Fall Armyworm in Corn: How to Spot, Scout and Manage It

In the Philippines, the first suspected case came from a cornfield in Piat, Cagayan on June 20, 2019. Scientists confirmed the species by DNA barcoding. Four months later the pest was in 83 towns and cities across 15 regions, according to the country report filed with the IPPC.

The Bureau of Plant Industry now leads a National Fall Armyworm Action Plan. It covers monitoring with pheromone traps, biological control, farmer training and research.

How to identify fall armyworm

• Eggs. Clusters of about 120 to 200 under the lower leaves, coated with scales from the moth's body.
• Young larvae. Small and greenish, feeding in groups. They scrape the leaf surface so it looks like a thin window.
• Older larvae. Brown to dark, up to 4 or 5 cm long, with three pale lines along the back and dark spots that carry short spines.
• The two marks that settle it. A pale Y on the head that stands on its arms, and four black dots forming a square on the body's last segment.
• Damage. Ragged holes in whorl leaves, eaten edges, and wet frass that looks like sawdust in the whorl. Later, larvae bore into the ears.

Fall armyworm damage on corn

Damage builds fastest at the whorl stage. The larvae hide deep in the funnel of young leaves and eat them before they open. On seedlings, they can also cut the plant at the base.

After that, they move to the tassels and bore into the ears. The USDA 2024 report on the Philippines says fall armyworm has severely hurt corn through stunting and damage to tassels and kernels, which cuts grain quality and yield.

Good control pays. In a Cagayan Valley IPM demonstration reported in May 2025, the IPM plot yielded 7,781 kg per hectare in the dry season. The usual farmer practice next to it yielded 2,417 kg.

How to scout your field

On anee.io you can put a weekly scouting task on the Activities board for every lot, dated from its own planting day. If you are not sure what you found, take a photo and ask Anee, the smart farm technician, in Tagalog or English.

Managing fall armyworm

Cultural control

• Plant together with the farms around you, and avoid planting next to older corn that already carries larvae.
• Keep the field and borders free of weeds, and follow balanced fertilization.
• Crush egg masses and young larvae by hand while you scout.
• Rotate crops when you can, and plow under infested stubble after harvest.

Natural enemies

The Cagayan Valley IPM protocol starts biological control early. Earwigs (Euborellia) go out at about 10,000 per hectare within five days after planting. Trichogramma chilonis cards follow at 50 per hectare between days 5 and 10. After that, sprays of Metarhizium and Beauveria, two fungi that infect caterpillars, come at set intervals.

Birds, ants, beetles and wild earwigs also eat larvae. So avoid broad spectrum sprays early in the season that would kill them too.

Insecticides by active ingredient

Pick by active ingredient and group, not by brand, and rotate groups between sprays to slow resistance. Aim the spray into the whorl, where the larvae hide, and hit them while they are small.

Active Ingredients on Philippine Labels

The table stops at the ten best. 8 more on Philippine labels for it are older or broad chemistry. The Pest Finder in anee.io lists every one, crop by crop, with the products sold here.

Resistance. Fall armyworm reached Asia carrying resistance to pyrethroids, organophosphates and carbamates, and some fields in China now respond less to chlorantraniliprole. Use one group for about 30 days, the life of one generation, then switch: 28, then 5 or 6, then 22A or 15. A group 28 seed treatment counts as the first window.

Note the last two rows. The insecticide Karate and the pyrethroid in Cymbush are familiar names at the agrivet store. But their Syngenta Philippines labels do not list fall armyworm on corn, and the Pacific pests fact sheet notes that the moth reached Africa already resistant to pyrethroids, among other insecticides. Ask your technician whether resistance is a problem in your area.

So choose a product whose FPA registered label names this pest on corn, and follow its rate and harvest interval. Read more in our guide to Karate, Cymbush and Selecron.

Fall armyworm or Asian corn borer?

Both caterpillars attack the whorl, so farmers often mix them up. The Asian corn borer larva is creamy to pinkish with dark spots, and it tunnels into the stalk. The FAW larva is darker, carries the upside down Y and the four dots, and feeds in the whorl without boring the stem, as the ASEAN FAW Action program notes. Name the pest first, because Trichogramma timing and labels differ between the two.

Fall armyworm FAQ