Читать книгу The American Flower Garden Directory - Buist Robert - Страница 7

In this department, insects begin to increase by hundreds, and too frequently their ravages are very obvious before their progress is arrested. We will treat of those which are most common, under their respective heads, with their nature and cure, as far as has come under our observation.

Aphis rosæ, of the natural order of Hemiptera, or what is commonly known by Green Fly, Green Lice, &c. infect plants in general, and are particularly destructive in the Hot-house to Hibíscus ròsa-sinénsis, Asclèpias, Crássula coccínea, Alstrœmèria, and many other plants of a free growing nature. They attack the young and tender shoots at the point, leaving a dark filthy appearance on the foliage. Many remedies for their destruction have been offered to the public by various writers, each equally secure in his own opinion. Extensive practice alone can show the most easy and effectual cure. Fumigating with tobacco is decidedly the most efficacious, and in the power of any to perform. Take a small circular furnace, made of sheet iron, diameter at top twelve inches, and at bottom eight; depth one foot, having a grating in it to reach within three inches of the bottom, which will leave space for the air to pass, and where the ashes will fall and be kept in safety, having a handle like a pail to carry it with. This, or any thing similar, being ready, put in it a few embers of ignited charcoal; take it into the centre of the house, and put on the coals a quantity of moist tobacco stems. If they attempt to blaze or flame, sprinkle a little water over them; and as they consume, continue to add tobacco until the house is entirely full of smoke, observing always to do it in still, cloudy weather, or in the evening. If it is windy, the smoke is carried off without having half the effect, and requires more tobacco. The house must be closely shut up. There are several plants whose foliage is of a soft downy nature, such as Helitròpiums, Callacárpas, Sálvias, and many of the Lantànas, Víncas, with several others, that cannot stand, without danger, strong fumigation. These should be put low down in the house, or under the stage. These fumigations will have to be repeated frequently, the time for which will easily be perceived; and, when required, ought not to be delayed. Several species and varieties of the same genus, Aphis, can be destroyed in the like manner.

Acaris tellurius, or red spider, is caused by a dry atmosphere, and its havoc generally is obvious before it is arrested. With its proboscis, it wounds the fine capillary vessels; and if the leaves are fine, they will appear as if probed with a needle, and yellowish around the wound. If they have farther progressed in their destructive work, the leaves will prematurely decay. On this appearance, turn up the leaf, and you will see them running about with incredible swiftness. Their body is of a blood colour, and their feet, eight in number, light red. When very numerous, they work thick webs on the under side of the leaf, and frequently all over it, forming a mass of half dead plants, decayed leaves, and thousands of spiders. The most effectual remedy is a thorough syringing with water, and profusely under the foliage. This being done every evening, will subdue and eventually banish them. Had the house been syringed two or three times per week, these intruders would not have appeared. It is said by some writers, that watering only reduces them to a temporary state of inaction, and will not destroy them. Laying aside the many prescribed nostrums, we assert that the pure element is the most effectual cure, as well as the most easy to be obtained.

Thrips, order Hemiptera, are insects so minute as scarcely to be perceptible to the naked eye. They generally lurk close to the veins of the leaves of plants, and frequently attack esculents. When viewed through a glass, they are seen, when touched, to skip with great agility. The larva is of a high brown, or reddish colour. The thrip has four wings, and walks with its body turned upwards. It frequently attacks the extremities of tender shoots, or young leaves, which become shrivelled, brown, and will rub to dust easily between the thumb and finger. When any leaves or shoots are perceived to be so, if you do not observe the green fly, expect the thrips. They may be destroyed by a fumigation of tobacco, in the same manner as the green fly. By the simple and expeditious method of fumigation, these insects and several others may be destroyed effectually at any time they appear.

Cocus hesperidus, or mealy bug, has appeared in the Hot-houses about Philadelphia within these few years, and, if not instantly destroyed, increases rapidly. It is of a white dusty colour, when broken, of a brownish red, generally covered with down, under which it deposits its eggs; and they, in a few months, come forth in great numbers. The cocus generally is of a dormant nature, but, in warm weather, they may be seen moving rapidly up the stems of the plants. Fumigating has no observable effect on these insects; therefore, as soon as they appear, recourse must be had to other means. The liquid made from the following receipt, is death to any of the Cocus tribe: Take two pounds of strong soap, one pound flour of sulphur, one pound of leaf tobacco, one and a half ounce of nux vomica, with a table spoonful of turpentine, which boil in four gallons of river water to three; then set aside to cool. When boiling, stir it well with a stick, continuing to do so until it is reduced as above. In this liquor immerse the whole plant, drawing it to and fro gently, that the liquor may penetrate every where.

This done, lay the plant on its side, until it begin to dry, then syringe well with clean water, and put it in its respective station. Where a collection of plants is free from any insects of the kind, every plant that is introduced, ought to be minutely scrutinized, that the unclean may be kept from the clean: the above insect will feed almost on any plant, but indulges on Crássulas, any of the bristly Cáctus, Gardènias, and in fact whatever is in the way.

Cocus —, or brown scaly insect, is frequently found on many plants, but we never could perceive that it does any other material injury, than dirtying them. We have always observed, that it is found in winter to abound most in those situations which are most excluded from air; therefore is of less importance than the other species, which eat and corrode the leaves of tender plants. A washing with strong soap suds will destroy them, or the above liquid will do it more effectually. Tie a piece of sponge on the end of a small stick, and scrub every leaf, stem, and crevice. Fumigating destroys the larvæ of this species.

Cocus —, or small white scaly insect, which generally infests Cycas revolùta and circinàlis, the varieties of Nèrium oleánder, Oleas, and several species of Acacias, may be destroyed by washing as above with a sponge, and a strong decoction of tobacco, using the liquid about the warmth of 100°. Being thus heated, it irritates the insect, when, by easing itself from its bed, the fluid passes under it, and causes immediate death. If it is not thus irritated, it adheres so closely to the foliage, that it will keep you at defiance. The under, or dark side of the leaves is its residence; and we have observed a plant in a house where there was only light on one side, with the dark side literally covered, while the light side was clean. So much for having houses with plenty of light. The effects of this insect are of a corroding nature, extracting all the juices from the leaf under it, even straining to the other side; and where they have got to the extremity, the foliage is completely yellow, and of a decayed appearance.

Cocus —, or turtle insect. We have never observed this insect arrive to any extent, but think that the Datura arborea is most infested with it. It is the largest of any genus known amongst us, and very like a turtle in miniature. On lifting it from the wood, to which it generally adheres, there appear to be hundreds of eggs under it, but fumigating completely destroys the larvæ. In our opinion this turtle insect is no other than the old female of the brown scaly insect, which swells to a large size before depositing its eggs. We have frequently observed the insect dead in this enlarged state, and question if this is the last stage of its transmigration. The male insect is winged, and very active in its movements.