APHIDES OR GREEN ELY.

Otago Witness, Issue 3112, 5 November 1913, Page 12

APHIDES OR GREEN ELY.

VIEWS OF AN EXPERT. Numerous inquiries having been received for information concerning the best methods of combating green fly, which infest peach trees roses, and other plants, the matter was referred to Mr J. C. Blackmore, exGovernment Pomologist, who, in the course of an interview with a Canterbury Times reporter, gave some interesting and instructive information. ITS LIFE HISTORY. “ Plant lice,” he said, “ are very peculiar insects. Popularly they are called green fly or green aphides. They are not all of one kind, but belong to different species, differing in their life-history, varying in form and living on different plants. Some species live only upon plants of one kind, the winged females spreading .the species only to other plants of the same sort, while the winged females of other aphides may live on entirely different plants from those preferred by the stem-mothers; but they return in the autumn, so that the eggs are laid upon the favourite food plant, of the spring. Of these spring forms the common green peach aphis is an example, the lifehistory and habits of which I gave about 12 months ago. “ The aphides live by sucking tbo sap from the plant. Some species feed on both the foliage and the roots, like the woolly aphis and the black peach aphis. The wingless form travels very little, as long as the food plant on which it is located will support it; but when food is becoming short those with wings migrate to other plants, and there start another colony. Those entomologists who have studied their feeding habits tell us that the mouth part sof aphides are not cutting or grinding instruments. but the outer parts are modified into sharp, tube-like beaks, which enclose the thread-like inner parts, with which the aphides pierce the surface of the leaves and suck up the flowing sap. The mouth of each little aphis is a little well-driving outfit, with a suction pump attachment. The wounds made by the aphis and the effects produced by its feeding eliffer with the species of aphis, and with the plant attacked. In some cases galls are formed upon the twigs, roots, or leaves, and in others the bark of the tender twig is pitted or scarred, but most commonly the prominent sign of the presence of the aphis is the curling up and withering of the leaves, from which the aphis lias pumped the can. The honey secreted by the aphis frequently coats the leaves, branches, and fruit with a sticky fluid, which soon becomes black and unsightly from a fungus which grows on it.

“ The life-history of the various species of aphides is one of the most peculiar and marvellous in all Nature. Economic entomologists have devoted much time and thought to the study' of their lives, their enemies, and the best methods of treatment for controlling their depredations, and a considerable amount of literature has been published relating to the life-history of the various species. Mr A. L. Quaintance, dealing with aphides in general remarks: 'The insects of the family aphid®, or plant lice, are specially remarkable on account of their mode of development. This will vary considerably according to the species, but at some time in the life of a species true sexes are produced, usually in the autumn, the female depositing eggs after the usual manner of insects. Eggs deposited in the autumn pass the winter in this condition, and their hatching in the spring is more or less coincident with the revival of growth of vegetation. From the winter eggs is produced a generation of females, usually wingless, which produce ngamically —that is, without the intervention of males—many species, as those under consideration, giving birth to living young. The adult aphides of the first generation are termed stem-mothers. The offspring of the stemmothers (second generation) may be winged Or wingless, or both forms may occur. They produce agamically. some species being oviparous, and depositing pseudooya, or eggs which do not require fertilisation for developing within the body of the parent, bring ford' young alive, the nseudoova developing wlfnin the body of the parentfl There may be a succession of generations produced agamically. With most species this mode cf reproduction continues until the approach of autumn, when the true

sexes appear and deposit eggs, or a species may be more or less biennial, some individuals producing two sexes every second year, with still other species, the true sexes of which are at present unknown. Agamical reproduction possibly continues for a series of years. The same species of aphide may present several forms, as wingless, agamical or winged agamical females, and the true sexual forme in the last may be winged, and the female wingless, or both sexes may be wingless. The different generations of a given species may vary more or less, and in some instances this is the case to such an extent that they appear to belong to distinct species. Their powers of multiplication are so great that if unchecked the product of a single insect during one season would run up into billions. There are, however, many drawbacks to their increase, among which arc certain weather conditions, parasitic and predatoryinsects, and fungus diseases. When one or more of these agencies are in abeyance, aphides may become very numerous and destructive locally or over a considerable range of country,

“ Some species of aphides change food plants during the year—for example, the hop aphis, so destructive to the hop, spends most of its time as an enemy of the plum. The green poach aphis spends part of its time on the peach and part of its time on various other plants, returning again to the peach to deposit its eggs during the autumn, thus passing the winter in the egg stage, the egg being deposited by the female during autumn around the buds of the shoots at crutches of limbs and in cracks .and under the scales of the bark of the peach tree.

