Flea Beetle

Phyllotreta cruciferae

Flea Beetle

Phyllotreta cruciferae

Flea Beetle

Phyllotreta cruciferae

Crucifer Flea Beetle (Phyllotreta cruciferae) – A Major Pest of Brassica Crops

Temperature & Humidity Preferences

• Optimal Temperature: Survives between 16°C – 32°C.
• Humidity: Affects beetle capture height.
• Weather Conditions: Rain and cool weather force beetles to take cover.

Identification

• Adult Beetles:
  • Blue-black, shiny, 3-4.5 mm long.
  • Use specialized hind legs to jump when disturbed.
• Larvae:
  • Creamy white, up to 7 mm long, dark spots on back.
• Species Variation:
  • Crucifer flea beetle: Uniform black and shiny (~2 mm long).
  • Striped flea beetle: Has two yellow stripes on its back.

Life Cycle

• Winter: Adults overwinter in shrubs/woody borders.
• Spring (May): Move into fields, feed, and mate.
• Eggs: Laid in soil near plants, hatch in 11-13 days.
• Larvae: Feed on root hairs, pupate underground in 2 weeks.
• Summer Generations:
  • First adult generation emerges in mid-June.
  • Second generation emerges in late July, feeding on fall brassica crops.
• Fall (September): Feeding declines, beetles move to forested areas for winter.

Crop Damage & Injury

• Feeding Pattern:
  • Adults create small round holes in leaves and stems.
  • Heavy feeding kills seedlings.
  • Moderate damage reduces yield & marketability.
• Crop Susceptibility:
  • Glossy-leaved crops (bok choy, Napa cabbage, mustard) → Highly attractive, whole leaf damaged.
  • Waxy-leaved crops (cabbage, broccoli, kale) → Less attractive, feeding restricted to leaf margins.
• Damage Window: From planting to harvest.