Corn Borer

Sesamia nonagrioides

1. Identification

• Common name: Maize stem borer, pink stem borer
• Scientific name: Sesamia nonagrioides Lefebvre
• Order: Lepidoptera
• Family: Noctuidae

2. Description of the pest

• Adults: Medium-sized moths (≈ 25–30 mm wingspan); forewings pinkish to brownish; hindwings whitish.
• Larvae: Cream to pinkish caterpillars, with a brown head; up to 30–35 mm long; develop inside the stem.
• Eggs: Laid in masses between the leaf sheaths, usually at the base of the plant.

3. Main hosts

• Maize.
• Sorghum.
• Sugarcane.
• Various wild grasses.

4. Symptoms and damage

• Perforations in young leaves (“windowing”).
• Perforation of the stem, with internal galleries that reduce sap transport.
• Damage to the apical meristem, which can cause “dead heart”.
• Stem breakage and lodging in severe attacks.
• Reduction in ear formation and in productivity.

5. Biological cycle

• Overwinters as a larva inside the stem or in crop residues.
• Adults emerge in spring and summer.
• Females lay eggs between the leaf sheaths.
• Caterpillars quickly bore into the stem, where they complete their development.
• Pupation inside the stem or in the soil.
• 2 to 3 generations per year, depending on climatic conditions.

6. Monitoring

• Observation of “windowing” in young leaves.
• Opening of stems to detect galleries and caterpillars.
• Light traps for the detection of adults.
• Historical record of the holding for risk forecasting.

7. Management measures

• Cultural: Destruction of crop residues; crop rotation; choice of less susceptible varieties; staggered sowing.
• Biological: Release of parasitoids (e.g.: Cotesia flavipes); conservation of natural enemies.
• Integrated protection: Intervention based on monitoring; application of selective methods compatible with beneficials; avoid late treatments due to the protection the stem provides to the caterpillars.

Bibliographic references

• EPPO Global Database – Sesamia nonagrioides.
• CABI Invasive Species Compendium – Sesamia nonagrioides.
• Eizaguirre, M. & Fantinou, A. (2012). Ecology and management of Sesamia nonagrioides.
• Pons, X. et al. (2005). Maize stem borers in Mediterranean regions.