Phytomyza gymnostoma Loew (Diptera: Agromyzidae), a leaf mining pest of leek and onion new to Britain.
Phytomyza gymnostoma, a serious pest of leeks, onions and chives in central Europe, is reported from Britain for the first time. In early December 2003, a private householder in Wolverhampton reported severe damage to his leeks which he has observed for the second successive year. P. gymnostoma was identified from these infested leeks based on pupae and adult characteristics. By the beginning of March 2004, the pest was also found in 10 separate allotment sites in Wolverhampton and at one site in Stafford, approximately 15 miles to the north. Leek was the principal plant infested, although one plot of onion also yielded P. gymnostoma pupae. In early June 2004, two further cases of P. gymnostoma infesting allotment sites were found at Wednesbury and Wednesfield, just to the south east and north east of Wolverhampton, respectively. Taxonomic descriptions are provided and damage symptoms are characterized.