Entomosporium Leaf and Berry Spot

Causal Organism: Entomosporium mespili

Crops Affected: Saskatoon berries

Disease Cycle:

• High humidity / precipitation and warm temperatures
• Spore dispersal is triggered by precipitation (rain or sprinkler irrigation)
• 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 also be present on twigs and branches
• May overwinter on fallen leaves & twigs (not proven conclusively)

Impact:

• Most serious disease of Saskatoon berry
• Infected fruit is downgraded or becomes unmarketable
  • Infected fruit become crunchy and may experience moisture loss
• Infection of greater than 6% of fruit surface area is considered unusable by processors

Symptoms:

Leaf Symptoms

• Small, angular brown spots
• Spots may grow & join together, with a yellow halo
• More severely infected leaves 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

Management:

• Ensure adequate air circulation through:
  • Pruning
  • Orchard orientation
  • Careful consideration of plant stand density
  • Control of weeds
• Apply water to the soil surface (never sprinkler applications)
• Apply preventative/protective fungicide sprays
• Fungicide Spray Timing
  • Flowering stages = White Tip, Petal Drop, Green Fruit (varies with product)
  • Make 1^st 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