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The Pamphlet Collection of Sir Robert Stout: Volume 62

The Remedies, and how to apply Them

The Remedies, and how to apply Them.

In talking to orchardists, one is told again and again that they have tried everything for the blights that so much beset them, and all without avail. Upon inquiring closely into these statements it is found in almost every case that there were several reasons why the trial of so many cures had given such poor results. The materials used were improper ones, or, at least, in improper quantities, at the wrong time, in unsuitable weather, not properly sprayed, the application not persisted in, and, in fact, from one cause or other, good reasons could be found in almost every case why the work had proved useless, or, in some cases, had actually done much damage to the trees. For instance, there is an orchardist whose name is well known as a grower of some very fine fruit. I mentioned to him kerosene emulsion as a most useful wash. He said, None of it for him; he had had quite enough of that stuff. Asking him for an explanation, he pointed out the remnants of a row of apple-trees which he told me he had treated with it for the mussel-scale. Certainly the trees in question were ruined. On being asked how he had applied the emulsion, he said he had filled a tin kettle with kerosene, and poured it slowly down the branches and trunks of the trees until they were soaked. The result of such treatment (pure kerosene, followed by a hot sun) was only what might have been expected. It is hoped the readers of this pamphlet may not fall into such disastrous mistakes.

In applying the remedies to the trees we must consider the period and manner of the attack made by the disease, whether of insect or fungus origin, and also the manner of action of the substance applied. Fungi living within the tissues of the host must be prevented from gaining an entrance to those tissues; fungi which live upon the surface of plants, or having their bodies soon exposed through the breaking-up of the epidermis, like the apple-scab, and black-spot on grapes, may be treated by curative methods: but those of obscure bacterial origin in the juices of the plant, such as the silver-blight of the plum in the South, and the collar-rot of the lemon in the North; and those that work beneath the surface, like the root-fungus, are not susceptible of prevention or cure by any spray-treatment we at present know. In these cases, as before mentioned, the knife is our only remedy.

In spraying for insect pests two great classes of spray are used—those which kill by contact, used for all sucking insects, such as scale or aphides; and those which kill by poisoning, used against all mas- page 6 ticating insects, such as the larvæ of moths and beetles, especially the codlin-moth.

Many fruit-growers complain of the burning of foliage and fruit resulting from the application of well-tried remedies. It is true that damage may result from the use of the most carefully-prepared wash at times. Explicit directions cannot be given for these cases. Much has yet to be learned by experiment, and each one must exercise judgment, and govern the applications by surrounding circumstances of time, weather, and so on.

During the growing season the strength of the solutions used is controlled by the power of the green tissues to resist their action. In the early part of the season, while the shoots and leaves are yet tender, weaker solutions than those which may be safely applied later in the season must be used.

There is great diversity of susceptibility to the caustic action of the remedies between different species of fruits. For instance, the peach is very tender, and will only withstand very weak solutions : there is even much difference in this respect between different varieties of the same species, those who have sprayed with Paris green have no doubt noticed how some varieties of apples suffer, while others do not. The condition of the weather at time of application is of considerable importance in this connection: if possible, spraying should only be done on calm, cloudy days, or, at least, towards evening. Spraying during very hot bright weather is dangerous : even sulphur alone has been known to cause a burning of the foliage under a hot sun.

Avoid making the applications excessive. Do not drench the trees, as then the liquid collects into drops, which under a bright sun act as so many burning-glasses, besides in great measure destroying the efficacy by collecting in small thick patches (and leaving the greater portion exposed) the material we desired to spread as a thin protective covering all over the surface of the leaves, fruit, or wood, as the case may be. With a suitable spraying apparatus, producing the finest mist-like spray, generally speaking, the plant-surfaces should be merely damped, as with dew. Perhaps the best method of producing a thin effective layer of the protecting material is to go over the trees twice each time of spraying. That is to say, the orchardist should give the tree he starts on a very light spraying, and pass on. By the time he has got through, the first trees will probably be dry, and are then gone over again. By this means all dripping and loss of material is avoided, while the best possible application of the remedy is made.