Swift moth caterpillars

• Swift moth caterpillars are the larvae of moths in the family Hepialidae
• They live in the soil and tend to feed on plant roots and at the base of plant stems especially herbaceous perennials
  Perennials are plants that live for multiple years. They come in all shapes and sizes and fill our gardens with colourful flowers and ornamental foliage. Many are hardy and can survive outdoors all year round, while less hardy types need protection over winter. The term herbaceous perennial is used to describe long-lived plants without a permanent woody structure (they die back to ground level each autumn), distinguishing them from trees, shrubs and sub-shrubs.
• The species that most often cause damage in gardens are the common swift (Hepialus lupulinus) and ghost swift moths (H. humuli)
• The caterpillars grow to around 45 mm long they are usually creamy-white in colour with brown heads. They have three pairs of legs at the head end and five pairs of clasping prolegs on their abdomen and are found often feeding in groups
• Cutworms can cause similar damage but these caterpillars are usually dirty greyish-brown in colour
• Adult swift moths lay their eggs during mid-summer and scatter there eggs whilst in flight, unlike most moths which land to lay their eggs
• The larvae take one or two years to complete their development

Large populations of swift moth caterpillars can cause affected plants to lack vigour and they may be killed. Roots of herbaceous perennials

Perennials are plants that live for multiple years. They come in all shapes and sizes and fill our gardens with colourful flowers and ornamental foliage. Many are hardy and can survive outdoors all year round, while less hardy types need protection over winter. The term herbaceous perennial is used to describe long-lived plants without a permanent woody structure (they die back to ground level each autumn), distinguishing them from trees, shrubs and sub-shrubs. such as Michaelmas daisy, paeony, chrysanthemum and strawberry are particularly at risk.

• The adult moths prefer to lay eggs where there is a dense vegetation cover, for example they often occur in larger numbers where turf has been dug up to make a vegetable or flower bed, large populations tend therefore to be temporary
• 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, wasps, hedgehogs and ground beetles. Cultivation of the ground can briefly expose the grubs to predators, such as birds
• Remove larvae from soil as they are found
• Biological control: a mixture of nematode species for controlling caterpillars and some other vegetable pests is sold as Fruit and Vegetable Protection and is available from some biological control suppliers. To be effective the nematodes need to be watered into moist soil while soil temperatures are in the range of 12-20ºC (54-68ºF). These temperatures occur between April and September. Nematodes should be applied as soon as possible after purchase, following the suppliers’ instructions. It may be necessary to water the soil before and after application to ensure the soil is sufficiently moist for nematode activity and survival. Repeat application may be necessary. Nematodes have the potential to infect non-target animals, they should therefore be used with care and only when there is a specific problem to treat.

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Biological control suppliers (pdf document)