Pacific Northwest Research Station

Title: Laminated root rot in a western Washington plantation: 8-year mortality and growth of Douglas-fir as related to infected stumps, tree density, and fertilization.

Author: Miller, Richard E.; Harrington, Timothy B.; Thies, Walter G.; Madsen, Jeff.

Date: 2006

Source: Res. Pap. PNW-RP-569. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 37 p

Station ID: RP-PNW-569

Description: A 4-year-old Douglas-fir plantation in the western Washington Cascades was monitored for 8 years after fertilization with potassium (K), nitrogen (N), and K+N to determine fertilizer effects on rates of mortality from laminated root rot (LRR) and other causes relative to a nonfertilized control. Each element was applied at a rate of 300 lb/acre on and around 0.2-acre plots replicated seven times in a randomized complete block design. Cumulative mortality from LRR did not differ significantly among fertilizer treatments, and losses were strongly related to density of infected stumps from the previous stand (r2 = 0.74). Mortality from disease and other sources accelerated during the 8 years of monitoring. Average tree growth and stand volume were greatest in treatment N and were reduced where N was combined with K. Continued monitoring is needed to identify potential longer term effects of the fertilizer treatments on susceptibility of Douglas-fir to LRR and Armillaria spp.

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Citation

Miller, Richard E.; Harrington, Timothy B.; Thies, Walter G.; Madsen, Jeff.  2006.  Laminated root rot in a western Washington plantation: 8-year mortality and growth of Douglas-fir as related to infected stumps, tree density, and fertilization..   Res. Pap. PNW-RP-569. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 37 p