Pests and Diseases of Grapes in North America
Phylloxera
The phylloxera (Phylloxera vastatrix Planch.) has four forms: the leaf-gall form, the root form, the winged form, and the sexual form. Individual leaf insects produce from 500 to 600 eggs, the root insect about 100, the winged insect from 3 to 8, and the sexual insect but 1. The last is laid in the fall on old wood; the following spring a louse hatches from it and at once goes to the upper surface of a leaf and inserts its beak. The irritation thus produced causes a gall to form on the lower side of the leaf. In fifteen days the louse becomes a full-grown wingless female and proceeds to fill the gall with eggs after which it dies. In about a week females hatch from the eggs and migrate to form new colonies. Several generations of females occur in a summer. At the approach of winter the lice go into the ground where they remain dormant until spring when they attack the roots forming galls analogous to those on the leaves and passing through a series of generations similar to those above ground. In the fall of the second year some of the root forms give rise to winged females which fly to neighboring vines. These lay eggs in groups of two or four on the wood of the grape. The eggs are of two sizes; from the smaller size, males hatch in nine or ten days; from the larger, females. In the sexual stage no food is taken and the insects quickly pair. The female produces an egg which fills its entire body and after three or four days lays it, this being the winter egg, the beginning of the cycle.

There are no remedies worthy the name and the only efficient preventive is to graft susceptible varieties on resistant stocks. Species are resistant about in the order named: V. rotundifolia, V. riparia, V. rupestris, V. cordifolia, V. berlandieri, V. cinerea, V. aestivalis, V. candicans, V. labrusca, V. vinifera.

Black Rot
Black-rot (Guignardia bidwellii (Ell.) V. et R.) usually appears first on the leaves where it forms circular, reddish-brown spots on which black pimples, or spore cases, develop. Within these spore cases, at maturity, are the summer spores. These are distributed by the elements to the growing parts of the plant and form new centers of infection. The diseased berries show analogous circular spots bearing spores and as the disease progresses the grapes wither, turn black, and become hard and shrivelled, sometimes clinging to the vine until the following spring. Growing shoots are attacked as well as leaves and fruit. During the winter and spring the resting spores are formed, usually upon the shrivelled berries.

Treatment consists of destroying as far as possible all diseased fruit, old leaves and prunings and in spraying thoroughly with bordeaux mixture as follows:―

1. Just as the pink tips of the first leaves appear.

2. From ten days to two weeks after the first spraying.

3. Just after the blossoming.

4. From ten to fourteen days after the third spraying.

5. After an interval of from ten to fourteen days from the fourth spraying.



Mildews

Downy Mildew
Downy mildew (Plasmopara viticola (B. & C.) Berl. & De Toni) is a troublesome fungus attacking all of the tender growing parts of the grape. It does most damage to the leaves, upon the upper surface of which it produces greenish-yellow spots of irregular outline. At the same time a loose white downy growth appears on the under side of the leaves. This growth consists of short filaments bearing spores, the summer spores, which are carried by the elements to other growing parts of the plant, thus spreading the disease. Affected berries, if young, first show a brown spot, and become covered with the gray down which distinguishes the fungus. On older berries the fungus causes a brown-purple spot which spreads until it takes in the whole berry, which then becomes soft and often falls, or they may become hard and persist. At this stage the disease is commonly known as "brown rot".  The winter, or resting, spores are produced in the tissue of fruit and leaves and with a thick protective covering. The winter spores are dark, almost black, in color. Downy mildew spreads and does most damage in hot wet weather. Spraying with bordeaux mixture as indicated for black-rot will keep downy mildew in check. 

Powdery Mildew
Powdery mildew (Uncinula necator (Schw.) Burr.) is caused by a fungus which lives on the surface of the leaves. It subsists by means of sucker-like organs which penetrate the walls of the surface layer of cells. The vegetative portion of the parasite consists of fine white filaments which spread over the surface of the leaves, shoots and fruit. In the summer these filaments send up short, irregular stalks upon which large numbers of barrel-shaped spores are produced in chain-like arrangement. These are the summer spores of the fungus. They are borne in greatest quantity on the upper surfaces of the leaves and give the leaf a gray, powdery appearance hence the name, powdery mildew. Affected leaves finally become light brown and often fall. Diseased fruits are gray in color, scurfy, become specked with brown, fail to develop and often burst on one side thereby showing the seeds. The winter or resting spores are borne in sacs, in the latter part of the season. The spore sacs, in their turn, are borne in small, black, spherical spore cases, each furnished with a number of slender appendages having curled tips. The powdery mildew, unlike most other fungus troubles of the grape, is most prevalent in hot dry weather. The disease is combatted by dusting with flowers of sulphur or by spraying with bordeaux mixture as for black-rot.


