Insecticides
The prompt destruction of injurious insects, immediately any are detected, is an important and essential operation to be performed in connection with all cultivated trees and plants. Insects of the most minute description increase with such rapidity, if left alone, that irreparable damage is soon caused to any subject they infest. An Insecticide is any composition prepared from ingredients destructive to insect life. Some Insecticides, too, are useful in checking or destroying low forms of parasitic plant life, such as Mildew, &c. To be effective and available for use on plants, it must be fatal to insects without in any way injuring the host. Plants which are leafless, and in a dormant state, will bear being washed with an Insecticide nearly or quite double the strength they could withstand when in full leaf; hence the importance of thoroughly cleaning plants, and also the house, during winter, when insects increase less rapidly than at other seasons, and are more concentrated on those parts of deciduous plants which remain. Tobacco, in one form or another, is, perhaps, the most useful substance entering into the composition of Insecticides. It may be soaked in water, for dipping plants, and the preparation made to any strength desired; used as a dry, ground powder, for dusting over the leaves or points of shoots; or burnt in houses, for the destruction of insects by the smoke. Soft Soap is a cheap and excellent Insecticide, used in many gardens to the exclusion of all other preparations. It may be readily dissolved in water at any time, and to any required strength, according as various plants may be able to withstand it. An ounce, or even less, to a gallon of water, will generally be sufficiently strong to use for sponging the leaves, or for dipping plants in. Nicotine Soap has some of the properties of tobacco; it is a good Insecticide, and may, when purchased, be readily prepared for use. Gishurst Compound, an old and well-known composition, in frequent use, and Fir-tree Oil, are soluble and useful Insecticides for general purposes. Directions for preparing them accompany each box or bottle sold; and it is rather important that they be followed, as far as possible, especially in the use of soft water. Petroleum--erroneously called paraffin, a different article--is very destructive, especially to Mealy Bug; but, unfortunately, it is insoluble in water, and requires very careful application. A small wineglassful to three gallons of water, is not too much in many instances; but it must be thoroughly mixed with the water by constant agitation, preferably with a syringe. Hellebore Powder is sometimes employed as an Insecticide, more particularly for the destruction of the Gooseberry Caterpillar; but, being a deadly poison, it must be carefully handled, and be afterwards washed off with clean water. Flowers of Sulphur, used either dry or mixed with water, is one of the best things for destroying or preventing the spread of Mildew. There are various other Insecticides sold, but those already noticed are mostly in general use, and answer their purpose, when properly applied, so far as can be expected of preparations. Their use and effect with, and on, different plants can only be treated of individually and after experience gained from experiments made according to the directions usually accompanying the respective preparations. It is much preferable to avoid, as far as possible, the use of Insecticides, especially those applied in a liquid state, as it is frequently a difficult matter, even with careful precautions, to kill insects entirely, without, at the same time, causing injury to the plants infested by them. If due care and attention be paid to watering, syringing, and ventilation, as well as proper repotting, &c., insects will not give much trouble. When the use of an Insecticide becomes requisite, it should be promptly applied, choosing an evening or a dull day for the operation, and afterwards removing all traces by clear water. Insect Powder--of which the basis is composed of the dried and powdered leaves and flowers of Pyrethrum roseum and P. cinerarifolium--is effective when dusted on infested plants.