Leopard moth

Leopard moth is a magnificent native moth in the British Islands, so named due to its black and blue patterned wings. The caterpillars of this moth can rarely be found feeding on trees from the Rosaceae family.

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Leopard moth (<i>Zeuzera pyrina</i>)
Leopard moth (Zeuzera pyrina)

Quick facts

Common name Leopard moth
Scientific name Zeuzera pyrina
Plants affected  Apple (Malus), cherry (Prunus), medlar (Mespilus), pear (Pyrus), quince (Cydonia), shadbush (Amelanchier), sorbus, whitebeam (Aria), alchemilla, and many other trees and shrubs
Main symptoms Frass and particles of wood around holes made by the caterpillars on stems and branches of young trees, yellow caterpillars with black head (60 mm long) in the tunnel
Most active Summer (August – May)
Distribution Widely distributed in England, and Wales

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What is a leopard moth?

Leopard moth, a particularly beautiful moth, gets its name from the black or blue specks on its wings. This a native moth, is one of the only three species of Leopard and Goat moths (family Cossidae) that are found in the British Isles. Leopard moths have 45-65 mm wide white and translucent wings with black or blue-black spots. Their bodies are similarly coloured. Male leopard moths are considerably smaller than the females and have antennae with narrow parallel projections or divisions that resemble teeth of a comb at the base. The adults leopard moths fly during the night but are attracted to light and can sometimes be spotted during the day resting on tree trunks. The adults are incapable of feeding. Leopard moths live in open woodland and scrub but can also be found in gardens and parkland.

Symptoms

Caterpillars of leopard moths can cause slight damage to trees. Fortunately, they do not feed on trees more than 15 years old and stems or branches more than 10 cm across. Caterpillar presence is indicated by accumulation of frass and wood outside holes in the tree. Larval food includes most shrubs and trees in the Rosaceae family such as apple, pear, quince, cherry, plum, and others such as black currant, grapevine, walnut, ash, privets, elms, oaks, and beech.

The caterpillars are present on the trees from August to May in the following year. In early summer, the pupa, which is 25-35 mm long and reddish brown, can be seen protruding on the branch where it remains after the adult leopard moth has emerged. 

Management

The presence of the caterpillars of this moth rarely cause significant damage in gardens and it can usually be tolerated. Caterpillars and associated moths are important as a food source for other garden wildlife and so should be preserved where possible.
Check susceptible plants frequently from summer onwards so action can be taken before damage has occurred.
  • Where possible tolerate populations of caterpillars, as butterflies and moths are an important part of the garden ecosystem
  • Encourage predators and other natural enemies in the garden such as birds, hedgehogs and ground beetles
  • There is no practical means to prevent egg-laying. Monitor plants from late-July and if a caterpillar is detected inside a branch or trunk, it can sometimes be killed by inserting a piece of wire until the caterpillar has been skewered
  • Pruning a tunnelled branch back to sound wood is an option
  • For holes in trees, it’s best to leave it to try and heal naturally. Binding and wrapping the cut is not recommended, as it is better to allow air to reach the wound and let it heal naturally. Wrapping or binding can cause dampness and lack of ventilation, encouraging the development of fungal diseases. Painting pruning cuts with wound paints is not recommended as this too may trap moisture and promote fungal growth
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Leopard moth (Zeuzera pyrina) on Apple (Malus)
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Leopard moth (Zeuzera pyrina)
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Leopard moth (Zeuzera pyrina) on Apple (Malus)
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Leopard moth (Zeuzera pyrina)
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Leopard moth (Zeuzera pyrina) on Apple (Malus)
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Biology


The moths lay eggs in June or July in wounds or crack in the bark, including adult exit holes from previous season. Each female deposits several hundred eggs, usually in batches. The caterpillars emerge from August and overwinter two to three times as larvae, and can be found in tree stems and branches till the following May.

Newly emerged larvae are pinkish with a frilly margin on their neck. The young caterpillars leave the egg mass and bore into the tree to begin feeding. Very young caterpillars may feed on leaf petioles and main veins, buds and shoots. The older larvae feed in the larger twigs and branches and are up to 60 mm long, yellow with large black head. The caterpillars can tunnel up the heart wood, forming a frass-filled gallery 40 cm or longer. Larval development is complete within 2-3 years. The larva pupates within its feeding gallery in a silken cocoon.

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