Cabbage Looper & Soybean Looper

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PestControlBasics Editorial Team

Reviewed by Derek Giordano · Updated 2026

Illustrated identification guide — PestControlBasics.com

🔍 Identification

Adults: medium-sized brownish moths with a distinctive silver figure-8 mark on the wing (visible at rest). Larvae: 30-38mm; yellow-green; 3 pairs of prolegs (instead of the usual 5) requiring the distinctive looping walk. Found on leaf undersides. Cabbage looper attacks all brassica family plants; soybean looper is a migratory pest of southern soybeans.

🧬 Biology & Behavior

Cannot overwinter above the frost line in most of the US — both species are migrants from the South, reinvading northern states each summer similarly to fall armyworm. Multiple generations per year in warm climates. Resistant to some synthetic insecticides due to agricultural exposure.

⚠️ Damage & Health Risk

Irregular leaf holes; complete defoliation of brassica plants in severe infestations; reduced soybean yield; head damage in cabbage and cauliflower.

🔧 DIY Treatment

Bt (Bacillus thuringiensis kurstaki) spray applied to leaf undersides when caterpillars are small — most effective organic treatment. Spinosad spray. Row covers (prevention for brassicas). For loopers in brassicas, apply Bt at egg hatch (look for eggs on leaf undersides).

👷 When to Call a Pro

Commercial soybean and vegetable operations use economic threshold-based spray programs.

❓ FAQ

How do I identify a looper caterpillar?

The looping walk is diagnostic — the caterpillar arches its midsection with each step due to having fewer prolegs than other caterpillars. Green color and finding it on brassicas or soybeans confirms the ID.

Is Bt effective against loopers?

Yes — Bt kurstaki is highly effective against young looper caterpillars. Apply to leaf undersides where caterpillars feed. Bt breaks down in UV light, so repeat every 5-7 days in outdoor conditions.

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 🐛 Cabbage Looper & Soybean Looper

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.

🐛 Cabbage Looper & Soybean Looper