Armyworm & Cutworm: Identification, Damage & Natural Control

Armyworm & Cutworm

Armyworms and cutworms are night-feeding caterpillars that chew foliage and sever young plants at the soil line, causing rapid stand loss in cereals, vegetables and row crops. Vegalab manages them with a two-part natural program: Larva Control for foliar larvae and Larva BioControl (beneficial nematodes) for soil-stage cutworms.

Common crops affected

Cereals
Corn
Brassicas
Vegetables

What is it?

Armyworms (Spodoptera and relatives) feed gregariously on foliage and can strip a crop in days; cutworms (Agrotis) feed at night and cut seedlings off at the base. Both are moth larvae whose populations can erupt after migratory moth flights.

How to identify it

Armyworm: smooth caterpillars with stripes, feeding in groups; ragged leaf feeding and “windowpaning” on young plants.
Cutworm: plump, greasy-grey larvae that curl into a C when disturbed; seedlings cut off at or just below the soil line.
Larvae shelter in soil, debris or leaf whorls by day and feed at night.
Sudden patches of toppled seedlings or rapid defoliation are key field signs.

Life cycle & spread

Moths migrate and lay egg masses; larvae develop over 2-4 weeks, then pupate in the soil. Several generations occur per season, and outbreaks often follow weather that concentrates moth flights.

Conditions that favour it

Outbreaks follow heavy moth flights, mild wet springs (cutworm) and lush early growth. Weedy fields and debris give larvae shelter.

Damage and how it spreads

Armyworms cause rapid defoliation; cutworms cause stand loss by severing seedlings — both can happen overnight, sometimes requiring replanting.

Monitoring & scouting

Scout at dusk or early morning; check soil and debris near cut plants; use pheromone traps for moth flights. Target early instars before they disperse.

How to control it

Treat early instars promptly;
address both the foliar and soil stages where present;
keep field margins and debris clean to reduce shelter.

Role	Product	Use
Primary control	Larva Control
Also apply	Larva BioControl

Preventing it next season

Early scouting after moth flights, clean field margins and debris, and prompt treatment of early instars before stand loss.

Not sure this is what's affecting your crop? Ask an agronomist about your crop →

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Frequently asked questions

What's the difference between armyworm and cutworm control?

Armyworms feed on foliage — use Larva Control; cutworms feed at the soil line and shelter in soil — add Larva BioControl nematodes.

How fast do they cause damage?

Often overnight — defoliation (armyworm) or cut seedlings (cutworm). Scout and act early.

Which crops are at risk?

Cereals, corn, brassicas, vegetables, turf and row crops.

Can I use both products together?

Yes — Larva Control targets foliar larvae and Larva BioControl targets soil-stage larvae; they're complementary.

When should I scout?

At dusk or early morning, when these night-feeders are active, and after moth flights.