Anthracnose
Anthracnose (Sphaceloma ampelinum De By.).―This disease attacks any of the tender portions of the growing vine. When the leaves are affected dark spots are first formed on their surface. As the disease advances these spots enlarge, and irregular cracks are often formed through the dead tissue. Frequently many of these small cracks run together, forming a long irregular slit through the leaf. Similar marks are formed on the tender shoots, though they are not so noticeable. When the fruit is attacked the disease is sometimes called bird's-eye rot. Circular spots are formed on the surface of the berry. The spots may be of different colors and usually have a dark border; as the spots enlarge and eat in, a seed is often exposed in the center. In rotting the tissue becomes hard and wrinkled. Sometimes the disease girdles the stem of a fruit cluster, cutting off the supply of sap from the grapes beyond the diseased line and causing them to shrivel and die.

Anthracnose does not spread as rapidly as some other vineyard diseases, neither does it yield as readily to treatment. When a vineyard is badly infested with anthracnose, it requires prompt attention and a careful treatment to control the disease. It is not satisfactorily controlled by bordeaux mixture alone. It is suggested that in addition to such treatment with this mixture as is given for black-rot the plan be followed which is advocated by certain European authorities, of applying a warm saturated solution of copperas (iron sulphate) in spring when the buds are swelling but before they begin to open. One per ct. or more of sulphuric acid may be added to the solution before it is applied. This solution must be handled with care as it is very caustic. It is applied with swabs or if the acid is not used it may be sprayed. It is essential that the work be done thoroughly, covering all the surface of the canes.

Yellow Leaf
Chlorosis or yellow leaf.―The name is applied to a grape disease in which the foliage turns yellow, later becoming brown. It is common in several parts of the State but more particularly in the Central Lakes district. Chlorosis is more likely to appear in wet seasons. Some varieties, as the Diamond, are much more susceptible than others. In some seasons portions of the leaves may become yellow but eventually regain their normal color so that at the close of the season the vine appears to be in a healthy condition. In other instances the yellow color extends over the entire leaf; brown, dead patches appear; the leaf curls and eventually drops from the vine. If the vine loses its leaves two or three seasons in succession it is likely to die. One striking peculiarity of the disease is the fact that a badly diseased vine may appear by the side of a perfectly healthy vine of the same variety.

The cause of chlorosis, as given by foreign investigators, is the presence of a large amount of lime in the soil which prevents the roots from taking up an amount of iron sufficient for satisfactory growth. Their experiments seem to show that the difficulty may be overcome by applying a small amount of sulphate of iron around affected plants. But since there are a number of good American varieties that are not subject to chlorosis, perhaps the better method to pursue is to plant only such varieties as are known to be free from this trouble.

The standard varieties given in the following list are, so far as we know, practically exempt from chlorosis: Moore Early, Concord, Winchell, Delaware, Worden, Niagara, Catawba, Vergennes and Agawam.

Fidia Beetle
The grape-vine fidia (Fidia viticida Walsh) is a robust beetle, a quarter of an inch in length, brown in color but whitened by a thick covering of yellowish-white hairs. The beetle lays its eggs in the cracks and crevices of the bark of the grape vines well above ground. The eggs are produced in large numbers, often as many as several hundred to the vine. Upon hatching, the larvae quickly worm their way into the ground and begin to feed upon the fibrous roots of the vine, passing from these to the larger roots.  Possibly the chief damage is done on the larger roots which are often entirely stripped of bark for a length of several feet. The larvae attain their full size, a half inch in length, by the middle of August, and then hibernate until the following June. The winter is spent in earthen cells. After about two weeks as pupae in June, the full grown beetles emerge from the ground and begin to feed upon the upper surface of the leaves, eating out the cellular tissue, thus skeletonizing the foliage. The adults disappear the succeeding August. The most efficient means of checking the fidia so far found is an application of an arsenical spray* applied during the time the beetles are feeding on the foliage.


