cabbage leaves and heads hatch from eggs laid by the common white butterfly (Fig. 295). There are several broods every season. If plants are not heading, spray with kerosene emulsion or with Paris green to which the sticker has been added. If heading, apply hellebore.
The cabbage aphides, small mealy plant-lice, are especially troublesome during cool, dry seasons when their natural enemies are less active. Before the plants begin to head, spray with kerosene emulsion diluted with 6 parts of water, or whale-oil soap, 1 lb. in 6 gal. of water.
The white maggots that feed on the roots hatch from eggs laid near the plant at the surface of the ground by a small fly somewhat resembling the common house fly. Hollow out the earth slightly around every plant and freely apply carbolic acid emulsion diluted with 30 parts of water. Begin the treatment early, a day or two after the plants are up or the next day after they are set out. Repeat the application every 7 to 10 days until the latter part of May. It has also been found to be practicable to protect the plants by the use of tightly fitting cards cut from tarred paper. (See page 187.)