1911 Encyclopædia Britannica/Phylloxera

by William Edward Garrett Fisher

PHYLLOXERA (Gr. φύλλον, leaf, and ξηρός, dry), a genus of insects belonging to the family of Aphidae, or Plant-lice, in the Homopterous section of the order Hemiptera. It is chiefly known from the causal relation of one of its species to the most serious of vine-diseases. The name was first given in 1834 to a plant-louse which was observed to “dry up the leaves” of oaks in Provence. About twenty-seven species are now known, all characterized by length not exceeding ·06 of an inch, flat wings, three articulations in the antennae, one or two articulations in the tarses, with digitules, but without cornicles on the abdomen.

The following full description of the only species which attacks the vine, the Phylloxera vastatrix, or grape-louse, is reprinted from the article Vine in the 9th edition of this encyclopedia.

“The symptoms of the disease, by means of which an infected spot may be readily recognized, are as follows: The vines are stunted and bear few leaves, and those small ones. When the disease reaches an advanced stage the leaves are discoloured, yellow or reddish, with their edges turned back, and withered. The grapes are arrested in their growth and their skin is wrinkled. If the roots are examined
Fig. 1.—Root-inhabiting Form (Radicola) of Phylloxera, with proboscis inserted into tissue of root of vine. numerous fusiform swellings are found upon the smaller rootlets. These are at first yellowish in colour and fleshy; but as they grow older they become rotten and assume a brown or black colour. If the roots on which these swellings occur be examined with a lens, a number of minute insects of a yellowish-brown colour are observed; these are the root-forms (radicola of Phylloxera (fig. 1); they are about ·8 mm. long, of an oval outline and with a swollen body. No distinction between head, thorax and abdomen can be observed. The head bears small red eyes and a pair of three-jointed antennae, the first two joints being short and thick, the third more elongated, with the end cut off obliquely and slightly hollowed out. Underneath, between the legs, lies the rostrum, which reaches back to the abdomen. The insect is fixed by this rostrum, which is inserted into the root of the vine for the purpose of sucking the sap. The abdomen consists of seven segments and these as well as the anterior segments bear four rows of small tubercles on their dorsal surface. These root-dwelling insects are females, which lay parthenogenetic eggs. The insect is fixed by its proboscis, but moves its abdomen about and lays thirty to forty yellow eggs in small clusters. After the lapse of six, eight or twelve days, according to the temperature, the larvae hatch out of the eggs. These are light yellow in colour and in appearance resemble their mother, but with relatively larger appendages. They move actively about for a few days and then, having selected a convenient place on the young roots, insert their proboscis and become stationary.
  Fig.—2. Phylloxera.
Winged female which lives on leaves and buds an lays parthenogenetically eggs of two kinds, one developing into a wingless female, the other into a male.They moult five times, becoming with each change of skin darker in colour; in about three weeks they become adult and capable of laying parthenogenetic eggs. In this way the insect increases with appalling rapidity: it has been calculated that a single mother which dies after laving her eggs in March would have over 25,000,000 descendants by October. If, however, the insect were content with this method of reproduction the disease could be isolated by surrounding the infected patches with a deep ditch full of some such substance as coal-tar, which would prevent the insects spreading on to the roots of healthy vines. The fertility of the parthenogenetically produced insects would also diminish after a certain number of generations had been produced.

As the summer wears on a second form of insect appears amongst the root-dwellers, though hatched from the same eggs as the form described above. These are the nymphs, destined to acquire wings; their body is more slender in outline, and at first they bear well-marked tubercles. After several moults the rudiments of two pairs of wings appear, and then the insect creeps up to the surface of the earth, and on to the vine. Here it undergoes its fifth and last moult, and appears as a winged female, capable of reproducing parthenogenetically The winged form has a slender body with distinct head (fig. 2). The eyes are well developed, with numerous facets; the antennae have three joints, the terminal one shaped like that of the root-dwellers. The wings are transparent, with few nervures, and are well adapted for flight. The anterior pair reach far beyond the end of the abdomen; the posterior are narrower and not so long. These winged forms are about 1 mm. long. They fly about from July till October, living upon the sap of the vine, which is sucked up by the rostrum from the leaves or buds. They lay their parthenogenetically produced eggs in the angles of the veins of the leaves, in the buds, or, if the season is already far advanced, in the bark. In very damp or cold weather the insect remains in the ground near the surface, and deposits its eggs there. The eggs are very few in number and of two sizes, small and large (fig. 3, b and c). From the larger a female (fig. 4) is hatched in eight or ten days, and simultaneously, for the first time in the life-history of the Phylloxera, a male (fig. 3) appears from the smaller egg. Neither male nor female has wings; the rostrum is replaced by a functionless tubercle; and there is no alimentary canal.

The female is larger than the male and differs from it and the other forms in the last joint of the antennae. The life of these sexual forms lasts but a few days, and is entirely taken up with reproduction. The female is fertilized by the male and three or four days later lays a single egg—the winter egg—and then dies. This egg is laid in the crevices of the bark of the vine, and as it is protectively coloured it is almost impossible to find it.

Fig. 3.—a, Male produced from small egg c, laid by winged female (fig. 2) b, large egg; c, small egg.		Fig. 4.—Wingless Female produced from large egg (fig. 3, b), laid by winged female (fig. 2).

Here the winter eggs remain undeveloped during the cold months; but in the following spring, as a rule in the month of April, they give birth to a female insect without wings, which resembles the root dwelling forms, but has pointed antennae. These forms are termed the stock-mothers; they creep into the buds of the vine, and, as these develop into the young leaves, insert their proboscis into the upper side. By this means a gall is produced on the under side of the leaf.

