Popular Science Monthly/Volume 5/June 1874/More About the Grape-Vine Pest
By CHARLES V. RILEY, M. A., Ph. D.
THE number of true (grape-vine) species of Vitis, with the cohering petals falling off when the flower opens, and bearing edible fruit, in the territory of the United States, is limited to nine. Of these, four species, viz., Vitis Labrusca, or Northern Fox; Vitis æstivalis, summer grape; Vitis riparia, river-bank grape; and Vitis vulpina, Southern Fox or Muscadine, are of chief practical consequence as having yielded our different cultivated varieties.
I will now proceed to indicate the relative susceptibility to the disease of the cultivated species and varieties. For the sake of conciseness, it will be best to indicate this susceptibility by letters and numerals, as follows:
European Grape (vinifera), 0, 3.—The very few exceptions, where galls have been found on the leaves of this species, will scarcely date the rule that it is free from galls. So likewise the few exceptional instances of the successful out-door growth of this in Missouri, which have come to my notice, and which it is unnecessary to detail here, do not affect the rule, and only prove that such vines can be grown outdoors when not destroyed by Phylloxera.
River-Bank Grape (riparia).—Alvey, a, 2; Cornucopia (hybrid with vinifera), 0, 2; Clinton, c, 1, where the leaf-galls are very abundant, the root-lice are generally less so, and vice versa. The roots have such vitality that disorganization does not always seem to follow the puncture of the louse, and new rootlets put out from the swellings with great vigor and thrift; Delaware, b, 2; Golden Clinton, a, 1; Louisiana (some say a seedling of vinifera, others, again, believe it æstivalis), a, 1; Marion, b, 1; Othello (hybrid with vinifera), a, 2; Taylor, c, 1, much as with Clinton.
Summer Grape (æstivalis).—Herbemont, a, 1; Cunningham, 0, 1; Cynthiana, a, 1; Norton's Virginia, 0, 1; Rulander, 0, 1; Telegraph, 0, 1.
Northern Fox (Labrusca).—Catawba, 0, 3, suffering almost as badly as the varieties of vinifera; Challenge (hybrid with vinifera), 0, 1; Creveling, a, 2; Concord, a, 1; Diana, 0, 2; Dracut Amber, 0, 1; Goethe (hybrid with vinifera) 0, 2; Hartford, 0, 2; Iona, 0, 3; Isabella, or seedlings thereof, 0, 2; Israella, 0, 1; Ives, 0, 2; Martha, 0, 1; Northern Muscadine, 0, 1; Rebecca, 0, 2; Salem, 0, 2; Wilder (hybrid with vinifera) 0, 1.
Southern Fox (vulpina), 0, 0.—From the investigations of Prof. Planchon, it results, as was anticipated from the great differences in character which it presents, compared with the others, that this species is entirely free from the Phylloxera in any form. The root is not only very tough, but has a perceptibly bitter taste, which doubtless renders it obnoxious to the insect. Prof. Planchon examined it thoroughly in North Carolina, where other vines in the vicinity were suffering from the insect.
From the above enumeration we may gather that, with the exception of vulpina no species of cultivated vine is entirely free from the attacks of either the gall-making or root-inhabiting types. Nevertheless vinifera is least and riparia most subject to the former; æstivalis least, and vinifera most subject to the latter.
Of vinifera, a few varieties, under certain conditions, seem to exhibit a power of resistance in this country; and it is singular that some relative immunity has not as yet been noticed among the varieties of this species in Europe.
Of riparia, the Clinton, Taylor, Golden Clinton, and Marion, seem best to resist.
Of æstivalis, all the species enumerated resist well, and I would especially mention Norton's Virginia, Herbemont, and Cunningham, as vigorous growers.
Of Labrusca, the Concord, Dracut Amber, Israella, Martha, North Carolina, and Wilder, resist well.
This enumeration is founded principally on the effects of Phylloxera in the central portion of Missouri, as ascertained by quite extensive notes and observations made during the past two years. I have also examined many of the varieties mentioned, with similar results, in portions of Kansas, Illinois, New Jersey, Pennsylvania, and New York. The Arnold's hybrids, so far examined, all suffer; but some of them more than others.
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. Such insecticides may also be used in this country where it is desired to save a few choice vines regardless of expense and time. 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. 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.
