The sooty blotch fungus (Gloeodes pomigena) was previously believed to exist in different mycelial forms. Research in the USA in the 1980s has shown that in fact sooty blotch is associated with at least three unrelated fungi: Peltaster fructicola, Geastrumia polystigmatis and Leptodontium elatius which correspond to the different mycelial types of Gloeodes pomigena.
Dominance of one particular species of the three fungi associated with sooty blotch varies according to its response to the environment, sensitivity to fungicides and competitive abilities on the fruit surface.
- However, the most recent research in the USA, combining molecular techniques with morphological characterisation has revealed that the sooty blotch fly speck complex (SBFS) is far more diverse than previously realised.
- Surveys of orchards in 14 eastern U. S. States in 2000 and 2005 uncovered 62 SBFS species in five taxonomic orders.
- Conventionally sprayed orchards had lower diversity in the SBFS complex than unsprayed orchards.
- Some SBFS species occurred in almost all orchards, whereas other species were regional in distribution or were found in only one or two orchards.
- Similar patterns patterns of SBFS diversity have been found in Germany, Serbis and Montenegro, Brazil, China, Florida and Costa Rica.
- It is likely that similar diversity in the SBFS complex exists in the UK but until this can be evaluated the disease will be referred to as sooty blotch caused by Gloeodes pomigena.
- In the USA the fungal species still originate from wild hedgerow trees and shrubs, so that the overall epidemiology is essentially unchanged, although fungicide efficacy may be affected.