title: Citizen science identifies the effects of nitrogen dioxide and other environmental drivers on tar spot of sycamore.
abstract: Elevated sulphur dioxide (SO2) concentrations were the major cause of the absence of symptoms of tar spot (Rhytisma acerinum) of sycamore (Acer pseudoplatanus), in urban areas in the 1970s. The subsequent large decline in SO2 concentrations has not always been accompanied by increased tar spot symptoms, for reasons that have remained unresolved. We used a large citizen science survey, providing over 1000 records across England, to test two competing hypotheses proposed in earlier studies. We were able to demonstrate the validity of both hypotheses; tar spot symptoms were reduced where there were fewer fallen leaves as a source of inoculum, and elevated nitrogen dioxide concentrations reduced tar spot symptoms above a threshold concentration of about 20 μg m(-3). Symptom severity was also lower at sites with higher temperature and lower rainfall. Our findings demonstrate the power of citizen science to resolve competing hypotheses about the impacts of air pollution and other environmental drivers.
authors.affiliation: Centre for Environmental Policy, Imperial College London, UK.
authors.forename: Laura
authors.initials: L
authors.lastname: Gosling
authors.affiliation: Stockholm Environment Institute, University of York, York YO10 5DD, UK. Electronic address: mike.ashmore@york.ac.uk.
authors.forename: Mike
authors.initials: M
authors.lastname: Ashmore
authors.affiliation: Sigma, Coventry University, UK; Institute of Zoology, Poznań University of Life Sciences, Poland.
authors.forename: Tim
authors.initials: T
authors.lastname: Sparks
authors.affiliation: Centre for Environmental Policy, Imperial College London, UK.
authors.forename: Nigel
authors.initials: N
authors.lastname: Bell
mesh_terms: D031002:Acer / Q000382:microbiology*; D000393:Air Pollutants / Q000032:analysis* / Q000737:chemistry; D000397:Air Pollution / Q000032:analysis; D001203:Ascomycota / Q000254:growth & development*; D004739:England; D004784:Environmental Monitoring / Q000379:methods*; D009585:Nitrogen Dioxide / Q000032:analysis*; D010935:Plant Diseases / Q000382:microbiology; D018515:Plant Leaves / Q000382:microbiology; D013458:Sulfur Dioxide / Q000494:pharmacology; D013696:Temperature
chemical_list: D000393:Air Pollutants; D013458:Sulfur Dioxide; D009585:Nitrogen Dioxide
keywords: Acer pseudoplatanus; Citizen science; Nitrogen dioxide; Rhytisma acerinum; Tar spot