This recent European introduction was first officially sighted in the summer of 1992 in Cambridge, Massachusetts. Since then it has spread to all the New England states and upstate New York, with devastating consequences for lily culture.
BIOLOGY: Adult lily leaf beetles are three-eighths of an inch long and have black heads and bright orange-red bodies. They overwinter in soil or plant debris and emerge in late March through June—about the time new lily shoots are emerging. After mating, females lay clusters of orange eggs on the undersides of lily (Lilium spp.) and fritillary (Fritillaria spp.) leaves. These eggs hatch in 7 to 10 days, and the small larvae—which are orange, brown, yellowish, or greenish—begin feeding on the undersides of the leaves. As a defense against predators, the larvae deposit their own feces on their backs. As they mature, they consume entire leaves, buds, stems, and even flowers. After two to three weeks, the larvae enter the soil to pupate. In another two to three weeks, adults emerge and feed until the fall. Reproduction does not occur again until the next spring.
SYMPTOMS: Defoliation begins with holes in leaves, buds, and flowers, but may continue until only the central stalk remains. This can have a catastrophic effect on the subsequent year’s plant growth. Lilies, and to a lesser extent fritillaries, are the only plants attacked by larvae; damage from adults has also been observed on nicotiana, Solomon’s seal (Polygonatum spp.), greenbrier (Smilax spp.), nightshades, hollyhock and various hostas.
CONTROL: Knock the adults into a container filled with an inch of soapy water. Remove egg masses from the undersides of the leaves. Squash young larvae.
The insecticide neem (azadirachtin) is most effective against newly hatched larvae. Imidacloprid (Bayer Advanced Rose & Rower Insect Killer Ready-To-Use) can be applied to the soil in early spring. Carbaryl (Sevin) is effective when applied to the newly emerging lily stems, but it is also harmful to bees and other insects.
Researchers at the University of Rhode Island are experimenting with biological control. Three parasitic wasp species from Europe were released in four New England states in 2003. One of them, Tetrastichus setifer, has provided considerable control at the release sites.—B.P.
Damage caused by larvae