Charles Valentine Riley

“ While, therefore, there is much yet to learn in the life-history of our Grape Phylloxera, the facts which I have already unequivocally stated, as well as those which I shall now proceed to give, remain indisputable, and do not seem fully to accord with Balbiani's discoveries.
As fall advances the winged individuals become more and more scarce, and as winter sets in only eggs, newly-hatched larvae, and a few apterous egg-bearing mothers, are seen. These last die and disappear during the winter, which is mostly passed in the larva state, with here and there a few eggs. ”

“ On the roots, the young lice attach themselves singly or in little groups, and thus hibernate. The male gall-louse has never been seen, and there is every reason to believe that he has no existence. Nor does the female ever acquire wings. Indeed, I cannot lay too much stress on the fact that gallæcola occurs only as an agamic and apterous female form. It is but a transient summer state, not at all essential to the perpetuation of the species. ”

“ Wherever they settle, the few eggs which each carries are sufficient to perpetuate the species, and thus spread the disease, which, in the fullest sense, may be called contagious. Whether in a state of nature these winged females show a preference for any one part of the vine in the consignment of their eggs, is not yet known. It is quite certain, however, that they do not reënter the ground. Neither do we know whether—in the light of Balbiani's discoveries regarding the European Oak Phylloxera—the young hatching from these eggs produce the diminutive sexual individuals already described. ”

“ An insect which has spread from the high table-lands of the Rocky Mountains across the Mississippi Valley to the Atlantic, and that flourishes alike in the Stales of Minnesota, Wisconsin, and Connecticut, and in Maryland, Virginia, and Texas—in fact, wherever the potato succeeds—will not be likely to be discomfited in the potato-growing districts of Europe. Some few, again, have ridiculed the idea of the insect's passage to Europe in any state, arguing that it is an impossibility for any coleopterous insect to be thus transferred from one country to another. ”

“ Issuing from the mouth of the gall, these young lice scatter over the vine, most of them finding their way to the tender terminal leaves, where they settle in the downy bed which the tomentose nature of these leaves affords, and commence pumping up and appropriating the sap. The tongue-sheath is blunt and heavy, but the tongue proper––consisting of three brown, elastic, and wiry filaments, which, united, make so fine a thread as scarcely to be visible with the strongest microscope––is sharp, and easily run under the parenchyma of the leaf. ”

“ Prophylactic Means of coping with the Disease.—It occurred to me that, by grafting the more susceptible on to the roots of the more resistant varieties, we might in a great measure counteract the disease, even if all other remedies failed. In the grape-growing districts of France, where the disease is so sweeping, and where the grape is so exclusively grown that its failure affects whole communities, the people may be obliged and can afford to go to much labor and expense in the use of insecticides to save their vines. ”

“ Why the Insect is more injurious in Europe than in America.—Without going into particulars, several good reasons may be given to explain the fact that Phylloxera is more devastating in the vineyards of France than in our own. There exists a certain harmony between the indigenous fauna and flora of a country, and our native vines are such as from their inherent peculiarities have best withstood the attacks of the insect. ”

“ In from thirty to forty days from the time the egg is deposited, the insect hatching from it goes through all its transformations and become a beetle, the pupa state being assumed under-ground. The prolificacy of the species may be imagined when it is remembered that the progeny of a single female may exceed a hundred millions in the course of a single season! The beetle feeds as well as the larva, though not so voraciously. ”

“ Injury caused by Phylloxera in America.—In this country, where, compared with Europe, land is so rich and abundant, we are apt to think lightly of injury to our crops, except when such injury becomes very great and wide-spread. It is a fact, long ago remarked by Dr. Fitch, State Entomologist of New York, that while in Europe the whole people become alarmed if a fifth of a given crop is destroyed by insects, the farmer here often thinks himself fortunate if he can save half the average yield from insect depredations. ”

“ 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. ”

“ The more Manifest and External Effects of the Phylloxera Disease.—The result which follows the puncture of the root-louse is an abnormal swelling, differing in form according to the particular part and texture of the root. These swellings, which are generally commenced at the tips of the rootlets, where there is excess of plasmatic and albuminous matter, [15] eventually rot, and the lice forsake them and betake themselves to fresh ones—the living tissue being necessary to the existence of this as of all plant-lice. ”

“ Yet the day is fast coming when the growing of superior varieties, which have for the most part failed, will alone be remunerative; and I believe that nothing will so tend to enable us to successfully grow them as a thorough knowledge of Phylloxera, which is, in reality, the principal cause of their failure. Take as an instance the case of the Catawba. It is in growing demand in the Mississippi Valley, as, so far, the best white-wine grape, and the only one extensively used in the manufacture of sparkling wines. ”

“ A vineyard should never be inundated for a longer period than two days in summer, or during growth; and though these brief inundations at that season affect only the few lice near the surface, and are by no means essential, they are nevertheless important auxiliaries to the more thorough fall or winter submersion, as they destroy the few lice which are always invading a vineyard in infested districts. ”

