The Raisin Industry / A practical treatise on the raisin grapes, their history, culture and curing

by Gustavus A. Eisen

—The caterpillars which trouble the raisin grapes are confined to three or four kinds. The most common and also the most destructive are the very large larvæ of the sphinx moth. The common grapevine sphinx (Philampelus achæmon) is a large larva, incorrectly called a worm, which is, when full grown, over three inches long. The color varies from bluish green to brown, with several lighter stripes on each side. The head is truncate, and the tail is furnished with a curved horn. The pupa hibernates in the soil below the vines, and is about half the size of the full-grown caterpillar. The full-grown moth is about two inches long by two and one-half inches between the outstretched wings. The eggs are laid by the moths on the leaves of the vines. Two broods of caterpillars appear yearly under favorable conditions, or else only one brood, which generally appears in the end of July. The caterpillars grow with great rapidity, and attain their full size in a few weeks. The pupæ hibernate in the soil and hatch the following summer.

Another large grapevine caterpillar is the Deilephila striata, which is about the same size as the Achæmon. The moth has more pointed wings, with narrow stripes, and the larva is brighter colored, often yellowish green, with several colored stripes on the sides. The eggs are not laid on the vines, but on the weeds on the vacant lands outside the vineyard, especially on species of Epilobium, but also on other weeds, and they hatch and feed on them. The caterpillars feed in ordinary years only on the weeds on which they are bred, but in other years which are especially favorable to their enormous increase they migrate to the vineyards and feed on the vines at the most alarming rate. The caterpillars of both the above large moths vary in color from green to brown or violet brown, but as a rule the Deilephila is more brightly colored than the Achæmon. The former is more active and often travels in enormous numbers, when it is called the army-worm. The Achæmon is more blunt at both extremities, the head being almost truncate.

Vineyard Scene, Rosedale Colony, Kern County, July, 1890.—Three Months After Planting.

Army-worms are smaller caterpillars, about one inch or more in length, which breed on the outside weeds, and which, when feed becomes scarce, migrate to the vineyards and feed on the vines. These caterpillars are the larvæ of smaller moths of various genera such as Prodenia and others.

Cutworms are other caterpillars of moths of the genus Agrotis, which feed on the branches of the vines, especially in the night-time, and in the daytime bury themselves in the soil beneath the vine. They are generally a gray or leathery color, while the army-worms are more violet and darker.

Damages.

—The damages from these various caterpillars are sometimes very large. Some years they occur in enormous quantities, and hundreds of tons of them may then be picked from a vineyard of a hundred acres of vines. The leaves are eaten by them, and the grapes are either scalded by the sun or do not attain their sweetness and coloring. Sometimes these various caterpillars are very common and destructive for one or two years in succession, after which they disappear and do not return to trouble the vines again for many years.

Remedies.

—The great caterpillars, after they have once infested the vineyard, can be destroyed by picking. A gang of men or boys should be furnished with buckets, which are besmeared on the inside with coal-oil. The caterpillars are picked and dropped in the buckets, from which they cannot crawl out, and when the buckets are half filled they may be emptied into trenches and covered up with soil.