Disease of the Month - Entomosporium Leaf and Berry Spot

 
  Hort Snacks - April 2018
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 Causal Organism: Entomosporium mespili

Crops Affected: Saskatoon berries

Disease Cycle:

  • High humidity / precipitation and warm temperatures
  • Spore dispersal is triggered by precipitation
  • Flourishes from early-May through mid-July
  • Optimal temperatures for development are 20-26C
  • Affects leaves of succulent new shoots and berries (immature to mature)
  • May overwinter on fallen leaves & twigs (not proven conclusively)
  • May also be present on twigs and branches
Symptoms:
  • Most serious disease of Saskatoon berry
  • Infected fruit is downgraded or becomes unmarketable
  • Infection of greater than 6% of fruit surface area is considered unusable by processors
    Leaf Symptoms
    • Small, angular brown spots
    • Spots may grow & join together, with a yellow halo
    • Leaves may turn yellow & may fall off if petioles are infected
    • Severe defoliation can reduce productivity
    Fruit Symptoms
    • Watery, greyish lesions
    • Fruit may become discoloured, disfigured, shrivelled or cracked
    • Fruit stalks may become infected
Entomosporium lesions - varying degrees - mild to severe
Blocky, angular lesions - low to medium levels of infection
Yellowing leaves + lesions
Severe infection
Photos by Robert Spencer
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Severe Entomosporium infection resulting in cracking and desiccation of fruit
Photo by Robert Spencer

Management:
  • Ensure adequate air circulation
    • Pruning
    • Orchard orientation
    • Careful consideration of plant stand density
    • Control weeds
  • Apply water to the soil surface (not sprinkler applications)
  • Apply preventative fungicide sprays
  • Fungicide Spray Timing
    • Flowering stages = White Tip, Petal Drop, Green Fruit (varies with product)
    • Make 1st application after first rain event that occurs 1+ days after flowering (when petals open up)
    • Connected to spore dispersal
  • Fungicide Selection
    • Chemistry/efficacy of products varies somewhat
  • Remember the Pre-Harvest Interval (PHI) as this sets limits on application timing
 
 
 
 
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For more information about the content of this document, contact Robert Spencer.
This information published to the web on March 26, 2018.