Pear Blight.—No. 2.
The mere "experience" of an individual, whether as a doctor of medicine, horticulture, or agriculture—however extensive, is comparatively worthless. Indeed the million "demonstrate it to be mischievous, judging from the success of quacks and empyrics as to money. An unlimited number of facts and certificates prove nothing, either as to cause or remedy."
Sir Isaac Newton's corpuscular theory "explained all the phenomena of light, except one," and he actually assumed, for it "fits." Nevertheless it will ever remain the most thinkable mode of teaching the laws of light, and it is not probable that any more than this will ever be accomplished as to any natural science—if that can be called science about which we must admit that "it is not so; but it is as if it were so."
Of more than 300 "Osband Summer" which I grafted on the Anger quince successfully, one remains, and this one was transplanted after they had fruited in a clay soil, to the same sort of soil between "the old standard" and a stable, both of which have occupied the same locality and within twenty yards, during much more than fifty years of my own observation—this "Osband Summer" flourishes. It has borne fruit in its present site, but grew so rapidly last year that the blossoms aborted thus illustrating the large proportion of vital force necessary to the production of fruit, as the site has a perennial supply of manure from the old stable. A number of standard trees, of the same variety, developed beautifully until they attained twenty or thirty feet, but then succumbed to the blight, after the first effort at fruiting. So also the Beurre Clairgean etc., etc. Their exposure to the same influences, and their growth during several years did not occasion the blight, but the debility which must inevitably attend fruiting seems the most prolific cause.
All the phenomena of pear blight can be accounted for, and we are greatly encouraged in protecting the trees therefrom if, we assume, it is only the result of weakness and deficient vitality; if so, as in epidemics, all the pear trees may be poisoned or ergotized, but only the weakest succumb; and perhaps this debility may be confined to one limb. The practical value of this view is manifest, as it is impracticable to avoid using the same knife, and remove every blighted leaf from the orchard. Moreover, if the limb is a large one, its prompt removal shocks the vitality of the whole tree[1] and thus renders other parts more vulnerable. On the contrary view, the limb may be allowed to drop by natural process, precisely as all trees in a forest shed their lower limbs, leaving hardly a cicatrice or scar, and this may be insured at any season by a cord of hemp twine, firmly bound around the limb. The inevitable strangulation, and the healing of the stump (without the mycelium of fungi which the knife or saw inevitably propagates by exposing a denuded surface, if not more directly) proceed more rapidly than the natural slough of limbs by starvation. Moreover the fruit may mature on such limbs during their strangulation, as this may not be perfected before the subsequent winter.
The next practical result of my view is the fundamental importance of all those means which are calculated to husband the vital force of the tree during its first effort to fruit; one of these is the use of a soil that will not produce more than twenty bushels of corn without manure, thus a large proportion of the setts will be aborted, but one half of what remains should be removed, and subsequently the area beneath the limbs should have a wheelbarrow of good compost.
D. S.
[1] Note.—The shock as to vital force is demonstrated by the fact that when young trees are not trimmed at all their girth increases more rapidly, and they bear fruit sooner. Moreover, when old trees are severely pruned (though not half the proportion of wood is removed) they fail to bear during the next year. I find that a hemp cord about the size of the stem of a tobacco pipe (one-fourth inch diameter) will soon become imbedded in the bark if firmly tied around a limb, and perhaps this size is more efficient than a thicker cord.