Lily Leaf Beetles

Watch Out For These Critters

These beautiful red beetles are adults of the lily leaf beetle, a relatively new pest to our area. These are native to Europe, and were discovered near Montreal in 1945 and Cambridge MA in 1992. In the last couple of years they have entered our area and are spreading fast.

Both adults and larvae cause considerable damage to lilies; they can and often do completely strip a plant of all foliage and flowers. The adults are easily recognizable – about ½ long and bright red. The larvae look a bit like slugs, but since they cover themselves with their excrement, before long they look mostly like insect poo.

If there are not too many, the best way to control them is to just pick them off the plant. RCGC instructor Roz Bliss demonstrated an ingenious method for catching hard-to-reach adults during a class at her house this summer: put some Tanglefoot (sticky substance available in garden stores) on the end of a long stick and touch the beetle with the sticky end. If you want to use an insecticide, some sources recommend neem, extracted from the neem tree. It will kill the small larvae and repel the adults; to be effective it must be applied every 5-7 days.

The good news is that this pest is under good biological control in France and Switzerland; current research in the US is focusing on parasitoids that may in the future be available here for control.

Lily leaf beetles cause the most damage on true lilies (Lilium sp.) and fritillaria and will only lay eggs and develop on these plants; they do not eat daylilies. They will feed lightly on several other plants including Solomon’s seal, nightshade, potato, hollyhock, hosta and nicotiana.