HAWK MOTHS AND CUTWORMS. The larvæ of upward of 50 moths feed on the foliage of the grape. Many of these are rare, yet many others are occasionally destructive. Aside from the leaf-folder already discussed, perhaps the leaf-feeding caterpillars oftenest the cause of important damage are the large green or brownish, usually horned, sphingid larvæ and certain cutworms. Hawk moths.-The larvæ of some ten species of hawk moths or sphingids occur on the grape, and nearly all are widely distributed. The one most frequently met with is the Achemon sphinx (Philampelus achemon Drury) herewith figured (fig. 103) to illustrate the characteristics of the group. The sphinx larvæ strip a branch at a time completely, and are, therefore, easily noted. They are not often very abundant and the injury is not usually great, except in the case of young vines, which may be entirely stripped and killed by a single larva. Hand picking is ordinarily the simplest and most satisfactory remedy. Cutworms.-The climbing cutworms have at times proved very destructive to the buds and foliage of vines, and in northern New York, and particularly in the raisin district of Fresno County, Cal., as much damage has been done by them as by any other insect enemy. Of the several species which in different localities have been troublesome, the worst record may be assigned to the dark-sided cutworm (Agrotis messoria Harr.) and the variegated cutworm (A. saucia Hbn.), both occurring throughout the United States, and the ones chiefly concerned in the region noted in California. Cutworms remain concealed in the ground during the day and climb up and strip the vines at night. They may be easily destroyed by the use of a poisoned bait of bran, arsenic (or paris green), and water, preferably sweetened with a little sugar. It should be distributed about the base of each vine in the form of a mash, a handful or so in a place. THE GRAPE LEAF-HOPPER. (Typhlocyba vitifex Fitch.) From midsummer to autumn, in increasing amount, the leaves of grapes are affected by a little jumping insect commonly known as the thrips, or leaf-hopper, which works in enormous numbers on the underside of leaves, causing them to appear blotched and scorched or covered with little yellowish or brownish patches, and eventually dry up, curl, and fall. This insect occurs with great regularity wherever the vine is cultivated, and yet so gradually is the damage done that, notwithstanding the great annual loss that must result to grape growers from this insect, no particular effort is ordinarily made to remedy the evil. The depredator is a very minute insect, not exceeding one-eighth of an inch in length, and has a peculiar habit of running sidewise when disturbed, like a crab, and dodging from one side of the leaf to the other. It jumps vigorously, like a flea, but also takes flight, rising in swarms when the vines are shaken. If examined without being too much disturbed, they will be noticed thickly clustered over the undersurface of the leaves, busily engaged in sucking the juices of the plant. Under a lens they will be found to vary considerably in color, and, in fact, they are supposed to represent a large number of distinct species, all closely allied, however, and possessing identical habits. The prevailing color is light yellowish green, with the back and wings variously ornamented with red, yellow, and brown. In the fall they become much darker, though retaining the wing patterns. In any vineyard usually one-half dozen or more color species will occur together, one or two of which will predominate, while only a few miles. distant some other forms will be the common ones. The insect figured FIG. 104.-Typhlocyba spp. a, T. comes Say, female; b, T. comes Say, male; c, typical form of They begin to appear on the vines in June, and gradually increase in numbers through July, August, and September, remaining on the vines until the leaves fall, and afterwards may be frightened up in swarms from masses of leaves about the vines. The winter is passed wherever protection may be secured from storms, particularly in masses of accumulated leaves, and especially where these have been blown up against logs or fences. In such situations the writer has observed them by thousands on warm days in early winter. All varieties of grapes are attacked, the thin-leafed sorts most injuriously, but vast injury is done to all, including the wild grapes, and at least one other wild plant-the redbud or Cercis canadensis. 3 A 95-15 Life history.-The eggs are thrust by the female singly into the substance of the leaf on the lower side, either into the midribs and large veins or in the intervening spaces. The young are much like the adults, except that they are smaller and wingless. They cast their skins three times before becoming full grown and acquiring wings, and the white cast skins remain attached to the undersurface of the leaves, frequently upward of 100 clinging to a single leaf. In the middle and southern portions of their range they undoubtedly pass through 4 or 5 broods annually, the life of a single generation probably covering about a month. Remedies. The prevention of injury by the leaf-hopper is a very difficult problem. The best chances of relief will come from taking advantage of its hibernating habit and collecting and burning all fallen leaves and any similar material about the vineyards which would furnish it with winter quarters. This will be effective in proportion to the thoroughness with which it is carried out, and the treatment must be extended over a considerable area to give much relief. In this connection it must be remembered that the leaf-hoppers coming from wild grapes or from near-by vineyards are