Kees van Frankenhuyzen
Canadian Forest Service

SERG Project #2003/04
Year of Project: 2003
Report Received: 2004

Of the 151 plots sampled by BioForest in the fall of 2003, only those plots that had an average of >3 larvae per branch were processed to estimate prevalence of Nosema. For those plots, larvae were randomly removed from the total obtained from the 6 washed branches up to a total of 30 per plot. Each larva was smeared, stained with naphthalene blue and examined microscopically for the presence of spores. If no spores were found in 20 fields-of-view, the larva was considered not infected. This way we obtained an average % infection for 96 of the 151 plots. The results (number of larvae smeared and % infection) are listed by plot number in Table 1. Infection estimates varied from 0 to 54%. A breakdown by region (Table 2) reveals that most of the infected plots were located in Northeastern and Central Saskatchewan. The distribution of infection levels was distinctly different between the two regions (Figure 1). In Central Saskatchewan, the frequency distribution was near normal with most of the plots in the 20-40% infection category, versus a skewed distribution in the Northeastern part of the province,with most plots in the <20% infection category.