The New International Encyclopædia/Tobacco Pests
TOBACCO PESTS. The tobacco flea-beetle (Epitrix parvula) is generally distributed throughout the United States. It is a minute, oval, reddish-brown species occurring upon many solanaceous plants, which makes its appearance in July, attacking the tobacco leaves, which soon present a spotted appearance. Afterwards these spots become holes and the leaf is practically destroyed. In the larval state the insect feeds upon the roots. The small holes eaten by the beetles become the entrance points of bacteria, which start a leaf-disease which may be more injurious to the plant than the actual work of the beetles.The so-called horn-worms, or ‘horn-blowers,’ of tobacco are the larvæ of two sphingid moths (Protoparce carolina and Phlegethontius celeus), large green caterpillars with oblique white stripes on the sides of the body, and the anal end of the body armed with a horn. These larvæ live upon tobacco leaves, transform to pupæ under the ground, and the moths issue in May or June.The eggs are laid singly on the under side of the tobacco leaf just at nightfall. There are two generations each summer in a large part of the tobacco-growing region. Two insects, both larvæ of noctuid moths, are known as ‘bud-worms’ in tobacco fields. They are Heliothis armiger (also known as ‘boll-worm’ (q.v.), corn-ear worm, and tomato fruit-worm), which preferably lives in the ears of corn until the grain becomes hard, and therefore works in tobacco usually only toward the end of the season, and Heliothis rhexiæ. The latter is the true bud-worm. (See Colored Plate of American Moths.) The adult is a small greenish moth, and the larva is found in the bud of the plant about the time it is ready to top. They transform to pupæ under the surface of the ground. A true bug (Dicyphus minimus) damages the second crop in late tobacco by puncturing the leaves and sucking the cell sap. Infested leaves become yellowish in color, somewhat wilted, and the older ones eventually split in places, becoming ragged. The bug, when immature, lives on the under side of the leaves, but the adults live both above and below. The eggs are deposited singly in the tissues of the leaf and hatch after four days. One entire generation is produced in fifteen days. Several other sucking bugs puncture tobacco leaves, but are not serious enemies of the crop, except, perhaps, the ‘green bug’ (Euschistus variolarius).
The tobacco leaf-miner, or ‘split worm’ (Phthorimæa operculella) hatches from eggs laid upon the leaves by a minute grayish moth, and bores between the surfaces of the leaf, making a flat mine often of considerable size. This insect is a cosmopolitan species and works upon potatoes as well as upon tobacco, boring into the tubers as well as the leaves. Several species of cutworms (q.v.) damage the tobacco plant early in the season. A mealywing (q.v.) (Aleyrodes tabaci) damages the leaves of tobacco in Europe and in the Southern United States. The common mealy-bug (Dactylopius citri) affects the plant, as also do several species of plant-lice. The tobacco thrips (Thrips tabaci) is an important enemy of tobacco in Bessarabia. It occurs upon many plants in the United States, especially upon onions, but has not been found upon tobacco.
Most of the insects mentioned may be destroyed by spraying the plants with an arsenical mixture. Nearly all of them feed upon solanaceous plants, and an excellent remedial measure is to allow a few weeds of this family, such as Solanum nigrum or Datura stramonium, to grow in the immediate vicinity of the field which is to be planted in tobacco. These weeds will act as traps for nearly all of the early tobacco insects, and they can be treated with heavy doses of Paris green for the leaf-feeding species, and with a spray of kerosene emulsion and water for the sucking bugs. Large numbers of these insects can be killed in this way, greatly to the protection of the young tobacco plants when they are set out.
Dried tobacco is attacked and frequently ruined, even after having been made up into cigars and cigarettes, by the so-called cigarette beetle (Lasioderma serricorne), an insect which works not only in tobacco, but in many other dried herbs as well as certain dried foods. It is a cosmopolitan species, and multiplies rapidly throughout the greater part of the year, feeding both as larvae and as adults. The ‘drug-store beetle’ (Sitodrepa panicea) and the common rice weevil (Calandra oryza) also feed upon dried tobacco. These insects are destroyed by fumigating the rooms or the establishments in which they occur with bisulphid of carbon or hydrocyanic acid gas.
All of the species above mentioned occur in the United States, although several of them are cosmopolitan. In Europe 144 species are recorded as occurring in tobacco fields. The most important of these, among the species which do not occur in America, is a tenebrionid beetle (Opatrum intermedium), which injures the plant by attacking the stems under ground. Consult Howard, The Principal Insects Affecting the Tobacco Plant (Washington, 1900).
a, tobacco flea-beetle (Epitrix parvula), greatly enlarged; b, leaves, as damaged by this flea-beetle; c, green bug (Euschistus variolarius).
a, moth of the true budworm (Heliothis rhexiæ); b, caterpillar of same; c, buds injured by false budworm (Heliothis armiger).