Native to Europe and North Africa, Lilioceris lilii was first found in Montreal back in 1945 and has since made its way into Ontario. Both adults and larvae feed on the leaves of all lily species, lily of the valley, Solomon’s seal and fritillaria and when an infestation is heavy, they will also eat the flowers, seed capsules and stems.
The beetle overwinters as a pupa in soil and debris to emerge in early spring as an adult to mate. The female lays 200-300 oragne eggs on the underside of leaves in rows which incubate over a period of 5-10 days. Newly hatched larvae feed on the underside of the leaf while mature ones have moved to feed on the upper surface of the leaves. This larval stage lasts 16-24 days and they are hard to distinguish as they are covered with a shielding case of their own slimy black excrement and resemble bird droppings to us, and any predators. The larvae bury into the soil to pupate in a protective cocoon and emerge as adults after about three weeks and in Ontario there can be two to three generations a year.
The adult is easy to see and identify; the bright red wing covers are candy apple red with contrasting black antennae, eyes, head, legs and underside. It is 6-8 mm long and can escape swiftly or will drop quickly to the ground when a shadow passes over it. Needless to say, they are hard to catch but hand picking is the best method to be rid of them and be vigilante about finding and destroying the eggs too. I've heard a chirping sound coming from an adult held in my hand which is made from a wing cover and an abdominal apparatus. Many gardeners will drop the beetles into a bucket of hot, soapy water while others with a stronger stomach will pick and squish. (the latter is me!)
In Britain they have come up with a remedy that works well as red lily beetles hate anything citrus. Combine 1 oz. of lemon juice, 1 oz. of horticultural oil and 4 litres of water. Shake and spray on the ground when lilies are emerging and continue to spray as needed, particularly after it has rained. You might want to save any citrus peels to spread on the ground around the plants affected by the beetle as well.