1. Effects and Impacts of SNC
2. SNC Treatments
3. Quantification, Assessment, and Severity Prediction
4. Tree Genetics, Resistance, and Improvement

Treatments to mitigate the affects of SNC have been shown to be effective, although applications of these treatments may or may not be economically or operationally viable, depending on goals and objectives of the landowner. Many fungicide application treatments have found increased levels of foliar retention (Manter and Kavanagh 2003). Early trials of aerial fungicide (BRAVO) treatments decreased infection rates and increased needle retention and growth rates (Johnson et al. 2003). (Figure 1a) However 5 years of spraying did not achieve complete control of the disease (presence of P. gaeumannii was still significant), and 2 yrs. after applications ceased infection levels did not differ between treated and untreated areas. Elemental Sulfur has also proved to be effective in reduction of foliage infection, but results may be short-lived. (Figure 1b) The cost-effectiveness of continued or periodic annual aerial spraying using fungicides is questionable, and needs further investigation (Stone 2005 annual report).

A positive growth response to thinning was observed at all levels of infection, although less so at high infection levels (Mainwaring et al. 2005), (Figure 1c) indicating growth can be accelerated and maintained, although responses on the most heavily infected sites may be too low when objectives are oriented strictly for timber production. If objectives range from production to diversity of stand structures thinning may be a more viable management option in highly infected stands. (Figure 1d)

El-Hajj,-Z., Kavanagh,-K., Rose,-C., and Z. Kanaan-Atallah. 2004. Nitrogen and carbon dynamics of a foliar biotrophic fungal parasite in fertilized Douglas-fir. New Phytologist. 163: 139-147.

Johnson, G.R., Gartner, B.L., Maguire, D., and A. Kanaskie. 2003. Influence of Bravo fungicide applications on wood density and moisture content of Swiss needle cast affected Douglas-fir trees. For. Ecol. Man. 186: 339-348.

Mainwaring, D.B., Maguire, D.A., Kanaskie, A., and J. Brandt. 2005. Growth Responses to commercial thinning in Douglas-fir stands with varying intensity of Swiss needle cast. Can. J. For. Res. 35: 2394-2402.

Figure 1A: Relationship between earlywood density and earlywood width in the outer tree rings for Bravo-treated and conrtol areas. (Johnson et al., 2003)

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Figure 1B: Comparison od P.gaeumannii infection index in one-year-old foliage (2004 foliage sampled in June 2005) for six sulfur treated and untreated plot pairs. (Stone, 2005 Annual Report)

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Figure 1C: postthinning/prethinning basal area growth predicted by the Swiss needle cast variant of ORGANON for pure Douglas-fir stands (site index 38.0 m at 50 years). (Mainwaring et al., 2005)

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Figure 1D: Annual basal area growth of Douglas-fir for 5 years following thinning: (a) average growth trend for each plot and (b) growth inplied by model [4], assuming mean values for basal area (26 m²/ha), crown length/sapwood area ratio (8.76 cm/cm²), and age (42.2 years). Averages were based on 41 plots with at least 5 years of posthinning growth. (Mainwaring et al., 2005)

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