some have supposed the soil to contain deleterious substances, or to be wanting in properties necessary to health. But in either case such a cause of the blight appears untrue, when we consider that trees suffer in all soils, rich or poor; that, in the same soil, one tree is blighted and the next tree escapes; that they will flourish for twenty years and then blight; that a tree partially diseased recovers, and thrives for ten or more years without recurrence of blight.

3. It has been attributed to violent and sudden changes

of temperature in the air and of moisture in the earth; to sudden change from sward to high tillage; and the result is stated to be an “overplus” of sap, or a “surfeit.” All these causes occur every year; but the blight does not every year follow them. Changes of temperature, and violent changes in the condition of the soil, may be allied with the true cause. But when only these things exist, no blight follows.

4. Others have attributed the disease to over-stimulation by high manuring, or constant tillage; and it has been said that covering the roots with stones and rubbish, or laying the orchard down to grass, would prevent the evil. Facts warrant no such conclusions. Pear-trees in Gibson County, Indiana, on a clay soil, with blue slaty subsoil, were affected this year more severely than any of which we have heard. Pears in southern parts of this State, on red clay, where the ground had long been neglected, suffered as much as along the rich bottom lands of the Wabash about Vincennes. If there was any difference it was in favor of the richest land. About Mooresville, Morgan County, Indiana, pears have been generally affected, and those in grass lands as much as those in open soils. Aside from these facts, it is well known that pear-trees do not blight in those seasons when they make the rankest growth more than in others. They will thrive rampantly for years, no evil arising from their luxuriance, and then suddenly die of blight.

5. It has been supposed by a few to be the effect of age, the disease beginning on old varieties, and propagated upon new varieties by contagion. Were this the true cause, we should expect it to be most frequently developed in those pear regions where old varieties most abound. But this disease seems to be so little known in England, that Loudon, in his elaborate Encyclopedia of Gardening, does not even mention it. Mr. Manning’s statement will be given further on, to the same purport.

6. Insect theory: The confidence with which eastern cultivators pronounce the cause to be an insect, has in part served to cover up singular discrepancies in the separate statements in respect to the ravages, and even the species of this destroyer. The Genesee Farmer of July, 1843, says, “the cause of the disease was for many years a matter of dispute, and is so still by some persons; but the majority are now fully convinced that it is the work of an insect (scolytus pyri).” T. W. Harris, in his work on insects, speaks of the minuteness and obscure habits of this insect, as “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.” Dr. Harris evidently supposed, until so late as 1843, that this insect infested only the pear-tree; for he says, “the discovery of the blight-beetle in the limbs of the apple-tree, is a new fact in natural history; but it is easily accounted for, because this tree belongs not only to the same natural 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 insect.” [See an article in the Massachusetts Ploughman, summer of 1843, quoted in Genesee Farmer, July, 1843.]

This insect is said to eat through the alburnum, the hard wood, and even a part of the pith, and to destroy the branch by separation of part from part, as a saw would. On these facts, which there is no room to question, we make two remarks.