Diamondback Moth (Plutella xylostella) – Brief Overview

Life Cycle & Development

• Completes metamorphosis with four instar stages.
• Total development time: 17 to 51 days, averaging 25-30 days, depending on temperature.
• Generations per year: Typically three (varies by climate).
• Egg stage:
  • Oval, flattened, yellow/pale green.
  • Laid in small groups (2-8 eggs).
  • Hatch in ~5.6 days.
• Larva stage:
  • Passes through four instars (3-10 days per stage).
  • Feeds on internal and external leaf tissue.
  • Moves rapidly backward when disturbed, dropping on a silk thread.
• Pupa stage:
  • Forms a delicate white cocoon on the host plant.
  • Lasts 7-14 days.
• Adult stage:
  • Weak fliers, mating occurs at night.
  • Females lay ~150 eggs on leaves.
  • Moths migrate from southern US via wind currents.

Plant Damage & Impact

• Larvae feed on leaves, leaving only veins.
• Severe damage disrupts head formation in cabbage, broccoli, and cauliflower.
• Infestation in florets can lead to crop rejection.
• First-generation causes less damage, but second-generation infestation is more destructive.

Key Characteristics

• When disturbed, larvae thrash and drop on silk threads.
• Larval body tapers at both ends with distinct V-shaped prolegs.
• Moths do not overwinter in cold regions, leading to yearly variations in infestation levels.