“ At this stage the outward symptoms of the disease first become manifest, in a sickly, yellowish appearance of the leaf and a reduced growth of cane. As the roots continue to decay, these symptoms become more acute, until by about the third year the vine dies. Such is the course of the malady on vines of the species vinifera when circumstances are favorable to the increase of the pest. When the vine is about dying it is generally impossible to discover the cause of the death, the lice, which had been so numerous the first and second years of invasion, having left for fresh pasturage. ”

“ Every egg brings forth a fertile female, which soon becomes wonderfully prolific. The number of eggs found in a single gall averages about 200; yet it will sometimes reach as many as 500, and, if Dr. Shimer's observations can be relied on, it may even reach 5,000. [10] I have never found any such number myself; but, even supposing there are but five generations during the year, and taking the lowest of the above figures, the immense prolificacy of the species becomes manifest. ”

“ These eggs are of two different sizes, the smaller being readily separated from the larger. They hatch in about a dozen days, the smaller giving birth to males, and the larger to females, which have neither mouth-parts nor digestive organs, and neither grow nor moult after birth. The sole aim of their existence is the reproduction of the species, and they crawl actively about and gather in little multitudes in the crevices and interstices which are afforded them. The male, except in size, seems to differ from the female only in having a small conical tubercle, which serves as sexual organ. ”

“ The males in all plant-lice are quite rare, and, in the great majority of species, unknown. Where known, this sex bears about the same relation to the female as the shorter and smaller Phylloxera just described does to the larger. These same differences observed in the winged insects obtain in the other species of the genus that are known, and have always been looked upon as sexual. Signoret, an authority on these insects, once so looked upon them, [11] but has lately declared the shorter form to be a female emptied of her eggs. ”

“ Direct Remedies.—The leaf-lice, which do not play such an important part in the disease as was at first supposed, may be controlled with sufficient ease by a little care in destroying the first galls which appear, and in pruning and destroying the terminal growth of infested vines later in the season. The root-lice are not so easily reached. As the effort will be according to the exigency, we may very naturally look to France for a direct remedy, if ever one be discovered. ”

“ It is barely possible that under certain circumstances, as, for instance, on our wild-vines, where the soil around the roots is hard and compact, gallæcola may become more persistent, and pass through all the phases belonging to the species without descending to the roots—the eggs wintering on the ground, or the young under the loose bark, or upon the canes. ”

“ 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. ”

“ In the one-jointed tarsus of the larva or newly-hatched louse, and in being always oviparous, it shows its affinities with the latter family; but in the two-jointed tarsus of the more mature individuals, and in all other characters, it is essentially aphididan. "In every department of natural history a species is occasionally found which forms the connecting link between two genera, rendering it doubtful under which genus it should properly be arranged. ”

“ More extensive experience has satisfied me that the hypothesis is essentially erroneous, and that, while the first galls may sometimes be produced by lice hatched from the few eggs deposited above-ground by the winged female, they are more often formed by young lice hatched on the roots, and which, wandering away from their earthy recesses, are fortunate enough to find suitable leaf conditions. ”

“ Usually, however, the natural enemies of the louse seriously reduce its numbers by the time the vine ceases its growth in the fall, and the few remaining lice, finding no more succulent and suitable leaves, seek the roots. ”

“ These will either prefer to confine their attention to varieties which resist the enemy, or abandon the business entirely. Yet, if it shall once be demonstrated that varieties which now fail may be grown when grafted on to those which resist, I see no reason why it should not become as much a custom and a maxim among grape-growers to use some other vine as stock for such varieties as the Catawba, for instance, as it already is among pear-growers to use the quince, or among cherry-growers to use Mahaleb, Mazard, or Morello, as stocks. ”

“ But I greatly fear that no direct remedy for such an underground enemy will ever be discovered, that will not entail too much labor and expense to be used, to any great extent, by our own grape-growers. ”

“ While the beetle, especially in the non-growing season, will live for months without food, the larva would perish in a few days without fresh potato-tops, and would, I believe, starve to death in the midst of a barrel of potatoes, even if it could get there without being crushed; for, while it so voraciously devours the leaves, it will not touch the tubers. The eggs, which are quite soft and easily crushed, could, of course, only be carried over on the haulm or on the living plant ”

“ The natural enemies of the species are encouraged by the intelligent cultivator, and poultry may be taught to feed upon it. Of over twoscore predaceous and parasitic species of its own class which I have enumerated, those herewith figured may be considered the most important. The only true parasite is a species of Tachina-fly (Lydella doryphoræ, Riley) , somewhat resembling a house-fly, which fastens its eggs to the doryphora larva. ”

“ The vapor of this sulphuret of carbon permeates the soil, and impregnates all the roots of the vine. The gas engendered is not, like the liquid itself, fatal to the vine, but invigorates it. Its effects are, however, sure death to the insect, and, if a vine is examined eight days after the treatment, the lice are found dead and carbonized. ”

“ There are various means of destroying the insect, and in the earlier invaded territory of the States, though it continues its ravages, thereby making the cultivation of potatoes more laborious, and increasing their market price, yet it is no longer dreaded as it at first was, for the reason that it is controlled with comparative ease. ”