The moth has a small, slender, grayish-brown body with folded wings. The wings of the male form three yellow diamond-shaped spots where they meet. Larvae feed on all plant parts, but prefer to feed around the bud of young plants. The young larvae mine between the upper and lower leaf surfaces. Look for young larvae emerging from small holes in the underside of the leaf.
Older larvae create irregular shot holes while leaving the upper surface intact.
Larvae often drop from the plant on silk threads as soon as the leaf is disturbed. Monitoring should begin when the plants are young. During cupping, larvae that feed on heart leaves are difficult to find unless the outer leaves are pulled back. Heart leaves of preheading plants should be examined if feeding damage is present. Their feeding on the bud may cause malformation of the cabbage head.