Western Red Cedar with Caterpillars: Prevention & Cure

Thuja plicata

Susceptibility: Moderate Severity: High Difficulty: Easy

Caterpillars on Western Red Cedar: What to Know?

Caterpillars on Western Red Cedar (Thuja plicata) is a pest condition with high severity. Western Red Cedar has moderate susceptibility to this disease. Caterpillars are the larval stage of moths and butterflies that feed voraciously on plant foliage, stems, flowers, and fruits. Common species include cabbage loopers, tomato hornworms, armyworms, and...

Western Red Cedar is a easy-care plant. Recovery from Caterpillars takes approximately 21 days with proper treatment.

Unlike fungal diseases, Caterpillars on Western Red Cedar responds quickly to integrated pest management. Without precautions, chemical treatments for Caterpillars can be harmful to pets. Use organic methods for Western Red Cedar in pet-friendly homes.

🔍 What Does Caterpillars Look Like on Western Red Cedar?

• Irregular holes and ragged edges on leaves
• Large portions of foliage completely consumed
• Dark cylindrical droppings (frass) on leaves and soil
• Visible caterpillars of various sizes on plant surfaces
• Skeletonized leaves with only veins remaining
• Bore holes in fruits, vegetables, and flowers
• Defoliation starting from leaf edges
• Stunted plant growth from severe feeding damage
• Presence of white cocoons or pupae on plants

❓ What Causes Caterpillars on Western Red Cedar?

→ Adult moths and butterflies laying eggs on host plants
→ Eggs hatching into hungry larvae seeking food
→ Warm weather accelerating reproduction cycles
→ Poor garden sanitation harboring overwintering pupae
→ Lack of natural predators in garden ecosystem
→ Dense plantings making detection difficult
→ Introduction from infected transplants
→ Nearby weeds serving as alternative host plants

💊 How to Treat Caterpillars on Western Red Cedar?

TLDR: Treat Caterpillars on Western Red Cedar with quick treatment (~11 days) or organic (~21 days). Western Red Cedar has moderate susceptibility to this disease.

⚡

Quick Fixes

Step 1

Hand-pick all visible caterpillars immediately and destroy in soapy water

Step 2

Mix emergency spray: 2 tablespoons dish soap + 1 quart water

Step 3

Add 1 teaspoon cayenne pepper or hot sauce to soap solution for added deterrent

Step 4

Spray solution directly on caterpillars and all leaf surfaces

Step 5

Use strong water spray from hose to physically dislodge caterpillars

Step 6

Remove severely damaged leaves and plant parts to eliminate hiding spots

Step 7

Repeat soap spray treatment every 2-3 days for one week

Step 8

Monitor plants twice daily and remove any new caterpillars immediately

🌿

Organic Treatment

Step 1

Inspect plants early morning or dusk when caterpillars are most active and visible

Step 2

Hand-pick caterpillars wearing gloves, placing them in jar of soapy water

Step 3

Check leaf undersides and stems for eggs (small clusters of white or yellow spheres) and crush them

Step 4

Mix Bacillus thuringiensis (Bt): 1-2 tablespoons per gallon of water in spray bottle

Step 5

Spray Bt solution thoroughly on all foliage, especially leaf undersides where caterpillars hide

Step 6

Apply Bt in late afternoon/evening when caterpillars are actively feeding for best results

Step 7

Reapply Bt every 5-7 days or immediately after rainfall

Step 8

Introduce beneficial insects: release ladybugs (1,500 per 1,000 sq ft), lacewings, or parasitic wasps

Step 9

Encourage natural predators by planting nectar-rich flowers (yarrow, dill, fennel) nearby

Step 10

Install bird feeders and water sources to attract insect-eating birds

Step 11

Apply diatomaceous earth around plant bases as physical barrier

Step 12

Continue monitoring and hand-picking for 3-4 weeks until no new caterpillars appear

🛡️ How to Prevent Caterpillars on Western Red Cedar?

TLDR: Prevent Caterpillars on Western Red Cedar with 9 essential preventive care practices.

✓ Inspect plants regularly, especially leaf undersides, for eggs and young larvae
✓ Remove eggs and small caterpillars by hand before populations explode
✓ Use floating row covers to exclude adult moths from laying eggs
✓ Maintain diverse plantings to attract beneficial predators
✓ Plant aromatic herbs (rosemary, sage, thyme) as companion plants to repel moths
✓ Keep garden free of plant debris and weeds that harbor pupae
✓ Rotate crop locations annually to break pest cycles
✓ Encourage birds by providing water sources and nesting sites
✓ Till soil in fall to expose overwintering pupae to predators and cold

🌱 How to Care for Western Red Cedar to Prevent Caterpillars?

💧 How to Water

Water regularly, keeping the soil consistently slightly moist—especially during the first 2 years after planting. Mature specimens can tolerate short periods of drought but do not tolerate prolonged soil drying. Avoid both overwatering and water stagnation. Mulching around the trunk is recommended to help retain moisture and protect the roots.

☀️ Lighting

The Western Red Cedar grows best in full sun (at least 6 hours a day) but also tolerates partial shade well. Avoid locations exposed to strong, dry winds or intense western sun during hot summers—high temperatures and drought are the main enemies of this species.

🪴 Ideal Soil

Prefers humus-rich, well-drained, but consistently moist soil—optimally sandy loam or fertile clay. It tolerates a wide pH range (5.5–7.5) and temporary flooding. It does not perform well in very dry, sandy, or poor soils. Annual organic mulching (bark, compost) around the root ball significantly improves the tree's condition.

Frequently asked questions

Can Caterpillars kill my Western Red Cedar?

Yes, without treatment, Caterpillars can be fatal to Western Red Cedar. Early detection and treatment are key.

How long does Western Red Cedar take to recover from Caterpillars?

With proper treatment, recovery takes approximately 21 days. Without treatment, it can take significantly longer.

Is Caterpillars contagious to other plants near Western Red Cedar?

Yes, Caterpillars can spread to nearby plants. Isolate the affected Western Red Cedar immediately.

See more: Western Red Cedar → See more: Caterpillars →