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University
of Rhode Island GreenShare Factsheets
Lily
Leaf
Beetle
Lilioceris lilii
Coleoptera: Chrysomelidae
Lilies have 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
area.
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.
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.
Recent efforts 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.
University of Rhode Island
Plant Sciences Department, 2002
Pesticides
are poisonous! Read and follow all safety precautions on labels.
Handle carefully and store in original containers out of reach
of children, pets or livestock. Dispose of empty containers
immediately, in a safe manner and place. Pesticides should never
be stored with foods or in areas where people eat.
When trade names are used for identification, no product endorsement
is implied, nor is discrimination intended against similar materials.
Be sure that the pesticide you intend to use is registered for
the state of use.
The user of this information assumes all risk for personal injury
or property damage.
For more
information, call the URI CE Gardening and Food Safety Hotline
at 1-800-448-1011 or (401)874-2929 from outside Rhode Island;
Monday-Thursday between 9 am and 2 pm.
University
of Rhode Island Cooperative Extension provides equal program
opportunities.
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