Rose Rust - Phragmidium mucronatum

Rose Rust (Phragmidium mucronatum) is a gall-causing rust that affects some wild Rosa species, including Dog-rose and Field-rose.  There is no host-plant alternation.  In spring bright orange aecia appear on the leafstalks, branches, leaf underside and any remaining hips. During summer yellow-orange uredinia then develop on the undersides of leaves, becoming interspersed with black telia in late summer/early autumn. It usually overwinters in the form of teliospores associated with fallen leaves.

The aeciospores and urediniospores have a small pore, and the teliospores have 6-8 cells and an apiculus.

Several other species of rose-rust may be present; refer to Redfern & Shirley 'British Plant Galls' (2023) and 'Plant Parasites of Europe' website for more details.

• Phragmidium tuberculatum can affect Rosa rubiginosa (Sweet-briar), Rosa caesia var. glauca and other wild and cultivated roses, and is said to be the commonest species on cultivated roses.  It has been recorded in VC55 but may have been overlooked or recorded as P mucronatum.  The teliospores have 5-7 cells with a well-defined apiculus and the aeciospores and urediniospores have a large pore.  
• Phragmidium fusiforme affects Rosa caesia var. glauca and Rosa pendulina; the teliospores have 10-12 cells.  It is said to be rare in the UK.  
• Phragmidium rosae-pimpinellifoliae affects Burnet Rose and its cultivated hybrids and varieties.

host

Photograph the rust on the host, both sides of leaf.  Ensure you have noted the host-plant species in your comments.  Microscopic examination may be needed, especially if recorded on a cultivated rose.

on wild roses, including Rosa canina and Rosa arvensis

.