In the garden: Stocks, wallflowers and other ornamental brassicas
On Crops: All members of the cabbage family
Throughout the UK (more common in the southern counties), Europe and worldwide, where brassicas are grown.
Diamondback moths first emerge during May. They are small greyish-brown moths around 8mm in length, elongated in shape and have a diamond pattern down their backs. Larvae are pale green and when mature can reach 1.2cm in length. When disturbed the larvae often fall from their host plants, hanging on by a thin silk thread.
Adult moths do not cause any damage. The larvae feed on the leaves and the damage progressively becomes more severe as the larvae grow. Interveinal tissue is usually eaten, resulting in a lace-work appearance on the leaves. Large infestations of diamondback moth larvae can often result in complete skeletisation of plants and total crop losses.
Regular observation of plants to find and remove early infestations. Sticky traps can be used to identify times when the adult moths are on the wing. Containing susceptible plants under a fine mesh or fleece cover or growing plants within a plastic tunnel will reduce the chances of infestation.
Insectivorous birds and predatory wasps should be encouraged into growing areas if possible.
Diamondback moths can complete their life cycle within a 15-30 day period during the summer months. Avoid planting succession crops when a diamondback moth infestation has occurred.