Saskatoon Leaf and Berry Spot Disease

Problem type: Disease

Name of problem: Saskatoon leaf and berry spot disease

Plant name(s): Saskatoon

Symptoms / Characteristics:
Small, angular brown leaf lesions may be surrounded by yellow halos. These lesions eventually expand and coalesce, causing the leaf to turn entirely yellow. Leaves may drop if the leaf stem becomes infected. Leaf symptoms typically appear first on succulent new growth on the base of the shrub. Infected fruit has grey, water-soaked lesions and may be disfigured, cracked and shriveled. Fruit stalks may also be infected.

Entomosporium mespili is the fungus that causes Entomosporium leaf and berry spot disease in saskatoon. A similar strain of the fungus also attacks hawthorn, mountain ash, apple and pear. The fungus tends to flourish when weather conditions include high relative humidity or rainfall and temperatures between 20 and 26ºC. Disease spread is amplified even further when plant or row density is high.

Control / Preventions:
Improving air circulation is a key preventative measure as excess moisture and warm temperatures facilitate infection and disease spread. This can be achieved by controlling weeds, pruning excess suckers, thinning seedlings and shrubs, and watering at the soil surface instead of using overhead irrigation. Saskatoons grown in dry, open areas are far less susceptible to the disease. Avoid high density plantings and high moisture areas. Although it is believed that removing leaf and fruit debris will not effectively reduce the disease incidence, a thorough fall clean-up is always a good practice. Registered fungicides are available if infection has already occurred.