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.
In 2019 diamond-back numbers are going to be monitored in two ways:
- Summarising records of sightings of diamond-back moth (and silver Y moth) in several northern European countries. These are moths captured or seen and reported on 'biodiversity monitoring' websites.
- Monitoring diamond-back moth in commercial crops - several UK brassica growers are going to monitor diamond-back moths in their crops using pheromone traps.
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|
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