Diamondback Moth

Diamondback Moth Life StagesDiamondback Moth Life Stages
Diamondback Moth Larvae Feeding on Cabbage Diamondback Moth Larvae Feeding on Cabbage
Diamondback Moth Caterpillar Feeding on a Brussel SproutDiamondback Moth Caterpillar Feeding on Brussel Sprouts
Diamondback Moths on a Sticky Trap Diamondback Moths on a Sticky Trap

HOSTS

  • Brassicas
  • Leafy Greens

DESCRIPTION

Diamondback Moth (Plutella xylostella) larvae are greenish-grey, and smooth with no stripes. They are a half inch long. Pupae are green and develop in a loosely spun,
lace-like cocoon that is attached to the leaves or stems. Adult moths are grey-brown with white/cream diamonds.

BIOLOGY

Egg | Larva | Pupa | Adult
Diamondback moths overwinter as adults in trash and debris in and around crop fields. Adults are migratory in northern Utah and resident in southern Utah. Larvae develop through through 4 instars and will pupate in a loose mesh cocoon on the host plant foliage. There are 4-6 generations per year in Utah.

SYMPTOMS

The larvae chew holes in leaves, and may occasionally cause serious defoliation. As caterpillars mature, their feeding intensifies, and they often move into the developing heads. Feeding damage often consists of the removal of all leaf tissue except the leaf veins, sometimes referred to as "window pane" damage. Larvae may also leave frass (fecal material) on plants.

SCOUTING

  • Regularly monitor plants for larvae and pupae and the characteristic "window pane" foliar damage.
  • Pheremone traps specific to diamondback moths attract adult moths to be counted.
  • Check field edges in areas near fields or weeds that had high diamondback moth populations. Adults commonly migrate to new areas from fields that have recently been harvested or disced under.

GENERAL MANAGEMENT

  • Hand remove caterpillars.
  • Use floating row covers.
  • Plant tolerant crop varieties.
  • Clean growing sites of plant debris after harvest.
  • Manage weeds to remove overwintering sites for pupae. 

INSECTICIDES

Diamondback moths are known to develop resistance to some insecticides. It is crucial to rotate insecticides groups to prevent the further resistance from being developed. 

Insecticides containing Bacillus thuringiensis var. kurstaki (Bt) and spinosad are effective in suppressing diamondback moth larvae.

 




Precautionary Statement: Utah State University and its employees are not responsible for the use, misuse, or damage caused by application or misapplication of products or information mentioned in this document. All pesticides are labeled with ingredients, instructions, and risks, and not all are registered for edible crops. “Restricted use” pesticides may only be applied by a licensed applicator. The pesticide applicator is legally responsible for proper use. USU makes no endorsement of the products listed in this publication.