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Ministry of Agriculture, Food and Rural Affairs

Flyspeck

Flyspeck on fruit
Click to enlarge.

Beginner

Scientific Name
Schizothyrium pomi

Identification

  • Appears as groups of few to several small (approximately 0.5 mm in size), sharply defined, shiny black fungal bodies on the surface of the fruit.
  • Fungal bodies appear to exist individually but are connected and form colonies.
  • Colonies vary in size but are usually in round or irregular groups 1-3 cm in diameter.

Often Confused With

  • Insect frass (particularly from the white apple leafhopper)- Frass tends to be less well defined than flyspeck, and rubs off more easily, particularly if wiped with a damp cloth.
  • Sooty blotch- Flyspeck colonies are distinct groupings of shiny, black fungal bodies on the fruit surface, while sooty blotch colonies look like olive green, to black smudges on the fruit which do not have distinct margins.

Period of Activity
This fungus becomes active at the end of early summer and continues to be a threat until harvest.

Scouting Notes
Monitoring should commence at mid summer and should continue until fruit is harvested. Fruit should be checked for any signs of infection. Beginning at mid season through to harvest, monitor 25 fruit in the interior canopy of 10 randomly selected trees. Symptoms are more likely found in poorly pruned trees in the wetter, foggy, slow-drying areas of the orchard.

Thresholds
There are no established thresholds for flyspeck. This disease usually appears in orchards that have reduced their summer fungicide program due to lack of apple scab. The safest approach to prevent flyspeck is protecting the fruit with fungicides throughout the summer, by applying fungicides regularly after 270 hr of accumulated wetting after petal fall.  During the months of August and September, another spray should be applied if more than 5 cm of rain falls since the last fungicide was applied. Particular attention should be paid to orchards that are in high-pressure areas.

Advanced

Scientific Name
Schizothyrium pomi

Identification
Flyspeck appears as groups of few to several small (approximately 0.5 mm in size), sharply defined, shiny black fungal bodies (thyriothecia) on the surface of the fruit. Although these fungal bodies appear to exist individually, they are connected by mycelium to form colonies. Colonies vary in size but are usually in round or irregular groups 1-3 cm in diameter.

The symptoms of flyspeck and sooty blotch frequently appear together. Both fungi grow only on the surface of the fruit, and do not damage the flesh.

Often Confused With

  • Insect frass (particularly from the white apple leafhopper)- Frass tends to be less well defined than flyspeck, and rubs off more easily, particularly if wiped with a damp cloth.
  • Sooty blotch- Flyspeck colonies are distinct groupings of shiny, black fungal bodies on the fruit surface, while sooty blotch colonies look like olive green, to black smudges on the fruit which do not have distinct margins.

Biology
The flyspeck fungus overwinters as thyriothecia on apple twigs, culled apple fruit and on numerous wild hosts including brambles, oaks and maple. Mature ascospores are released during rainy periods for a one to two month period beginning at bloom. Warm and wet or humid (>96% relative humidity) conditions are conducive to the spread of the disease. In the lab, conidia germinate from 8-24°C and colony development occurs at 12-24°C. Symptoms are visible 10-12 days after infection under optimal conditions but may not appear in orchards for one month under less then optimal conditions.

Since the flyspeck fungus overwinters outside the orchard, there is not a huge risk of fruit infections until border row host plants begin producing second generation spores (conidia). This generally occurs at approximately 270 hr of accumulated wetting (hr AW) after petal fall, which usually occurs four to six weeks after petal fall. At this time, secondary spread of flyspeck occurs when conidia produced by non-orchard hosts are blown into apple orchards, causing the majority of infections that appear on fruit during the late summer. In orchards where fungicide protection is discontinued in early June, flyspeck infection on fruit becomes visible around 540 accumulated wetting hours after petal fall (AWPF) when another generation of flyspeck is completed. Flyspeck also appears in September or October in orchards that have received summer sprays. In these cases, late summer rains often remove fungicide protection allowing fruit infection to occur prior to harvest. In these late season infections, flyspeck can suddenly appear on a high proportion of fruit within a few days.

Period of Activity
Flyspeck is a summer disease that appears on apple fruit from mid summer to harvest. Fruit can become infected at any time after trees are exposed to 270 hr of accumulated wetting counting from petal fall (usually occurs four to six weeks after petal fall). First symptoms usually appear by early to mid July. In orchards receiving summer fungicide sprays, flyspeck usually appears in September or October. These late season infections usually develop after late summer rains remove fungicide residues, leaving fruit vulnerable to infection prior to harvest. During these conditions, flyspeck can appear suddenly on a high proportion of fruit within a few days. In orchards where fungicide protection is discontinued in early June, flyspeck infection on fruit becomes visible around 540 accumulated wetting hours after petal fall (AWPF) when another generation of flyspeck is completed.

Scouting Notes
Monitoring should commence at mid summer and should continue until fruit is harvested. Fruit should be checked for any signs of infection. Beginning at mid season through to harvest, monitor 25 fruit in the interior canopy of 10 randomly selected trees. Symptoms are more likely found in poorly pruned trees in the wetter, foggy, slow-drying areas of the orchard.

Thresholds
There are no established thresholds for flyspeck. Both flyspeck and sooty blotch are controlled with most of the fungicides that are effective for apple scab (see OMAFRA Publication 360, Guide to Fruit Production).  This disease usually appears in orchards that have reduced their summer fungicide program due to lack of apple scab. The safest approach to prevent flyspeck is protecting the fruit with fungicides throughout the summer, by applying fungicides regularly after 270 hr of accumulated wetting after petal fall. Late season (September or October) infections can occur in orchards where late summer rains have removed fungicide residues, so re-apply fungicides in late August or September if more than 5 cm of rain have occurred since the last fungicide was applied.  

Management Notes

  • The presence of these diseases is an indication that fungicide surface residues are lacking or very low.
  • The development of flyspeck is highly dependent on the microclimate surrounding the fruit, so be sure to undertake practices that facilitate drying of the trees and fruit.
  • The most important practice for reducing damage by these diseases is proper pruning to maintain an open tree canopy. Researchers have shown that summer pruning reduces the incidence of flyspeck by almost 50% in unsprayed orchards.
  • Thinning clustered fruit and summer pruning help promote better air circulation and improve coverage of fungicides.
  • Removing alternate hosts, especially brambles from the orchard and surrounding hedgerows, helps reduce inoculum.
  • Flyspeck is controlled with most of the fungicides that are effective for apple scab. In Ontario and the northeastern United States, fungicides applied to apples from mid June through August provide subsequent control of flyspeck and sooty blotch.
  • See OMAFRA Publication 360, Guide to Fruit Production - Chapter 3 Apples (PDF) or Apple Calendar only (PDF- :
  • The safest approach to prevent flyspeck is protecting apple fruit with fungicides throughout the summer, recognizing that conidia infects fruit at any time after trees are exposed to 270 hr of accumulated wetting counting from petal fall. Coverage is essential for the efficacy of late summer fungicide sprays so travel speed, water volume and using a surfactant to enhance wetting are important.
  • Research suggests fungicides applied in early summer do not eradicate pre-existing infections, and those infections can resume growing and become visible on the fruit in September when the fungicide residues are depleted.