With the early onset of warm temperatures, the development of many Saskatoon berry crops is well advanced in the 2006 season. It is definitely time to be actively managing disease this year. For the most important diseases, protection of the bloom stage from infection by plant pathogens is one of the most important management decisions you can make towards ensuring a productive year.

A simple way to sum up Saskatoon Berry Disease Management is the phrase: Protect the flowers from rain showers. In other words, employ practices that reduce the surface wetness provided from rain periods that cause disease. The wetness period can be reduced through adequate spacing of plants, removal of suckers that can increase canopy density and lengthen drying times, and watering the plants at the ground as opposed to overhead irrigation. These practices are not always enough to prevent a disease outbreak, however. Application of a recommended fungicide to ensure the flowers are protected from disease causing fungi is often necessary in Manitoba.

Entomosporium Leaf and Berry Spot

Plants that are left unprotected during a rainfall, are at great risk of severe crop losses. If a disease outbreak caused crop losses last year in your orchards (in 2005, Entomosporium Leaf and Berry Spot was a big problem in many orchards) favourable conditions this year will likely mean problems, if no successful attempts at management are made. Once the flowers and fruit are infected, those fruit are unmarketable.

Due to the influence of environmental factors on plant development, the time and duration of the bloom period will vary from year to year and from location to location. The bloom period, which extends from the green tip stage to petal fall (descriptions of the growth stages can be found at the end of this article), is the best time to manage a number of Saskatoon berry diseases (Remember—Protect the Flowers from Rain Showers). Fortunately, there is also little foliage present at this time, and good spray coverage is relatively 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 the majority of flowers in the orchard are fully open; by this time some will be past full bloom, while others will be at earlier stages.

The chart below lists the timings for fungicides registered for use on Saskatoon berry (Amelanchier alnifolia) for three diseases of concern in Manitoba. It is recommended that fungicide applications be avoided when the flowers are in full bloom, to avoid any problems during pollination.

Entomosporium Leaf and Berry Spot (Entomosporium mespili)
and Saskatoon-Juniper Rust (Gymnosporangium clavipes)
Fungicide Recommendations:

Powdery Mildew (Podosphaera clandestina) Fungicide Recommendations:

 

Description of Growth Stages:

References:
St. Pierre, R. 1999. Growing Saskatoons: A Manual for Orchardists. 5th Edition. University of Saskatchewan.