Fall armyworm (FAW) [Spodoptera frugiperda] is an insect pest with moths as the adult stage and larvae (caterpillars) as the destructive stage.

In Kenya, the pest was first reported in March 2017 in Western Kenya and has since spread countrywide. The pest attacks a wide range of crops but maize and sorghum are the most preferred hosts. It can cause up to 100% yield loss if left uncontrolled.

This blog post provides information on the identification and management of the pest.

Identification of Fall Armyworm

Fall armyworm has 4 main stages of development: Egg, Larva, Pupa, and Adult.

The complete life cycle takes 40-47 days depending on the prevailing weather conditions. It takes short periods under warm conditions.

• Fall armyworm adult moths lay eggs in batches on host plants, normally on young leaves.
• The white egg masses are normally covered with wool-/ cotton-like material of the adult moth scales.
•  The larvae have 6 developmental stages (instars) that are the destructive stages and take the longest time in the life cycle.

Indicators of fall armyworm attacks

There are two ways of knowing whether a crop has a FAW attack:

1. Presence of any of the stages of fall armyworm (eggs, larvae, pupae and adults).
2. Damage caused by fall armyworm larvae on an infested crop.

How to identify FAW caterpillars

• The 1st instar larvae are very small and dark grey in colour. The 2nd and 3rd instars are greenish or yellowish-brown in color and have hair-like spikes.
• The 4th to 6th instars are brownish and have a characteristic light-colored “inverted Y” mark on the head front, which links with the middle thin stripe.
• There are 4 black dots in a square formation on the rear abdominal segment.

Damage Symptoms

• Young larvae (1st to 3rd instar stages) feed on leaves, causing transparent window pane-like damage, initially appearing as “scratch marks” on the leaf.
• Older larvae (4th to 6th instars) cause large ragged and elongated holes on leaves, leading to a shredded appearance.
• At the reproductive stages of the host plant, older larvae clip the tassels, make shot holes on ears and feed on grains.
•  Larvae produce large amounts of frass (excreta) as they feed and grow.