Q. How can I control red lily beetle?
The red lily leaf beetle (Lilioceris lilii), native to Europe and Asia, arrived in the northeastern U.S. in the 1990s. Unfortunately, if uncontrolled, this persistent pest will completely defoliate and ultimately kill all true lilies (Lilium species) and Fritillaria, its primary targets.
The bright red adult beetle overwinters in soil and emerges in spring, when it lays eggs in lines on the underside of leaves. After 7-10 days, the eggs hatch into larvae. That's when the destruction begins. Larvae consume all leaves within their reach and may start in on flower buds.
Hand-picking the larvae and adult beetles is effective, although of course time-consuming. Squash both and drop into soapy water. When disturbed, adult beetles fall onto soil on their backs, which makes them difficult to see. Placing a light-colored cloth under plants before hand-picking will enable you to find fallen beetles.
Neem oil is effective against adults and small larvae. Make sure that the oil you buy contains azadirachtin, the active ingredient in neem products. Apply every 5-7 days. The larvae have a wet, slimy excrement covering that provides them some protection from insecticide, so make sure each application is heavy and complete.
Try to use lily varieties that are more resistant to the red lily beetle. NYBG research indicates that Asiatic hybrids are most susceptible. To date, the three most resistant lilies in our tests are Lilium henryi ‘Madame Butterfly’, Lilium speciosum ‘Uchida’, and Lilium ‘Black Beauty’.
Entomologists at the University of Rhode Island have identified several European parasitic wasps that are potential effective biological control agents against this pest. This research is ongoing; the wasps are not yet commercially available.
For tips on a variety of gardening topics, see our Plant Information Guides.
- Courtesy of NYBG Plant Information Service