Diamondback moth

Diamondback moth (Plutella xylostella, DBM) is a small, grey-brown moth, a pest that is present worldwide wherever its brassica host plants grow. Find out recommended crop protection and management for this pest.

What is the impact of diamondback moth?

Host crops include cabbage, cauliflower, broccoli, kale, brussels sprouts and swede, as well as ornamental brassicas and brassica weeds.

Growers have reported crops of brussels sprouts where the whole crop has been affected by DBM damage, with 40% losses, swede with 15% losses and cabbage 10% losses.

See how devastating the impact of DBM can be on crops by watching this clip from the BBC.

Diamondback month (DBM) has the capacity to multiply rapidly in warm temperatures, especially where its natural predators have been wiped out by use of pyrethroid insecticides. At 8˚C it takes 117 days to complete its life cycle, but at 28˚C it takes only 12 days.

Latest diamondback moth information for growers

DBM is often described as a 'super pest' because it has a rapid life cycle and has been found to be resistant to some insecticides.

Research on diamondback moth

In 2016, Dr Steve Foster at Rothamsted Research tested three DBM samples for resistance, from Lincolnshire, Suffolk and Scotland. All three samples were resistant to pyrethroid insecticides.

Since then, samples have been tested each year as new populations of moths arrive in the UK. A total of 11 DBM samples have been tested, representing all the main brassica growing areas of the UK, over a period of four years.

Every sample contained moths that were resistant to pyrethroid insecticides but were susceptible to diamides and spinosad.

A workshop was held in January 2017 to find the lessons learnt from the 2016 DBM outbreak and the information is still relevant today:

Crop protection for diamondback moth

Where pyrethroid-resistant DBM caterpillars are present, growers are likely to get poor control from pyrethroid sprays. Read about alternative products that can be used to help control DBM in the table linked to below.

Plant protection control products for DBM control, March 2021

AHDB Pest Bulletin

The AHDB Pest Bulletin provides forecasts and up-to-date reports for most key field crop pests, including DBM. Alerts are sent weekly in the growing season, with monitoring information to give growers early forecasts for several different pests. For DBM, this is based on data collected from DBM traps located in commercial brassica fields throughout the UK.

In addition, records of citizen science sightings of migrant moths (diamond-back moth and silver Y moth) that are pests of UK vegetable and salad crops have been summarised on a daily basis throughout the season. These are moths captured or seen in several countries and reported on 'biodiversity monitoring' websites.

Learn more about the AHDB pest bulletin and sign up to receive alerts

Useful links

Further information and resources on DBM

Related research projects and information