In the course of a year or two we shall be able to fairly judge of the efficacy of the plan; for, aside from the trials that I am making in this country, others are being made on an extensive scale in France. Quite a number of plants for the purpose of experiment were sent over there from this country in the spring of 1872; and the demand has now become so great that a single firm, Isidor Bush & Co., of St. Louis, has this winter received orders for about four hundred thousand cuttings to be consigned to one place, Montpellier, and consisting of such varieties as have been recommended by myself and Prof. Planchon, as best resisting the disease. There is every reason to hope for the best results from these importations, as those vines, such as Herbemont, Cunningham, Concord, Clinton, etc., which best resist here, and which were planted there in 1871 and 1872 in Phylloxera-infested districts, have, thus far, done surprisingly well, as MM. J. Leenhardt, Pomier, V. Pulliat, and others, testify. Experience, so far as had in America, also promises the best results.
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.
The next most efficient aid in the destruction of the leaf-lice is found among the lace-wing flies, one species of which, more especially, viz., the Weeping Lace-wing (Chrysopa plorabunda Fitch), I find very frequently within the galls, devouring their contents. These
flies are known as well by their brilliantly golden eyes as by the peculiarly offensive odor, as of human ordure, which some of them emit. The eggs are adroitly deposited (Fig. 2, a) by the parent at the tips of long silk-like stalks, in order to prevent first-born larvæ from exercising
Lace-wing fly.—a, eggs; b, larva; c, cocoon; d, fly, the wings to the left omitted.
their cannibalistic propensities on their yet unborn brethren. The larva (Fig. 2, b) is very rapacious, and, when ready to transform, winds itself up into a wonderfully small cocoon (considering the size of the insect which makes it and which issues from it), which is spun
from the extremity of the body, and from which it issues, when about to acquire wings, through a neatly-cut, circular aperture. Next in order, as Phylloxera enemies, may be mentioned the Ladybirds Cochinella), especially certain small dark-brown species belonging to the genus Scymnus, and whose young, thickly covered with white and evenly-shorn tufts of a cottony secretion, are frequently found at their good work within the galls. Pillowing these may be mentioned, as auxiliaries, certain Syrphus-fly larvæ, which, being blind, go groping about among the eggs and young lice, which they seize and suck to
death. Also certain orange larvæ of a smaller two-winged fly (Leucopis); a few genuine bugs (Heteroptera), and notably the Insidious Flower-bug (Anthocoris insidiosus, Say, Fig. 6), and certain smaller Hymenopterous parasites.
The enemies known to attack the Phylloxera underground are, naturally enough, fewer in number. In one instance I have found a Scymnus larva at the work six inches below the surface, and there is a Syrphus fly (Pipiza radicum, W. and R., Fig. 7) whose larva lies underground and feeds both on the apple-tree-root louse, and on this
Root-louse Syrphus Fly.—a, larva; b, pupa; c, fly.
grape-root louse. Wonderful indeed is the instinct which teaches the blind larva to penetrate the soil in search of its prey; for the egg must necessarily be laid at the surface. But, though the underground enemies of its own class are few, I have discovered a mite which preys upon this root-inhabiting type, and which renders efficient aid in keeping it in check in this country. This mite (Tyroglyphus phylloxeræ Planchon and Riley, Fig. 8) belongs to the same genus as the cheese and meal mites (T. zivo, Linn.), and the species (T. entomophagus Laboulbène) which infests preserved insects, and is such a pest in cabinets.
Phylloxera Mite.—a, dorsal; b, ventral view of female; c, mouth-parts magnified; d, f, g, h, forms of tarsal appendages; e, veutral tubercles of male.
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. But, of all the innumerable plans, patented or non-patented, that have been proposed, of all the many substances that have been experimented with, under the stimulus of a large national reward, no remedy has yet been discovered which gives entire satisfaction, or is applicable to all conditions of soil. Nor is it likely that such a remedy ever will be discovered. A large majority of the remedies proposed, such as the planting of Madia saliva among the vines, or inoculating them with the essence of Eucalyptus globulus, are, upon their face, absurd. These we will pass by, and briefly mention only those which have been more or less productive of good.
Submersion, where practicable, and where it is total and sufficiently prolonged, is a perfect remedy. This is what even the closet-student might expect, as he finds that excessive moisture is very disastrous to the lice. M. Louis Foucon, of Graveson (Bouches-du-Rhône), France, has abundantly proved its efficacy, and has, by means of it, totally annihilated the insect from his vineyard, which was suffering from it four years ago. From his experience we may draw the following conclusions: 1. The best season to submerge is in autumn (September and October), when the lice are yet active, and the vines have ceased growing. Submergence for twenty-five to thirty days, at this season, will generally rout the lice. 2. A submergence of forty to fifty days in winter is required, and even where the water is allowed to remain during the whole of this season the vineyard does not suffer. 3. 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. These summer inundations will be necessary only after the winged insects begin to appear; and three or four, each lasting less than two days, made between the middle of July and the fall of the leaf, will effect the end desired. 4. An embankment should be made around the vineyard, in order that the water may evaporate and permeate the earth, but not run off and carry away any nutritive properties of the soil.
