Widespread latent infection of Cryptostroma corticale in asymptomatic Acer pseudoplatanus as a risk for urban plantations

Abstract

Summary Sooty bark disease (SBD) caused by the pathogen Cryptostroma corticale is currently one of the risks to the population of Acer pseudoplatanus in Europe. After a number of records of symptomatic and dead trees in Prague, assessment of the latent non‐symptomatic stage of SBD was questioned as a means to forecast the health risk of the A. pseudoplatanus population. We used two methods of early detection of C. corticale in non‐symptomatic trees: cultivation from wood tissue on agar plates and a culture‐free approach based on nested PCR with newly designed species‐specific primers. The pathogen was detected in 25% of 112 examined trees from seven localities in Prague, but the disease incidence might be higher if more A. pseudoplatanus trees in Prague were included and if the crown infections were considered. The presence of C. corticale was positively correlated with discoloured wood, but its presence did not depend on the occurrence of external symptoms. Infected trees were more frequently found in groups on steep sites at higher elevations. In addition, heavier NOx pollution combined with more paths and roads increased the incidence of C. corticale.

Occurrence but not intensity of mortality rises towards the climatic trailing edge of tree species ranges in European forests

“…Tree mortality can be affected by other factors, such as wind disturbance, snow damage, pest emergence, fires or pathogens, which we did not include in our study. For instance, Fraxinus excelsior mortality has been related directly to the pathogen Chalara fraxinea (Kowalski, 2006), and Acer pseudoplatanus is threatened by several pathogens spreading rapidly in Europe [e.g., Eutypella parasitica and Cryptostroma corticale (Kelnarová et al., 2017; Ogris et al, 2006)]. The relatively low variance explained by our models for some species ( Acer pseudoplatanus , Fraxinus excelsior , B. pendula , Castanea sativa and Pinus nigra ) could be related directly to these missing factors.…”

Sooty bark disease of maples: the risk for hypersensitivity pneumonitis by fungal spores not only for woodman

“…Healthy trees can be asymptomatically affected by C. corticale as an endophyte while impairment of the tree, e.g., by drought may lead to a higher risk to contract on SBD [4,26]. It is to assume that latent infections by C. corticale are widespread, also in urban plantations of maples [14].…”

“…The thermophilic C. corticale profits of lack of water and heat stress in long-lasting summers [25]. Further stressors for the maples such as flooding, high nitrogen oxide concentrations and unfavourable on-site conditions also favour the spread of SBD [12][13][14]. It was found that urban conditions with climate extremes, higher temperatures and air pollution at traffic roads or paths lead to more SBD infection of sycamores [14].…”

“…A study from Prague, Czech Republic, provided indications that for prevention of SBD of maples, and, as a consequence, of MBD of humans, removing of infested trees may slow down the spreading of the disease [14].. Indeed, less A. pseodoplatanus trees with obvious SBD were found in parks than expected after the park management of Prague removed diseased trees a few years before.…”

“…There are indications that outbreaks of SBD will become more frequent in the future due to climate change. In the last years, severe drought and heat periods, as well as prolonged flooding, resulted in higher outbreaks of the disease [12][13][14]. Therefore, it can be assumed that the resulting MBD, a hypersensitivity pneumonitis (HP) [15], will occur more frequently in the future.…”