Friday, May 21, 2004
Lily Leaf Beetle
When and where found: I found my first one this year on May 8 on the lily plants. There have been new ones every few days since then. They turn up in the spring almost as soon as their host plants come into leaf. They have been found in Massachusetts this year as early as April 18 and last year were found up through mid-October.
Host plants: A rose by any other name may smell as sweet, but a lily by another name (like daylily) does not smell as sweet to the lily beetle. Daylilies, members of the genus Hemerocallis, are immune to attack. The beetle will lay its eggs only on true lilies and fritillaria, but it can be found eating the leaves of Solomon's seal, nicotiana, and potato plants. The true lilies, members of the genus Lilium, include the Asiatic, Oriental, Easter, Tiger and Turk's Cap lilies.
Distinguishing characteristics: The adult beetle is about 1/4 to 3/8 of an inch long; the body is bright, shiny and scarlet; the head, legs, antennae, and underside are black. The beetle is as attractive as the larva is repulsive. If your lily leaves are a bit ragged and you look underneath them and see clumps of brownish black muck, those are the larvae . wearing coats of excrement. Like most caterpillars, they eat a lot and so their coats continue to pile up into a rather effective "fecal shield."
Life cycle: Anytime from late March to the end of June, adult lily leaf beetles emerge from their winter shelter to feed and mate. Females each lay up to 450 reddish orange eggs in small batches in rows on the underside of lily and fritillaria leaves. The eggs hatch in about a week and the larvae eat for 2 to 3 weeks before dropping to the soil where they pupate for another 2 to 3 weeks. The new season adults don't mate until the following spring; they feed until fall and then winter over in soil or plant debris in the garden or nearby woods.
Immigration and biological control: The lily leaf beetle is native to Europe. It was discovered in Montreal in 1945 and did not show up in Massachusetts until 1992 when the first recorded sighting was made in Cambridge. It has now spread into all the New England states where unlike Europe, there are no natural predators. Scientists at the University of Rhode Island have released a parasitic wasp as part of a test for biological control in Boston and in Cumberland, R.I.
Other controls: "Seek and destroy" works well if you have only a few host plants. You can squish the beetles and the eggs in your fingers. The larvae are more of a challenge — they are so revolting not even Fear Factor has shown an interest in them. I usually pick the leaf with the larvae on it, and squish the whole thing with my shoe. The more often you look, the more likely you will find the eggs before they hatch. If you want to use insecticide, the recommended one is Neem. If you do nothing, the larvae will eventually kill the plants.
References: University of Rhode Island, Plant Sciences Dept at www.uri.edu/ce/factsheets/ ; UMass Extension at http://www.umassgreeninfo.org/fact_sheets/defoliators /lily_leaf_beetle.html; Boston Globe, July 18, 2002, Lilies Losing the Battle Against Hungry Beetles.
Any kind of information for the Biodiversity Corner is encouraged. If larvae with fecal shields are not your cup of tea, please feel free to submit a column, or tell me what you are finding, or send me a photo. The only requirements are that the subject exists in the wild and was seen in Carlisle. Send a note to Kay Fairweather at 392 School St., Carlisle MA 01741 or to firstname.lastname@example.org.
© 2004 The Carlisle Mosquito