Bastard-Toadflax Rust (Puccinia thesii)
Key Details
| Taxonomic Groups: | Fungus or lichen > fungus > Fungus |
| Red List Status: | (Not Relevant) [(not listed)(nr)] |
| D5 Status: | |
| Section 41 Status: | (not listed) |
| Taxa Included Synonym: | (none) |
| UKSI Recommended Name: | Puccinia thesii |
| UKSI Recommended Authority: | (Desv.) Chaillet |
| UKSI Recommended Qualifier: | (none specified) |
| Red List Citation: | (not listed) |
| Notes on taxonomy/listing: | (none) |
Criteria
| Question 1: | Does species need conservation or recovery in England? |
| Response: | Yes |
| Justification: | Assessed as Endangered (2006), but also reliant on a host plant (Thesium humifusum) that has suffered an ongoing decline in the UK. The host plant, and therefore this fungus is mostly restricted to southern England, with considerable decline in its outlying populations towards East Anglia |
| Question 2: | Does recovery/ conservation depend on species-specific actions? |
| Response: | Yes |
| Justification: | Without evidence of the current national status of this species it will be very difficult to assess if there are any other species-specific actions required for its conservation; or if it is need of conservation at all. |
| Question 3: | At a landscape scale, would the species benefit from untargeted habitat management to increase habitat mosaics, structural diversity, or particular successional stages? |
| Response: | No |
| Justification: | There is no evidence that an increase in the structural diversity of the habitat will directly benefit this species. |
Species Assessment
| Current step on the Species Recovery Curve (SRC): | 2. Biological status assessment exists |
| Recovery potential/expectation: | Low - Policy conflict (detail in comments) |
| National Monitoring Resource: | Opportunistic - insufficient |
| Species Comments: | A rust fungus that is wholly reliant on the success/distribution of a specific plant species, (Thesium humifusum) which is not part of the TSRA project. The reproductive biology of the semi-parasitic host plant is not fully understood, but many of the factors contributing to its decline are. It is these factors that include nitrogen enrichment, scrub encroachment and agricultural use of downland that are need to be remedied. |
Key Actions
Key Action 1
Proposed Action: An assessment of the necessary national species records should be made according to IUCN guidelines to provide a recognised redlist status criteria for this species.
Action targets: 2. Biological status assessment exists
Action type: Status survey/review
Duration: 1 year
Scale of Implementation: National
High priority sites: N/A
Comments: As no IUCN recognised assessment exists for this species, this action should be prioritised.
Key Action 2
Proposed Action: Collect seed of host plant and investigate dispersal, germination and growth requirements for ex situ cultivation and introduction to suitable sites.
Action targets: 6. Recovery solutions trialled
Action type: Ex situ conservation
Duration: 3-5 years
Scale of Implementation: ≤ 20 sites
High priority sites: N/A
Comments: For this fungus species to begin recovery, the host plant species will need to undergo some combination of protection/translocation to improve host plant availability.
Key Action 3
Proposed Action: Following a programme of ex situ cultivation and reintroduction of the host plant to new sites, a pilot study for introducing the rust fungus to the new populations should be trialled.
Action targets: 6. Recovery solutions trialled
Action type: (Re-)introduction
Duration: 3-5 years
Scale of Implementation: ≤ 20 sites
High priority sites: N/A
Comments: Following the reintroduction of the host plants, advice and guidance should be given to land managers about providing the best management to maintain a 'healthy' population of the host plant.
Acknowledgment:
Data used on this website are adapted from Threatened species recovery actions 2025 baseline (JP065): Technical report and spreadsheet user guide (Natural England, 2025). Available here.