Scheme of the Various Forms of Phylloxera vastatrix.

A. Root-infesting forms, ♀

Root-infesting forms, 2nd generation, ♀ Winged forms, ♀
Root-infesting forms, 3rd generation, ♀ &c.

Wingless female Male.

Winter egg

Stock-mother.

Gall-producing ♀ Root-infesting ♀

ditto A.

The gall is cup-shaped, and its outer surface is crumpled and covered with small warts and hairs. The opening upon the upper surface of the leaf is protected by similar structures. Within this gall the stock-mother lives and surrounds herself with numerous parthenogenetically produced eggs—sometimes as many as two hundred in a single gall; these eggs give birth after six or eight days to a numerous progeny (gallicola), some of which form new galls and multiply in the leaves, whilst others descend to the roots and become the root-dwelling forms already described. The galls and the gall-producing form are much commoner in America than in the Old World.

The particular species of phylloxera which attacks the vine is a native of the United States, probably originating among the wild vines of the Colorado district. It was first observed in 1856 by Asa Fitch (1809–1878), who did not suspect its mischief, and called it Pemphigus vitifoliae. In 1863 it was independently discovered by Westwood in an English vinery at Hammersmith; he was ignorant of Fitch's observation, and called it Peritymbia. vitisana. From 1858 to 1863 there were many importations of American vines for grafting purposes to Bordeaux, Roquemaure and other parts of France, England, Ireland, Germany, Portugal, &c. It is practically certain that the deadly phylloxera was imported on these plants. A year or two later certain vine-growers in the South of France began to complain of the new vine-disease. M. Delorme, of Arles, in 1865, appears to have been the first who recognized its novelty and had a presentiment of disaster. The disease steadily spread outwards in concentric circles from its first place of lodgment near Roquemaure. Within two or three years whole departments were infested. In 1866 a second centre of infection made its appearance near Bordeaux. The vine-growers were at their wits' end to account for this new plague, which threatened to be even more costly than the oïdium. The completeness of the ruin which threatened them may be illustrated by the statistics for a single commune, that of Graveson, whose average annual production of wine in the years 1865–1867 was about 220,000 gallons. In 1868 this fell to 121,000 gallons, in 1869 to 48,400 gallons, in 1870 to 8800 gallons, and by 1873 to 1100 gallons.

In 1868 Planchon proved that the disease was due to a new species of phylloxera, which was invariably found on the roots of the affected vines, and to which he accordingly gave the prophetic name of Phylloxera vastatrix. During the next ten years a series of students, of whom only Riley and Balbiani need be mentioned here, worked out the natural history of Phylloxera vastatrix, and proved its identity with the American grape-louse. Its devastations rapidly assumed gigantic proportions. In France, where the disease was by far the most prevalent-owing in great part to the obstinacy with which the vine-growers at first refused to take any reasonable precautions against its spread—M. Lalande, president of the chamber of commerce at Bordeaux, in 1888 calculated the direct loss to the country by the phylloxera at 10 milliards (£400,000,000), or double the indemnity which had been paid to Germany in 1871!

The phylloxera has made its appearance in almost every vine growing country in the world. Thus it appeared in Austria-Hungary in 1868; in Italy, in spite of the frantic efforts made—as in other countries—to keep it out by strict legislation against the import of vines, in 1879; in Russia in 1880; in Germany, on the Rhine and Moselle, and in Switzerland in 1872; in Madeira, Spain and Portugal, about 1876. The pest even crossed the oceans, and appeared in Australia, at Geelong, about 1880; it has since twice broken out in Victoria, and has ravaged the vineyards of South Australia and New South Wales. At the Cape, in spite of a long endeavour to prohibit the import of the phylloxera, it appeared about 1884. In 1885 it crossed the Mediterranean to Algeria. There was only one country where its ravages were long unimportant; that was its home in the United States, where the native vines had become, by the operation of natural selection, immune to its attacks. Yet no imported vine has ever lived there more than five years, and in 1890 the phylloxera crossed the Rocky Mountains, and seriously damaged the vineyards of California, where it had previously been unknown.

Three different methods of fighting the pest have been successfully adopted. One is to kill the phylloxera itself; another, to destroy it along with the infected vines, and plant fresh and healthy plants; the third, to adapt the secular therapeutics of nature, and to introduce American vines which a long acquaintance with the phylloxera has made immune to its ravages. Insecticides, of which the bisulphide of carbon (CS₂) and the sulpho-carbonate of potassium (KSCS₂) remain in use, were injected into the earth to kill the phylloxera on the roots of the vine. These methods were chiefly advocated in vineyards of the first class, where it was worth while to spend a good deal of money and labour to preserve the old and famous vines: the Chateau Leoville Poyferré and Clos Vougeot are instances. Some good judges attribute the peculiar and not unpleasing flavour of certain clarets of 1888 to means thus adopted to kill the phylloxera. The second plan was largely adopted in Switzerland and on the Rhine, where measures resembling those taken with cattle suspected of anthrax were applied to all diseased vineyards. The third plan, which consists in replanting the affected vineyard with American vines—such as the Vitis labrusea, V. riparia, V. rupestris or V. monticola—has proved the most generally successful.

A very good bibliography will be found in Les Insectes de la vigne, by Professor Majet of Montpellier (1890), which is the best book on the subject. Reference may also be made to the classic memoirs of Planchon, culminating in Les Mœurs de la phylloxera de la vigne (1877); Dreyfus, Uber Phylloxerznen (1889); Lichtenstein, Histoire du phylloxera; the Rapports annuels à la commission supérteure du phylloxera; and the excellent Report on Phylloxera drawn up by the Hon. J. W. Taverner (Victoria, 1899, No. 68).  (W. E. G. F.)