How to Eliminate Bagworms from Arborvitae

📋 Steps

Remove every bag you can reach right now (fall-spring)

In fall, winter, or spring: pull off and destroy every bag you can reach by hand. Each bag contains up to 1,000 eggs. A ladder, pole pruner, or long reach extends your range. Bag and discard them — don't drop on the ground where eggs still hatch. This reduces next year's population by 50-90% with zero chemical cost.

Mark June 1 as your annual spray date

Bt kurstaki spray on arborvitae and juniper in the first 3 weeks of June, when bags are tiny (under 1cm) and larvae are in early instars, provides 80-90%+ kill. After July 4, chemical control is much less effective as caterpillars mature inside protective bags.

Apply Bt kurstaki spray in June to all foliage

Mix Bt kurstaki (DiPel, Thuricide) per label and spray all foliage to the point of runoff. Cover all branch tips where bags form. Repeat in 7-10 days for complete coverage. This is OMRI organic — safe for all beneficial insects except caterpillars.

For July-August infestations: switch to spinosad

If you missed the June Bt window, spinosad spray is more effective on larger caterpillars. It's not as effective as early Bt but provides meaningful knockdown on partially mature larvae.

Set a permanent calendar reminder for June 1 every year

Bagworm management is an annual commitment. The population resets each spring from overwintering eggs. A June 1 calendar reminder ensures you never miss the spray window again.

💡 Tips

Arborvitae killed by bagworms does not recover — prevention is far cheaper than replacement
Heavy bagworm years follow warm winters and early springs that allow higher egg hatch survival and faster larval development
On small trees you can reach fully, hand-picking in fall removes more of next year's population than any spray applied too late
Bagworms also attack apple, cherry, rose, and many deciduous trees beyond arborvitae and juniper — check ornamental trees in the vicinity

⚖️ Educational use only.

💰 Cost to Fix This Problem

Approach	Typical Cost	Best For
DIY materials only	$25–$75	Mild or early-stage infestations
Professional service (one-time)	$150–$400	Active infestations or when DIY has already failed
Ongoing service contract	$400–$800/yr	Prevention and long-term peace of mind

Approach

Typical Cost

Best For

DIY materials only

$25–$75

Mild or early-stage infestations

Professional service (one-time)

$150–$400

Active infestations or when DIY has already failed

Ongoing service contract

$400–$800/yr

Prevention and long-term peace of mind

Costs vary by region, property size, and severity. Get at least two quotes before hiring.

✅ How to Know It's Working

Pest control success is measured in weeks, not days. Here's what to look for:

Week 1–2: You may see increased activity as pests are flushed from hiding. This is normal.

Week 2–4: Activity should drop noticeably. Bait traps or sticky monitors should show declining counts.

Week 4–6: New activity near zero. Any resurgence means a population was missed or re-introduction occurred.

💡 Monitoring tip: Place sticky traps in corners and along walls before you start treatment. Counting catches weekly gives you objective data on whether the population is declining.

👷 When to Call a Professional

DIY is appropriate for small, contained infestations caught early. Call a licensed professional when:

You've tried DIY twice with no lasting improvement

The infestation involves a wall void, crawlspace, or area you can't safely access

There's a health risk involved (hantavirus, anaphylaxis risk, etc.)

The problem covers more than one room or a large outdoor area

You have children, elderly, or immunocompromised individuals in the household

⚠️ Rule of thumb: If you've spent more on DIY materials than a professional visit would cost, it's time to call.

❓ Frequently Asked Questions

When should I treat for Japanese beetles?

Adult season runs late June through August. Apply milky spore or beneficial nematodes to lawn areas in late August-September to kill grubs before winter. For adult control, hand-pick in early morning or apply neem oil.

Do Japanese beetle traps work?

Bag traps attract 5-10 times more beetles than they capture, often increasing plant damage. University research consistently recommends against using traps near gardens. If used, place them at least 50 feet from garden areas.

Will treating my lawn for grubs stop adult beetles?

It reduces next-generation beetles from your property, but adults fly up to 5 miles. Neighborhood-level grub management over several years is needed. In the meantime, hand-picking and neem oil protect individual plants.

What plants do Japanese beetles prefer?

Roses, grape vines, linden trees, birch, crabapple, and raspberry bushes. Less-preferred plants include boxwood, dogwood, holly, magnolia, and most evergreens.

How to Eliminate Bagworms from Arborvitae and Juniper

📋 Steps

💡 Tips

💰 Cost to Fix This Problem

✅ How to Know It's Working

👷 When to Call a Professional

❓ Frequently Asked Questions