Insects That Attack Tobacco

D. J. Caffrey.

Tobacco is subject to damage by several species of insects from the time the seedlings develop in the plant bed until the crop is harvested, during the time it is in storage, and after the manufactured products have been prepared and offered for sale.

The insects that attack the seedling tobacco or the growing crop include hornworms, flea beetles, aphids, cutworms, green June beetle larvae, tobacco budworms, and wireworms.

Others, less widely distributed, are webworms, thrips, grasshoppers, mole crickets, vegetable weevils, midge larvae, slugs, and suckflies.

The cigarette beetle commonly infests practically all types of tobacco in storage. Stored tobacco of the flue-cured domestic and imported Turkish types used in making cigarettes is also menaced by the tobacco moth. All kinds of tobacco products cigars, cigarettes, smoking and chewing tobacco, and snuff may be mutilated and contaminated by the cigarette beetle.

Despite many years of research and the development of fairly good remedies, insects continue to cause impressive losses an estimated loss of 100 million dollars annually to the growing crop and 5 million to 10 million dollars to the stored and manufactured product in recent years. One appreciates the losses when he remembers that tobacco has been a commercial crop in the United States since 1612, it had a farm value of more than 1 billion dollars in 1950, and in that year was grown on 1,593,900 acres through the Southern, Central, and Eastern States.

In plant beds the tobacco seedlings are attacked commonly by flea beetles, larvae of the green June beetle, and aphids; more rarely, by cutworms, mole crickets, black European slugs, vegetable weevils, grasshoppers, and the larvae of midges.

Tobacco moth. A, Larva; B, pupa; C, adult; D, eggs.

Flea beetles (principally the tobacco flea beetle and the potato flea beetle) are serious pests of seedling tobacco in many districts. Their depredations often lead to the total destruction of the young crop. A way to combat them is to construct the plant beds with tight side walls and a tight cloth cover, which keeps out the flea beetle adults. If that is not enough, dusts or sprays containing DDT, cryolite, or rotenone are effective.

The larvae of green June beetles cause damage in plant beds by burrowing in the soil, uprooting the small seedlings, or covering them with soil. The burrowing also causes an excessive aeration of the topsoil, which often leads to the drying out and death of the seedlings. The pest can be controlled by the use of a poison bait, consisting of parathion, or barium, sodium, or potassium fluosilicate mixed with wheat middlings and scattered on the plant bed. Equally effective results are had by applying a dust mixture or a drench containing parathion (or a dust mixture containing lindane) to the plant-bed surface. Ordinary gasoline may also be effective against the larvae when it is applied to the plant-bed soil through holes large and deep enough to enable the level of the gasoline poured into each hole to remain at least 2 inches below the soil surface. This procedure keeps the gasoline away from the roots of the small tobacco plants, which it would injure. After the gasoline has been applied the holes are plugged with lumps of moist soil.

In many districts aphids ( principally the green peach aphid) have become a major pest of tobacco. Some infestations start in the plant bed and, if they are not controlled, may be carried on the seedlings to the fields in which they are transplanted. The plants in the plant bed therefore should be inspected frequently to determine if aphids are present. A dust mixture containing parathion will control them. Because aphid infestation in the plant bed may originate from certain weeds and such cultivated crops as collards, broccoli, or turnips, it is important during the early stages of the tobacco crop to remove weeds from the plant bed and its vicinity and locate the plant bed at some distance from cultivated crops infested with aphids.

Several species of cutworms may do extensive damage to plant beds in a short time. Some species overwinter in the soil as larvae. When temperatures are favorable they feed voraciously on the small plants. Even plant beds that are sterilized by burning or steaming should be examined carefully for cutworm damage. If the damage continues, a bait containing paris green or sodium fluosilicate in wheat bran should be applied evenly over the bed. Baits containing toxaphene or chlordane and dust mixtures containing DDT applied to the surface also have given good results.

In the South, mole crickets often cause serious losses by uprooting and covering the seedlings with soil. The bait of paris green or sodium fluosilicate in bran or a spray containing parathion will get rid of them.

The black European slug frequently invades tobacco plant beds. It devours the seedlings, particularly along the margins of the bed. It can be controlled by hydrated lime or air-slaked lime applied just inside the plant-bed walls. A poisoned bait containing metaldehyde or a dust mixture containing parathion, applied to the surface of the bed, also is good.

The vegetable weevil feeds in both the adult and larval forms on seedlings. Dusts containing DDT or lead arsenate control the pests and prevent their spread through fields when the seedlings are transplanted.

Several species of grasshoppers and midge larvae (Tendipedidae) sometimes infest the plant beds. The grasshoppers can be controlled by the bait mentioned for cutworms or mole crickets or by a dust containing toxaphene applied to the plant-bed surface. Midge larvae sometimes are abundant enough to cause damage by burrowing and aerating the soil so that the plants dry out. DDT, applied to the soil surface as a dust, is a good remedy.

NEWLY SET TOBACCO plants are often damaged severely by flea beetles, cutworms, wireworms, aphids, and (less commonly) by webworms.

Flea beetles often are particularly destructive during the wilting stage, before the plants are established in their new environment. Much damage can be avoided by making applications of dust mixtures or sprays containing DDT or cryolite to the plants before they are taken from the plant bed. The beneficial results of those insecticides usually last 7 to 10 days and their use then makes it unnecessary to apply special insecticides later. But if one has to fight the beetles on the newly set plants in the field, dust mixtures containing DDT or cryolite can be used to advantage. All surplus plants in the beds should be destroyed as soon as transplanting has been completed in order to eliminate them as a source of breeding and food material for flea beetles, which may be in nearby tobacco fields; The surplus plants can be destroyed by plowing or harrowing the plant beds thoroughly.

Several species of cutworms attack newly set tobacco plants. The most effective insurance against them is to apply a poisoned bran bait containing paris green or sodium fluosilicate before the plants are set in the field. As many cutworms are active at night, broadcasting the bait over the field in the late afternoon has given best results. Even with this precaution, damage after plants are set sometimes occurs in spots in the field. That problem can be solved by scattering a small amount of the bait next to the plants in the affected parts of the field but in doing so one has to be careful to put the least possible amount of the poisoned bran on the plants because any bait that lodges on the tobacco leaves may cause injury.

Several species of wireworms have been considered among the most important pests of newly set tobacco plants. Chlordane or parathion, mixed in small amounts with the water used during transplanting, are effective against them. Ample transplanting water should be used in order to insure a good distribution of the insecticide ingredients in the soil immediately surrounding the transplants. Large, stocky transplants should be used because they suffer less damage than smaller plants do.

Aphids, which ordinarily do not seriously damage tobacco in the transplanting stage, can be reduced by applying a dust mixture containing either parathion or tetraethyl pyrophosphate immediately before the plants are pulled for transplanting. Such applications usually protect the plants from aphids while they are being set and are becoming established in the field.

Sod webworms, sometimes known as tobacco crambids, feed on the roots and bases of the newly set plants. An efficient remedy consists of a bait containing paris green, oil of mirbane ( nitrobenzene), and cornmeal, applied to the plants immediately after transplanting or as soon as damage is noticed in the fields.