Zebra Caterpillar

Melanchra picta

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Hosts

• Field-grown hemp
• Many vegetables, flowers, grains
• Some trees

Description

Recently-hatched larvae are whitish in color with black spots. As they grow, they develop longitudinal black and cream stripes and black and cream stripes running the length of the body. The head and legs are brown to orange in color. The adult moth has a chestnut or reddish-brown color and the hind wings are whitish with light brown edges. The abdomen is light gray. 

Life Cycle

Egg | Larva | Pupa | Adult

• 2-3 generations per growing season starting in May and mid-summer.
• Adults lay masses of up to 100 eggs on foliage.
• Young larvae feed gregariously and then disperse on the plant or to new plants.
• Mature larvae drop from the plant and pupate in the soil.
• Overwinter as pupae in soil.

Damage Symptoms

Young larvae feed gregariously, causing skeletonized foliage. They disperse around the plant and to other plants as they age. 

Time for Concern

Late spring until the end of the growing season.

When and Where to Scout

• Scout for egg clusters on or under leaves and for groups of young larvae starting in June.
• Look for symptoms of foliar damage. Most damage is likely to occur in mid-to-late summer.

Threat Level

Low. Foliage damage on hemp is limited and is not expected to affect yield.

Occurrence in Utah

This insect occurs in Utah, but has not been identified as a pest in Utah hemp, It has been seen damaging hemp in neighboring states.

Management

• Natural enemies typically keep populations below damaging levels.
• Insecticide treatment is not usually required.
• Remove weeds and other plant debris surrounding hemp.
• Hand-pick and destroy larvae.

Time for Concern: Late spring until the end of the growing season.

When to Consider Treatment

If chronic infestation has been experienced, or if large population sizes are consistently present.

Look-alikes

None.

Photo Credits

• Whitney Cranshaw, Colorado State University, Bugwood.org

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