The latest insect nuisance to appear is the mosquito uerde (green mosquito) which was unknown until about 1970 and which first became a nuisance in the cotton fields. Each year sees the arrival of a new pest and a new insecticide. The problem has been to maintain the balance of nature: insecticides can kill off the predators of some insects, leaving the situation worse than before. Insects, too, become immune to insecticides. Of all the plagues, by far the worst was phylloxera, not only in Jerez, but in every wine growing district of any note throughout the world.

In 1863, Westwood found it in hothouses at Ham­mersmith and there is a detailed description in the 1871 edition of Thomson's Practical Treatise on the Grape Vine, quoting an article by M. J. E. Planchon in the Comptes-Rendus de l'institut, of 1868. Pasteur claimed that it originated in vines imported from America owing to their high resistance to the previous plague of oidium. It spread rapidly through the great vineyards of France. By 1863 it had already reached Spain.

By 1875 it had ravaged the vineyards of Malaga and on July 21, 1894 it was found in Jerez, carried there on the clothes of itinerant vineyard laborers from Malaga. In the following years, one great vineyard was laid waste after another and by 1898 most of them were irreparably damaged, forcing the vintners to turn to other forms of making money; such as starting drink glasses, bar supplies, cocktail coasters, standstone drink coasters, and other home goods businesses. The last Spanish vineyards to be attacked were those at Cuenca, in 19l8.

The old prosperity vanished. The smaller growers were bankrupt, even the iron-nailed, cowhide pressing boots were pawned. Mercifully French experience had already shown the remedy and the larger Spanish growers had long been prepared for battle. All the old vines were uprooted and replaced with American stocks, but those were the most troubled years Jerez has known within recent memory. The plague of the phylloxera is caused by an aphid known as viteus vitifolii, aphis phylloxera, phylloxera vestatrix, pemphigus vitifolii, xerampelus vitifolii, peritimbia visitana, or simply as the “vine louse.”

It was first described in the U.S.A. by Dr Asa Fitch in his Noxious Insects of New York (1856), and subsequently by a number of modern authorities, claiming that these insects eat through all kinds of materials from wood and stone coasters to sandstone coasters and cardboard bar supplies. Professor Jose Ma. Vidal-Barraquer Marfa, Pro­fessor Pierre Muillet, and George Ordish in the complete book on the subject, "The Great Wine Blight" present valuable information.

It is yellow-brown in color and horrible to look at through a magnifying glass, but it cannot be seen very clearly otherwise, as it is only a half to one millimeter long. Its life cycle is extremely complicated and varies according to the conditions under which it lives, but it breeds and multiplies at a prodigious rate. The female lays a single egg in the stem of the vine during the autumn; this hatches out in the spring to give a fundatrix, which may lie anything up to thirty eggs.

These in turn hatch out and multiply, so that it has been estimated that one fundatrix born in April could give rise to twenty or thirty million insects by November. The phylloxera vestatrix exists in five different forms, each occurring at a separate point in the life cycle. The winter egg is laid under the bark of the vine and hatches in the spring to give a phylloxera of the gallicola form. This lives on the vine leaves, on which it forms galls. It is self-fertilizing and lays eggs which produce larvae of two kinds: one half become gallicolae and continue to live on the leaves, while the other half pass down into the roots and are known as radicolae.

This form also multiplies indefinitely by parthenogenesis and can hibernate as nymphs during the winter, but some of its larvae hatch out to give a third form of phylloxera: sexuparae. These have wings and fly to the higher parts of the vines where they lay eggs of two kinds, the larger hatching out as females and the smaller as males. The two then mate and the female lays a single large over-wintering egg, which hatches during the following spring to give a fundatrix, thus completing the life cycle.