Flea Beetle
Grape-vine flea-beetle (Haltica chalybea Ill.).―The adult insects are shining steel-blue flea-beetles measuring about one-fifth of an inch in length. They live during the winter under the bark of the old vines or in rubbish in the fields. They emerge from their winter quarters during the first warm days of spring, and feed upon the opening buds and young leaves. Egg-laying begins late in April or early in May. The eggs are placed singly near the buds or upon the leaves and hatch in about ten days. The young larvae are dark brown in color but soon become prominently marked with black dots and patches. They are full grown in from three to four weeks at which time they measure about a quarter of an inch in length. They feed on the leaves devouring only the soft parts at first, but finally eating irregular holes through the leaves. When ready to pupate they go a short distance into the ground. The adults emerge during the latter part of June or early in July. They probably feed during all of the summer, finally seeking shelter for the winter as above indicated.

The vines should be sprayed with paris green*, one pound to fifty gallons of water, just before the buds begin to swell or with some other arsenite.  Much pains should be taken to make this application thorough. Later when the worms appear on the leaves, paris green may be applied at the usual strength, one pound to 150 gallons of lime and water, or combined with bordeaux mixture. Both upper and under surfaces of the leaves should be covered. Applications of arsenicals for the grape-vine fidia will help greatly to keep this insect in check.
     *[This information is provided ONLY for historical accuracy. Please do not spray arsenic in any form on your garden, vineyard or orchard! Paris Green and other arsenicals are deadly toxins, stay in the soil basically forever and have been completely abandoned by farmers, (but not the turf-chemical industry- check the label of your crabgrass killer. If you see anything like "cacodylate" in the ingredients, this is arsenic! Leave it on the shelf! It should be illegal. -ASC]

Leafhopper
Grape leaf-hopper (Typhlocyba comes Say).― There are several species of leaf-hoppers which attack the grape but this species is probably the most common in this State. These little leaf-hoppers are often erroneously called thrips. The adult insects measure about one-eighth of an inch in length. They vary greatly in color but the prevailing color is usually light yellowish-green. The back and wings are ornamented with bright red, yellow and brown. They are found upon the vines from spring until fall. They feed together, sucking the sap from the leaves, principally from the under surface, causing them to turn brown in patches. The eggs are deposited singly in the tissue of the under surface of the leaves. The young resemble the adults in form but are not provided with wings and are green or yellowish-green in color. There are several broods during the season. Some of the adults of the last brood hibernate in any convenient rubbish about the vineyard. Treatment for young hoppers should be made early in July. To obtain the best results use whale-oil soap** at the rate of one pound to ten gallons of water, directing the spraying with the hand. Vineyards and adjacent land should be kept as free as possible from grass and weeds as they afford shelter to the insect.
   [**Modern soap-sprays are more effective and don't require whaling. -ASC]

Berry Moth
Grape berry moth (Polychrosis viteana Clem.).―The young caterpillars feed within the grapes finally causing them to turn dark colored and to wither. This injury is sometimes mistaken for the black-rot, downy mildew, or "brown-rot," powdery mildew, and anthracnose, or "bird's-eye rot" black-rot. After devouring the soft parts of one grape the caterpillar goes to another, fastening the two together by a silken thread. This may be continued until several in a bunch have been destroyed by one caterpillar. The young caterpillars are very light green in color with a brown head. When full grown they measure about one-fourth of an inch in length and are dark olive green in color tinged slightly with red. The cocoon is formed on a leaf and is partially composed of two small pieces cut out of the leaf. The adults of the spring brood emerge in from twelve to fourteen days. The fore-wings have a bluish tinge and are marked with brown, while the posterior wings are dull brown. The moths are small measuring nearly half an inch from tip to tip when the wings are spread. The eggs are probably laid late in June or early in July. There are two broods annually in, this State. As the caterpillars spend most of their lives within the grape berries, spraying does not entirely control the pest. Yet the arsenicals applied for the grape-vine fidia will help much in keeping it in check. Picking and destroying the infested fruit and the leaves containing the cocoons helps much.