(Concluded from page 113).

The only disease to which the Pear is liable in this country, so far as I have ever seen or been able to ascertain, is canker: there may be others of which I am not aware, but never having come under my observation, I shall confine myself to this one, which at all events works great havoc in many places. Various causes are assigned for its appearance, and surrounding circumstances often come in for a share of the blame. Any or all of these may to a great extent be the cause of it, yet it is our firm opinion that where the trees planted have been selected to suit the climate, and treated something after the fashion already recommended, the disease may at all events be greatly modified, if not entirely prevented. Mr Thomson in the 'Gardener's Assistant,' see page 509, cautions against extremes of moisture and dryness, and goes on to say that "where canker makes its appearance the soil should not be made too rich, for over-luxuriance of growth seems to encourage the disease, at least in our variable and ungenial seasons." Now I find, in turning back to page 499 of the same work, that he says, in speaking of the soil suitable for the Pear, that "it is essential that the tree should start vigorously, and therefore, if the soil is not naturally very rich, a compost in which to plant the tree should be formed.

A mixture of good turfy loam and farmyard manure will be very suitable." Now I cannot reconcile these two facts, that first he should recommend a very rich compost as being best suited for the Pear, and afterwards say that the soil should not be too rich, as such will encourage the disease. It is our opinion that the soil he has recommended is exactly what the Pear requires and flourishes best in, but that he makes a mistake in thinking that too rich a border is the harbinger of this disease: in fact, the reverse is our opinion, for we think that a poor and cold soil has far more to do with it than anything else. Let any one who is troubled with canker make the following experiment, and prove the fact for himself. His border may be made up of the very best and most suitable soil for the Pear, and he may be of opinion that over-richness is the cause of it. Let him, however, examine, and he will find that the roots of his trees have gone beyond the depth of his prepared border, and penetrated into the cold and bad subsoil. Now I know it is a very prevalent belief that a tree will not leave the good soil prepared for it and enter that which is inferior in quality.

All this I believe to be perfect moonshine, as I have seen the reverse over and over again, one or two instances of which I may give. Seven or eight years ago I saw a vine-root at Dalkeith, which had passed away from the well-made borders, pushed its way through a broad gravel-walk, and was found a great distance down in the vegetable ground - if I remember correctly, 73 or 93 feet from the vinery. The next case is that of a young vinery which was planted here in April last year, and for which a border of 8 feet wide, 4 inside and 4 outside, was provided, of the best materials to be had, and which was deemed sufficient to keep them growing for the season. In January of this year, when removing the remainder of this inside border, to be replaced with good soil for their further progress, we found that hundreds of the roots of the young vines were running through the cold sour material that formed the original border made fifty years ago - many of these roots having penetrated to distances of 2 and 3 feet.

We have brought forward these instances to prove the fact that, plant in the best materials to be got, if you allow the tree its own way it will in a short time penetrate the cold and unwholesome subsoil, which will gradually poison the sap, the result of which will be canker, and consequently premature decay. The true causes of canker in the Pear or any other tree are twofold; viz., a too cold and too moist soil to live in. If the roots penetrate to a depth of 4 feet, the fact is, that at that depth the soil is several degrees colder than at 2 or 3 feet, and as a consequent result the tree is longer in a dormant state, and has not the time and opportunities necessary for making and ripening its wood. And further, at that depth the soil is generally soaked with water, which surcharges the whole system of the tree with aqueous matter; and as there is no outlet for it in the shape of perspiration until the season advances, the tree, when it begins to grow, rushes into rapid growth, and makes what are called soft watery shoots, which never ripen properly, and which tend to encourage the disease.

The only cure for canker is to lift all affected trees, remove the deep-penetrating roots, drain the border thoroughly, plant the trees afresh in a good sound compost, and attend regularly to root-pruning for all time to come. If these things are attended to, we are very sanguine that the results will prove good.

The insects which attack the Pear are more numerous than the diseases. The first we will notice is the scale Aspidiotis ostreaeformis, which is a very small insect (oyster-shaped, as the name indicates), but which often does a vast amount of damage by attacking trunk and branches as well as the fruit. It is always of the same colour as the bark upon which it lodges, and being so small, it may pass a long time unobserved, unless a strict watch is kept for its appearance. They have a hard and shining look, and often are dotted all over the branches like thousands of little specks, if allowed to breed to any extent. When they become very numerous, they not only lodge upon and injure the bark, but also attack the fruit, which after being attacked is almost useless for any purpose save the kitchen, as they adhere so firmly to the skin that they cannot be removed without much injury to the fruit. The best and most effectual cure for them is to syringe the trees in winter with boiling water. This may be done without the least fear of harm to the trees in mild open weather, when they are quite dormant.