PHYLLOXERA, a genus of insects belonging to the group Phylloxerinae of the family Aphididae which comprises the aphides (q.v.) or plant lice. The Phylloxerinae are sometimes placed in a separate family of their own, since they differ from true aphides in characters exhibited in the wing-veins, and also in the fact that the parthenogenetic forms lay eggs instead of producing living young. The genus Phylloxera includes over 3o species, the best known being the grape Phylloxera (P. vastatrix), which is native to the United States. It was imported into Europe between 1858 and 1863, when American vines were brought over for grafting purposes, and has since reached almost every vine-growing country in the world. The first definite European record was in England in 1863 ; soon afterwards it was identified in France where it rapidly spread through the vineyards of that country. By 1885 it had extended to most other European grape-producing coun tries and had reached Algeria, Australia, and the Cape. It was first discovered in California in 188o, but there is evidence that it was present in that State from about i858, being intro duced along with American vines from east of the Rocky Mountains. It was the advent of the highly susceptible European grape that led to the Phylloxera becoming a pest in the Cali fornian vineyards. The presence of this insect is manifested by the vines being stunted and bearing smaller and fewer leaves.
When the disease is advanced the leaves are discoloured and galls are present on their under surface. These galls are wrinkled and hairy and their cavity communicates by means of an opening upon the upper surface of the leaf. If the roots be examined, numerous knotty swellings are found upon the smaller rootlets ; at first yellowish in colour and fleshy, they finally assume a brown or black colour and become rotten. At the same time the grapes themselves are arrested in their growth and their skins become wrinkled. The damage wrought by the Phylloxera is occasioned by the extrac tion of the sap by means of the piercing auctorial mouth-parts of this insect, and the subsequent deformation of the plant that is brought about. Millions of acres of vineyards have been destroyed by this pest, and, when at its worst in France, it is stated to have ruined 2,500,000 acres which represented an annual loss in wine products of £50,000,000.
The complete life-history of Phylloxera is briefly as follows : A single egg is laid by the fertilized female on the bark of the vine where it passes the winter. It hatches in spring into a wingless female or fundatrix which, creeping into an opening bud of the vine, forms a gall on the young leaf and lays therein a number of eggs. The latter develop into further wingless forms or gallicolae which multiply rapidly and produce new generations of gall-formers on the leaves. Among their progeny there appear, later in the season, wingless females of different behaviour, the radicolae (fig. I), which pass to the roots. The radicolae con
tinue reproducing generations of their own kind, but among them winged migrants (fig. 2) eventually appear. These occur from July until October and fly to other vines where they lay two kinds of eggs—small male-producing eggs and large female-producing usually fail to develop in the absence of certain American vines and the gallicolae generations are consequently rare. Reproduc tion and spread are brought about by the radicolae, many of which hibernate and continue multiplying in spring. According to the German authority Boerner, there is a race of Phylloxera found in Lorraine which produces galls on European vines, but not on most American varieties, and he has given this Lorraine race the distinctive name of pervastatrix.
Scheme of the complete life-cycle of Phylloxera Winter egg Fundatrix 9 Gallicolae 9 Gallicolae 9 Radicolae 9 etc. /\\ Radicolae 9 Win etc. Wingless 9 Wingless 6 Winter egg Many control measures have been suggested against the Phylloxera but few have been generally adopted in practice. The enforcement of quarantine regulations precluding the distribution of rooted vines from infested areas is important. The utilization of vine-stocks less susceptible to the root-feeding form of the insect is generally recognized. Varieties of American grapes, such as Vitis riparia, V . rupestris, V. berlandieri and their hybrids, are not seriously injured by the radicolae, and by growing these varieties, or using them as stocks upon which the susceptible European varieties have been grafted, injuries by the pest have been greatly reduced. In certain cases the injection of carbon bisulphide into the soil to kill the root form of the insect has been profitable. The flooding of infested vineyards has been a recog eggs. The true sexual forms derived from these eggs (fig. 3) are small wingless individuals with vestigial mouth-parts and an aborted alimentary canal. Fertilization takes place and each fertilized female deposits a single over-wintering egg which hatches into a fundatrix as already described. All the rest of the reproduction of the species is by means of parthenogenesis (q.v.).
It is noteworthy that in Europe and California the fundatrices nized procedure where conditions are favourable.