Cabbage moth

Plutella xylostella


Order Lepidoptera, Family Plutellidae


Host plants

The species is widely distributed. It attacks cruciferous plants – both cultivated and wild: head cabbage, cauliflower, leaf cabbage, kohlrabi, turnip, radish, rapeseed, oilseed rape, mustard, shepherd’s purse, and others.

Life cycle


The cabbage moth develops 4–6 generations per year and overwinters as a pupa, and in more southern regions also as an adult insect under plant residues, soil clods, and dry leaves.

Green moth sitting on a leaf, with a characteristic elongated shape and light brown coloration.

Egg laying

Females lay eggs singly or in small clusters (usually 3 to 5 eggs) on the underside of leaves, mainly along the veins and on the leaf petioles. The average fecundity ranges from 70 to 150 eggs, with a maximum exceeding 300–350.
Caterpillars of the first generation usually feed on cruciferous weeds. The most damaging in our conditions are the caterpillars from the second and subsequent generations.
Microscopic view of yellow insect eggs located on a leaf.
Larva of the cabbage moth presented in a detailed view, approximately 1 mm in size.

Larva

The caterpillar is green to yellow-green, with a brown head. The body bears small warts from which black hairs emerge. Its length reaches 9–11 mm.
The pupa is spindle-shaped, light green to yellowish toward the end of the pupal stage. It is enclosed in a loose silken cocoon and reaches up to 8 mm in length.


Damage


The newly hatched larvae initially mine the leaves from the underside and feed on the parenchymal tissue. They remain inside the mines for 2–3 to 5 days, after which they leave them (as they grow) and continue feeding by scraping the lower epidermis and parenchyma of the leaves, without affecting the upper epidermis. Older larvae chew holes in the leaves of varying size and shape. These holes are significantly smaller than those caused by cabbage white butterflies or noctuid moths. Very often, the larvae feed on the tender central leaves, completely destroying them. Damaged plants form small, deformed heads.
The diamondback moth is a particularly dangerous pest for cauliflower. In this crop, the larvae penetrate into the curd and feed on the inflorescences. In all cruciferous crops, they also damage buds, flowers, pods, and the apical parts of the plants. Larvae can also be found inside rapeseed pods, feeding on the seeds, while the last generation mines and feeds on the cotyledons and the first leaves of emerging winter rapeseed.
Cabbage with leaf damage caused by moths, showing holes and injuries.

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