Cryptostroma corticale and its relationship to other pathogens and pests on Acer pseudoplatanus

In the present study, 20 sycamore maples (Acer pseudoplatanus L.) were evaluated on eight plots (160 trees) affected by sooty bark disease (SBD), caused by Cryptostroma corticale (Ellis & Everh.) P.H. Greg. & S. Waller in Northern Bohemia, Czech Republic. Mortality and presence of common pest taxa were assessed for each tree. Data were statistically evaluated using frequency and principal component analyses. The presence of C. corticale and Prosthecium pyriforme Jaklitsch & Voglmayr were positively related, with a significantly higher occurrence on dead trees. Rhytisma acerinum (Pers.) Fr. and Aceria macrorhyncha Nalepa were also positively related. However, the presence of Drepanosiphum platanoidis Schrank was not clearly related to the other evaluated taxa. Furthermore, C corticale was not present on Norway maple trees (Acer platanoides L.) growing on the plots. The results suggest that (i) the mortality of the sycamore was caused by C. corticale, while P. pyriforme was only an accompanying weak pathogen; (ii) R. acerinum, A. macrorhyncha, and D. platanoidis did not cause the mortality of the sycamore and their presence was not related to C. corticale infection; and (iii) planting more resistant maple species on sites susceptible to attack by SBD, particularly when stressed by drought, is recommended.