Diamond-back moth
The diamond-back moth (Plutella xylostella) is a pest of brassica crops including oil seed rape. It is a relatively small moth so the eggs can be hard to find. Newly-hatched caterpillars burrow into the foliage to feed but then come out onto the leaf surface as they grow larger and cause characteristic ‘windowpane’ damage (second image down).
The diamond-back moth does not overwinter very successfully in the UK and infestations in early summer usually arise as a result of migrations from continental Europe (Chapman et al., 2002). These occur when the wind direction is favourable and when there is a large population of moths ready to migrate.
During summer 2020 we took part in a Dutch project called 'Towards Sustainable Cabbage Cultivation'. We were asked to send the diamond-back moths that we captured to the Dutch researchers so that they can analyse their DNA and try to work out where the moths are coming from. Moths are being collected from pheromone traps set in several European countries. They are working on several topics associated with pest management in cabbage. We have not received an update on the project yet.
Some of our work on diamond-back moth in the UK has been published in the journal 'Insects': 'Phenology of the diamondback moth (Plutella xylostella) in the UK and provision of decision support for Brassica growers'.
The diamond-back moth completes its life-cycle fairly rapidly – development times in days for the different life stages at different temperatures (data from Liu et al., 2002) are shown below.
| Temperature oC | Development time in days | Development time in days | Development time in days | Development time in days |
| Egg | Larva | Pupa | Total | |
| 8 | 20.8 | 55.5 | 40.4 | 116.7 |
| 10 | 15.4 | 42.4 | 29 | 86.8 |
| 12 | 12.8 | 30.8 | 21.2 | 64.8 |
| 14 | 8.4 | 19.8 | 12.7 | 40.9 |
| 16 | 6.4 | 16.1 | 10.6 | 33.1 |
| 18 | 4.7 | 14 | 7.9 | 26.6 |
| 20 | 4 | 11.3 | 6.3 | 21.6 |
| 22 | 3.5 | 9.3 | 5.3 | 18.1 |
| 24 | 3 | 7.7 | 4.5 | 15.2 |
| 28 | 2.4 | 6 | 3.6 | 12 |
Further information
Liu et al., (2002). Development and survival of the Diamondback Moth (Lepidoptera: Plutellidae) at constant and alternating temperatures. Environmental Entomology 31, 221-231.
Chapman JW, Reynolds DR, Smith AD, Riley JR, Pedgley DE and Woiwod IP (2002). High-altitude migration of the diamondback moth, Plutella xylostella, to the UK: a study using radar, aerial netting and ground trapping. Ecological Entomology 27: 641-650
Adult diamond-back moth
Caterpillars and damage
Damaged plant
Moths captured in light trap June 2016
Moths captured in pheromone trap June 2016