BIOLOGY: Mature larvae are small, green caterpillars with three dark stripes running the length of the body. The caterpillars are about 10 mm (approximately 3/8 inch) long and will wriggle vigorously when probed or otherwise stimulated. Adults are small (17mm or 2/3 inch), brownish moths. Overwintering adults lay eggs on the plants in early spring. Larvae emerge in early May, feed through July, pupate and emerge as adults in late summer.
DESTRUCTIVE STAGE: Larvae (leaf feeding)
IMPACT TO HOST: Larvae attack poison hemlock by rolling leaves and feeding on foliage, flowers, and buds.
REDISTRIBUTION: Larvae can be collected in late June and early July using picking leaf rolls off of plants. A typical release is 250 adults.
BACKGROUND: Poison hemlock is a European native, growing 6 to 10 feet tall. It is commonly found along waterways, roadsides, and field edges and tolerates poorly drained soils. It has been mistaken for parsley and wild carrot. All parts of the plant are toxic.
OTHER COMMON NAMES:
DESCRIPTION: This biennial has a large taproot. The stems have purple spots, especially at the bases. Leaves are finely divided, having a fern like appearance. Leaf stems clasp the main stem. The tiny flowers are in umbrella-shaped clusters on the ends of individual stalks. Bloom is late spring into early summer.
CONTROL: Biocontrol is available and offers fair to good control. Herbicides can offer excellent control when applied to actively growing plants between rosette and bloom stages.
