Asiatic lily boring insect, red lily beetle, scarlet lily beetle, lily leaf beetle and Lilioceris lilii are all names of the insect that eats leaves, stems, flowers and buds of lilies and other members of the Liliaceae family, completely destroying a flower bed within days. These beautiful flowers favored by gardeners for their attractive blooms and ease of maintenance are susceptible to this insect that causes severe damage if left untreated.
According to the University of Rhode Island Landscape Horticulture Program, the Asiatic lily boring insect is native to Europe. It was limited to Montreal, Canada for decades after it was discovered there in 1945, but eventually spread westward and southward, with the first official reported sighting in Cambridge, Massachusetts in 1992. Because of the insect's strong hiding and flying abilities, many local gardeners thought these arrived with bulbs imported from Europe. They then spread to different parts of the United States due to transplanting infested bulbs.
The lily leaf beetle belongs to the family Chrysomelidae and order Cleopatra. An adult has an attractive scarlet-colored 1/4- to 3/8-inch long body and black legs. The head, large eyes, antennae, underside and legs are all black, forming a striking contrast against the deep red forewings that are shiny and dimpled. The Asiatic lily boring insect flies and hides well and squeaks loudly if disturbed to deter predators.
The beetle overwinters in the soil or plant debris and emerges in spring. Females lay around 450 orange-red cylindrical eggs in one season, while some lay them in two growing seasons. They lay these in an irregular line on the lower surface of lily leaves, usually along the midrib, thus concealing them. The eggs take between a week to 10 days to hatch. The hatched larvae feed on the lower side of the leaf first, slowly working their way to the rest of the lily plant. They feed continuously for 24 days before burrowing themselves in the ground to pupate. The larvae emerge as adults in 20 days and feed until the arrival of winter.
Adult beetles and larvae cause severe damage to many types of true lilies including Asiatic, tiger, Turk's cap, Oriental and Easter. Day lilies are not true lilies and are therefore not susceptible to damage by this harmful insect. They first feed on the leaves, removing the foliage completely before advancing to the stems. Larvae cause more damage than adults.
Handpicking larvae and adult beetles is the most effective means of controlling them. Although there are no registered chemicals for controlling lily leaf beetle, insecticides containing methoxychlor, carbaryl and malathion are harmful to other insects but control large populations. Insecticides containing neem-based products kill larvae and deter adults without harming other insects.