The lily leaf beetle is a notorious pest affecting lilies and fritillaries, and has become a major concern for gardeners and horticulturists alike. This invasive insect, scientifically known as Lilioceris lilii, is originally native to Eurasia and was introduced to North America in the mid-20th century through shipments of plant materials from Europe. Since then, it has gradually spread throughout regions in the United States and Canada, causing significant damage to native and cultivated lily gardens.
One key characteristic to identify a lily leaf beetle includes its bright red or scarlet color, which makes it easily noticeable on the plants. Their lifecycle involves the adult beetles laying eggs on the leaves of lilies, which then develop into larvae that feed voraciously on the foliage, causing substantial damage to the plants. To effectively manage this pest, it is crucial to understand their life cycle and adopt the right control measures.
A few methods for controlling the lily leaf beetle are:
- Regularly monitoring your garden to keep an eye out for their presence
- Hand-picking adult beetles and larvae (dispose of them in soapy water)
- Encouraging natural predators (like parasitic wasps) by planting plants that attract them
- Spraying insecticides selectively to minimize harm to beneficial insects
Identification and Appearance
- Color: Bright red
- Head: Black head
- Antennae: Black antennae
- Legs: Black legs
Adult lily leaf beetles, or Lilioceris lilii, are easily recognizable due to their bright red color with a black head, antennae, and legs. These beetles measure about 6-8 mm in length.
- Color: Brownish-orange
- Body: Covered in black, excrement-like matter
The larvae of the lily leaf beetle look quite different from the adults. They have a brownish-orange color and are often found covered in a black, excrement-like matter for protection. The larvae also feed on lily leaves and can cause significant damage to the plants.
Life Cycle and Development
The lily leaf beetle (Lilioceris lilii) lays its eggs on the undersides of leaves. Some characteristics of these eggs include:
- Color: Orange-red
- Quantity: Up to 12 per leaf
- Hatch time: 1 week
Eggs are typically laid in lines on true lilies and fritillarias, which are their preferred host plants.
The hatched larvae are slug-like grubs with the following features:
- Color: Brown or green
- Size: Up to 2/5 inch
- Behavior: Feeding and causing damage to the leaves
Larvae feed on foliage for about 2-3 weeks before moving on to the pupate stage.
When the larvae are ready to pupate, they crawl down to the ground and create a small chamber. This pupation process takes around two weeks. The beetles then emerge as adults.
Lily leaf beetles overwinter as adults in sheltered locations such as leaf litter, debris, or in the soil. Once the temperatures warm up, they become active again and start laying eggs, thus completing their life cycle.
Damage and Effects on Lilies
Lily leaf beetles (LLB) primarily damage true lilies (Lilium spp.) and fritillaries (Fritillaria spp.). The adults and larvae feed on the leaves, causing:
- Holes in the foliage
- Notches on the edges of leaves
- Defoliation (complete removal of leaves)
These pests can cause significant damage to the appearance and health of lilies, affecting their bloom and growth.
Defoliation can happen within just a few days, as the beetles rapidly consume the leaves. Some species particularly vulnerable to defoliation include:
- Asiatic lilies
- Oriental lilies
- Easter lilies
- Tiger lilies
However, plants like lily of the valley (Convallaria majalis), Solomon’s seal (Polygonatum), and daylilies are not affected by LLB.
Lily foliage may show signs of early damage due to the feeding by LLB larvae, which create distinct, irregular holes in the leaves.
|Affected Lilies||Unaffected Plants|
|True Lilies||Lily of the Valley|
Examples of the hole damage caused by the beetles can be seen here.
Apart from holes, notches on leaf edges are another indicator of LLB presence. These notches, caused primarily by the adult beetles, reduce the plant’s ability to photosynthesize and grow properly.
Plants Affected by Lily Leaf Beetles
Lily leaf beetles (LLB) mainly affect plants in the Liliaceae family, but they don’t cause significant damage to hosta species. Unlike true lilies, hostas are less prone to attack as they belong to a different plant family.
Calla lilies also experience minimal impact from LLB, as they are not considered true lilies. However, it’s crucial to stay vigilant and monitor these plants for any signs of infestation.
The following plants are susceptible to lily leaf beetles:
- True Lilies: These include Lilium species and hybrids commonly found in gardens.
- Fritillarias: Also part of the Liliaceae family, they serve as an attractive food source for LLB.
