THE PHYLLOXERA.

Auckland Star, Volume XXXI, Issue 291, 7 December 1900, Page 3

THE PHYLLOXERA.

HOW ITS PRESENCE IN THE VINEYARD MAY BE DETECTED.

("W rynberg Times.")

The following memorandum of the symptoms of the presence of the phylloxera on the vine has been published for general information:— First—The presence of Phylloxera vastatrix is not immediately signalised by any .one sharply defined symptom. A vine newly attacked by a small number of phylloxera can hardly ever be detected among healthy vines, unless evidence other than that of mere inspection of the foliage leads up to close search' among the roots. So vigorous is the normal growth of the vine, so tolerant is it of hard usage, that its roots will for a long time continue to absorb enough food from the soil, both for the parasitic insects established upon them and for the plant itself. Hence the phylloxera may exist for a whole season without exciting sus-

picion. Second—The first indication of commencing exhaustion, due to the phylloxera increasing in number, sucking away so much sap as to stint the upward flow into the stem and disorganising the vascular structure of roots by punctured wounds, is something similar to what may be seen in any free-growing plant that has by neglect become "pot-bound." Everybody, knows this peculiar condition. The young shoots grow slowly, the buds seem unable to start their leaves fairly out, the leaf stalks are short and weak, the internodes too slender for health and yet become hardened on the outer surface. The skin of the leaf looks as if varnished, and feels hard and dry to the touch. Ultimately the green tissue becomes yellow or even brown, dies, and the leaf drops. A gardener accustomed to go his rounds among a limited number of plants every day, like a medical man among his patients, detects such symptoms in a very early stage. Root mischief going on is plain to the educated eye. The plant is knocked out of the pot, examined and new conditions and regimen imposed at once.

Third—Now, what takes place in a pot-bound plant, whose rootlets seek food and find none,. is imitated pretty closeiy by a vine whose root-drawn food is being stolen by phylloxerae. After the mischief has gone on for one or perhaps two seasons, there results a considerable impoverishment of the usual generous supply passed up by the roots. One sees the symptoms enumerated above one after the other—slow growth of young parts, tendrils sluggish in turning, leaves with a hardened and parched, aspect and readily broken off at the foot-stalk, ultimately assuming a sickly-green hue and dropping exhausted before their-time.

Fourth—This condition of things has unquestionably been present in some Cape vineyards for several seasons without attracting special notice. The vines have been said to be "going back," and dryness, moisture, an impervious clay subsoil, with many other supposed causes, have in turn been credited with the mischief. After several seasons the phylloxeriscd vine becomes utterly exhausted, makes a last effort to respond to the stimulus of the spring season by putting forth weak shoots about a span long, and succumbs entirely when the hot, dry weather sets in.

Fifth—When the first symptoms of rootmischief betray themselves in stem and foliage so clearly as to attract attention, it may be taken for granted that the evil is far advanced. On digging up the old root, with such care as to avoid the white or pale-brown rootlets, a sharp eye will detect a dull-yellow powdery appearance on the Bark or in crevices and angles. This, on examination with a very ordinary lens, will be seen to consist of hundreds of little wingless, yellowish lice, and perhaps many more egg-like bodies ready to be hatched. Often there are none at all on the old root. Then they will be found in clusters upon the pale-coloured young rootlets. Sixth—Most persons have observed tha. when certain flies prick a stem or leaf to insert an egg in the puncture, the tissues swell up around the place and form a distorted lump of gall. Just so here. The phylloxerae prick the succulent rootlets and suck their juices. When this puncture and suction has taken place, a sort of root-gall of more or less distinct character is formed by the injured tissue. Then, comparing a phylloxerised rootlet with a perfectly healthy one, the great difference caught by the eye at a glance is as follows: , Seventh-Without help of a lens, a phylloxerised rootlet appears tangled, as if the original direction of growth had been sharply turned aside again and again. It recalls the writhing attitude of a worm. At short distances it is swollen into irregular sub-cylindrical galls of variable size with intervening portions of smaller diameter. Search with a lens is almost certain to show abundance of the wingless lice crawling on the root galls, or hiding in the loops of the tangled fibrils. The egg-like bodies (pseudova) will also be visible. But some rootlets may be found presenting numerous characteristic swellings, yet without a single phylloxera. Comparing these with the former ones, it will be seen that the swellings are flaccid, sapless, and generally brownish with incipient decay. There is scarcely anything left in them but woody fibre. The phylloxerae have been there, have drained the tissues dry, and have crawled away to a new and succulent rootlet. Eighth—A healthy vine rootlet, on the contrary, has almost always a very regular distribution of its parts. There is a main axis, like a smooth piece of twine, and if it tapers it does so evenly and not by sudden prominences and knots. The side fibrils follow the same orderly branching. Their tips, where alone they grow in length, are slightly enlarged, but even there one sees nothing like the knoobled galls of the phylloxerised root. Ninth—The diameter of the roots is excessively variable, altering with the s&rt of vine with the depth, and probably ciuite as much also with the mechanical and chemical character of the soil. But this condition holds good in all cases; normal vine rootlets are evenly cylindric,

tapered off without irregular breaks and enlargements—phylloxerised rootlets are distorted, bent, gnarled, and as it were, formed of alternating swollen portions and thinner portions.

Tenth—The test of a suspected vine, then, is the growing rootlets, especially the apical growing part of the current season, for roots do not elongate throughout their whole length, but grow longer solely by increase at the tip. The yellowness of the foliage may be deceptive and arise from minor causes—for instance, too shallow trenching, sudden, drought and wind following unseasonable rains, and so forth. But a peculiar drj'ing up of the leaves at the edgejf >while the centre remains green, is a frequent accompaniment of phylloxera and should arouse suspicion.

Eleventh—ln examining a vineyard showing dead or dying vines, such as are descried in paragraph 4, it will often happen that no living phylloxera can be detected on the very worst c^jtrnples in the area. In that case, the observer must work outwards, taking one of the apparently perfectly healthy vines of the next row, or the next but one. The parasites will be there, newly arrived, having left the spot where food, formerly plentiful, has now failed them.

Twelfth—Hence the deceptive character of mere foliage signs of health cannot be too strongly insisted on. The growth of the vine is so vigorous, that it is possible for every stock in a plot of several thousands to be affected, although only an insignificant central patch shows a slight yellowish tinge, and perhaps only half a dozen stocks are obviously dead or dying. In all eases, three or four trials should be made in different spots, laying bare the roots, noting their appearance, and passing every suspicious rootlet under the scrutiny oi' the lens.