548. In order to clear trees, especially wall-trees, of in sects and their eggs and larva, and to prevent the breed ing of these, the trunk, branches, and even twigs, are, by careful. horticulturists, regularly washed with some pene trating liquid every winter. Some of the most experienc ed practical gardeners in Scotland have followed this plan, tedious and laborious although it may seem, for a number of years past, and have found the greatest benefit result from it. They have very generally adopted a mixture re commended by Mr Nicol, and from his writings, therefore, the recipe shall be given : ‘, Take of soft soap, 21b; flower of sulphur 21h.; leaf or roll tobacco 21b.; nux vomica, 4 oz.; turpentine, a gill English measure. These ingredients are to be boiled in eight gallons English of soft or river water, down to six gallons." This mixture is applied by means of a house-painter's brush and a sponge, generally when in a milk-warm state. All the branches in succession are loosened from the wall, and completely rubbed or anointed on every side, particular attention, being paid to the cleans ing of angles or cavities. If the trees have been much Overrun with insects, even the wall should be anointed, or brush completely to anoint the branchCs of the tree. should be done in March ; and if heavy rains do not im mediately wash away the coating of paint, the breeding of the insects at the proper season is prevented, and their de struction thus ensured.
Several of the diseases of plants, we have thus seen, arise from the attacks of insect assailants. Some more of these remain to be mentioned, and also a few enemies of larger size.
Enemies to Garden productions.
111 the trellis in the case of espalier trees. This operation may be performed any time from the beginning of November till the middle of February.
549. Sir George Mackenzie has lately communicated to the Caledonian Horticultural Society, the result of an ex tensive experiment of anointing the stems and branches of trees with oil, or oily matter, for the purpose of destroying the eggs and ptipx of insects. The experiment has suc ceeded beyond expectation ; but care must be taken not to touch the buds, particularly those which are to produce blossoms. Apricot and cherry trees are the only kinds which seemed to suffer injury from oil, every other kind having made vigorous shoots, and the bark of those which had a diseased appearance having sloughed, and shown the advance of new healthy bark ; and aphides, ke. seem ing to have been banished.
The same gentleman has discovered a nocturnal enemy in a Curculio, supposed to be C. vastator, whose ravages have been attributed to caterpillars. This kind of weevil conceals itself during the day about the foot of the stems of trees in the earth, from which, owing to its brownish grey colour, it is difficult to distinguish it ; and at night it crawls up, and attacks the young shoots and blossoms. It is very destructive to young grafts. The method which Sir George Mackenzie took to destroy them was, to tread the earth about the loot of the stems of the trees, at night when the weevils were on the trees, and putting small flat stones, pieces of slate, or the like, on the trodden space. In the morning the enemy having retreated under these, were destroyed. The trees and grafts should, however, oc casionally be examined by candle light, and the insects picked off. They have been found sometimes to harbour
also in the clefts of branches, and about portions of dead or decayed and rugged bark.
550. Mildew consists in a thin whitish coating, invest ing the leaves especially of peach-trees and the finer kinds of fruits. It is observed that it commonly appears in the warm months, when the ground is dry, the weather calm, and when hazy vapours or slight fogs appear in the even ings. It is a remark of experienced gardeners, that trees washed during winter with such a liquid as that above de scribed, are scarcely ever known to be affected with mil dew, probably owing to the leaves being perfectly healthy and able to withstand the immediate cause of the evil, whether it be minute fungi or the slime of aphides. Wash 'ing the foliage with the garden-engine is found very useful in removing the mildew or in stopping its progress.
551. What is called the scale seems to be the nidus of an insect, or a collection of its minute eggs, covered with a thin pellicle. It very much resembles a drop from a spermaceti candle. The hatching of the eggs and conse quent bursting of the pellicle, have been observed and de scribed by Mr Thomas Thomson, an excellent Scottish gardener. It generally appears in August, and it continues in the state of a scale during the winter. The larva; usually emerge about the time when the trees are in blossom, and they immediately begin to devour the tender parts of the flower. Afterwards, as they acquire strength, they attack the young leaves and even the new shoots of the trees. When about to undergo their transformation, they involve themselves in leaves drawn together with fine silky from this retreat they come forth in the form of small moths, but the species has not been ascertained. The most effectual method of destroying these scales consists in removing them with the nail of the finger at the time of winter dressing. In rainy weather they are most discerni ble, being of a lighter colour than the wet bark. Another simple method of overcoming them is, to make a paste of fine clay of the consistence of thick paint, and with a coarse 552. AI:hides or green-flies, of many species, very much annoy wall-trees in the spring and early part of summer, attacking the leaves while just expanding, and preying much about the points of the young shoots. A fumigation with tobacco is the common cure, and it very generally proves effectual. In the case of wall-trees, a large cloth, preferring one that is waxed or oiled, is placed over the tree, and the tobacco smoke applied under it with bellows; the wall and the tree are previously wetted with the garden engine, the moisture having a tendency to detain the smoke. The tree is then briskly washed with the force pump, and the border is delved over, so as to bury the stunned aphides. In the same way gooseberry or currant bushes may be freed from them. In hot-houses the fumi gation is easily performed, while the doors and sashes are kept close. It is likewise very readily accomplished in melon or cucumber frames, the crops in which are some times infested. In the kitchen-garden, kidney-beans arc subject to the attacks of aphides; and in the flower-garden, rosebushes are peculiarly obnoxious to them.