Taphrina johansonii causes galls on the catkins of Grey Poplar and Aspen, causing the individual fruits to become swollen and bright yellow.  The whole catkin may be affected, or just a few fruits.

There is some confusion regarding this species and Taphrina rhizophora, which is said to cause similar galls on White Poplar

host

Photograph the galls on the catkins.  Ensure you have identifed the host tree. It can be difficult to separate White and Grey Poplars at catkin-time, when the leaves have just emerged. It may be becessary to ask a botanist to confirm the tree species, or to re-visit the site later in the year when the leaves are fully developed.  In cases where the host species is unclear, microscopic examination of the Taphrina spores may be needed.

Grey Poplar and Aspen

Spring

Rare.   See Smith, P.A.  2024.  A Spring gall - Taphrina johansonii.  Cecidology 39 2-5

Rare.  First discovered in central Leicester in April 2026, and subsequently in a few other sites near the City.