Cabbage moth

Mamestra brassicae

Life cycle

The cabbage moth has a wide distribution in parts of Europe.

Under ideal conditions, its life cycle can complete in as little as 30 days, of which 4 to 8 days as an egg, 11 to 12 days as a larva, 10 days in pupation and 5 days as an adult moth.

 

 

The 1st generation moth emerges in different forms depending on the area, usually in May-June.

The 2nd generation moth emerges in July-September.

A temperature threshold of 10°C and an optimum temperature of 19-21°C are required for the development of the summer generation pupae.

 

A temperature threshold of 10°C and an optimum temperature of 16-25°C is required for egg development.

For caterpillar development, a temperature threshold of 9°C and an optimum temperature of 16-30°C.

 

Oviposition

The female moth lays eggs singly but collects many of them on the same surface. A single female can collect up to 350 eggs on the underside of a leaf.  Female life span 2-3 weeks. Average fecundity 600 eggs, maximum 2,700. Eggs are yellowish white, oblong and ribbed, laid in batches in the shape of an irregular polygon. Usually 20 to 150 eggs are contained in one batch, located on the underside of the leaves. The eggs are laid from May to June.They hatch within 5 to 12 days. The incubation period depends largely on environmental factors, especially temperature. Incubation ranges from 6 days at 25 °C to 12 days at lower temperatures.

The egg is usually 1,2 mm in diameter.

Larva

The caterpillar goes through six developmental stages. The total development time of this larva is 4 to 6 weeks and the final body length varies from 40 to 50 mm.

The larvae feed on the leaves of plants at night. They are usually found on the underside of the leaves of the host plant near the ground. They are gregarious in their initial stage and particularly damaging by the fourth instar. During the first three phases, larvae feed heavily and may skeletonize the leaves on which they were laid and to which they migrate. During the fourth phase, larvae tends to bury themselves in the pith of many fruits, vegetables and plants, rendering them unpalatable. In addition, the larvae leave waste excrement on the foliage of their chosen host plants, transferring fungal and bacterial infections onto it.

Pupae

When pupating, the larvae bury themselves in the soil where they remain until the adults emerge.The pupae are brown and shiny. They may develop once or twice during the year, usually in winter. The pupae develop in cocoons which are found in the soil at a depth of 2 to 10 mm. They are usually 20 mm long.

Adults

Adult moths emerge from pupae during the months of May and June. Their appearance is similar to that of many other moths in the same family; they are gray, black, green, or brown with a delicate pattern of lines and spots all over the adult’s body. The wingspan varies between 34 and 50 mm.

Shortly after emergence, adult moths mate. The moth is most active at night when it flies between plants and feeds. During the day, the adult moth seeks shelter under the leaves of surrounding plants.