southwestern corn borer larva 5 copy.jpg

Southwestern corn borer


  • Adult: Dull white moth with a snoutlike mouth.
  • Larvae: Initially very light gray with a brown head and rows of dark spots. Over time, the spots fade and the larvae turn yellow-white.
  • Eggs: Greenish-white at first but within a few days develop three red transverse lines. 

Timing of damage: First generation: V6 to VT. Second generation: V12 to R6.

Type of damage: First generation: Leaf feeding, tunneling into the midvein and boring into stalks. Second generation: Leaf feeding and boring into stalks, tassels, ears and shanks. Larvae are known to bore into the stalk and tunnel down through it.

Scouting: Inspect 20 plants in five locations. First generation: Record whorl feeding. Second generation: Record eggs and live larvae in the ear zone.

Economic threshold: When 35% of the whorls show fresh feeding and larvae are present. Timing is critical; once in the stalk, borers cannot be controlled.

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