Disease of the Month - Entomosporium Leaf and Berry Spot

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 20-26°C
• 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

• 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

• 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