Diamondback moths discovered overwintering in Somerset

Scientists have found diamondback moth (DBM) caterpillars surviving in UK Brassica crops this winter and are recommending growers check their own crops for the pest now.

Previously considered a migratory pest, recent research from AHDB indicated that diamondback moths could be surviving UK winters.

AHDB’s Dawn Teverson, and Rosemary Collier from Warwick Crop Centre have been out in the field hunting for the caterpillars and found the pest on the underside of leaves in un-netted swede crops, located in the south west of England.

Seven caterpillars were found in one field where there had been crop damage earlier in the season and one caterpillar was found in a second field where there was little evidence of crop damage.

Swede grower Andrew Rutherford has suspected for some time that the pests were overwintering in netted crops in the UK and the visit to Somerset on 18 January confirmed this.

The caterpillars have been taken to Warwick Crop Centre and will be kept outside to find out if they survive until spring.

Actions

As there is a possibility that populations will build up un-noticed in the spring, Brassica growers are recommended to check over-wintering crops for the pests.

The caterpillars are very small and can be difficult to find. Look underneath the leaves and towards the mid-rib of the leaf for the best chance of spotting them.

If you find any DBM caterpillars, please contact dawn.teverson@ahdb.org.uk. AHDB may require further samples for testing to help inform control strategies.

Research at Rothamsted by Steve Foster has confirmed that samples of DBM from all over the UK have tested resistant to pyrethroid insecticides. As pyrethroids kill the beneficial insects that help to keep populations of DBM in check, it is important that growers do not use pyrethroids as part of their integrated pest management programme.

Article source/image credits: AHDB