Part 72

In priming before the sap begins to rise freely, no sap should follow the knife in a healthy tree. But in trees which have been affected with blight, a sticky, viscid sap exudes from the wound.

4. Trees which ripen their wood and leaves early, are seldom affected. This ought to elicit careful observation; for, if found true, it will be an important element in determining the value of varieties of the pear in the middle and western States, where the late and warm autumns render orchards more liable to winter blight than New England orchards. An Orange Bergamot, grafted upon an apple stock, had about run out; it made a small and feeble growth, and cast its leaves in the summer of 1843, long before frost. It escaped the blight entirely; while young trees, and of the same kind (we believe), standing about it, and growing vigorously till the freeze, perished the next season. I have before me a list of more than fifty varieties, growing in the orchard of Aaron Alldredge, of Indianapolis, and their history since 1836; and so far as it can be ascertained, late-growing varieties are the ones, in every case, subject to blight; and of those which have always escaped, the most part are known to ripen leaf and wood early.

5. Wherever artificial causes have either produced or prevented a growth so late as to be overtaken by a freeze, blight has, respectively, been felt or avoided. Out of 200 pear-trees, only four escaped in 1832, in the orchard of Mr. Reagan. These four had, the previous spring, been transplanted, and had made little or no growth during summer or fall. If, however, they had recovered themselves, during the summer, so as to grow in the autumn, transplanting would have had just the other effect; as was the case in a row of pear-trees, transplanted by Mr. Alldredge in 1843. They stood still through the summer and made growth in the fall—were frozen—and in 1844 manifested severe blight. Mr. Alldredge’s orchard affords another instructive fact. Having a row of the St. Michael pear (of which any cultivator might have been proud), standing close by his stable, he was accustomed, in the summer of 1843, to throw out, now and then, manure about them, to force their growth. Under this stimulus they were making excessive growth when winter-struck. Of all his orchard, they suffered, the ensuing summer, the most severely. Of twenty-two trees twelve were affected by the blight, and eight entirely killed. Of seventeen trees of the Bell pear, eleven suffered, but none were killed. All in this region know the vigorous habit of this tree. Of eight Crassane Bergamot (a late grower), five were affected and two killed. In an orchard of 325 trees of 79 varieties, one in seven blighted, 25 were totally destroyed. Although a minute observation was not made on each tree, yet, as a general fact, those which suffered were trees of a full habit and of a late growth.

6. Mr. White, a nurseryman near Mooresville, Morgan County, Indiana, in an orchard of from 150 to 200 trees, had not a single case of the blight in the year 1844, though all around him its ravages were felt. What were the facts in this case? His orchard is planted on a mound-like piece of ground; is high, of a sandy, gravelly soil: earlier by a week than nursery soils in this county; and in the summer of 1843 his trees grew through the summer; wound up and shed their leaves early in the fall, and during the warm spell made no second growth. The orchard, then, that escaped, was one on such a soil as insured an early growth, so that the winter fell upon ripened wood.

7. It may be objected, that if the blight began in the new and growing wood, it would appear there; whereas the seat of the evil, i. e. the place where the bark is diseased or dead, is lower down and on old wood. Certainly, it should be; for the returning sap falls some ways down before it effects a lodgment.

8. It might be said that spring-frosts might produce this disease. But in the spring of 1834, in the last of May, after the forest-trees were in full leaf; there came frost so severe as to cut every leaf; and to this day the dead tops of the beech attest the power of the frost. But no blight occurred that year in orchard, garden or nursery.

9. It may be asked why forest-trees do not suffer. To some extent they do. But usually the dense shade preserves the moisture of the soil, and favors an equal growth during the spring and summer; so that the excitability of the tree is spent before autumn, and it is going to rest when frost strikes it.

10. It may be inquired why fall-growing shrubs are not always blighted, since many kinds are invariably caught by the frost in a growing state.

We reply, first, that we are not to say that every tree or shrub suffers from cold in the same manner. We assert it of fruit-trees because it has been observed; it must be asserted of other trees only when ascertained.

We reply more particularly, that a mere frost is not supposed to do the injury. The conditions under which blight is supposed to originate are, a growing state of the tree, a sudden freeze, and sudden thawing.

