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
Adult Beetles
- 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.
Larvae
- 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
Eggs
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.
Larval Stage
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.
Pupate
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.
Overwintering
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
Feeding Damage
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.
Defoliate
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.
Holes
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 |
| Fritillaries | Solomon’s Seal |
| Canna Lilies | Daylilies |
Examples of the hole damage caused by the beetles can be seen here.
Notches
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
Hosta Species
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
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.
Susceptible Plants
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.
Not Affected
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 |
| Fritillarias | Highly susceptible |
| Solomon’s Seal | Moderately susceptible |
| Hollyhock (Alcea) | Less susceptible |
| Lily of the Valley (Convallaria majalis) | Less susceptible |
| Nicotiana | Less susceptible |
| Potatoes (Solanum tuberosum) | Not affected |
| Bittersweet | Not affected |
| Daylilies (Hemerocallis spp.) | Not affected |
Control and Management
Hand-Picking
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
Insecticides
There are several insecticides2 that can help control lily leaf beetles when used according to the label directions:
| Insecticide | Pros | Cons |
|---|---|---|
| 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.
Bug Control Recommendation Tool
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
Footnotes
- https://ag.umass.edu/greenhouse-floriculture/fact-sheets/lily-leaf-beetle ↩ ↩2
- https://hort.extension.wisc.edu/articles/lily-leaf-beetle/ ↩ ↩2
- https://www.canr.msu.edu/news/lily_leaf_beetle_watch_out_for_this_garden_pest ↩ ↩2
- https://extension.usu.edu/pests/research/lily-leaf-beetle ↩ ↩2
- https://www.epa.gov/ingredients-used-pesticide-products/pyrethrins-and-pyrethroids ↩ ↩2
- https://www.stopthebeetle.info/biocontrol.html ↩ ↩2
- https://hort.extension.wisc.edu/articles/lily-leaf-beetle/ ↩ ↩2
- https://ag.umass.edu/landscape/fact-sheets/lily-leaf-beetle ↩ ↩2
- Wisconsin Horticulture ↩
- Wisconsin Horticulture ↩
- USU ↩
- USU ↩
2 Comments. Leave new
I found bugs in my house in Wisconsin that is very similar to the Skeletonizing Leaf Beetle. The shape is exactly the same, with the exception of the antennae being shorter. The ones I had looked a little less green, when they fly the look brown, but on closer examination they are green. And the head area is more brown and less yellowish. Could this still be the same type of bug? I haven’t been able to find anything else even close. I tried to get a picture but it was too blurry.
Gorgeous!