Official CIMMYT translation
Home Pests and diseases


Common names:
Armyworm, African armyworm (Okalambo), Rice armyworm.
Latin names: Spodoptera and Pseudaletia spp. Common species include Pseudaletia unipuncta (Haworth) and Spodoptera exempta (Walker).

Damage to plants 

  • Entire leaves and young plants can be consumed during severe infestation.


  • ‘Window pane’ damage to leaves caused by newly emerged larvae, which feed by scraping the leaf surface without perforating it.
  • Ragged leaf appearance from the leaf edges inwards, also due to feeding.
  • Under severe infestation the entire foliar tissue might be lost, with only midribs remaining.  Lower leaves are consumed first.
  • Large number of caterpillars migrating across fields and roads.
  • Worm frass (feces) on the ground below plants.

Factors favoring insects / pest development

  • Moths are attracted to vegetation and therefore no-tillage maize and weedy fields are targets for oviposition.
  • Prevailing wind currents can aid adult moth dispersal.
  • Cold, wet planting seasons that follow drought years favor armyworms due to a reduction in natural predators and parasitoids.   

Geographical distribution

  • Armyworm is globally distributed through the tropics and subtropics.
  • It is also found in Europe, Russia, and the United States.

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