Mullein Moth
Cucullia verbasci
A moth whose boldly marked caterpillars feed openly on mullein (Verbascum) and related plants, stripping the leaves and flower spikes. The drab adult is easy to overlook, but the conspicuous black-and-yellow caterpillars can defoliate a plant in days. It is a common pest in Britain and Europe.
🔎 How to spot it
The caterpillar is one of the most distinctive going, nearly two inches (up to about 50 mm) long, with a pale bluish-gray to whitish body boldly patterned with black and bright yellow spots, and it feeds out in the open by day and night. The adult is a cryptic moth with a forewing up to about 24 mm, subtly shaded in light and dark brown with a scalloped wing edge and a small tuft above the head, looking much like a sliver of wood or bark.
🥀 Damage it causes
The caterpillars feed gregariously and conspicuously, demolishing the foliage and chewing into the flower spikes; a bad infestation can strip a plant of its leaves and ruin the bloom from late spring into midsummer. The plant is rarely killed and an established perennial mullein usually recovers, but the display for the season is lost.
🛡️ Prevent it
Because this is a beloved garden caterpillar and harmless to people, many gardeners simply tolerate it for its wildlife value and grow enough mullein to share. Where the planting must be protected, check the plants regularly through late spring and pick the caterpillars off by hand, which is easy since they feed in the open.
🧯 If it is already here
Hand-picking is the recommended control, and chemical sprays are generally discouraged on a pest that is so easy to remove and that supports garden biodiversity. If you want the caterpillars elsewhere, move them to a wild mullein, figwort, or buddleia rather than killing them.
💡 Good to know
There is one generation a year: adults fly in spring, around April to June, eggs are laid from May into July and hatch in about ten days, and the caterpillars are fully grown in roughly thirty days before dropping to pupate in the soil in a very tough cocoon from which the moth may not emerge for several years. Besides mullein the caterpillars also feed on figwort and buddleia.
For educational and informational purposes only. Pest control advice is general guidance drawn from university cooperative extension sources; always identify a pest positively and read and follow the label on any product before use, especially around food crops, children, and pets.