THE APHIS OFFENSIVE

Otago Daily Times, Issue 23685, 17 December 1938, Page 26

THE APHIS OFFENSIVE

FAVOURED BY DROUGHT We sometimes see it stated that aphides are easiest among garden foes to eradicate; maybe so, but we fear the greater truth is that, when they come in strength oi numbers, as'they have done of late, they are not banished before the plants or trees attacked have suffered to a serious extent. A most serious point about the common greenfly is the possibility that they may convey dangerous and destructive virus diseases to plants which hitherto were clean and healthy. That possibility is due in no small degree to the industrious little ant, which makes a practice of conveying a few selected aphides from a crowded plant to a fresh one, where feeding tor the aphides is more abundant. The ants do this because, they, in turn, feed upon the sticky substance exuded by the aphides. Sprays Kill Aphis by Contact

For that one reason, it is well worth while, as a purely precautionary or preventive measure, to spray plants.which are clean with a simple, quassia-soft soap wash. Neither anis nor greenfly will be keen upon crawling upon stems and leaves covered witn a thin film of such wash. Apart from the advantage of that means of prevention it is generally conceded that insecticides which kill by contact are more effective than poisons. Aphides do not chew and eat leaves of plants, as do caterpillars and slugs; they thrust a probiscis into the cells of a leaf and suck the sap, which is not affected by poisons deposited upon the outer skin of the leaf. The insecticides which are most effective against sucking pests are such as coat over and clog their hides, causing paralysis. It would be superfluous here to name insecticides of this character, while so many excellent brands are advertised; the important point is to exercise care in mixing or diluting the wash according to manufacturers' instructions, and then to apply in such a manner that particles of the finely-divided spray actually touch the bodies of the pests. Bear in mind that there are usually more of the flies on the undersides of the leaves than on top. A spraying machine with a fine spray nozzle and a good driving force behind it, is a sound and economical investment. The next best thing is a well-made syringe, .with the nozzle set at an angle so that spray may be directed upward or downward as required. Quite unsuitable is a watering can, which merely sends out streaming jets, wide apart, wasting most of the fluid on the ground. Not every spraying preparation is wholly soluble; in some cases the effective ingredients are held in suspension, and on that account the fluids should be frequently stirred or well shaken in the container to maintain equalised strength. It is not only advisable, but we consider it absolutely necessary, to wash thoroughly every sprayed plant or tree with plain water the day following use of an insecticide. This not only clears away the carcasses of dead insects, but also removes any sediment of the spray which, if left on the foliage, is calculated to hamper the leaves in their natural function of respiration. It is practically certain that, in the case of badly-infested plants, a second application of insecticide will be required two days, or, at most, three days, after the first. There will certainly be some survivors from one spraying, and even a few aphides breed so rapidly that the trouble will soon be as great as ever unless they are demolished while partially weakened. For plants of soft growth and delicate foliage, the spraying machine or syringe may be used for the plain water washing; for fruit trees and stout, resistant plants, one may use a garden hose with a good force of water.

All this may seem to involve a great deal of labour, but it is better to do such a task thoroughly and get rid of the foes, than to adopt half-measures and fail to achieve one's purpose.—Amateur Gardening.