Wingspan 6 to 8 mm. One of the palest of our Nepticulids, with a buff ground-colour, slightly darker mottling and yellowish head with white eyecaps.

The stem mine on Broom is a long dark gallery; the egg filled with dark frass remains at the start of the mine

The stem mines are almost identical to those of Leucoptera spartifoliella (the eggs of which may also remain at the start of the mine - ref. British leafminers, accessed 02/03/2025). 

Adult Stem mine

Photograph of egg position is essential when recording the stem-mine. It is recommened that the moth is reared out from mines for certain ID

Areas where the larval foodplant, Broom is present.

The adult moths are on the wing between June and August, and can be beaten from the foodplant.

The larva mines not in leaves, but under the bark of twigs of Broom (Cytisus scoparius). 

The species is probably fairly frequent throughout much of the British Isles, but easily overlooked. In the Butterfly Conservation's Microlepidoptera Report 2011 this species was classified as local.

It appears to be uncommon in Leicestershire and Rutland, where there are few records. L&R Moth Group status = D (rare or rarely recorded). 

http://www.leafmines.co.uk/html/Lepidoptera/T.immundella1.htm

https://bladmineerders.nl/parasites/animalia/arthropoda/insecta/lepidoptera/monotrysia/nepticuloidea/nepticulidae/trifurcula/trifurcula-immundella/