Ten-lined June Beetle: What Every Homeowner in the West Needs to Know

If you live in Utah, California, or Colorado, the Ten-lined June Beetle may already be a visitor to your yard — and not a welcome one. This native insect has been observed in increasing numbers across the western United States, raising concerns for homeowners and land managers who want to protect the health of their trees. While its threat level is considered moderate, early identification and timely action are the best tools you have.

Here's everything you need to know about Ten-lined June Beetle identification, symptoms, and treatment options.

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What Is the Ten-lined June Beetle?

The Ten-lined June Beetle is an insect pest that has been documented through research-grade observations across the western United States. Like many beetles in its family, it has a life cycle that includes both larval and adult stages — each of which can interact with your trees and landscape in different ways.

The threat it poses is rated moderate, meaning that while it is not typically a tree killer on its own, infestations left unchecked can contribute to declining tree health, particularly in trees that are already stressed by drought, poor soil conditions, or other pressures common in the West.

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

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How to Identify the Ten-lined June Beetle

Ten-lined June Beetle identification starts with knowing what to look for. This beetle is notably large compared to many common garden insects, making it somewhat easier to spot during its adult emergence period. The distinctive markings that give this beetle its name — bold lines running along its body — make it recognizable to observant homeowners.

Beyond spotting the adult beetle itself, here are some general signs that beetle activity may be present in your landscape:

• Adult beetles may be found near outdoor lights at night during warmer months, as many beetles in this family are attracted to light during their active season.
• Larval grubs may be present in the soil near the root zones of affected trees, though they are hidden underground and harder to detect without digging.
• Soil disturbance or soft, spongy ground near tree bases can sometimes indicate subsurface larval activity.

Not sure what you're dealing with? Use our diagnosis tool to get a more personalized assessment based on what you're observing in your yard.

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Where Is the Ten-lined June Beetle Spreading?

Current observations place the Ten-lined June Beetle across three key states:

• Utah
• California
• Colorado

Research-grade iNaturalist observations have documented this insect actively in the wild across these regions. If you are a homeowner or land manager in any of these states — particularly in areas with established conifers or ornamental trees — it is worth staying vigilant, especially during the warmer months when adult beetles are most active.

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Ten-lined June Beetle Treatment Options

The good news is that Ten-lined June Beetle treatment options are available, and acting during the right stage of the insect's life cycle significantly improves your results. Here are the three primary approaches:

1. Targeted Insecticide Application Applying an appropriate insecticide can be effective, but timing is critical. Treatments should be timed to coincide with the vulnerable larval stage in the soil or during adult emergence above ground. Always follow label directions carefully, and consider consulting a professional to ensure you're using the right product at the right time.

2. Biological Control Agents For homeowners who prefer a lower-chemical approach, biological control is worth exploring. This includes encouraging or introducing natural predators and parasitoids into your landscape. Options may include predatory beetles, parasitic wasps, or the application of Bacillus thuringiensis (Bt), a naturally occurring soil bacterium used against certain insect pests. Biological controls work best as part of an integrated pest management strategy.

3. Infested Material Removal Pruning and removing infested branches and plant material can help reduce the pest population and limit spread. Remove fallen debris from around the base of your trees, as this material can harbor eggs or larvae. Dispose of any removed material away from healthy trees — do not compost it on-site.

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When to Call an Arborist

While proactive homeowners can take meaningful steps on their own, there are situations where professional help is the right call:

• You're unsure whether what you're seeing is actually Ten-lined June Beetle or a different pest
• The infestation appears widespread across multiple trees
• Your trees are already showing signs of decline or stress
• You want to apply insecticide treatments safely and effectively
• You'd like a full property assessment and integrated pest management plan

An ISA Certified Arborist can assess the severity of an infestation, recommend targeted treatments, and help you build a long-term tree health strategy. Use our find an arborist tool to locate a certified professional in your area.

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Staying informed is your first line of defense. Monitor your trees regularly, act early when you notice something unusual, and don't hesitate to seek expert guidance when the situation calls for it. Your trees are a long-term investment — protect them accordingly.