The lily beetle (Lilioceris lilii) is a notoriously invasive non-native pest for UK gardeners who love lilies (Lilium), fritillaries (Fritillaria), and giant lilies (Cardiocrinum). Both the adult beetles, with their striking bright red bodies and black heads, and their unpleasant-looking larvae are voracious feeders. 

The adults emerge in early spring, often as soon as lily shoots appear, and begin feasting on leaves, stems, and, crucially, flower buds. They lay distinctive orange to reddish eggs in neat lines on the undersides of leaves, which quickly hatch into larvae. 

These larvae cause the most significant damage, covering themselves in their own black, slimy excrement (a “faecal shield”) to deter predators, which makes them resemble bird droppings and creates a mess. A severe infestation can quickly defoliate a plant, weaken the bulb, and lead to sparse or entirely absent floral displays in subsequent years.

Dealing with lily beetles requires diligence and a multi-faceted approach, as they are prolific breeders and have few natural predators in many regions where they have become invasive. The most effective organic method is to consistently hand-pick both adult beetles and larvae. 

Adult beetles often drop to the ground and play dead, revealing their black undersides to blend in with the soil. To make collection easier, place a light-colored sheet or newspaper under the plant before shaking them off. The larvae, despite their unsightly coating, can also be wiped off, or the infested leaves can be removed.

 Chemical pesticides are generally ineffective and are not recommended, as they can harm beneficial insects and pollinators. Regular monitoring from early spring onwards is key to catching infestations before they become overwhelming and to protect your beautiful lily displays.