Cutworm

📐 FIELD GUIDE ILLUSTRATION

Original illustration by PestControlBasics.com. Use the labeled features above to confirm your identification.

🔬

PestControlBasics Editorial Team

Reviewed by Derek Giordano · Updated 2026

🔍 Identification

Larvae: 30-50mm; grey to brown to black; smooth or slightly granular skin; C-shaped curl when disturbed; found in soil 1-3 inches deep during daytime. Several species: black cutworm, variegated cutworm, dingy cutworm. All attack the same way — severing stems at soil level at night.

🧬 Biology & Behavior

Adults are noctuid moths that lay eggs on grass and weeds in late summer. Larvae overwinter in soil and become active in early spring when soil warms. They cut stems at night then retreat into the soil. They can also climb plants to feed on foliage. One generation per year for most species.

⚠️ Damage & Health Risk

Severed seedling stems at soil level; overnight loss of entire rows of transplants; wilted seedlings leaning but still attached; reduced stands requiring replanting.

🔧 DIY Treatment

Diagnose by digging 1-2 inches in soil near damaged plants — the cutworm will be curled there. Cutworm collars (paper cups or cardboard rings pushed 1 inch into soil around each transplant) physically prevent cutting. Diatomaceous earth around transplants. Spinosad spray or granules incorporated into soil pre-plant. Beneficial nematodes (Steinernema carpocapsae) applied to moist soil.

👷 When to Call a Pro

For large field vegetable operations, pre-plant spinosad or chlorpyrifos incorporation addresses the population before transplanting.

❓ FAQ

How do I know if cutworms cut my seedlings?

Dig 1-3 inches into the soil directly at the damaged plant base. If a cutworm cut the plant, you'll find the C-shaped grey-brown caterpillar curled in the soil within a few inches of the cut stem. If nothing is found in the soil, investigate slugs (slime trail) or wind damage as alternative causes.

Do cutworm collars really work?

Yes — physical collars are one of the most effective protective measures for transplants. A barrier of cardboard, foam cup, or plastic pushed 1 inch into the soil and rising 2-3 inches above creates an obstacle the cutworm cannot cross easily. Most cost-effective for small plantings; impractical for large-scale production.

Factor	Details
U.S. Range	All or most U.S. states
Regional Detail	Distribution varies — consult your local extension service for regional prevalence data.

Factor

Details

U.S. Range

All or most U.S. states

Regional Detail

Distribution varies — consult your local extension service for regional prevalence data.

📅 Treatment Timing Guide

Treating at the right time dramatically improves results. Pest control timed to the life cycle uses less product and achieves better long-term control.

Period	Action
Spring	Inspection and perimeter treatment before pest season starts.
Summer	Active monitoring and targeted treatments as needed.
Fall	Preventive treatment before overwintering pests seek entry.

Period

Action

Spring

Inspection and perimeter treatment before pest season starts.

Summer

Active monitoring and targeted treatments as needed.

Fall

Preventive treatment before overwintering pests seek entry.

💰 Professional Treatment Costs

Service Type	DIY Cost	Professional Cost
Initial inspection	Free (self-inspect)	$75–$150 (often credited to treatment)
One-time treatment	$30–$100 in materials	$150–$500
Annual service contract	N/A	$400–$900/year
Severe infestation	Often ineffective alone	$500–$2,500+

Service Type

DIY Cost

Professional Cost

Initial inspection

Free (self-inspect)

$75–$150 (often credited to treatment)

One-time treatment

$30–$100 in materials

$150–$500

Annual service contract

N/A

$400–$900/year

Severe infestation

Often ineffective alone

$500–$2,500+

Prices vary by region, property size, and infestation severity.

❓ Common Questions About 🐛 Cutworm

How do I confirm I actually have this pest (not something similar)?

The most reliable confirmation is a physical specimen — capture one and compare to reference images on this page. For cryptic pests (bed bugs, termites), look for secondary signs: frass, shed skins, mud tubes, or bites with a specific pattern. When uncertain, a professional inspection is faster than months of misidentification.

Can I treat this myself or do I need a professional?

DIY is effective for small, accessible infestations caught early. Professionals are worth the cost when: the infestation is inside wall voids or structural elements, multiple rooms are affected, you have health-risk pests (hantavirus, venomous species), or DIY has already failed twice.

How long until the infestation is completely gone?

Expect 3–8 weeks for most infestations with proper treatment. Insects with dormant life stages (pupae, eggs) extend the timeline because those stages are impervious to most insecticides. Follow-up treatments at 2 and 4 weeks catch each new cohort as they emerge.

What's the most common mistake people make treating this pest?

Treating only the visible pest population while ignoring the harborage site, entry point, or breeding location. Killing adults provides temporary relief but the population rebuilds from hidden egg cases, pupae, or new arrivals through unaddressed entry points.

🐛 Cutworm