Part 19 (1/2)
[Ill.u.s.tration: FIG. 39. Injuries caused by beetles of the grape root-worm.]
Two methods of control have been devised: destruction of the beetles before they lay their eggs; and destruction of the pupae while in the ground. When the beetles are present in large numbers, many of them may be destroyed by spraying with a mixture of cheap mola.s.ses and a.r.s.enate of lead, using mola.s.ses at the rate of two gallons to a hundred gallons of water and the a.r.s.enate of lead at the rate of six pounds. This should be followed by a second spraying a week later, using bordeaux mixture (4-4-50) and three pounds of a.r.s.enate of lead.
This second spray serves to repel migrating beetles from the vines.
The mola.s.ses spray is ineffective unless several days of fair weather follow the spraying, as rain washes the material from the foliage.
Bordeaux mixture is not easily affected by rain. In moderately infested vineyards, bordeaux mixture and a.r.s.enate are used instead of mola.s.ses and a.r.s.enate of lead, followed in about ten days with a second application of the same material.
An effective method of reducing the number of beetles is the destruction of the pupae. This is best done by leaving a low ridge of earth under the vines at the last seasonal cultivation to remain until most of the larvae have pupated, and then be leveled with a horse-hoe and later with a harrow. The horse-hoe and harrow crush many of the pupae and break the cells of others to the great destruction of the pest. This latter method of control is not adequate in itself and in bad infestations both should be used. When the infestation is only moderate, this latter method is not advised, owing to the lateness of the time of horse-hoeing. It is good horticultural practice to horse-hoe the latter part of May or early June. To wait for the pupal stage of the root-worm delays the work until numerous small roots start which would be destroyed by the horse-hoe. Spraying will control a moderate infestation.
_The grape-vine flea-beetle._
In the warm days of May and June when the buds of grapes are swelling, a s.h.i.+ning steel-blue beetle may often be found in the vineyards of eastern America feeding on the tender buds of the grape. From its color the insect is often called the steely-beetle, and from its activity and habit of jumping it is known as the flea-beetle (_Haltica chalybea_). The vine is seldom seriously injured by this pest but many buds are destroyed, causing the loss of the fruit that should have developed from the buds. It is true that new buds often develop after the injury, but these, as a rule, produce only foliage.
[Ill.u.s.tration: FIG. 40. Eggs of grape-vine flea-beetle.]
The life history of the flea-beetle is such that the pest is not hard to control, the chief steps in its development being as follows: The beetles deposit small orange-colored eggs, cylindrical in form, ill.u.s.trated in Fig. 40, about the buds and in crevices of the bark of the canes in May or June. Most of these eggs are hatched by the middle of June. The larvae feed upon the foliage until about July first and then crawl to the ground in which they form cells and pupate. The latter part of July the adults emerge and seek wild vines upon which they feed, entering hibernation rather early in the fall. The beetles hibernate under leaves, in rubbish and in the shelter of the bark of trees and vines, but emerge in the warm days the following spring to seek vineyards.
Two methods of control have been developed to keep this pest under.
The vines should be sprayed with three pounds of a.r.s.enate of lead in fifty gallons of water when the larvae are feeding on the foliage; or the beetles when feeding may be knocked into a pan containing a shallow layer of kerosene. The former is the cheaper and more effective method provided the grape-grower has the foresight to discover the larvae, since the larvae of this summer produce the beetles that will destroy the buds next spring. When the adults migrate from wild vines, or the larvae were not destroyed in the vineyard, collecting the adults is the only practical method. The destruction of wild vines near a vineyard helps to give immunity from this pest.
_The rose-chafer._
The rose-chafer (_Macrodactylus subspinosus_), a long-legged beetle of a yellowish-brown color, about a third of an inch in length, often appears in vineyards in vast swarms toward the middle of June in northern states and about two weeks earlier in southern states east of the Rocky Mountains. Often they overrun gardens, orchards, vineyards and nurseries, and usually, after having done a vast amount of damage in the month of their devastating presence, the beetles disappear as suddenly as they came. Vineyards on or near sandy soils are most often infested, the larvae of the beetle seeming to live in considerable numbers only in these light soils. The chief damage to the grape is done to the blossom; in fact the insects, after feeding on the blossoms during the blossoming period, usually migrate to blossoms of any one of several shrubs. The larvae feed on the roots of gra.s.ses, having particular liking for the roots of foxtail, timothy and blue-gra.s.s.
Some knowledge of the life history of these beetles is essential to effective control. The beetles emerge as adults in June and after feeding a short time begin to mate, although egg-laying does not take place until the insects have been out for a fortnight or more. The females burrow into the soil and deposit their eggs, seldom more than twenty-five in number, which begin to hatch in about ten days. The young larvae feed during the remainder of the summer on roots of gra.s.ses. They are seldom found deeper than six inches while feeding, but as cold weather approaches they burrow deeper to avoid sudden changes of temperature. The following spring they again come near the surface to feed. The grubs form cells from which the pupae emerge, as we have seen, about the middle of June, timing their appearance very closely to the blossoming of Concord grapes.
