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Plutella xylostella (L.)
Plutella maculipennis Curtis

Insecta, Lepidoptera, Yponomeutidae .

Diamond-back moth

Description, Biology, Life Cycle, Damage, Common Names, Images

- Adult: 15 mm wingspan. Reddish head. Extremely elongated fore wings, narrow, rounded at their extremity, yellow brown punctuated with darker zones; distinctly fringed posterior margin, bordered by a clear band, whitish and undulated. Much shorter hind wings, pointed, distinctly fringed, dark grey. At rest, the wings form a roof and the antennae project anteriorly (*) .
- Egg: oval, quite elongated, very small (0.5 to 0.25 mm), flattened base, pale yellow (*) .
- Larva: 15 mm, narrow, tapered at both ends. Pale green or greyish abdomen, brown-black head, dark prothorax dotted with black. This caterpillar is agile and, at the slightest contact, twists about and falls to the ground.

- Cosmopolitan insect, the moth lives on all wild and cultivated Brassicaceae: cauliflower, cabbages, rape, field mustard (Sinapsis arvensis).
- The moth flies at night-fall. Its flight is jerky and short. The lifespan of the female is on average 16 days.
- Fecundity: about 160 eggs deposited singly or in clusters of 2 to 6, on the underside of the leaves, along large veins.
- Egg: embryonic development lasts 4 to 8 days.
- Larva: the neonate caterpillar crawls on the underside of the leaf and then starts to form a gallery (*) .
After 3 to 4 days, it leaves the gallery, spins a few silk threads and moults; the larva then gnaws the under surface of the leaf except for the veins but also attacks the upper surface.
Eighteen days later, the caterpillar weaves a large silky sheath, fastened to the veins, on the underside of the leaf and pupates there (*) .
- pupa: 8 mm, fusiform, first light green or yellowish, becoming darker as the imaginal moult approaches.
Pupal development lasts 8 days.

[R]Life Cycle
- 3 to 6 generations per year.
- The moths emerge from the overwintered pupae at the end of May. Scarce, they often pass unnoticed.
- The second flight occurs at the end of June; the moths are more numerous and, in July and August, damage is greater. In autumn, the caterpillars spin cocoons for themselves denser than the spring and summer cocoons, and then hibernate.

Damage is important on cabbages. The caterpillars first gnaw the outer leaves (*) and then progressively move towards the young central leaves. They unite them with silken threads and soil them with their frass.

[R]Common Names
DE: Kohlschabe, Kohlmotte ES: Polilla de la col FR: Teigne des crucifères IT: Tignola delle crucifere PT: Traça das couves GB: Diamond-back moth

[R] Images

  1. Plutella xylostella (L.) Adult on a cabbage (Coutin R. / OPIE)
  2. Plutella xylostella (L.) Oeufs (Coutin R. / OPIE)
  3. Plutella xylostella (L.) Young larva stripping a cabbage leaf (Coutin R. / OPIE)
  4. Plutella xylostella (L.) Larva on cabbage leaf (Coutin R. / OPIE)
  5. Plutella xylostella (L.) Damage on cabbage The areas stripped by the young larvae and sections totally consumed by the older larvae can be seen.
  6. Plutella xylostella (L.) Reticulated cocoon (Coutin R. / OPIE)

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