Tortoiseshell beetles (Aspidomorpha spp.)
Adults are broadly oval and shield-like, 6-8 mm long, and may be brightly coloured. They lay eggs singly or in batches on the underside of sweet potato leaves; sometimes the eggs are covered by a papery layer. The larvae are oval, flattened and spiny. Some species of tortoiseshell beetle larvae hold their tails up over their back, usually with excreta and previous cast skins. The pupa is less spiny than the larva, and is fixed to the leaf.
Both larvae and adults feed on leaves. The young larvae scrape on the upper surface of the leaves leaving the lower surface intact, while older larvae and adults eat large round holes in the leaves. Severe attacks can sometimes skeletonise the leaves and peel the stems. The damage on leaves is conspicuous, but generally is not of economic importance.
- Usually control is not necessary, removal of nearby alternative host plants may reduce the tortoiseshell beetle populations.
- Alternatively, planting far away from alternative host plants may help reducing damage to sweet potatoes. Alternative host plants include morning glory, coffee, potatoes, beets, and various flowers.