Protecting saskatoon berries’ bloom stage from infection by plant pathogens is an important part of maintaining top production potential.
Philip Northover, a pathologist with Manitoba Agriculture, said “protect the flowers from rain showers” is a simple way to sum up saskatoon berry disease management.
Practices that reduce surface wetness from rain will also lessen disease severity. This wetness period can be reduced by adequately spacing plants, removing suckers that can increase canopy density and lengthen drying times, and watering the plants at the ground rather than overhead irrigation.
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When these practices are not enough to prevent a disease outbreak, it often becomes necessary to apply a recommended fungicide to ensure the flowers are protected from disease-causing fungi.
Plants left unprotected during a rainfall are at risk of severe crop losses. If a disease outbreak caused crop losses last year in an orchard, favourable conditions this year will likely mean problems if no attempts are made to manage for these diseases. Fruit becomes unmarketable once infected.
Because of environmental factors, time and duration of the bloom period varies by year and location. The bloom period, which extends from the green tip stage to petal fall, is the best time to manage many saskatoon berry diseases.
Another advantage is that little foliage is present at this time, which means good spray coverage is easy to achieve.
Timing for fungicide applications is often based on an estimate of when a certain proportion of the flower buds are fully open. For purposes of pest management, the term “full bloom” refers to the point at which most flowers in the orchard are fully open. By this time some will be past full bloom, while others will be at earlier stages.
Fungicide applications should be avoided when the flowers are in full bloom to prevent problems during pollination.
When controlling entomosporium leaf and berry spot and saskatoon-juniper rust, apply Funginex DC between flower bud break and white tip stage. The fungicide is limited to one application a year because it has a 60 day pre-harvest interval.
Kumulus DF is recommended only for entomosporium leaf and berry spot. The first application should be between the flower bud break and green tip stage. The second application is recommended 10 to 14 days later, with a third application 10 to 14 days after that.
Kumulus can be used all season, but applications within a week of harvest may leave a sulfur smell on the fruit.
Topas 250 EC and Mission 418 EC have the same active ingredient. The first application should be at the white tip stage, a second application at the petal fall stage and a third application at the green fruit stage.
Topas and Mission have a 38 day pre-harvest interval and no more than three applications are recommended per season.
Nova 40W is recommended for powdery mildew control. The first application should be at flowering, a second made at the small green berry stage and a third at the green berry stage. Nova has a 14 day pre-harvest interval.
Saskatoon growth stages
Green tip – Occurs when the first leaves are still expanding, flowers remain green and there is no visible portion of the petals yet. The green of the sepals is the only visible part of the flower.
White tip – Occurs when the white tips of the petals are just becoming visible.
Tube – Flower petals are elongated at the base and more apparent, but not open.
Balloon – The petals and receptacles are increasing in size, individual petals are beginning to be noticed, but flowers are not open yet.
Full bloom – Petals are open, internal flower components are visible.
Petal fall – Petals have started to shrivel and fall away from the flower.
Fruit set – Petals are gone, leaving a green cup-shaped structure.
Green berry-fruit – No longer cup shaped, berries are small, green and rounded.
Small green – Fruit is taking on a rounded appearance, still green in colour. This is an intermediate stage between fruit set and green berry.
