From the time tomato plants are set in the field until the fruit has ripened they are subject to the attacks of insects which frequently cause serious injury. On the whole, however, the tomato is not so susceptible to damage as are some related crops—such as the potato.
Cutworms.—Of insects most to be feared and of those which attack the plants when they are first set out are cutworms of various species. The grower is as a rule quite too familiar with these insects, and no description of their methods is necessary, beyond the statement that they cut off and destroy more than they eat and re-setting is frequently necessary. The best remedy is a poisoned bait, prepared by dipping bunches of clover, weeds, or other vegetation in a solution of Paris green or other arsenical, 1 pound to 100 gallons of water. These baits are distributed in small lots over the ground before the plants are set, the precaution being observed that the land is free for two or three weeks from any form of vegetation. This will force the hungry "worms" to feed on the baits, to their prompt destruction. A bran-mash is also used instead of weeds or clover, and is prepared by combining one part by weight of arsenic, one of sugar, and six of sweetened bran, with enough water added to make a mash. The baits are renewed if they become too dry, or they can be kept moist by placing them under shingles or pieces of board.
FIG. 35—CUTWORM AND PARENT MOTH (Feltia subgothica)
(From Chittenden, U. S. Department of Agriculture)
Flea-beetles attack the plants soon after they are set, and their injuries can be prevented by dipping the young plants before setting in a solution of arsenate of lead, about 1 pound to 50 gallons of water, or Paris green, 1 pound to 100 gallons. If this precaution has not been observed a spray of either of these arsenicals used in the proportion specified will suffice, repeating if the insects continue on the plants. In the preparation of the spray a pound of fresh lime to each pound of the arsenical should be added; or, better yet, Bordeaux mixture should be employed as a diluent instead of water. This mixture has some insecticidal value, is a most valuable fungicide, and is also a powerful deterrent of flea-beetle attack, acting to a less degree against other insects which are apt to be found on the tomato. In applying any spray a sprayer costing not less than $7 is a positive necessity.
FIG. 36—FLEA-BEETLE
Does great injury to young plants. Much enlarged. Actual size shown by line at right. (From Chittenden)
FIG. 37—MARGINED BLISTER BEETLE
The Colorado potato beetle, or "potato bug," sometimes injures tomatoes, but not as a rule when potatoes are available. This suggests the use of potatoes as a trap crop, planted in about three rows completely around the field of tomatoes. The arsenicals used in the same proportion as for flea-beetles will destroy the potato beetle. It is necessary to keep the trap potatoes well sprayed to prevent them from breeding on these plants and migrating to the tomatoes. Potato beetles can also be controlled by jarring them from the affected plants into large pans containing a little water on which a thin scum of kerosene is floating.