Lily Beetles

Lily Beetles (Lilioceris lilii) are a damaging pest insect for lily (Lilium spp.) growers. The pest chews on the leaves, flowers and stem leaving them looking ragged. If the pest numbers are high enough complete defoliation can occur. Early detection and vigilance are key to managing this pest naturally.

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Damage to Plants

Both the larvae and the adults feed on mainly Asiatic lilies and fritillaries. They also feed on Oriental lilies, rubrum lilies, Turk’s cap lilies, native North American lilies, Solomon’s seal, lily-of-the-valley, potato, flowering tobacco, hollyhock, and hosta, but to a lesser degree. The leaves are generally the preferred food but the stem, buds, flowers and seed pods may also be eaten. Plants will look ragged and chewed on and can be completely defoliated. In the larvae stage the brown fecal shield, the insect covers it’s self in can be quite unsightly.

Meet the Pest

Adults: have black heads with big eyes and long black, segmented antennae. The slim thorax and hardened forewings (elytra) are a shiny scarlet red colour, these wings cover the black elongated abdomens and are quite pitted. The legs are fairly long and also black in colour. The overall length of the beetle is just under 1/2″ about 8-11mm.

Larvae: pass through 4 instar stages and size varies according to developmental stage they are at. At maturity they reach about 8-10 mm. They appear as soft brown, squishy masses but the real insect is hidden beneath a fecal shield. The slug-like larvae can vary in colour from red, orange, yellow, green or brown with a black head.

Pupae: are bright orange in colour and encapsulated in a white silken cocoon located in the soil.

Eggs: are laid on the underside of leaves and are about 1-2 mm in length. They are laid in irregular rows of about 2-16 eggs. The eggs start off a baize colour but mature to a reddish-orange colour.

Life Cycle

Lily beetles over winter as adults in the soil or plant debris. In April when the daffodils are blooming, they begin breaking dormancy, mate and start laying eggs on fritillaria. As the lilies begin to break through the ground in May they begin feeding on the lilies and laying their eggs on the underside of the leaves. The oblong shaped eggs begin hatching in about a week. All in all, a female lily beetle can lay up to 450 eggs per season. The larvae feed for about 2-3 weeks then enter the soil to pupate. The adults emerge 2-3 weeks later and feed until fall. They then enter shaded, moist and protected areas of soil or plant debris to overwinter. There is one generation per year.

Management and Control

Physical control:

  • Hand picking the adult beetles or tapping them into a container of warm soapy water works well. They are quick to either fly away or drop to the ground on their backs so that their black undersides camouflage well with the soil. Hold your container under them and give them a gentle tap into the warm soapy water.
  • Larvae can be scraped off and destroyed.
  • Scout the underside of leaves for egg masses and remove those leaves and destroy.

Plant resistant varieties: such as Lilium henryi ‘Madame Butterfly’, Lilium speciosum ‘Uchida’, and Lilium ‘Black Beauty’ (Robert Childs, Updated by: Tawny Simisky on 4/24/2020).

Biological controls: as a non-native insect there are no natural predators here in North America. However in Europe there are a few parasitoids that kill the larvae. Research on these parasitoids has been on going and in Canada the parasitic wasp Tetrastichus setifer, has been released in New England, Ottawa and southern Alberta with good results.

Natural Pesticides:

  • A heavy application of neem oil applied every 5-7 days, will help to control the larvae and may help to deter the adults (Stack P. A., 2009). The young larvae are the most vulnerable to the spray.
  • Spinosad (a naturally occurring soil bacterium), applied at regular intervals can be helpful in controlling this pest. Note: this product is currently not available in Canada
  • Talcum powder has also had some effect at controlling all stages of this pest (Plantlilies.com, (2007)).

Chemical Pesticides: carbaryl (Sevin) and Malathion (check with your region to see what is legal for you to use).

References:

CABI, (Updated by: Marc Kenis 03/11/2008), CABI Europe – Switzerland). Lilioceris lilii (lily leaf beetle). Invasive Species Compendium. https://www.cabi.org/ISC/datasheet/30800

Childs R., (Updated by: Tawny Simisky on 4/24/2020).  Lily Leaf Beetle. UMass Extension Landscape, Nursery and Urban Forestry Program. https://ag.umass.edu/landscape/fact-sheets/lily-leaf-beetle

Olds College, (n.d.). The Lily Beetle. https://www.oldscollege.ca/about/campus/botanic-gardens/central-gardens/taxonomic-collection/the-lily-beetle/index.html

Plantlilies.com, (2007). Pests and Diseases Lily Beetle – ALBERTA. https://plantlilies.com/lily-culture/pests/lily-beetle-alert-alberta.html

Stack P. A., (collaborating researcher, Hampden, Maine; with Professor Eleanor Groden and Extension Professor, . Lois Berg Stack), (2009). Bulletin #2450, Lily Leaf Beetle. https://extension.umaine.edu/publications/2450e/

Whitman A., (updated 01/25/2021). Controlling Lily Leaf Beetles. https://www.gardeners.com/how-to/lily-beetle/8090.html

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