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.

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.

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:

• Read about growers' perspectives on DBM, from Andrew Rutherford
• Learn about DBM biology and control
• Tracking information from the 2016 outbreak of DBM
• Look at information on DBM management from Davide Grzywacz at the Natural Resources Institute

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.

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.

Further information and resources on DBM

• Download this poster to learn more about DBM and its life cycle from IRAC
• Visit the Agricology website to read about dealing with diamondbacks
• Phenology of the Diamondback Moth (Plutella xylostella) in the UK and Provision of Decision Support for Brassica Growers
• Visit the Wiley Online Library to read more on the study of high-altitude diamondback moth migration

Related research projects and information

• Read about the related research project – Lettuce and baby leaf salads: Investigation into control measures for Silver Y moth and caterpillars
• Learn about insecticide resistance status in UK brassica crops
• Factsheet: Practical measures to prevent and manage insecticide, fungicide and herbicide resistance for horticultural crops
• Read the AHDB encyclopaedia of pests and natural enemies