Life Cycle
The rate of development of larvae is temperature dependent. There are 4 larval stages (instars). Caterpillars are active, slender, green worms with microscopic hairs. The larval period varies from 6 to 30 days. On young cabbage and on watercress, early larval instars migrate to the growing point and cause extensive feeding injury. The damage caused by the larvae feeding is often very severe and in most areas good quality cabbages cannot be grown unless the insect is controlled. Adults are small, grayish moths, approximately 1/3 inch in length. When the wings are folded, the moths have a line of three diamond-shaped markings that occur along the middle of the back. Males and females are the same size.
Females live from 7 to 47 days and males live from 3 to 58 days. The number of eggs laid per female may range from 18 to 356. Oviposition normally begins on the day of emergence lasting about 10 days. The number of eggs produced by a single female is influenced by photoperiod, temperature, and age or condition of larval food.
