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Lilium Pests

Lily Leaf Beetle - Lilioceris lilii (Scop)

Importance

Lilies have long been favored by gardeners for their unsurpassed beauty and relative ease of maintenance. The arrival of the lily leaf beetle in North America has complicated lily culture and gardeners throughout the area. 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 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. In Canada their range is from parts of Quebec and Southern Ontario and reports of them in Portage la Prairie here in Manitoba. 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 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, 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 stage 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.

Webmaster note: (NEEM is not registered for sale or use as a pesticide in Canada)

 

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.

Reprinted with permission of the University of Rhode Island. - Biological Control Laboratory, Department of Plant Sciences, University of Rhode Island, Kingston, RI 02881 2/98

 

Adult Lily Beetle  

 

 

 

 

 

Lily Beetle Larvae

 

 

 

 

 

 

The U of RI are working toward parasitoid releases in Canada over the next few years.  It is a little hard to evaluate parasitoid activity this season since it seems to rain every day, but it appears that the beetle population is way down where we have established T. setifer.  Lisa Tewksbury of the university lab who, in addition to coordinating parasitoid release and evaluation, is also evaluating lily leaf beetle resistance among lily species and varieties.  That work also looks very promising and can already recommend at least 'Black Beauty' and L. henryi as beetle resistant.  We're working with several cultivars right now and always seeking additional material for trial.

 To help us keep track of the beetle’s distribution in Manitoba please report any sightings to the editor to be reported to MRLS Board Members

Nigel Strohman at 476-3225

Email: nigel@lilynook.mb.ca