The non-native destructive pest was found on imported New Zealand Wisteria by a nurseryman in the Midlands in June this year.
Principal plant health and seeds inspector Derek McCann said: "This is an unusual one - the authorities are taking it very seriously. It's a wake-up call to the sort of things that can come in. It shows that even established trade, which should be clean, can throw up problems and underlines the need for vigilance."
Although the nursery destroyed the plants, eight other consignments of host material were sent by the same supplier in New Zealand on 4-5 June and were subsequently delivered to UK nurseries.
A further suspected finding of larva in one of those consignments was reported in July.
Oemona hirta is found throughout its native New Zealand. It affects mainly Citrus but 130 genera are recorded as being susceptible to attack.
FERA has now launched a rapid assessment for Oemona hirta and Diaphania perspectalis (box tree caterpillar).
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