- Solomon’s Seal: Although not primary targets, they can be affected by LLB.
Less Susceptible Plants
Some plants are less prone to LLB infestations:
- Hollyhock (Alcea): Not a preferred food source for LLB.
- Lily of the Valley (Convallaria majalis): Another less susceptible plant.
- Nicotiana: Generally avoided by LLB as they belong to a different plant family.
The following plants remain unaffected by LLB:
- Potatoes (Solanum tuberosum): Despite being popular garden vegetables, potatoes aren’t impacted by LLB.
- Bittersweet: This plant isn’t targeted by the scarlet lily beetle.
- Daylilies (Hemerocallis spp.): As related in a source, daylilies are not at risk for attack from LLB.
|Plant||Susceptibility to LLB|
|Hosta Species||Less susceptible|
|Calla Lilies||Less susceptible|
|True Lilies||Highly susceptible|
|Solomon’s Seal||Moderately susceptible|
|Hollyhock (Alcea)||Less susceptible|
|Lily of the Valley (Convallaria majalis)||Less susceptible|
|Potatoes (Solanum tuberosum)||Not affected|
|Daylilies (Hemerocallis spp.)||Not affected|
Control and Management
One effective method to control the lily leaf beetle is by hand-picking. This involves examining your lilies frequently and removing any beetles, larvae, or eggs you find. Larval stage beetles can be identified by their excrement-covered bodies1. When hand-picking, you can:
- Collect the beetles in a container filled with soapy water to kill them
- Crush the beetles, larvae, or eggs with your fingers or a tool
There are several insecticides2 that can help control lily leaf beetles when used according to the label directions:
|Neem oil||Rarely harms beneficial insects3||May require multiple applications|
|Spinosad||Effective against larvae4||Can be harmful to pollinators|
|Imidacloprid||Long lasting||Can be toxic to beneficial insects|
|Permethrin||Fast acting||Harmful to beneficial insects|
|Cyhalothrin||Effective||Can harm beneficial insects|
|Deltamethrin||Broad spectrum||Toxic to fish and aquatic invertebrates|
|Pyrethrin||Derived from chrysanthemum flowers5||Can be harmful to beneficial insects and the environment|
It’s essential to apply insecticides carefully, considering the potential negative effects on beneficial insects and pollinators.
Natural Predators and Beneficial Insects
Some natural predators are known to help manage lily leaf beetle populations. For example:
- Parasitic wasps, like Tetrastichus setifer6, can lay their eggs inside lily leaf beetle larvae, causing their death
- Ladybugs and lacewings may prey on lily leaf beetle eggs7
Introducing these beneficial insects into your garden can help reduce the number of red lily beetles. However, their effectiveness in controlling the scarlet lily leaf beetle population is not guaranteed. It is essential to combine different strategies such as hand-picking or insecticides, especially in severely infested areas like the New England states8.
Geographical Spread and Impact
The lily leaf beetle (LLB), also known as the scarlet lily beetle, is an invasive insect originating from Eurasia1. First reported in North America within Montréal, Canada around World War II2, it quickly spread throughout the region, causing significant harm to both native and cultivated lily species3.
LLB eventually reached New England in the 1990s4. Since then, it has spread throughout much of North America5, having an adverse impact on susceptible lilies and fritillaries in home gardens and commercial spaces alike6.
Adult beetles are known for their bright red color, while larvae and eggs are associated with feeding damage to lilies7. Moreover, adult beetles reproduce rapidly, leading to wider infestations and increased damage to lily plants8.
Some key characteristics of the lily leaf beetle:
- Bright red adult beetles9
- Eurasian origin10
- Notable damage to lilies and fritillaries11
- Rapid reproduction and spread12
Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.
Letter 1 – Skeletonizing Leaf Beetle
May 29, 2011 11:22:19 AM PDT
found in montano de oro state pakr, CA
Interestingly, when we searched BugGuide for the identity of this Skeletonizing Leaf Beetle, we discovered an image posted there that we also have on WTB?, but which has been unidentified. The larvae of this beetle, Trirhabda flavolimbata, feed on the leaves of Baccharis. We were uncertain if they were Sawfly Larvae or Leaf Beetle Larvae, and now we know that they are the latter.
Update: May 29, 2011 3:22 PM PST
In a moment of clarity, we realized all we need to do is to copy the previous posting onto the chronological end of this posting.