“ The hatching of the eggs of the greeil peach aphis takes place when the buds have scarcely begun to swell, a fact that is not generally understood, but one of very great importance in its relation to the control of the pest by means of a spray. The aphides which hatch from eggs that have remained on trees over winter are known to entomologists as stem-mothers, and their progeny are born alive, and just as soon as the buds on infected trees begin to unfold the stem-mother with her progeny arc ready to enter therein. At first they appear to prefer feeding in the blossoms, but after these fall, quite serious injury is often done by their feeding on the leaves. It is fortunate for the fruit-grower that this post cannot, or docs not, spend its entire existence upon the peach, but leaves it for more succulent vegetation. “ Shortly after the fruit of the peach is well formed winged aphides begin to appear in the colonies. These fly away to other food plants. During the summer it feeds upon a wide variety of plants, comprising most of the common garden vegetables and weeds, and infests many outdoor garden plants as well as plants growing under glass. During the autumn the last winged generation of aphides to appear is known as the autumn or fall migrants, because of the fact that they leave the vegetation upon which the summer has been spent, and migrate to peach trees. These autumn migrants do not deposit eggs, but give birth to true sexual forms—males and females. After feeding for a time and becoming mature the female deposits her eggs in the manner previously explained.” REMEDIES. “ The best time to spray to kill the aphides,” continued Mr Blackmore, ‘‘is during early spring, immediately the eggs arc observed to bo hatching out. No doubt many persons would probably have a* hard time to detect the little aphides when they are first hatched, but the importance of spraying at this time should be sufficient reason to learn by the aid of a hand lens to find them. I have made a number of different tests with various insecticides in order to determine their value, first, as an egg-destroyer; secondly, to kill the young aphides when they are first hatched out; thirdly, to kill the aphides about the time when the stem-mothers arc matured. The results of these spray investigations indicate that the lime-sulphur solution may be efficiently used for the control of the green peach aphis when applied just before or after the eggs hatch. That period is generally about the time buds begin to swell. Good results were also obtained with tobacco preparations, kerosene emulsion, and solutions of soft soap and quassia, at the strength usually used, applied when the eggs wore hatching out; but none of the latter sprays proved as effective when applied two weeks after the aphides were hatched. At this time the stern-mothers are nearly mature, and are to a great extent somewhat resistant to the action of insecticides unless used at such strength that may lead to foliage-injury, if excessive quantities are used. It is very difficult to succeed in killing the whole of the matured aphides by spraying Into in the spring, no matter what insecticide is used, because the leaves tend to curl and provide such protection for the aphides that only the most thorough work can result in much good. It would seem that from my own experiments and from those of others that have been recorded just as the eggs are beginning to hatch is a favourable time to spray for its control. Lime-sulphur solution proved to be a perfect spray at this time, giving a little better result than kerosene emulsion, tobacco preparations, or itoft soap and quassia, which gave good results if when the eggs are liatching

‘ I should not omit to mention that a peculiarity in connection with the lifehistory of the green peach aphis is that in mild climates the pest may live over winter on vegetation that remains green throughout the winter season, so that there would bo a possibility of peach trees becoming re-infested from these sources even though the eggs were all killed by an insecticide. or fail to hatch because of unfavourable weather conditions or other causes.

“ Besides the green peach aphis there are various species of aphides well known to the horticulturist and agriculturist, each differing somewhat in its life-history, several of which are very troublesome, such, for instance, as the common cabbage aphis (A. brassiere), also several which infest the rose, each known under its scientific names— Scphonophera rosea, S. palida, and Nyrus rosarum. Then, again, there are other kinds of aphides which infest distinct species of plants grown under glass, as well as in the open air, but to enumerate them all would serve no useful purpose. For the ,—... .

glass, there arc efficacious contrivances of various sizes for applying tobacco smoke and other fumes for their destruction. There are also many excellent proprietary insecticides for spraying and syringing plants under glass, and useful and ingenious contrivances for applying. Some of these insecticides are, however, much too expensive for outdoor application on large plants. They, however, save the trouble of pro-

paring by those who require only a small quantity. Aphides are no doubt one of the greatest pests which rose-growers have to contend against. An effective standard remedy in use by many rose-growers is prepared in small quantities as follows: —Take 4oz of quassia chips and boil them in one gallon of water for 15 minutes; then strain, and while cooling dissolve in the liquid 4oz of soft soap, and add two gallons or three gallons of soft hot water. Rose-growers apply it at this strength with syringe or spray-pump as a spray to the upper and under sides of the leaves during the evening, and wash over with clean water the next morning to rinse off the leaves the dead aphides and any soapy appearance. Use frequently', or as often as needed. It is considered not advisable when the sun is out. Nicotine soap and various tobacco preparations are all useful, especially' kerosene emulsion if the oil is very carefully emulsified, otherwise it is liable to injure the foliage. The aphides upon the foliage of plants grown indoors are easily killed by applying the same remedies. Set the plants out of doors, and sprinkle or spray them well, or dip the growing parts of the plants into such solutions, or the aphis may also be killed by holding the plants in the steam of a tin kettle for a brief time while it is just hot enough that one can bear to hold the hand over it without scalding during the same period of time.”