The varied success which has attended the different attempts to rout the enemy by inundation, is owing to the lack of thoroughness in many of them. The ground must be thoroughly soaked for a sufficient length of time. Temporary irrigation does not accomplish the end, for the reason that it does not reach all the lice, and does not break up the numerous air-bubbles which form in the soil, and prevent the drowning of many of the insects.
On our best hilly vine-land thorough submersion is impracticable, but on our bottom-lands some of the grapes, which fail now, may be made to succeed by its means.
Of 140 different applications made by an intelligent and competent commission in the department of Hérault, France, most of the pure insecticides proved valueless. Many of them, such as carbolic acid, oil of cade, arsenious acid, sulphide of calcium, sulphide of mercury, arseniate of potash, etc., etc., will effectually kill the insect when brought in direct contact with it; but, in field-practice, they can either not be brought in this direct contact, or else cannot be used strong enough to kill all the lice without injuriously affecting the vine.
Carbolic acid added to water, at the rate of about one per cent., applied by pouring into deep holes, made by a crow-bar or auger, has given satisfactory results; and a thorough application of soot has also been strongly advocated by those who have tried it. In the experiments that I have been able to make, in a small way, a thorough mixing with the soil of a cheap carbolic powder, prepared by G. Mallinckrodt & Co., of St. Louis, has given good results.
The latest insecticide that has attracted attention and given great hopes in France is the bisulphide of carbon. It seems to have been used as early as 1869 by Baron Thenard, but was brought prominently before the public last autumn by Messrs. Monestier, Lautand, and D'Ortoman, who first proposed to introduce it at a great depth in the soil, so as to utilize its vapor. A vapor will naturally have the advantage over a liquid, as it will more effectually permeate the soil and reach the lice. The following is the method of procedure in their own words:
"Make three holes around the vine, the depth to vary according to nature of soil, but generally about 21⁄2 feet (80 centimetres). Hitherto we have made these holes with a pointed iron bar, driven by a maul. When the hole is made the bar is withdrawn, and a tube, furnished with a funnel at one end, is inserted in its place. About two ounces of sulphuret of carbon are then poured into the tube, which is immediately corked.... 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. At the end of fifteen days nothing but the effects of the lice is seen. Long and corroborative experience has demonstrated that about four ounces (100 grammes) of the liquid is sufficient for an ordinary vine; but sprinkling on the surface must be carefully avoided, as it is then very injurious to the vine; whereas as much as a pound may be made to penetrate the soil without injury to the roots."
Soon after the announcement of this method, I employed it as a test on three vines, which I knew to be infested with Phylloxera, using three ounces to the first, six ounces to the second, and nine ounces to the third, the soil being a light clayey loam. At the end of twelve days I found plenty of living lice on the first and second vines, and such were found long afterward, though in small numbers, up to the time of the freezing of the ground. On the third vine all the lice were evidently charred, but the vine was also plainly injured, as the leaves wilted as though they had been scorched, though, whether from the vapor issuing from the ground, or from the injury to the root, it was impossible to determine—I think, however, from the former, as the larger roots were yet alive late in the season, and the vine seems, at this writing, to be living.
After very careful and laborious experiments made in France at different points, and on different kinds of soil, by a commission specially charged with studying the action of this chemical, under the method proposed by Messrs. Monestier, Lautand, and D'Ortoman, it fails to fulfill the sanguine expectations of these gentlemen. The liquid is costly, its application is laborious, and there is great difficulty in reaching and killing all the lice without injuring the vine. Great caution must also be had in its use, as it is extremely volatile and explosive, the vapor igniting at a great distance from the vessel containing it.
While, therefore, not very satisfactory results have followed the use of pure insecticides, the application of fertilizers, intended to invigorate the vie, and at the same time injure the lice, has been more productive of good. Especially has this been the case with fertilizers rich in potassic salts and nitrogenous compounds, such as urine.
Sulphuret of potassium, dissolved in liquid manure; alkalino-sulphates, with copperas and rape-seed; potassic salts, with guano; soot and cinders, are, among other applications, most favorably mentioned.
Range of the Insect in America.—As already intimated, the insect is indigenous to the North American Continent. I have been able to trace its existence, with absolute certainty, as far back as 1834; for, in the herbarium of Dr. Engelmann, there are specimens of Vitis monticola (Buck) that were gathered that year in Texas by the botanist Berlandier, and which have Phylloxera galls upon the leaves; while specimens of riparia in the same collection, and gathered in Missouri in 1845, also have the leaves disfigured by the same gall.
