Fall armyworm
The invasive whorl-feeder that became maize’s number-one pest — caught early it is manageable, left late it strips the crop.
- Pest type
- Whorl-feeding caterpillar
- Attacks
- Whorl & leaves (later cobs)
- Worst in
- Early vegetative maize
- Main risk
- Rapid defoliation of young crop
Overview
Fall armyworm (Spodoptera frugiperda) is an invasive caterpillar that reached India in 2018 and rapidly became the most serious pest of maize, and a threat to sorghum and other crops. The moth lays egg masses on the leaves; the young caterpillars scrape the leaf, then move into the central whorl of the plant and feed there, protected.
Whorl feeding leaves the tell-tale damage: rows of ragged holes and windows across the emerging leaves, and a mass of wet, sawdust-like frass (droppings) in the whorl. A young maize crop can be severely defoliated within days if the pest is not caught early, which is why frequent scouting from emergence and prompt action at the young-larva stage matter more than any single spray.
How to identify it
- Ragged holes and elongated "windows" across young leaves, and a whorl full of wet, sawdust-like frass.
- A caterpillar with a pale inverted-Y mark on the head and four dark spots in a square on the second-to-last segment — the key identifiers.
- Egg masses covered in greyish felt-like scales on the underside of leaves.
- Later in the season, caterpillars may bore into the cob through the silk or the side.
The damage it does
- Extensive ragged feeding on whorl leaves that can severely defoliate a young maize crop within days.
- Damage to the growing point in heavy attacks, killing or stunting the plant.
- Later cob boring that directly reduces grain yield and lets in rot.
- Fast build-up — one uncontrolled generation seeds the next, so early lapses are costly.
When to act
- Scout twice a week from crop emergence, checking the whorls of a set number of plants and recording the percentage showing fresh damage.
- Act at the young-larva stage on the recommended threshold (commonly around 5–10% damaged whorls in early-stage maize — follow the local advisory).
- Pheromone traps for fall armyworm help detect the moths and time action; the young-larva window is when control works best.
Organic & cultural control
- Hand-pick and crush egg masses and young caterpillars in small plots, and apply dry sand or ash into the whorl, which abrades the larvae.
- Release Trichogramma egg parasitoids and spray Bt or entomopathogens (Metarhizium/Beauveria, or SfNPV) against young larvae.
- Set fall-armyworm pheromone traps for monitoring/mass-trapping, keep bird perches, and avoid staggered maize sowing that gives a continuous food bridge.
- A vigorous, well-fertilised crop outgrows early whorl damage better than a stressed one.
Chemical control
- Direct the spray into the whorl, where the caterpillar hides, and treat while larvae are young — CIB&RC-registered options include emamectin benzoate 5% SG, spinetoram 11.7% SC and chlorantraniliprole 18.5% SC.
- Whorl application (spray directed down into the funnel) is far more effective than a blanket foliar spray.
- Rotate insecticide groups to slow resistance, and observe the label pre-harvest interval, especially on green cobs.
- Confirm the current recommendation and dose for your area with your local KVK or the state agriculture advisory.
Crops most at risk
Where this problem is called out in our crop guides — open a crop for the full package of practices.
Frequently asked questions
My young maize has ragged holes and wet sawdust in the whorl. What is it?
That is fall armyworm — ragged holes and windows on the leaves with wet, sawdust-like frass packed into the central whorl. Look for a caterpillar with a pale inverted-Y on the head and four dark spots on the rear segment. Act quickly at this young-larva stage by spraying into the whorl.
Why spray into the whorl instead of over the whole plant?
Because the fall armyworm caterpillar hides and feeds deep in the central whorl, a blanket spray over the leaves largely misses it. Directing the spray (or dry sand/ash) down into the whorl reaches where the larva actually is, which is why whorl application is far more effective than a general foliar spray.
Is fall armyworm new to India?
Yes — it is an invasive pest that arrived in India in 2018 and spread rapidly to become the main pest of maize. Because it builds up fast and can develop resistance, manage it with regular scouting, biocontrol (Trichogramma, Bt), pheromone traps and threshold-based, rotated whorl sprays rather than routine calendar spraying.
Symptoms and control measures follow ICAR, KVK and state agricultural-university package-of-practices; any named chemical is a registered use. Always read the product label and confirm the dose for your crop and zone. editorial policy.