Many use small scissors, with which the caterpillars are cut in twain while sitting on the vines. This will do for wine grapes, which are grown higher above the ground, but will hardly be proper on the low Muscat vines, as the contents of the caterpillars are apt to soil the grapes.
I have used Buhach sprays with great success. Ten pounds of Buhach, with a hundred gallons of water, brought the caterpillars down from the vines in forty-five minutes after spraying. As some, however, recovered, it is best to kill as many as possible of those which fall to the ground by punching them with a stick. The cost of Buhach is, however, great, and the difficulty of encountering favorable weather is such that this remedy is not apt to be extensively used.
When the vineyards are threatened by the invasion of the army-worms, or by the striped Deilephila caterpillar, the best remedy consists in trenching. A narrow trench, say one foot or more wide and two feet deep, with perpendicular sides, should immediately be dug around the vineyard. If water is at hand, fill the trench with water, on which some coal-oil may be poured,—enough to cause a film on the surface. If no water can be had, a log or scantling may be continually dragged up and down the furrow or trench, so as to crush the caterpillars before they can crawl out. In many places, however, the trench alone will do the work, as the caterpillars will generally not be able to get up the other side of the trench. What few crawl up can easily be kept down by hand-picking.
If certain attractive flowers, such as honey-suckles or petunias, are planted on a small bed in the vineyard, say near the house, the moths will come to them to feed from all the surrounding neighborhood. Only one small bed should be planted on every vineyard. A boy with a butterfly net, posted at each flower bed at sundown, can catch hundreds of moths every evening, and considerably reduce their number and prevent them from breeding.
BLACK-KNOT.
Characteristics.
—The woody or spongy excrescences which appear on the vines, and which are known as black-knots, are really only a wart-like growth, the origin of which is entirely unknown. It is supposed that an insufficient outlet for the sap in the spring caused by too close pruning is the chief cause. Certainly closely pruned vines are more subject to the black-knot than long pruned vines, but on the other hand neglected vines which have had no cultivation, and which accordingly could hardly have had too rapid a flow of sap, suffer more than any others. The woody warts appear quite frequently on the ends of the spurs of the old wood, or on places of last year’s growth which have been wounded or injured in some way, but never on the green wood. They vary in size from that of a pea to that of lumps weighing several pounds. When present in small quantities, the warts cause no injury, but when they become larger the vines may even die. These black-knots always die with the year, and never survive to the next season. At the end of the season, they burst open and then often display black spores of fungi, which, however, are only parasitical growths on the already decayed wood, and not the cause of the disease. As I said, it is generally supposed that the flow of sap is during spring time so great that it ruptures the cells of the vine and causes the warts to form. Under the microscope, however, there are no such ruptured cells visible. It is more natural to suppose, that through the accumulation of sap an irritating poison is originated, which causes the warty growth to form in a manner similar to the formation of galls. On sandy soil the black-knot is the most common, probably on account of the earliness and the natural warmth of this kind of soil.
Remedies.
—So far no decidedly successful remedy has been found. Some growers advise leaving plenty of spurs on the vine, so as to give a sufficient outlet to the sap, but it remains to be seen if this will mitigate the evil. If the black-knot should be very destructive, a cutting out of the same in summer time while they are forming would be beneficial. This could best be done in June and July. Mixtures of coal-oil and lime, etc., have been used during the winter after the vines were already pruned, but, as the black-knot is then already dead, no advantages can result from this remedy.