MINERAL OILS FOR THE DESTRUCTION OF INSECTS.

Globe, Volume XXII, Issue 2090, 4 November 1880, Page 4

MINERAL OILS FOR THE DESTRUCTION OF INSECTS.

Recently a good deal haa been said about the use of mineral oils for the destruction of insects of many kinds, both snob os attack plants cultivated tinder glass, as well as those that are grown in the open air; and, like most other things employed for a like purpose, there is much difference of opinion expressed respecting it, some who have used it insisting that it is the most efficacious remedy for the destruction of insects, particularly those that affect plants grown in artificial heat, where the insaote are usually the most difficult to kill without injury to the plants, by reason of the latter being more tender through the conditions under which they are grown; others who have tried paraffin condemning it on account of the harm they allege it does to the plants. After repeated trials on such plants as I have an opportunity of experimenting upon, and personal observation of its use by others, I feel satisfied that the oil (or oils) generally sold under the name of paraffin oil, when employed with the care that such a powerful agent needs, is one of the greatest boons to gardeners for the destruction of the many insect pests with which plants are beset. Bat it is well to be quite clear what is meant. From what I have experienced in its use, I have no hesitation in saying that the best and safest for use is not paraffin at; all, but rock oil, or petroleum, not much purified, which in this condition mixes much better with water than if highly rectified, when, in proportion to its purity, it has a greater tendency to float on the top of the water, ond in this way is liable to reach the surface of the leaves in an insufficiently dilated state. And this view of the matter is held by a friend of mine who, for some years before anything was said in the gardening papers about the use of paraffin for the destruction of insects, had been experimenting and used it largely to an extensive general collection of plants, both ctove and greenhouse, as well as ont-door subjects. I find that for all ordinary purposes, in the destruction of mealy bug, brown scale, thrips, red spider, or aphides, a largesized wineglasafnl to a gallon of water is enough, and it is much better to uso it diluted to this extent than stronger; for at this strength it will kill every insect it touches, and, even if it is applied in a stronger state, it will, like other similarly applied remedies, generally fail to reach the whole of the inaeots at the first dressing, consequently necessitating a second application, so that nothing is gained by naing it at a strength likely to run risk of injuring the plants. I may here remark that this oil is of snch a nature as not to admit of its being employed in a careless, off-hand fashion, or by people who are not sufficiently acquainted with the various degrees of susceptibility to injury in cultivated plants from contact with any matter of a character like this, except in a highly dilated condition; and I have no doubt that where injury has followed its use the cause is traceable to want of enough care or knowledge. The oil has euoh a determined disposition to float on the top of the water, even when used as I have already suggested, in only a' partially refined state, that nothing less than keeping the water briskly and continually stirred whilst it is being applied, either by an ordinary garden pump or a syringe, will suffice.

Ail acquaintance of mine who uses it in his rose house, where a good many of the plants are planted out, fills bis gardsn engine on wheels, and runs it into the house, one individual stirring it up all the time the other is pumping and directing the oil-impregnated water through a fine hose all over the plants ; and this is done not only in the summer when the leaves are hard, but in the early spring, when the forced foliage k tender, os often as any insects make their appearance. But care is taken that the tub is not pumped all out, or so as to empty it lower thtn within five or six inches of the bottom, for, stir it up as you will, it is as little disposed to mix with the water that very much more than a proportion of oil such as is safe to come in contact with the plants, will still keep on the top, and which, if the whole was pumped out, would thus roach them. When a syringe is used care must be taken that, in addition to the water being continuously stirred whilst the work is going on, each syringeful is drawn from below the surface and that at least two or three inches of the water from the bottom is not used without the addition of more water. For a like reason, it k not as well to dip plants in this liquid as it is to apply it to them by engine or syringe. Those who have any knowledge of such matters will easily see that in dipping a plant it will inevitably get a larger snare of the oil that is swimming upon the top than it would receive through the syringe ; and, when dipping k resorted to, I should advise its being confined to plants that have considerable substance in their leaves, and to take the precaution, immediately previous to their being dipped, of syringing them freely with clean water, so as to wet the entire surface, as in this: state much less of the oil will stick to them. Subjects like cinerarias, calceolarias, fnohsiai, or anything with soft leaves, should always be syringed or dipped in clean water immediately before, so as not to leave time for their drying previous to the paraffin being applied. For all such things as gardenias, stephanutis, and other thiok-leaved subjects, which naturally are less liable to injury from anything of so powerfully penetrating a character than things that are softer in their tksues, all that k necessary k to keep the material continually agitated whilst it is being used. Such pests as mealy bug are killed by it in a few minutes after being touched ; and it k of so searching & nature that it spreads and penetrates to every crevice or inequality of the bark, and in this manner reaches the eggs as well as the mature insects in a way that nothing else will do. For fruit trees infested with American blight it k better, I find, to ase the mixture at something like double the strength necessary for plants such as those I have already mentioned ; and the way in which the pest can insinuate itself into every crack makes it mush better to lay the dressing on with a brush. For rases and other outdoor (lowering plants, I look upon the mineral oil, applied as described with the engine or syringe, as affording very great advantages. In the effectual way in which it kills aphides and other pests to which roses more than most things are subject, it has no equal. Anyone who has syringed roses with tobacco water will have noticed how readily it runs off the aphides, seldom effecting a clearance without several dressings; whereas the mineral oil water adheres and kills them at once. The cost of the article k another important matter. Tobacco water and other remedies hitherto used for washing plants in the open air Jjecome expensive when they have to be used in any considerable quantity, whereas the use of petroleum reduces the expense to a mere fraction. Such as u suitable for the purpose can be bought for from Cd to 7d per gallon, if taken in any considerable quantity; and even at the rate of the ordinary commodity sold for burning, say 3d a quart, it will not cost so much as a farthing a gallon ready for use. Tobacco water leaves the foliage is a dirty, unsightly state, for which reason it is often inadmksible for use with plants growing upon walls ; with petroleum so little sediment k left as to be scarcely perceptible. I have often used flowers in bouquets, or other ways, from plants that were thoroughly washed with it the day previous.

I have not tried it on peach trees to rid them of aphides, yet see no reason why they should not bear it when the frnit is set; but this can be easily ascertained by trying its effect on a few branches, for it is not well to ran risks with these, as they are more impatient than most things, even from the time the bloom-buds are formed; and on this account it is better always to proceed with caution in any dressing that is applied to them. Neither would it be advisable to use petroleum on such plants os orchids, or anything of a very soft or tender nature. But for the generality of the ordinary plants cultivated in gardens, I think it will turn out a boon in clearing them of the insects to which most of them are so subject, and which absorb very much labor, and have hitherto involved considerable cost, in keeping them down.