Fall Armyworm in Maize: How to Scout, When to Spray and What Works

Since it arrived in East Africa in 2016, fall armyworm has become the most damaging maize pest for many farmers in Kenya, Uganda and Tanzania. The good news: farmers who scout regularly and act early lose far less than those who spray by calendar or wait until damage is obvious.

Know what you are looking for

Young larvae scrape the leaf surface, leaving small, papery 'windows'. Older larvae chew ragged holes and hide deep in the whorl, leaving moist, sawdust-like frass. A mature larva has an inverted 'Y' on its head and four dark spots in a square near its tail.

A 10-minute scouting routine

1. Walk a 'W' pattern across the field, starting at least 10 steps in from the edge.
2. Stop at 5 points and check 10 consecutive plants at each — 50 plants in total.
3. Count plants with fresh damage (windowing or holes with fresh frass).
4. Scout twice a week from emergence to tasselling; the first six weeks matter most.

Control options that work

Cultural control

• Plant early and at the same time as neighbours, so fields are not attacked in sequence.
• Intercrop with beans or desmodium; diverse fields support natural enemies.
• Keep maize well fed — vigorous plants tolerate more leaf damage.

Chemical control

When the threshold is reached, apply a registered insecticide into the whorl, early in the morning or late afternoon when larvae are active. Targeted products for caterpillars generally outperform older broad-spectrum pyrethroids against fall armyworm. Rotate between insecticide groups to delay resistance, and never exceed the label rate.

When to call for help

If damage is spreading despite spraying, or you are unsure of the pest, send a clear photo of the larva and damage to our agronomy team on WhatsApp. We will confirm the pest and recommend a product and rotation plan for your stage of crop.