The scarlet lily beetle, red lily beetle, or lily leaf beetle (Lilioceris lilii), is a leaf beetle that eats the leaves, stem, buds, and flowers, of lilies, fritillaries and other members of the family Liliaceae. It lays its eggs most often on Lilium and Fritillaria species. In the absence of Lilium and Fritillaria species, there are fewer eggs laid and the survival rate of eggs and larvae is reduced. It is now a pest in most temperate climates where lilies are cultivated.

Description

This lily beetle belongs to the order Coleoptera, and the family Chrysomelidae, the leaf beetles. The adult lily beetle is about in length, with relatively long legs and antennae. Its elytra (harder forewings) are bright scarlet and shiny. Its underside, legs, eyes, antennae and head are all black. It has large eyes, a slim thorax, and a wide abdomen. Each antenna is made up of 11 segments. The eyes are notched and there are two grooves on the thorax.

This lily beetle may be confused with the cardinal beetle (Pyrochroa serraticornis), which also has red elytra and a black underside. The wing cases of the lily leaf beetle are dimpled and are shinier and more rounded than those of the cardinal beetle, which are relatively dull, and narrower, flatter, and more elongated. The cardinal beetle also has comb-like antennae. The lily leaf beetle is herbivorous, while the cardinal beetle preys on insects. The lily leaf beetle is also confused with unspotted ladybirds, but it is narrower in shape. Since then it has spread from Surrey in southern England as far north as Inverness, Scotland. It is also found in Ireland. It emerges in spring to feed and mate.

An adult that senses danger displays a defense mechanism, thanatosis, becoming motionless, folding up its appendages and falling with its black under surface facing up, thereby helping it camouflage with the ground to get away. If unable to escape, they are also able to ‘squeak’, by rubbing two parts of their body together, which may be used to startle the attacker.

This process is known as stridulation and could even shock a bird or any other predator that may attack the lily leaf beetle.

Control

The most surefire strategy for preventing infestation by any pest is to avoid planting susceptible plants in the first place, with lily beetle this necessitates avoiding growing so many desirable cultivars of Lilium, that other strategies may be preferred. Regular handpicking and crushing of eggs, larvae and adults is effective if somewhat laborious. Domestic insecticides registered for general leaf beetle control containing carbaryl, methoxychlor, malathion and rotenone can prove useful in controlling populations. Products based on neem extracts are useful in killing very young larvae and repelling adults without comparable harm to other insects, although this option is perhaps less effective than handpicking. Neem products should be applied every 5 to 7 days after egg hatch. Thiacloprid is also effective.

Biological control

In Europe, total parasitism rate in the last instar stage averages about 90% on wild Lilium martagon, 75% in gardens and 60% in cultivated lily fields. Most lily leaf beetle parasitoids are wasps that lay eggs inside the host and effectively kill all infected individuals. Diaparsis jucunda (Ichneumonidae: Tersilochinae), dominates over 90% of the parasitoid infections in lily leaf beetle. However, in gardens and commercial fields, Tetrastichus setifer (Eulophidae: Tetrastichinae) and Lemophagus pulcher (Eulophidae: Campopleginae) become the dominant parasitoids in the later season. The European parasitoid wasp Tetrastichus setifer was used in Massachusetts from 1999 to 2001; the experiment showed reduction of the beetle population. Population decline was also observed at another experiment site in Rhode Island. In 2003, another parasitoid, Lemophagus errabundus, was released in Massachusetts and is now established in the region.

References

Bibliography

  • Royal Horticultural Society: Lily beetle
  • see also