A smut fungus forming minute spore balls in senescing leaves of Hydrocharis morsus-ranae (frogbit).
Sori occuring in pale spots on leaves of Hydrocharis morsus-ranae (frogbit), inconspicuous, forming minute black or grey balls when held up to the light and examined with a hand lens, or when illuminated from below under a dissecting microscope. Spore balls up to 260 μm diam., spherical to ovoid, pale brown, gregarious or scattered, immersed in senescing leaf tissue; exterior comprising a relatively smooth continous outer single layer of joined prismatic and radially arranged spores; interior a central network of loosely woven, pale brown, septate hyphae.
Description adapted from Spooner (2006). Additions and amendments to the list of British smut fungi. Mycologist, 20(3), 90-96.
Listed as a species of principal importance for the conservation of biodiversity in England, under Section 41 of the Natural Environment and Rural Communities (NERC) Act 2006.
Not formally assesssed. Its host plant (Hydrocharis morsus-ranae) has been officially Red List assessed as Vulnerable A2c in Great Britain due to population decline; and unofficially assessed as Vulnerable A2c in England, and as Near Threatened in Wales. Tracya hydrocharidis is an obligate biotrophic parasite, and in GB&I is restricted to this host. It should therefore be assessed as being at least as vulnerable as its host.
An obligate biotrophic parasite colonising leaves of Hydrocharis morsus-ranae.
Widespread but rarely recorded across southern England (South Somerset VC5, North Somerset VC6, East Sussex VC14, Surrey VC17, Oxfordshire VC23, East Suffolk VC24, East Norfolk VC27), with a single record from Wales (Montgomeryshire VC47). Recorded in Northern Ireland (Fermanagh VC H33) in 1948.