Diamondback Moth

Diamondback moth (DBM) is present worldwide wherever its brassica host plants grow. 

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 - with 40% losses, swede with 15% losses, and cabbage 10% losses. The impact of DBM on crops can be devastating, as is clearly demonstrated by this BBC video report.

DBM has the capacity the multiply rapidly in warm temperatures, especially where it’s natural predators have been wiped out by use of pyrethroid insecticides. At 8°C, it takes 117 days to complete its lifecycle but at 28°C, it only takes 12 days.

Latest Diamondback Moth information for growers

DBM is often described as a 'super-pest' because it has a rapid lifecycle and has been found to be resistant to some insecticides. 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 pyrethroids insecticides but were susceptible to diamides and spinosad. 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).

Previously considered a migratory pest, recent research indicated that DBM could be surviving UK winters. In January 2018, AHDB and Warwick Crop Centre discovered the pest surviving in un-netted swede crops in the south-west of England. This may be due to the warmer winters that we have been experiencing in recent years.

Crop protection

Where pyrethroid-resistant caterpillars are present, growers are likely to get poor control from pyrethroid sprays. Alternative products should be sought from the table below.

Plant protection control products, updated March 2020


Activity alerts

Keep up to date with the latest DBM pest activity by signing up to receive AHDB Pest Bulletin alerts by filling in the AHDB Keeping in touch form. The bulletin is sent weekly from April to October, with trap monitoring information to give growers early forecasts based on data collected from DBM traps located in commercial brassica fields throughout the UK.

You can also monitor DBM activity on the AHDB Pest Bulletin, hosted by Syngenta and the AHDB Pest Blog provides regular updates on pest activity as the information comes in.

AHDB and Warwick Crop Centre are also monitoring the activity of DBM and silver Y moth on the continent and have set up a web page to summarise the numbers of sightings recorded on web sites in six countries (UK, Belgium, Netherlands, Sweden, Norway, Finland). 

A DBM lifecycle and further information about the worldwide situation is available at IRAC.

Relevant AHDB literature applicable to diamondback moths includes:

Factsheet: Practical measures to prevent and manage insecticide, fungicide and herbicide resistance for horticultural crops The AHDB Encyclopaedia of pests and natural enemies of field crops

Related research projects

Lettuce and baby leaf salads: Investigation into control measures for Silver Y moth and caterpillars