New Picea hosts for Chrysomyxa ledi and Thekopsora areolata

A severe epidemic of Chrysomyxa ledi needle rust occurred over large areas in northern Finland in 2015. In late summer, young current‐year cones and needles of 7–8 Picea species were sampled in a northern botanical garden, and the frequencies of cone rusts, Thekopsora areolata, Chrysomyxa pirolata and C. ledi, were investigated in cones, and C. ledi was investigated in needles. In addition, the frequency of C. ledi was estimated visually in current‐year needles of ca. 400 trees of 17 species and varieties of Picea in the garden. Chrysomyxa pirolata was absent in cones of all Picea. No cone rusts were observed in cones of P. rubens and Picea mariana. Aecia of Thekopsora areolata occurred moderately in cones of P. abies (26% of cones) and rarely in P. engelmannii (3%) and P. omorika (6%). Chrysomyxa ledi was the most frequent rust in cones; aecia occurred abundantly in cones of P. abies (100%), P. engelmannii (69%), P. glauca (45%) and P. omorika (41%), and occasionally on P. pungens (13%). Thekopsora areolata from cones of the three Picea species showed 100% similarity in ITS2 sequence to one another and to samples in the GenBank. Samples of Chrysomyxa from needles and cones of Picea and leaves of Ledum palustre had ITS2 sequences 99.9%–100% similar to one another and 99.8%–100% similar to the closest sequence of C. ledi and C. rhododendri in the GenBank. Thekopsora areolata was recorded for the first time in cones of P. omorika and C. ledi in cones of P. engelmannii and P. pungens. In current‐year needles of Picea, C. ledi was abundant on P. abies, P. obovata, P. engelmannii, P. jezoensis, P. glauca and P. sitchensis, the rust was scarce on P. asperata var. nobilis, P. mariana, P. pungens and P. omorika, and the rust was absent on P. glehnii and P. rubens.