Many aphides, &c., puncture the leaves, suck out the sap, and induce va:ious local deformations, arrest of growth, pustular swellings, &c., and if numerous all the evils of defoliation may follow.
White or grey spots may be due to Peronospora, Erysiphe, Cystopus, Entyloma and other Fungi, the mycelium of which will be detected in the discoloured area; or they may be scale insects, or the results of punctures by Red-spider, &c. Yellow spots, and especially bright orange spots, commonly indicate Rust Fungi or other Uredineae; but Phyllosticta, Exoascus, Clasterosporium, Synchytrium, &c., also induce similar symptoms. Certain Aphides, Red-spider, Phylloxera and other insects also betray their presence by such spots.
In many cases the punctures of Aphides and Coccideae are shown to be responsible for such exudations, and at least one instance is known where a FungusClaviceps-causes it.
- Many ants feed largely and some almost entirely on the saccharine secretions of other insects, the best known of which are the Aphides (plant-lice or " green-fly ").
Species of aphides may be removed by tobacco infusion, soapsuds or other solutions.
Aphides are born, as a rule, alive, and the young soon commence to reproduce again.
Aphides often ruin whole crops of fruit, corn, hops, &c., by sucking out the sap, and not only check growth, but may even entail the death of the plant.
Some aphides live only on one species of plant, others on two or more plants.
For piercing-mouthed pests like Aphides no wash is of use unless it contains a basis of soft soap. This softsoap wash kills by contact, and may be prepared in the following way: - Dissolve 6 to 8 lb of the best soft soap in boiling soft water and while still hot (but of course taken off the fire) add 1 gallon of questions involved, under their own headings.
Through the summer months by virgin females - the egg developing within the body of the mother - is described at length in the articles Aphides and Phylloxera.
His attention having been drawn to the blighting of the young shoots of fruit-trees, which was commonly attributed to the ants found upon them, he was the first to find the Aphides that really do the mischief; and, upon searching into the history of their generation, he observed the young within the bodies of their parents.
When cultivated in greenhouses liliums are subject to attack from aphides (green fly) in the early stages of growth.
Several other varieties of galls are produced by Aphides on species of Pistacia.
Lichtenstein has established the fact that from the egg of the Aphis of Pistachio galls, Anopleura lentisci, is hatched an apterous insect (the gall-founder), which gives birth to young Aphides (emigrants), and that these, having acquired wings, fly to the roots of certain grasses (Bromus sterilis and Hordeum vulgare), and by budding underground give rise to several generations of apterous insects, whence finally comes a winged brood (the pupifera).
Destroy aphides and other insects by syringing with tobacco water, or by fumigating, or by dusting with tobacco powder.
- Watering, ventilating and fumigating (or the use of tobacco in other forms for destruction of aphides) must be attended to.
Slug-worms or saw-fly larvae require treatment by washing with soapsuds, tobacco and lime-water or hellebore solution, and Aphides by syringing from below and removing all surplus young twigs.
Saprophytic bacteria can readily make their way down the dead hypha of an invading fungus, or into the punctures made by insects, and Aphides have been credited with the bacterial infection of carnations, though more recent researches by Woods go to show the correctness of his conclusion that Aphides alone are responsible for the carnation disease.
Apart from their importance from the economic standpoint, Aphides are chiefly remarkable for the phenomena connected with the propagation of the species.
If, however, the food-plant is grown in a conservatory where protection against cold is afforded, the aphides may go on reproducing agamogenetically without cessation for many years together.
Closely related to the typical aphides is Phylloxera vastatrix, the insect which causes enormous loss by attacking the leaves and roots of vines.
Buckton, British Aphides (Ray Soc. 1876-1883); also ECONOMIC ENTOMOLOGY.