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Diamond-back Moth

Plutella xylostella

Diamond-back Moth, Cabbage Moth

A close up of a Diamond-back Moth Plutella xylostella on a leaf
Plutella.xylostella.7383 by olei@despammed.com (CC BY-SA 2.5)
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The Diamond-back Moth is named after the cream, diamond-shaped band that's formed when the wings close at rest. They're particular pests of plants belonging to the Brassica family. They're a nomadic species, flying long distances at a time. It's now intercepted all the continents and has become established in most countries.
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Traits

The caterpillars will attack the leaves of Broccoli, Brussels sprouts, Cabbage, Chinese cabbage, Cauliflower and Collard greens.

Appearance

Adult moths display grey-brown wing colouration. There's also a cream coloured, diamond-shaped band that runs vertically down the back. The wings are narrow, spanning 1.5cm in total when in flight. The length of the body is around 6mm. The antennae are considerably long (about the same as the body). Larvae are tiny green caterpillars with black dots. They begin feeding within the leaves, mining the internal tissues. Usually, they're too small at this point so go unnoticed. After the first moult, they emerge, where they move to graze beneath the leaf.

Symptoms

Notches, holes and bites, missing from plant foliage. Translucent windows, or 'shot holes' in the leaves of plants. Small, green, caterpillars beneath the leaves. Faint, pale green/brown mines may be seen beneath leaves. Small brown pupae may be seen beneath leaves. If infestations are heavy, sometimes whole leaves can be lost.

Activity

Nocturnal

Personality

Order

Lepidoptera

Family

Plutellidae

Metamorphosis

Complete

Distribution

Worldwide

Biological treatment

These moths have initially been controlled using conventional pesticides. However, overuse of these resulted in a tolerance to build in populations. Research has found that these moths are attracted to a variety of plants. Yet, not all are suitable for their larvae. It's now advised to plant wintercress around desirable crops. The moths are attracted enough to lay their eggs, yet upon hatching the larvae can't persist.

Attracts

Mustard

Brassica spp.

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