The remedies advised for the apple tree Aphides, are equally applicable to those of the cherry, and their natural enemies are the same and equally efficacious; but Aphides have internal foes likewise, that may be named here. The Ichneumon-flies are parasitic, their larvæ feed upon the substance of the Aphides. The genus Aphidius is particularly provided to furnish parasites to these insects, in which they deposit a single egg selecting a louse of the proper size to sustain their progeny: the egg hatches to a larva, which exhausts the Aphis by the time it has attained its growth, when the poor creature fastens itself securely to the leaf, and dies, leaving its carcase a secure resting place for the pupa of the Ichneumon. These parasitic-insects, which feed internally upon the Aphides, are as effective in their destruction as the Aphis-lions, or any other class of their enemies.[33]
Aphis persicæ, or the Peach Tree-louse, punctures the leaves of this plant, and Dr. Fitch[34] thinks, is the common though not the only cause of the curl in the peach tree leaves. Our intelligent orchardists have found these insects occasionally in the curled leaves of the peach, but do not agree with this distinguished entomologist, in considering them a cause of that malady.
Aphis vitis?, or the Vine Aphis, is often quite troublesome on vigorous young shoots of the grape vine, both wild and cultivated, particularly the former. These insects soon cripple the growth of the shoot. The species is not known to be different from that of Europe. This insect is briefly mentioned by T. Glover, in Patent Office Rept. for 1854, p. 79. Dr. Fitch describes as a grape leaf-louse, the Pemphigus vitifolia, which inhabits the gall-like excrescences upon the foliage of some varieties, particularly those with thin leaves.
Aphis ribis, (Linn.), is the Aphis of the currant. It causes the leaves to present a blistered appearance above; the lice are found on the under side; the wingless are pale yellow, the others have glossy wings, mostly black, with abdomen light green.[35]
Aphis lanigera, now called Eriosoma, or the Woolly Aphis, was first described in 1801 as infesting the apple trees in Germany. It has been noticed in England in 1787, and has since acquired the name of American Blight, from the erroneous supposition that it had been imported from this country; but it was known to French gardeners for a long time previous.
The eggs of this insect are microscopic, and are enveloped in a cottony substance. They are deposited in chinks of bark, and crotches of limbs, at or near the surface of the ground. When first hatched, the insects are covered with short down; as they grow, the down increases in length. When fully grown, they are one-tenth of an inch long; the head, antennæ, sucker, and skins, are blackish, the abdomen of a honey-yellow color. Their punctures produce warty excrescences, the limbs become sickly, the leaves turn yellow and drop off, and the whole tree perishes as the insects spread over it. The remedies appear futile on badly affected trees. Young trees were treated by painting over the affected parts with a mixture of melted resin and fish oil, in equal parts, applied warm. Sir Joseph Banks removed them with a stiff brush. Spirits of tar, turpentine, oil, and soft soap, have been recommended. After scraping off the rough bark, wash the tree with alkaline solution, apply the same to the main roots after laying them bare of earth.[36]
Phemphigus pyri, Eriosoma pyri, (Fitch), or Pemphigus Americanus?, (Walker), is the Apple-root Blight. It produces a similar condition in the roots, and was also called the American Blight in England. It is composed of warty excrescences upon the roots, containing in their crevices minute lice, having their bodies covered with a white cottony substance. Removal of the earth, and the application of soapsuds, has been recommended as a probable remedy for the injuries done by this insect.[37]
Psylla Pyri.—Some Aphides have the power of leaping, like the leaf-hoppers, but they differ from those insects in having very large transparent upper wings, which cover the sides of the body like a steep roof. The genus embracing these insects, is called Psylla. One of the species was observed by Dr. Harris, upon a pear tree. They live by suction, and having gorged themselves, the juice runs down on the bark, producing a blackish color; young trees suffered excessively. As Dr. Phumb, of Salisbury, Conn., had observed them in 1833 on some imported pear trees, of which he lost several hundred in a few years, Dr. Harris suspected the insect to be the Psylla pyri, of Europe. Kollar recommends brushing off the insects, and crushing them under foot; and also advises to destroy the winged females in the spring. This being tedious and uncertain, it is recommended to wash the twigs with a brush, dipped in a mixture of strong soapsuds and flowers of sulphur, before the buds expand, to deter the insects from laying their eggs. A weaker solution, or the whale oil soap, might kill the young insects after they have fastened upon the bark, if applied with a syringe.[38]
Cicada septendecim, or the Seventeen-year Locust, as it is erroneously called, is no Locust at all, but should be called Cicada, because, as already stated, when considering the order Orthoptera, the true Locusts, are, what we call Grasshoppers.
This insect is remarkable for the long period of its pupal existence, which is subterranean, and during which it feeds upon the juices of roots. In its perfect state, it does not eat, and is neither able to bite nor to sting. The injury it does to our orchards is effected by its piercer in depositing its eggs, causing twigs to break and fall off. There are several Harvest-flies that belong to this order.