(back to the previous page)

UNIVERSITY OF RHODE ISLAND

COOPERATIVE EXTENSION

Lily Leaf Beetle   

Lilioceris lilii (Scop)

Importance

Lilies have long been favored by gardeners in the northeast for their unsurpassed beauty and relative case 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 it. 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 100 miles from Boston, in many cases with the assistance of gardeners. At present the infested area in the USA extends a bit past route 495 around Boston also including much of the Cape and coastal New Hampshire, reaching just into Maine. Gardeners who are transplanting bulbs and other garden plants should be careful not to move these beetles to an uninfested area.

We found that lily leaf beetles will taste or feed lightly on many plants including Lilium sp., Fritillaria sp., Polygonatum sp. (Solomon's seal), Solanum dulcamara (bittersweet nightshade), S. tuberosum (potato), Smilax sp., Nicotiana sp., and other plants. However, Lilioceris lilii 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.

Biology

The lily leaf beetle adult is a striking insect with a bright scarlet body and black legs, head, antennae, and undersurface. The adults are 1/4-3/8' long, and they will squeak if you squeeze them gently, they do this 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.

Control

If you only have a few plants in your garden, hand-picking adults and eggs can be effective (we prefer not to handle larvae). The insecticides carbaryl (Sevin) and malathion arc 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, a newly registered 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 5-7 days after egg hatch. We also found the systemic insecticide Merit (imidacloprid) to provide effective control when applied to the soil in the spring when foliage begins to show but this material is not readily available to homeowners for this purpose.

Our recent efforts on the lily leaf beetle have concentrated on biological control. We have found this insect to be under good biological control in France where at least two species of parasitoids routinely attack it. We have these two parasitic insects in our quarantine laboratory on campus where we are conducting basic experiments on parasite biology and host specificity - perhaps eventually leading to a release in the USA.

(back to the previous page)

UNIVERSITY OF RHODE ISLAND

COOPERATIVE EXTENSION

Lily Leaf Beetle   

Lilioceris lilii (Scop)

Importance

Lilies have long been favored by gardeners in the northeast for their
unsurpassed beauty and relative case 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 it. 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 100 miles from Boston, in many cases with the assistance of
gardeners. At present the infested area in the USA extends a bit past route 495 around
Boston also including much of the Cape and coastal New Hampshire, reaching just into
Maine. Gardeners who are transplanting bulbs and other garden plants should be careful not
to move these beetles to an uninfested area.

We found that lily leaf beetles will taste or feed lightly on many
plants including Lilium sp., Fritillaria sp., Polygonatum sp. (Solomon's seal), Solanum
dulcamara (bittersweet nightshade), S. tuberosum (potato), Smilax sp., Nicotiana sp.,
and other plants. However, Lilioceris lilii 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.

Biology

The lily leaf beetle adult is a striking insect with a bright scarlet
body and black legs, head, antennae, and undersurface. The adults are 1/4-3/8' long, and
they will squeak if you squeeze them gently, they do this 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.

Control

If you only have a few plants in your garden, hand-picking adults and
eggs can be effective (we prefer not to handle larvae). The insecticides carbaryl (Sevin)
and malathion arc 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, a newly registered 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 5-7 days after egg hatch.
We also found the systemic insecticide Merit (imidacloprid) to provide effective control
when applied to the soil in the spring when foliage begins to show but this material is
not readily available to homeowners for this purpose.

Our recent efforts on the lily leaf beetle have concentrated on
biological control. We have found this insect to be under good biological control in
France where at least two species of parasitoids routinely attack it. We have these two
parasitic insects in our quarantine laboratory on campus where we are conducting basic
experiments on parasite biology and host specificity - perhaps eventually leading to a
release in the USA. To help us keep track of the beetle’s distribution, please report
any sightings more than 50 miles from central Boston. (401) 874-2750

Biological Control Laboratory, Department of Plant Sciences, University
of Rhode Island, Kingston, RI 02881 2/98

Reprinted with permission of the University of Rhode Island.

(back to the previous page)