I was preparing dinner the other night and noticed tenanted mines on the sugarsnap peas I was about to cook! They were purchased from Tesco, Princes Risborough (Bucks, VC24) and originate from the USA. They are tenanted, and appear to be a Liriomyza species.  Following a post on the UK leafminers which seemed to confirm my initial diagnosis of genus.  As this is a potential notifiable pest species (and I wanted to find out what it was!), I sent the bag of peas to FERA, and Chris Malumphy has provisionally identified my mines as Liriomyza huidobrensis, a South American species.

Chris informed me that:

Between 1996 and 2011, the Plant Health and Seeds Inspectorate intercepted Liromyza mines on imported peas in England and Wales on more than 180 occasions (unpublished data from the Fera eDiag database). The majority of mined peas have been imported from Africa (Kenya, Tanzania, South Africa, Uganda, Zambia, Zimbabwe) and Central America (El Salvador, Guatemala). In all cases where the species was confirmed in association with imported pea pods, the culprit was Liriomyza huidobrensis (Blanchard). The latter is a regulated pest in the European Union. In almost all cases, the Liriomyza larvae were reared to adulthood to confirm the species.

The incidence of Liriomyza mines on imported pea pods in England and Wales has decreased dramatically since about 2006, which is likely to be due to improved quality control and pest management.

We do not have any interception records of Liriomyza on fresh pea pods imported from the USA

The larva did not survive the journey to FERA, so cannot be reared through, so Chris is awaiting DNA sequencing to confirm the ID.  

Whatever the species is, it is a new one for me, so this all goes to show that you never know where that next new species is going to come from!