We have seen that the Southern Fox (vulpina) is the only species that is totally exempt from both leaf and root lice. This species is of no value whatever in the latitude of St. Louis, and does not flourish above latitude 35°. It cannot, therefore, be made of any avail here, and it is doubtful whether, in the blighted French vineyards, they will be able to profit much by its immunity. I fear that it will hardly flourish even in the extreme southern portion of that country; while the great difference between its wood and that of the other cultivated species must render it difficult to successfully graft these upon it.
Other Preventive Measures.—In planting a new vineyard the greatest care should be taken not to introduce the Phylloxera on the young plants; and a bath of weak lye or strong soap-suds before planting will, perhaps, prove the best safeguard.
Remembering that the lice are spreading over the ground from July till fall, and principally in the months of August and September, a thorough sprinkling of the surface at this season with lime, ashes, sulphur, salt, or other substance destructive to insect-life, will no doubt have a beneficial effect in reducing their numbers and preventing their spread.
The insect has been found to thrive less, and to be, therefore, less injurious, in a sandy soil; while a mixture of soot with the soil has had a beneficial effect in destroying the pest. I have therefore recommended, for the more susceptible varieties, that they be planted in trenches, first prepared with a mixture of sand and soot: an addition of lime and ashes will also prove beneficial. There is every reason to believe that vines are rendered less susceptible to the disease by a system of pruning and training that will produce long canes and give them as nearly as possible their natural growth. Numerous instances are on record, and have come under my notice, of thrifty vines grown upon trees, or upon houses, with scarcely any pruning, and generally in firm, compact soil; while in the same neighborhood the same kinds of vines, in open culture, have been sickly or have failed.
Natural Enemies.—There are a number of different predaceous insects which serve to keep the leaf-lice in check; but, as the injury is mostly done underground, it will suffice to enumerate the principal of these in this connection. The most efficient is a black species of fringe-wing, or thrips, with white wings (Thrips phylloxeræ of my MS.). The egg, which is thrice as large as that of the louse, ellipsoidal and with a faceted surface, is deposited within the gall among the more legitimate inhabitants; and the young Thrips, which differ from their parents not only in lacking wings, but in being of a blood-red color, with only the extremities and the members black, play havoc with the lice. They are active, supple creatures, and turn up menacingly the posterior part of the body when disturbed. They are found in several different kinds of Phylloxera-galls, and do more than any other species to keep the leaf-inhabiting grape Phylloxera within bounds.