particularly apt to hibernate in woods, returning to the vineyards again the following spring. Direct measures against this insect consist in spraying with kerosene emulsion or the use of tarred or kerosene shields. The great activity of the insect makes spraying under ordinary circumstances with caustic washes somewhat ineffective, but if the application be made in the early morning or late evening, especially if a cold or moist day be chosen, when the insects are somewhat torpid, considerable benefit will result. The emulsion should be diluted with nine parts water. Applied under the circumstances described, a great many of the leaf-hoppers will be wet with the emulsion or will fly back to the leaves and get it on their bodies before it will have evaporated. The shield method should be used in the warm part of the day, when the insects are most active. A frame with cloth stretched over it and saturated with kerosene or diluted tar may be carried along between the vine rows, the vines being agitated at the same time. The insects will fly up, and all of those striking against the screen will either adhere to the tar or get wet with the kerosene and perish. The shield method, to be effective, must be continued every day or two until relief is gained. THE GRAPE-BERRY MOTH. (Eudemis botrana Schiff.) As the grape berries become full grown and begin to ripen, often many of them will be observed to be discolored, and if these be examined a burrow will be found eaten through the pulp from the discolored spot, and within it a whitish larva. These injured berries begin to appear while the fruit is young and green, and as it ripens they increase in number. Frequently several of these discolored and shriveled berries will be fastened together by silken threads intermixed with the excrement of the larvae and the sticky grape juice, the larva having passed from one to another. The appearance is not unlike that produced by black rot, and is often confused with the latter. As the larva becomes mature it changes to an olive-green or dark-brown color, and not only excavates the pulp, but burrows into the seeds of the grape. It is very active and is apt to wriggle out of the grape and escape. When full grown, the larva attains a length of about one-third of an inch, and, abandoning the grape, cuts out of a grape leaf a little flap, which it folds over and fastens with silk, forming a little oblong case, in which it changes to a chrysalis. The little slate-colored moth with reddish-brown markings on the forewings appears in ten or twelve days, drawing its chrysalis partly Fra. 195. --Eudem is botrana. a, moth; b, larva; c, pupa; d, folded leaf with pupa shell projecting from case cut from the leaf; f, grapes, showing injury and suspended larva, natural size-all except f much enlarged (original). after it and depositing eggs for an additional brood of larvæ. The last brood of larvæ remains in the leaf cases through the winter. The moths coming from these hibernating chrysalides appear in carly spring, and the first brood of larvæ lives on the leaves, tendrils, and blossoms, there being, of course, no grapes for them to infest. This insect was imported many years ago into this country from southern Europe, where, in Austria and Italy particularly, it is very injurious and has two or three near allies which affect grape leaves and fruit in the same way, but which, fortunately, have not, as yet, been imported into this country, or if so, have not become numerous enough to be recognized. Our grape berry moth is widely distributed, occurring probably wherever the grape is grown to any extent, from Canada to Florida and westward to California. It attacks all varieties, but is especially destructive to grapes with tender skins and such as grow in compact bunches. The records of the Department show also that this insect is a rather general feeder, and it has been bred from seed bunches of sumac and the leaves of tulip and magnolia. It sometimes enters the leaf galls of the phylloxera and eats not only the interior of the galls, but, as observed by Mr. Pergande, the young and mother louse also. It has proved particularly destructive at times in Ohio, Missouri, and Pennsylvania, and in many cases from 50 to 75 per cent of the crop has been ruined by it. It is probably three-brooded, except in its more northern range, the first brood developing on the leaves in May and June, the second brood on green grapes in July, and the third brood on ripening grapes in August and September. The early brood of this insect is so scanty that it is rarely noticed, and hence protective steps are seldom taken. Later in the season it multiplies with great rapidity, and particularly does it become numerous and destructive if grape gathering be deferred until a late period. Remedies.-The use of poisons is not practicable except against the first brood, which develops on the green parts of the vine, and here the result is doubtful, because it is more than likely to breed on a great variety of foliage, and spraying would not afford much protection. Bagging the grapes as soon as the fruit sets will undoubtedly protect them from this insect, and at the same time from black rot. Of greater practical value, especially in larger vineyards, is the prompt collection and burning of all fallen leaves in autumn, thus destroying the hibernating larvæ and pupæ, and also the collection and destruction of diseased fruit wherever feasible. Early gathering and shipping or disposal of fruit otherwise is a particularly valuable step, as it insures the removal of the larvæ in the grapes from the vineyard if not their destruction in wine making. All fallen fruit should also be gathered and destroyed. |