Skeletonizing Leaf Beetle Larvae on Baccharis
caterpillars in coyote brush (Baccharis pilularis) in Carpinteria, CA
Tue, Mar 31, 2009 at 9:38 PM
I’m not sure what these green caterpillars are. There were hundreds of them in the Coyote Brush (Baccharis pilularis) at the Carpinteria Salt Marsh Nature Park this past weekend.
Carpinteria Salt Marsh Nature Park, Carpinteria, CA
We will check with Eric Eaton, but we believe these are Sawflies and not Caterpillars. Sawflies are the larval form of a non-stinging member of the order of insects that includes ant, bees and wasps, Hymenoptera.
Hard to tell from the image, but either sawfly larvae or chrysomelid leaf beetle larvae.
Letter 2 – St. Johnswort Beetle
Metallic Green Beetle?
Location: About 200’ elevation, 1 mile north of Oregon boarder and 40 miles from Pacific Ocean
November 23, 2010 1:59 pm
This is a lady bug sized beetle that I found on a plant that I think is St. John’s Wort.
The grass seed was grabbed when capturing the insect. They seem to drop quickly from the plant they are on when they are being pursued.
I have not found any identification for this insect. There does not seem to be any damage to the plant from this insect. I have seen a dozen or so on a plant at one time. They seem to mostly be around the flower clusters before blooming.
You have my permission to use these images.
I would also appreciate a reply if you know what this is and if it is a beneficial or an insect that should be watched.
Thank you for your time,
Signature: Jim Koepke
Your beetle is Chrysolina hyperici, commonly called the St. Johnswort Beetle. It is an introduced species, that according to BugGuide, can be found from “Nova Scotia to Ontario, plus British Columbia and adjacent parts of United States native to Europe and Asia.” BugGuide also indicates: “Introduced to North America to control growth and spread of St. Johnswort, and to reduce the spread of native St. Johnswort disease (Colletotrichum gloeosporioides) Adults are more tolerant of cooler and wetter summers than the related Chrysolina quadrigemina, whose larvae and adults are killed by May frosts, and whose adult dormancy is disrupted by summer rains.” BugGuide describes its food and feeding habits as: “larvae feed during the night on shoot tips and basal and developing leaves of St. Johnswort (Hypericum spp.) adults feed in clusters during the day on flower buds and terminal leaves of St. Johnswort.” The British Columbia Government Forest Practices Branch website has this information on this biological control agent : “Early spring larvae feedings on fleshy new growth cause the most damage. This timing is the controlling key. Although adult feeding can be impressive, it has less impact than larvae feeding. Heavy fall feeding may cause some impact on the plants ability to overwinter.“
Letter 3 – Spiny Leaf Beetle from Australia
Subject: aussietrev Another Spiny Leaf Beetle
Location: Nth Burnett. Queensland Australia
December 5, 2012 11:06 pm
Here is an Australian Spiny Leaf Beetle to go with that one from Indonesia. These are minute. This one is sitting on a blade of grass.
Thanks for help identifying the Indonesian Spiny Leaf Beetle and your own submission of its Australian relative is a marvelous addition to our archives.
Letter 4 – Red Shouldered Leaf Beetle
what is this bug?????
Could you please identify this bug that has demolished my vegetable garden in plague proportion, I live on the sunshine coast in Queensland Australia. REGARDS
We tried to locate the species of your Leaf Beetle, but could not positively identify it. It is in the Family Chrysomelidae.
I have a beetle ID for you
I am writing in response to one of the id requests you received 12/06/2006 from Wayne on the Sunshine Coast, Queensland. The little red and yellow beetles demolishing his vegie garden are Red-shouldered Leaf Beetles – Monolepta australis. They are very common in these parts and obviously have good appetites. Hope this helps. Keep up the good work. Regards,
Letter 5 – Rosemary Beetle from Israel
Subject: Iridescent Beetle?
Geographic location of the bug: Israel
Time: 01:30 PM EDT
Your letter to the bugman: Dear bugman,
Found this small iridescent beetle in our garden and was able to catch the colors in this picture. With spring in full bloom, I’m excited to go out everyday to see what critters I find…
How you want your letter signed: T.M.
We suspected this was a Leaf Beetle, and we located a very similar looking mating pair of Chrysolina coerulans angelica on Israel’s Nature Site (scroll down) but your individual has many more alternating stripes on the elytra. We searched the genus and we believe your individual is a Rosemary Leaf Beetle, Chrysolina americana, which we found on iNaturalist.
