LEAFLETS FOR GARDENERS AND FRUITGROWERS.

Otago Witness, Issue 2252, 29 April 1897, Page 7

LEAFLETS FOR GARDENERS AND FRUITGROWERS.

No. 20 — Phylloxera. By T. W. Kirk, F.R M.&., F.L.S., &s., London, Govein- | ment Biologiafc. j The existence of fchio insect in one localily in i Auckland wrs reported iv 1885, and efforts mads to exterminate ifc ; but again, st the end of 1889 and early in 1890. was found in several ! places iv 'oho immediate vicinity of Auckland, i and also tit Whancßret. There waa no legislation under which the Government of tho day could compel the destruction or treatment of infected ■ vineß. Special reports were made fay Mr I MnMwrtl, Professor Kick, and others, all urging thftfi stringent measures should be taken. A bill dealing w;th the matter tvrb drafted, bub did not pass Parliament. However, a gentleraxa, Mr Alla.ii "Wrigbfc, was appointed by : tho Government to make a careful examination of tho vineries, vineyards, aud nurseries around Auukland, with instructions to 'try to ■ secure the destruction of the infected viaeo. lie succeeded in having * considerable dumber 1 burned and the giound oaloined. This, it was ' thooaht. had exterminated the pent, and nothing ; nioift \»nn heard of the matter till after tha pre1 lent Department of Agriculture was Kefc up. I Early lait year the Government of Victoria, ab i the request of thia colony, very generously allowed their viticulfcural expert, Signor Rom?o Bragato, to visit New Zealand for the purpose of examining the various districts and reporii ing on their suitability to grorciDg vines for I wine-production. He spent nearly two- months in New JBeftlaud, aud~ it waa while travelling I the northern dißtricts that he discovered the '< presence of phylloxera in a vinery at Mount! Eden, Auukland. He at once placed the specimens obtained in my hands, and from theso most of the drawings in Plate 11 wero reade. Captain Bcoun, F.E.S , tho local Government eutomologiKt, was Inter iufoi'tned of Bignor Rragalo'« discovery, and requested to make a careful and exhaustive examination of all vineries, vineyards, and nurseries in bis district;. As a result of his investigations it in evident that, though the pest has been found on several properties on which it bad not before been noleJ, tho area infested remains about; the same as iv 1090, and from this some persona have argued that there in little danger of tiia insect spreading in New Zealand no as to rsuse serious trouble. No ituch conclusion }a iv any way warranted by the evidence ; for, in the fist place, it muib be remembered that a considerable number cf vine« were destroyed in 1390, with a view to the extermination of the f.h>Ucxa<:ft ; that the pset, though evidently nob .<mpr,ri!»B*;d, us was hoped. received a 6evera check. JSscondiy, vins-growiag is in its infancy in this colony, and, while considerable disfcacccH exist batween our vineyards, and the vineyards themselves are small, tho facility for dissemination ara -small. - Now, however, the* viticulture has received a stimulus, and many peseouß are planting, or arranging to *plant, large atei's, the risk of spreading the disease by means of cuttings, young plants, &c,, is very considerable; aud, in view Of the enormous losses sustained by older countries and by the Australian colonie', it is manifestly the auby of all concerned to avoid the possibility of disseminating this insignificant yet devastating enemy of the vigneron. ' In view "of the immense importance of the suV.ject I venture to appeal to all interested in fcha progress of viticulture to combine to aid the authorities in devising and carryiug out; means for the suppression of phylloxera ere ib be too late. Let us take warning by our experience of the codlin moth, which has been neglected till now it causes the loss of many hundreds of pounds sterling per annum. Had systematic warfare been organised against the moth yearß ago, we should not hear the continued wail which now ascends frdm the throats of colonial fruit-growers. Every season that systematic and simultaneous action is postponed does but aggravate the disease, tend to still further postpone the cure and increase the loss o? the producer. Phylloxera has probably been more studied by economic entomologists than any other speci ?s affecting commercial crops and products. It is a native of America, and is found on the wild vines of that country, where, however, it doea little damage compared with .the wholesale destruction and desolation which followed its introduction to the wine-producing countries of the Old World. There are three species. Two of them (P. punctata and P. qUercus) damage oak trees ; the, third is the much-dreaded vine-louse, P. vasbabrix, which has caused -fcho loss of so muoh money, besides a large amount of misery and suffering in some parts of France and othef countries. Like other upbids, the phylloxera ara aga

