Both adult scarlet lily beetles and their grubs eat holes in the leaves of lily plants often leading to leaf drop that weakens the plant. The bulbs become smaller and flowering in subsequent years is reduced. They will also eat flower buds, leading to a reduction of the flower display.
The adult scarlet lily beetle is 6mm to 8mm long with a black head and legs. The bright red wing coverings are easily spotted, but the insect has a cunning defence mechanism that makes physical capture difficult. When disturbed, it drops to ground level, turns upside down where its black underside is difficult to locate. The grubs of the pest are even more sly, covering themselves with their wet, black excrement, which protects them from predator attack while they openly eat the lily leaves and flower buds.
Treatment and control
Non-chemical control: Remove any adult Scarlet Lily beetles by hand and dispose of them.
Spray with a general insecticide: Infested plants can be treated with acetamiprid, a systemic insecticide that gets inside the plant to control grubs and adults. Spray lilies with BugClear Ultra Gun! as soon as the first grub or adult is spotted. A further treatment 3 weeks later will help to control any grubs that may have hatched from previously laid eggs.