The larvae of "Pieris rapae" are a common caterpillar pest in horseradish gardens. They are called cabbageworms. The adults are white butterflies with black spots on the forewings. They are seen flying around the plants during the day. The caterpillars are green with faint yellow stripes running lengthwise down the back and sides. Full grown caterpillars are about in length. They move slowly when poked. They overwinter in green pupal cases. Adults start appearing in gardens after the last frost and are a problem through the remainder of the growing season. There are three to five overlapping generations a year. Mature caterpillars chew large, ragged holes in the leaves leaving the large veins intact. Handpicking is effective for control.