tremely 'prolific, tfhey, in various stages, infest the root, wood, and leaf of the vine. About 15 months ago Mr Despeieses, of the New South Wales Department of Agriculture, published such an admirable, and at the same time brief, account of the metamorphoses of this iueeob that ib is almost impossible to improve upon its for practical workers. I have therefore ventured to reproduce here this dear and lucid description of its life history : — "Taking in rotation this biological cycle, at the atart, when- the young leaves just appear in the spring, we notice first an elongated, smooth egg — omm 26 by Oram 12 — which when first laid is of a white-lemon colour, and which gradually assumes a darker colour. This is the white egg, which, after putting on a rougher surface, hatches (second metamorphosis) and gives life to a small insect; with a round body, with top like that ©f a turtle, and coming to a point at the back. [Plate I, fig. 4-.] • "It is cut into transverse segments. The head has a pair of .eyes, which would tend to show that, although the creature lives in the soil, it may have to come up to light on the surface. It possesses two feelers, made up of three I segment?, the last of which is the longest, and ! is bevel-shaped. " The most important organ of all, in its relation to the vine, and the weapon whioh causes all the mischief, is the rostrum or needleshaped beak, which is thrust to one-third of iti length into the young rootlet, on which the insect thus fastens itself, while the sap rises by capillary force into this hollow and pointed mouthpiece, which is so articulated that it can either remain flat against the body of the inseot or stand erect, as when ready to pierce the tissues of the roots or of the leaf of the vine, as the case may be. "Toe newiy-born phylloxera, under the compulsion of circumstances which have nob yeb been sufficiently threshed out, either crawl towards the upper surface of the young leaves, on which they attach themselves by means of their beak to the leaf, forming a gall on the spot (hence (ho name ' gallicole ' given to this form) or make for the rcot?, and for this reason are called ' radicole.' " Strangely enough, the gallicole phylloxera are common enough on American vines, while very scarce on the European sorts. This might be the explanation of the fact that the leaf gall form of the phylloxera nan never been observed in Australia, where no American vines are as yet cultivated in the districts wbete the pest has broken out— Geelong and Bendigo in Victoria and the Cumberland district in New South Wales. '•Whether the phylloxera directs itself towards the leaves or towards the roots, it undergoes three moultings before it gets to the perfect j state, each moulting taking place in three to five days. During these successive moul&inga the insects pass from a light yellow to a dirty green yellowish and brown colour, while their egg sacs increase in volume and "cause them to swell. This first form is asexual, and they lay fertile eggs without the assistance of a male. "The gallicole phylloxera, having stuck to the upper surface of a tender leaf, lives on the cap of the plant ; a small cup-shaped gall is formed round it, in which it lies still and lays its ova (about 60 in three weeks), which, on hatching in a week or so, produce new broods of phylloxera, whioh emigrate towards young leaves and produce fresh galls in summer only. In this manner six to seven generations of gsllicole phylloxera are produced in one season, and they gradually become less and less fertile. "When winter sets in they go down towards the roots, where they remain in a dormant state all through the cold season, and they sometimes remain and multiply there. Although this form doss not do much harm to the leaves, yet they are very dangerous, in so far as they spread the disease more easily and are very prolific. "This form of the phylloxera, however, is not often seen on the leaves of the Vitis vinifera, or European vines, but more commonly goes through its various transformations on the roots, thus undermining the vines and committing its ravages where it can with the least treasure of certainty be attacked. The name phylloxera (• leaf drier '), which would apply in the case of the variety which attacks the oak, seems, therefore a misnomer in the case of P. vantatrix of the vine, whioh would more properly deeerve "the name of Rhizocera, or ' root drier.' " Whether gallicole or radicole, the egg-laying phylloxera, stuck fast to the vine by means of its beak, lays around her small heaps of ellip-soid-shaped eggs, Omm 24 by Omm 13, which, sulphur-yellow at first, assume by degrees a .smoky-grey colour, and in about a week's time j hatch and produce young larvte, whioh are yellow, turning to brown as they grow older, j and like their mothers soon begin to perform j the same funotion of multiplication of their species. . j "Third Metamorphosis. — We have seen that from the fundamental eggs the mother's philloxera issue, some settling on the leaves (gallicole) and some on the roots (radicole}. " Now, about midsummer, and after the third poulting, when the insect is full-grown, some, instead of settling, in life as egg-laying insects, grow more elongated, assume a fawn colour, and soon show, on the sides and under the skin, the black sheaths cf the first pair of wings eet on the mesothorax. These constitute the •nymphs.' "On the back they have tubercles ; their antenna) are longer than in the case of the mother insect. These nymghs are not immobile on the roots, but always move about in a f assy sort of way. When they have reached this stage they leave the rootlets and come close up to the surface of the soil, ready to crawl up the stump, and then, after first moulting, are changed into— " Fourth Metamorphosis, Winged Phylloxera. These insects, of a golden yellow, soon after the moulting, turn to a much deeper fawn or orange colour. Unlike the nymphs, they do cot possess tubercles. The mesothorax, to which are attached the wings, contrasts strongly with the yellow of the body; the upper, wings, which are of large size, are striped longitudinally with a yellow band, and are strongly ribbed. On the whole, they are not unlike those of some microscopic cicada. "It is not, however, by means of the wings only that the phylloxera is enabled to direct its course towards the vines it lives on. It is armed with powerful eyes, containing many lenses, which apparently enable it to detect vines at a long range of vision, as well as long Antennee or feelers with auditive and smelling tor tactile glands, whioh eeem to be of use in its distribution. Like the wingless phylloxera reviewed above, this winged form, which are » trifle larger in size than their original parents, are all females. They only lay a very limited number of eggs, varying from two to seven. '* Fifth Metamorphosis.— These eggs are male end female (c) ; they vary in -size, the male eggs being smaller than the female ones, and ■ -fctie latter generally outnumber the first. "' It is by means of its powerful flying apparatus that the winged phylloxera at swarming time is carried away by the wind ; and this explains how it is that, whenever other agencies do not step in and favour its spread over the country, the progressive invasion of phylloxera can generally be followed in the direction of (the prevailing winds. Thera are in«t*n<ses ou

