Wild blueberry : disease incidence in different management zones.

Lowbush blueberry, grown in a 2-year cycle (vegetative and production), is a major crop in the Saguenay-Lac-Saint-Jean area (Quebec) where the production represents more than 85% of the entire blueberry harvested in the province of Quebec. There are three major diseases that affect lowbush blueberry: septoria (Septoria spp.) and valdensinia leaf spot (Valdensinia heterodoxa), and monilinia blight (Monillinia vaccinia-corymbosi). Prothioconazole is usually applied during the vegetative year to control diseases. In 2016, two fields were selected near Normandin (Quebec) and four different management zones were determined according to apparent soil electrical conductivity and elevation in each field. In each of these zones, in 2017 (vegetative year), four N fertilisation rates (0, 30, 60, 90 kg N ha-1) with or without prothioconazole (192 g a.i. ha-1) were applied in a split-plot design, where the main plot was the N fertilisation rates and the subplot was fungicide. The objective was to determine if N fertilisation and the application of fungicide could affect the incidence of the three diseases. Septoria and valdensinia incidence was rated on five plants per plot that were randomly identified at the beginning of the season. On each of these plants the five youngest leaves were used to assess the disease severity index (DSI). In 2017, the incidence of septoria leaf spot was very low and there were no valdensinia leaf spot. Nitrogen rate and fungicide had no effect on disease incidence or DSI. In 2018, monilinia blight will also be rated and results will also be presented.