Mourning Cloak: What Homeowners Need to Know About This Tree Insect

If you've been tracking tree health in California, Ohio, Colorado, Minnesota, or Illinois, you may have come across reports of the Mourning Cloak — an insect that has drawn the attention of arborists and naturalists alike. Rated as a moderate severity threat, this insect is worth understanding before it becomes a bigger problem on your property. Read on for everything you need to know about Mourning Cloak identification, symptoms, and treatment options.

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What Is the Mourning Cloak?

The Mourning Cloak is an insect pest that has been documented through research-grade observations on iNaturalist, a widely respected citizen science platform used by naturalists and professional ecologists. Its presence in the wild has been confirmed across multiple U.S. states, making it a legitimate concern for homeowners and land managers who care about the long-term health of their trees.

While the Mourning Cloak is currently classified as a moderate threat, that designation shouldn't invite complacency. Moderate-severity insects can still cause meaningful damage to trees — particularly those already stressed by drought, disease, or environmental pressures — and early intervention is almost always more effective than waiting.

For a complete breakdown of this pest's biology and history, visit our full ailment details page.

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How to Identify the Mourning Cloak

Mourning Cloak identification starts with careful observation of your trees and the insects found on or around them. Because specific symptom data is still being gathered for this pest, it's especially important to document what you see and cross-reference it with professional resources.

Here are some general identification steps to follow:

• Inspect your trees regularly, paying close attention to leaves, bark, and branch tips for any signs of feeding damage, webbing, or unusual clustering of insects.
• Photograph any insects or damage you observe. Clear, close-up photos from multiple angles are invaluable for accurate identification.
• Note the timing and location of your observations. Which trees are affected? Are symptoms appearing on new growth or older foliage?
• Use our diagnosis tool to submit your observations and get guidance from our plant health database.

If you're unsure whether what you're seeing is related to Mourning Cloak or another issue entirely, professional assessment is the safest path forward.

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Where Is the Mourning Cloak Spreading?

Current data places the Mourning Cloak in the following states:

• California
• Ohio
• Colorado
• Minnesota
• Illinois

If you live in one of these regions, your trees may be at a higher risk of encountering this insect. That said, insect populations are dynamic — they shift with climate, host tree availability, and seasonal conditions. Homeowners in neighboring states should also stay alert and continue monitoring their trees throughout the growing season.

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Mourning Cloak Treatment Options

The good news: there are three established treatment approaches available for managing Mourning Cloak on your property. The right choice will depend on the severity of the infestation, the type of trees involved, and your preferences regarding chemical versus biological methods.

1. Targeted Insecticide Application Applying an appropriate insecticide can be an effective Mourning Cloak treatment when timed correctly. Timing is critical — applications should coincide with the vulnerable larval or adult emergence stage for maximum effectiveness. Always follow label directions carefully, and consult a professional if you're uncertain about product selection or application rates.

2. Biological Control Agents For homeowners who prefer a more ecologically integrated approach, biological controls offer a compelling alternative. This includes introducing or encouraging natural predators and parasitoids such as predatory beetles and parasitic wasps. For caterpillar-stage pests, Bt (Bacillus thuringiensis) is a widely used microbial insecticide that targets larvae with minimal impact on non-target species.

3. Infested Material Removal Physical removal of infested plant material is a critical component of any management strategy. Prune and destroy affected branches, remove fallen debris that may harbor eggs or larvae, and dispose of all material well away from healthy trees. This reduces the reservoir of insects available to re-infest your landscape.

A combination of these approaches is often the most effective strategy, especially for moderate infestations.

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When to Call an Arborist

While some Mourning Cloak management steps can be handled by attentive homeowners, there are clear situations where professional expertise is essential:

• The infestation is widespread or rapidly progressing
• You're unsure of the correct identification and don't want to apply treatments unnecessarily
• The affected trees are large, mature, or high-value specimens
• You want to develop a long-term integrated pest management plan
• Previous treatment attempts have not produced results

An ISA Certified Arborist can assess the full picture — tree health, infestation extent, site conditions — and recommend a targeted plan. Use our find an arborist directory to connect with a qualified professional in your area.

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Staying informed is the first step in protecting your trees. If you suspect Mourning Cloak activity on your property, don't wait — early action keeps moderate problems from becoming serious ones.