Pest of the month: Cycad blue butterfly

Pest of the month: Cycad blue butterfly (Theclinesthes onycha)

Category name: Caterpillars1612-cycad-blue-butterfly

Importance: Major, when susceptible cycads are grown in areas with cycad blue butterfly (mainly Queensland and New South Wales)

Similar to: None

Description: Eggs laid singly on new and unfurling leaves in spring to autumn. Eggs are pale white-blue, small (about 0.5mm in diameter) and disk shaped.

Immatures: Caterpillars are green when they hatch and become brown to dark brown as they grow larger. They typically feed on young, soft leaves and hide under the leaves and in the crown. They are nocturnal. Larvae mainly attack Cycas spp. and occasionally Lepidozamia sp. Larvae are oval shaped with mouthparts and legs concealed from above; they do not look like typical caterpillars.

Adult: Butterflies have pale brown wings with a metallic blue or purple hue on the upper surface. The lower surface is light brown with white lines. The posterior margins of hindwings have orange and black eye patterns and a small ‘tail’. They are small to medium sized butterflies with a wingspan of about 25-30mm.

Damage: Larval feeding defoliates young leaves before they elongate and mature. As a result, when defoliated leaves finally elongate and mature they can appear ragged, tattered and unsightly. Damaged leaves that are not completely consumed dry out and die, giving a burnt appearance. Controls need to be applied when new growth begins to unfold.

Further industry pest information is available at

An initiative of the National Nursery Industry Biosecurity Program (NY15004) and the ‘Building the resilience and on-farm biosecurity capacity of the Australian production nursery industry’ Project (NY15002).