long been favored by gardeners in the Northeast for their unsurpassed
beauty and relative ease of maintenance. The recent arrival of the
lily leaf beetle in Boston has complicated lily culture and gardeners
throughout the area should be on the lookout for this insect. The
lily leaf beetle, native to Europe, was discovered near Montreal,
Canada in 1945. Its damage was limited to the Montreal area for
decades, but recently it has spread to the south and west. The beetle
was first officially sighted in Cambridge, Massachusetts in the
summer of 1992. Many gardeners in the area believe it came in with
bulbs shipped from Europe. The beetles are strong fliers and excellent
hiders. They have spread as much as 150 miles from Boston, in many
cases with the assistance of gardeners. At present the infested
area in the USA reaches into all of the New England states, including
southern Connecticut and northern Vermont. Not all areas are yet
infested and gardeners who are transplanting bulbs and other garden
plants should be careful not to move these beetles to an uninfested
Lily leaf beetles
will taste or feed lightly on many plants including Lilium
spp., Fritillaria spp., Polygonatum spp. (Solomon's
seal), Solanum dulcamara (bittersweet nightshade), S.
tuberosum (potato), Smilax spp., Nicotiana spp.
and other plants. However, they will only lay eggs and develop on
Liliuim species (Turk's cap lilies, tiger lilies, Easter
lilies, Asiatic and Oriental lilies), and species of Fritillaria.
The lily leaf
beetle adult is a striking insect with a bright scarlet body and
black legs, head, antennae, and undersurface. The adults are 6 to
9 mm (1/4 to 3/8 inch) long, and they will squeak if they are squeezed
gently--a defense mechanism to deter predators. Adults and older
larvae feed on leaves, stems, buds, and flowers of the host plant.
Adults lay their eggs on the underside of leaves in an irregular
line. The reddish/orange eggs take from 7-10 days to hatch under
normal conditions. Females lay up to 450 eggs, sometimes over two
growing seasons. Larvae resemble slugs with swollen orange, brown,
yellowish or even greenish bodies and black heads. Larvae tend to
cause more damage than adults. Larvae are distinctive and repulsive
in that they secrete and carry their excrement on their backs. Younger
larvae feed for 16-24 days, primarily on the underside of leaves.
Larvae enter the soil to pupate; pupae are florescent orange. New
adults emerge in 16-22 days and feed until fall. They do not mate
or lay eggs until they emerge the following spring in late March
through June. Lily leaf beetles overwinter in the soil or plant
debris in the garden or woods, sometimes a distance away from the
host plants. Adults prefer environments that are shaded, protected,
cool, and moist.
beetle (R. A. Casagrande)
If you only
have a few plants in your garden, hand-picking adults and eggs can
be effective (we prefer not to handle larvae, although there is
no danger in doing so). The insecticides carbaryl (Sevin) and malathion
are effective on adults and larvae. However, carbaryl is highly
toxic to bees and malathion is also toxic to many non-target insects.
To date, our material of choice for treating flowers is neem, an
insecticide based upon extracts from the neem tree. Neem can be
purchased at garden centers under the trade names Turplcx, Azatin
EC, Margosan-0, Align and BioNeem. Neem kills larvae and repels
adults. Neem is most effective on first instar larvae; it must be
applied every five to seven days after egg hatch. The insecticide
imidacloprid also provides effective control. It is available in
several formulations from Bayer including foliar sprays, soil drenches,
and fertilizer stakes.
to control the lily leaf beetle have concentrated on biological
control. The lily leaf beetle is under good biological control in
France and Switzerland, where at least four species of parasitoids
attack it. We have released one species of European parasitoid in
Boston, MA and Cumberland, RI, and we are conducting basic experiments
on parasite biology and host specificity with the other parasitic
insects in our quarantine laboratory on campus--perhaps eventually
leading to additional releases in the USA.
of Rhode Island Plant Sciences Department, 2002