The methods of control are three, namely: destruction of the larvae; cultivation to kill the pupae; and spraying to kill the beetles. Since the larvae feed on the roots of gra.s.ses in sandy soils, it is easy to locate the feeding ground of the pest and plant it to cultivated crops which destroy the gra.s.ses and therefore the larvae. The second method of destruction is similar, consisting of cultivation to kill the pupae.
This is accomplished by thorough cultivation during the pupating stage to break the cells and crush the pupae, thus preventing the emergence of the beetles. The third method, however, is the most effective and consists of spraying the vineyard with a sweetened a.r.s.enical spray.
The spraying should be done as soon as the beetles appear, using a.r.s.enate of lead six pounds, mola.s.ses one gallon and water one hundred gallons. It is often necessary to make a second application a week later. If rain occurs within thirty-six hours after spraying, the application should be repeated as soon as the weather clears.
_The grape leaf-hopper._
From Canada to the Gulf and from the Atlantic to the Pacific, wherever the grape is grown, the small leaf-hopper (_Typhlocyba comes_) infests the grape in greater or less numbers, feeding on the lower surface of the leaf. Grape-growers commonly call these insects ”thrips,” a name, however, which really belongs to a very different cla.s.s of insects.
The injury done by this pest varies greatly with the season and the locality, in some regions it being comparatively harmless and in others exceedingly destructive in seasons when it occurs in abundance.
There is great variation also in individual vineyards, those near favorable hibernating places and early spring food plants often being injured seriously season after season in succession. These leaf-hoppers obtain their food by piercing the epidermis on the under side of the leaf surface and sucking the sap, and add further injury by inserting their eggs underneath the skin of the leaf. The punctures greatly decrease the starch-producing area of the leaf with the result that the vigor of the plant is lowered, and the quality of the fruit decreased.
[Ill.u.s.tration: FIG. 41. First four stages of the grape leaf-hopper.
(Enlarged.)]
[Ill.u.s.tration: FIG. 42. The fifth and the mature stages of the grape leaf-hopper. (Enlarged.)]
The life history of the leaf-hopper is very well known. The eggs are deposited in June or early July, and hatch from June 15 to July 10 in New York, the season being earlier or later as one goes south or north. The young leaf-hoppers are wingless, the nymph stage, but reach the adult stage in late July and August, at which time many of them mate, and eggs are laid from which a second brood may develop, although usually only one full brood is produced in a season in the northern states. Figures 41 and 42 show the several life stages of the leaf-hopper. Insects which become adults in the latter part of July feed on the foliage until autumn and then seek winter quarters, pa.s.sing the winter in the adult stage under fallen leaves, in dead gra.s.s or other similar protection. The hibernating place must be dry and for this reason sandy knolls are most favored by the insects. The adults emerge in the warm days of spring and then seek food first on the strawberry, then migrate to red and black raspberries or blackberries, if raspberries are not present. They remain upon these hosts until the grape leaves expand and then migrate to these to feed, lay their eggs and die.
Three methods of control are in use to prevent the ravages of the leaf-hopper: avoiding the planting of raspberries near grapes; spraying with contact insecticides; and the destruction of hibernating places. Since the leaf-hoppers feed especially on the raspberry before the leaves of the grape have expanded in the spring, avoiding planting these two plants near each other is a very effective method of control. The contact spray must touch the body of the insect and must, therefore, be applied before the nymphs develop wings. The best spray is a half pint of Black Leaf 40 to a hundred gallons of water or bordeaux mixture. It is applied to the under side of the foliage by a trailing hose or by an automatic grape leaf-hopper spray devised by F.
Z. Hartzell and described in bulletin 344 of the New York Experiment Station. The destruction of hibernating places is almost as effective a method of control as spraying. All weeds and strong-stalked gra.s.ses which die in the fall and all rubbish in the vineyard should be destroyed. It is quite worth while, also, to burn leaves and rubbish in fence rows and waste places near infested vineyards in the autumn or early winter. Cover-crops which remain green during the winter do not harbor the leaf-hoppers.
_The grape-berry moth._
This pest is widely distributed, attacking the grape wherever grown in North America. The insect feeds on all varieties but is especially destructive to grapes with tender skins and such as grow in compact bunches. Its work is detected usually in compact grape cl.u.s.ters where a number of berries are injured by a ”worm.” The ”worm” is a dark-colored caterpillar, the larva of the grape-berry moth (_Polychrosis viteana_.) There are two broods of this caterpillar, the first of which feeds on the stems and external portions of the young berries, while the second attacks the berries. The loss to the fruit-grower is of two kinds, the loss of the fruit and the marring of cl.u.s.ters which entails the cost of picking out worthless berries.