record, however, when they have been observed stuck ou the window panes of railway carriages, and in this manner oarried to distant parts, where, without any reason, phylloxera-infested patches are at times detected *amongst vineyards situated aloDg the railway line. . " Sixth Metamorphosis. —As shown in the figures, the eggs of the winged phylloxera are covered with little hollow cells and wrinkles. From the large-sized eggs come out females without wings, and from the smaller onss equally apterous males, which are also smaller than their mates. 16 is on the under side of the leaves that they are generally laid and hatched. These insects, .which by nature are meant to reproduce their specie?, are not possesned of any feeding organs, and have no rostrum. The wholi of their attention is thus concentrated towards love making, the female possessing only one egg-sac of large dimensions. As soon as ever the males are half out of the shell which contains them they chow signs of impatience, and make strong attempts to get at the female?, with several of whom they couple within a short space of time. "Ssveuth Metamorphosis. —As soon as ever they are impregnated the females crawl down towards the woody part of the vine, and almost invariably amongst the cracks of the bark of two-year-o'd wood deposit their solitary egg, an operation accompanied with violent contractions of the mother's body, who, exhausted, dies alongside the egg she has brought forth. Many of these female phylloxera do not get impregnated when males are rare, hut they l&y their egg in a similar manner and perish after having performed the task. "This egg- is cylindrical, Bpotted, and is attached to the back by means of a pedicel. The egg expands slighly after having been laid, and, from a yellow shiny colour at first, changes to a dark olive green with slight wrinkles later on. " From this egg in tho spring comes out an egg-la j ing insect, which will be the mother and founder of a new brood of phylloxera."—(Despeisses.)