MSU Extension Integrated Pest Management

Sooty blotch

Disease

Sooty blotch

Peltaster fruticola (Johnson, Sutton, Hodges) Leptodontium elatius (G. Mangenot) De Hoog Geastrumia polystigmatis Batista & M. L. Farr, and other fungi

Distribution: Sooty blotch and flyspeck occur almost everywhere apples are grown and often occur together; more severe in humid and warmer climates.

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Sooty blotch and flyspeck are found together on the same fruit and affect only the epidermal layer of the fruit (A). Sooty blotch appears as various shades of olive-green on the surface of the fruit. Colonies range in shape from nearly circular colonies with distinct margins to large, amorphous colonies with diffuse margins (B). The variation in colony appearance can be attributed to the interaction among the different fungi causing the disease and environmental conditions, specifically temperature and relative humidity.

• Crops Affected: apples, pears

  Management

  The primary means of managing sooty blotch and flyspeck is through the scheduled use of fungicides from mid-June through August. However, summer pruning and regular mowing helps to reduce disease pressure by lowering orchard humidity and promoting quicker drying of fruit surfaces. In addition, removal of raspberry and other brambles along the orchard border reduces outside sources or inoculum.

  Similar Species

  Flyspeck colonies appear as distinct groupings of shiny, black fungal bodies on the surface of the fruit. The number of colonies or "specks" range from a few to over fifty per grouping.