How to identify a Fall Army worm
- Fall Army worm eggs are normally whitish/cream in color when fresh, but turn dark/grey when they are about to hatch.
- They are normally covered in fine hairs and white wool-like material.
- Laid in clusters between 100-299 eggs per cluster on the upper or lower sides of the leaf, the stalk and funnel of the maize plant.
- Eggs normally hatch within 2-3 days after being laid
Image Source: CABI
Fall Armyworm larvae (caterpillar)
- The young caterpillars spin silken threads that they use to move from one plant to the other aided by the wind.
- Newly hatched caterpillars are green in color during the 1st-2nd instars and turn brown to black from 3rd to 6th
- The fall army worm caterpillars have a dark head with a pale, upside down Y-shaped mark on the front.
- The big caterpillars have four raised dark spots that form a squarepattern on the 2nd to the last segment when seen from above.
- The caterpillars can live for 12-20 days depending on the temperature and other environmental conditions.
- They like hiding in the funnels during the day to prevent being seen.
- Newly hatched caterpillars are normally black in color, and move in a mass away from the other eggs towards the maize funnel.
- They normally hide inside the maize whorl during the day and mainly come out in the evening and early in the morning. This is mainly to feed and cause crop damage.
- If you detect tiny holes, large ragged holes and orange sawdust-like material on leaves, be sure that you have Fall Army worm infestation in your crop.
- Fall Army worms are cannibalistic and tend to fed on younger caterpillars.
Image: Syngenta seed care
Fall Army worm pupa
- The pupa is reddish brown in color and forms a cocoon of about 20-30mm in length and is oval in shape. They are mostly found in the soil 2-8cm deep.
- The pupa lives for 12-14days before the moth emerges.
Fall Army worm moths
The moths can fly long distances in a single night, mate and lay eggs. A female moth can lay up to 1500eggs in her lifetime.
- The moth is grey brown in color
- Male moth: Has conspicuous white spots on the tip and center of the forewings. The forewings are grey and brown in color.
- They live up to 2-3 weeks before dying
- Migratory and can travel long distances
Symptoms of pest damage
- Check for small to large irregular and elongated holes on the leaves.
- Window panes of translucent patches are caused by small FAW in the 1st – 2nd
- Large irregular elongated holes on leaves are caused by the big FAW in the 3rd – 6th
- Sawdust-like material(“frass”) in the maize funnel or on the leaves, tassels and cobs show heavy infestation in the plant
Difference between a fall army worm and African army worm
African army worms may seem similar to fall army worms, but have some distinctions. The fall army worm normally creates small holes in the stem of maize crops which is contrary to African army worms.
For African army worms, they normally hatch somewhere outside the farm and then steadily eat their way through everything in their path as a group. However, for the fall army worm moth, it lays its eggs on the host plant. The larvae fall army worm does not eat everything, but as it grows moves up the maize plant causing more damage. The fall army worm also makes a lot of yellowish debris and whitish powder on the leaves and funnel where they are.