Rust of Saskatoon Berries

Disease Cycle. 2 hosts required to complete entire sexual cycle: cycles between species; may increase as specific spore types on each host. Galls on junipers produce jelly-like orange-brown “horns” in wet springs, releasing spores: typically in May-June; spores can travel several kilometres to infect Saskatoon berry plants. Leaves and fruit may be infected, causing characteristic swellings and growths. Infection and spread favoured by temperatures between 10-24°C with wet plant surfaces. Moist or rainy conditions can increase spore production and spread of infection. Spores produced on Saskatoon berries will infect junipers, completing life cycle.
Symptoms. Early symptoms include yellowish spots and swellings on leaves and fruit. Swellings grow to become firm spiky outgrowths from leaves and fruit. Twigs and branches may swell and be distorted. Orangey rusty powder evident on and around outgrowths.