Letter 6 – Rosemary Leaf Beetle
What is this little beauty ??
I noticed this little guy on my lavender plant here in London, never seen anything like this before – assumed it was an exotic ladybug but not found anything that looks like this on the net. Could you shed any light ? An almost metallic shine in green/silver with striking thin red stripes. A pic is attached.. Here’s hoping ! Thanks
The Rosemary Leaf Beetle, Chrysolina americana, is a Mediterranian species that feeds on rosemary and lavender. The use of these plants in English gardens has resulted in the Rosemary Leaf Beetle expanding its range. According to the Royal Horticural Society website, it has become an established pest in England.
Letter 7 – Rosemary Leaf Beetle from England
Subject: Metallic wheeled beetle
Location: Buckinghamshire, England
February 22, 2015 12:06 pm
Hello, I’m a gardener living in the south of England. I saw these beetles living on a rosemary bush. There was about 15-20 of them. I saw the over two seasons on the same rosemary bush but never anywhere else in the garden or in England for that matter.
Signature: Jackson Rowe
You have the hands of a gardener. Your beetle is a Rosemary Leaf Beetle, Chrysolina americana, which is sometimes called merely a Rosemary Beetle. Knowing that it feeds on a single plant in your garden, Rosemary, is a good way to search for its identity. According to UK Safari: “Despite the scientific name, this beetle is a native of southern Europe. It was first noticed in the U.K. in the early 1990’s and has since become well established.” You can locate additional information on the Royal Horticultural Society website where it states: “The larvae and adults feed on the foliage of rosemary and related plants. Rosemary beetle is a pest that eats the foliage and flowers of various aromatic plants, such as rosemary, lavender, sage and thyme. Initially rosemary beetle was found mainly in London gardens, but it is rapidly spreading and is becoming widespread throughout England and Wales, and possibly further north.”
Letter 8 – Rosemary Leaf Beetle from UK
Subject: Beautiful Beetle!
Location: Sidcup, Kent – England (UK)
May 6, 2013 3:54 pm
I’ve lived in South East London since a child and never seen one of these before. I saw two this afternoon on a Rosemary bush and Pineapple Broom at the end of our garden. We have an area of unmanaged scrub at the end of the garden where there are a number of fallen /rotting trees, so we usually see quite a few beetles. But these are new to me and I can’t find any pictures on line to identify them by.
Can you help, Bugman?
I have more photo’s at other angles if you want them.
Signature: Alun Harrison
Because we haven’t received a new photo of this species in several years, we couldn’t recall the name of this Rosemary Leaf Beetle. At first we had trouble finding the identity when we searched the scientific family name Chrysomelidae, but once we switched to the common name Leaf Beetle, we quickly found this Rosemary Leaf Beetle identified on FlickR. A You Tube video indicates the Rosemary Leaf Beetle successfully invaded the UK in 2002 though it was most likely introduced prior to that. The Rosemary Leaf Beetle, Chrysolina americana, is native to the Mediterranean region, but the cultivation of its food plants like rosemary and sage has allowed it to expand its range.
Wow! That was amazingly quick. Thank you for that info, Daniel. I will follow the advice for hand removal since we do use the herbs for culinary purposes, but feel terrible about harming such beautiful creatures.
I will look at perhaps providing more ‘sacrificial’ lavender for them until I read up on their potential “pest” status.
My very best regards & thank you for your response.
Letter 9 – Skeletonizing Leaf Beetle
Hello, can you help ID this bug? I have looked through many sites and have not found a photo that matches.
This beetle is a new one for us. It is in the Family Chrysomelidae – Leaf Beetles and the Subfamily Galerucinae – Skeletonizing Leaf Beetles. We actually located the species on BugGuide. It is Omophoita cyanipennis.
Letter 10 – Striped Willow Leaf Beetle
Subject: Can’t ID this beetle
Location: The Nature Conservancy – Hassayampa River Preserve, Wickenburg, Arizona
August 15, 2012 6:03 pm
I looked through a dozen pages of pictures trying to ID this beetle but didn’t find anything. Can you ID him for me?
Signature: Adam Bloomer
It didn’t take us too long to identify your Striped Willow Leaf Beetle, Disonycha alternata, thanks to the extensive archive on BugGuide. We took the liberty of cropping your image and repositioning your name on the file so that it would better fit our website format.