We find, in consequence, that the insect is very generally distributed over the States. I have myself found it in Kansas, Iowa, Illinois, Missouri, Michigan, Ontario, New York, New Jersey, Pennsylvania, and Maryland, and have abundant evidence of its occurrence in Connecticut, District of Columbia, North Carolina, Texas, and as far south as Florida. It doubtless occurs in all the intermediate States. There is every reason to believe, however, that, like so many other animals which occur on the eastern slope of the Rocky Mountains, but are unknown on the western slope, this Phylloxera is not indigenous to the Pacific half of the continent. I have, so far, been unable to trace its existence with any certainty in California; and to its non-existence there the California grape-growers doubtless owe, in great part, their success in the cultivation of the European vine. Yet I have strong evidence that around Sonoma the insect already occurs, and has done much damage; and it may have been introduced either from the Eastern States or from Europe into other parts of that country. It, therefore, behooves our friends of the Golden State to carefully look into this matter, and to endeavor, by taking the proper precautionary steps, to prevent a repetition of the disasters which have followed the introduction and spread of Phylloxera in Europe.
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. Vines have died year after year in our vineyards, and very little notice has been taken of the fact; while certain varieties have continually failed until they have come to be discarded as unprofitable and useless. 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. Yet it is, in this part of the country, one of the most susceptible to the Phylloxera disease, and its successful growth becomes more and more uncertain. If by a thorough understanding of the disease, and by the system of grafting which I have suggested, this vine can be successfully grown in the Mississippi Valley, it is safe to say that the value of our vineyards will be doubled; as the Concord, which is now the main reliance, and which makes but an inferior wine, has already so glutted our markets as scarcely to pay the grower.
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. The European vine, on the contrary, succumbs more readily, not only because of its more tender and delicate nature, but because it has not been accustomed to the disease—there being, doubtless, a parallel between this case and the well-known fact that diseases and parasites which are comparatively harmless among peoples long accustomed to them, become virulent and often fatal when first introduced among hitherto uncontaminated peoples.
Then the particular natural enemies of the insect which belong to its own class, and which in this country help to keep it within due bounds, are lacking in Europe; and it will require some time before the closely allied European predaceous species will prey upon and check it there to the same extent.
The Phylloxera will, also, other things being equal, have an advantage in those countries where the mildness and shortness of the winter allow an increase in the annual number of its generations. Finally, the differences in soil and in modes of culture have no insignificant bearing on the question in hand. Though Phylloxera, in both types, is found on our wild vines, it is very doubtful if such wild vines, in a state of nature, are ever killed by it. With their far-reaching arms embracing shrub and tree, their climbing habit unchecked by the pruner's knife; these vines have a corresponding length and depth of root, which render them less susceptible to injury from an underground enemy. Our own method of growing on trellis approaches more nearly these natural conditions than that employed in the ravaged French districts, where the vines are grown in greater proximity and allowed to trail on the ground, or are supported by a single stake.
The American Oak Phylloxera (Phylloxera Rileyi).—There are several described and undescribed species of Phylloxera in this country, most of them inhabiting leaf-galls made on our different hickories. The species herewith figured is the only external feeder known in America, and it is briefly alluded to in this connection to show that, as with the grape Phylloxera, it does not need a "winter egg" to enable it to hibernate, but passes the winter in the larva state (as at Fig. 9),
firmly attached to the tender bark of the younger twigs, and thus braving all the vicissitudes and inclemencies of that season. In the summer it is found on the underside of the leaves of our white and post oaks, fixed in the centre of a yellowish spot caused by its puncture, and showing most on the upper surface, so that on a badly-infested tree the leaves all look speckled, and seared, and withered. It presents all the different forms and the same biological characteristics that I have described and detailed of the grape Phylloxera.
We have, in the history of the grape Phylloxera, the singular spectacle of an indigenous American insect being studied, and its workings understood in a foreign land, before its presence in its most injurious form was even suspected in its native home. The Franco-Prussian War, with all its fearful consequences to France, has passed away; the five milliard francs (one thousand million dollars) have been paid, as indemnity to her victors, in so short a time that the civilized world looked on in wonder and astonishment. Yet this little Phylloxera, sent out, doubtless, in small numbers, by some American nurseryman, a few years since, continues its devastating work, and costs that unfortunate country millions of francs annually. The last German has been removed from French soil—at terrible cost, it is true—but the Phylloxera army remains; and, if another five milliard francs could extirpate the last individual of this liliputian insect-host from her soil, La belle France would be cheaply rid of the enemy. Had the world, twenty years ago, possessed the knowledge we at present have of this insect and of its dangerous power, a few francs might have originally stayed its invasion of that great vine-growing and wine-making country. Needs there any more forcible illustration of the importance of economic entomology!