Sod Webworm Identification

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PestControlBasics Editorial Team

Reviewed by Derek Giordano · Updated 2026

Illustrated identification guide — PestControlBasics.com

🔍 Identification

Adults: small moths (15-20mm) that fly in a zig-zag pattern over lawns at dusk; hold wings rolled tightly against body when resting. Larvae: 15-25mm; green-grey with dark spots; live in silk-lined tubes at the soil surface. Evidence: irregular brown patches in July-August; birds feeding intensively in patches; silk tubes visible when lawn is parted.

🧬 Biology & Behavior

Adults lay eggs on grass; larvae hatch and feed on grass blades at the surface. Multiple generations/year in the South. Damage peaks in July-August during hot, dry weather. Cool-season grasses most susceptible during summer heat stress.

⚠️ Damage & Health Risk

Irregular brown patches appearing suddenly in summer; birds feeding in affected areas; grass blades cut at the base; damage expands rapidly in hot dry weather.

🔧 DIY Treatment

Confirm: sod webworm damage leaves roots intact; white grub damage means roots are eaten and turf peels like carpet. Spinosad or Bt kurstaki spray in late afternoon when larvae emerge. Bifenthrin for fast knockdown. Apply when larvae are actively feeding (late afternoon to evening).

👷 When to Call a Pro

Large lawn areas benefit from professional boom sprayer application for uniform coverage.

❓ FAQ

How do I tell sod webworm from white grub damage?

Peel back a damaged patch: webworm damage — roots intact, grass snapped at blade level. White grub damage — roots gone, turf peels off soil like carpet. This single test settles it definitively.

When to spray for sod webworms?

Late afternoon or early evening when larvae emerge from silk tubes to feed. Morning applications are much less effective — larvae hide during daytime. Spinosad is most effective on actively feeding caterpillars.

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 🐛 Sod Webworm — Complete Guide

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.

🐛 Sod Webworm — Complete Guide