We would here add, that many things are yet to be ascertained before this theory can be considered as settled; as the actual state of the sap after congelation, ascertained by experiment; the condition of sap-vessels, as ascertained by dissection; whether the congelation, or the thawing, or both, produce the mischief; whether the character of the season following the fall-injury may not materially modify the malignancy of the disease; seasons that are hot, moist and cloudy, propagating the evil; and others dry, and cool, restraining growth and the dsease. It is to be hoped that these points will be carefully investigated, not by conjecture, but by scientific processes.

11. We have heard it objected, that trees grafted in the spring blight in the graft during the summer. If the stock had been affected in the fall, blight would arise from it; if the scion had, in common with the tree from which it was cut, been injured, blight must arise from it.

Blight is frequently caused in the nursery; and the cultivator, who has brought trees from a distance, and with much expense, has scarcely planted them before they show blight and die.

12. It is objected, that while only a single branch is at first affected, the evil is imparted to the whole tree; not only to the wood of the last year, but to the old branches. We reply, that if a single branch only should be affected by fall-frost, and be so severely affected as to become a repository of much malignant fluid, it might gradually enter the system of the whole tree, through the circulation. This fact shows, why cutting is a partial remedy; every diseased branch removed, removes so much poison; it shows also why cutting from below the seat of the disease (as if to fall below the haunt of a supposed insect), is beneficial. The farther the cut is made from that point where the sap has clogged the passages, the less of it will remain to enter the circulation.

13. Trees of great vigor of constitution, in whose system but little poison exists, may succeed after a while in rejecting the evil, and recover. Where much enters the system, the tree must die; and with a suddenness proportioned to the amount of poison circulated.

14. A rich and dry soil would be likely to promote early growth, and the tree would finish its work in time; but a rich and moist soil, by forcing the growth, would prepare the tree for blight; so that rich soils may prevent or prepare for the blight, and the difference will be the difference of the respective soils in producing an early instead of a late growth.

IV. REMEDY.—So long as the blight was believed to be of insect origin, it appeared totally irremediable. If the foregoing reasoning be found correct, it will be plain that the scourge can only be occasional; that it may be in a degree prevented; and to some extent remedied where it exists.

1. We should begin by selecting for pear orchards a warm, light, rich, dry and early soil. This will secure an early growth and ripe wood before winter sets in.

2. So soon as observation has determined what kinds are naturally early growers and early ripeners of wood, such should be selected; as they will be least likely to come under those conditions in which blight occurs.

3. Wherever orchards are already planted; or where a choice in soils cannot be had, the cultivator may know by the last of August or September, whether a fall-growth is to be expected. To prevent it, we suggest immediate root-pruning. This will benefit the tree at any rate, and will probably, by immediately restraining growth, prevent blight.

4. Whenever blight has occurred, we know of no remedy but free and early cutting. In some cases it will remove all diseased matter; in some it will alleviate only; but in bad blight, there is neither in this, nor in anything else that we are aware of, any remedy.

There are two additional subjects, with which we shall close this paper.

1. This blight is not to be confounded with winter-killing. In the winter of either 1837 or 1838, in March a deep snow fell (in the region of Indianapolis) and was immediately followed by brilliant sun. Thousands of nursery-trees perished in consequence, but without putting out leaves, or lingering. It is a familiar fact to orchardists, that severe cold, followed by warm suns, produce a bursting of the bark along the trunk; but usually at the surface of the ground.

2. We call the attention of cultivators to the disease of the peach-tree, called “The Yellows.” We have not spoken of it as the same disease as the blight in the pear and the apple, only because we did not wish to embarrass this subject by too many issues. We will only say, that it is the opinion of the most intelligent cultivators among us, that the yellows are nothing but the development of the blight according to the peculiar habits of the peach-tree. We mention it, that observation may be directed to the facts.

Read before the Indiana Horticultural Society, and communicated by Mr. Beecher to Hovey’s Magazine of Horticulture, December, 1844.

Lindley’s Horticulture, p. 81-82.

See Lindley, p. 32.

PROGRESS OF HORTICULTURE IN INDIANA.