Honey Fungus: A Silent Killer Distribution of Armillaria and its effect on an old growth Douglas-fir/ Western Hemlock Forest Michael Gudmundson and Jim Lutz

Introduction: Armillaria root disease is found in many Results: temperate and tropical forests throughout Figure 2 the world. It is responsible for on average Figure 3 2-3 % of mortalities in infected forests. This root disease is caused by many 6% Snag DBH vs Mortality species of fungus from the Armillaria (1112) genus. They are commonly referred to as 5% (181) Honey Fungus. This fungus spreads 4% mainly through the interaction of tree roots. (5564) 3% The Wind River Forest Dynamics Plot (4768) shows evidence of an infection by 2% Armillaria. However the Extent of the infection has not been studied or mapped. 1% (42)

Research Question : 0% How much of the WFDP is infected and 0-3 cm 3-6 cm 6-9 cm 9-12 cm >12 cm what are the effects of Armillaria on the Vine Maple plots mortality? 10% Map of the estimated area of coarse roots for all susceptible species. Each circle is the coarse root Snag DBH vs Mortality area of a single tree. (13) Methods: 8% At establishment, The Wind River Forest (256) Dynamics Plot was a 25.6 ha permanent 6% plot in which 30,973 woody stems ≥ 1 cm 4% dbh where tagged 2% (1028) and mapped. (7872) (1425) The plot contains 26 different tree, 0% 0-30 cm 30-60 cm 60-90 cm 90-120 >120 cm shrub and liana cm species. After establishment Western Hemlock each woody 4% stem ≥ 1 cm dbh Snag DBH vs Mortality (47) was measured and 3% mortality data, including factors associated with death, Map of the estimated area of coarse roots for all trees whose mortalities show Armillaria as a factor 2% was collected on all trees that died from associated with death. establishment until the 2016 field . season. Figure 1 1% (506) Using the mortality data we (421) determined all tree species which have Percent mortality by species (298) (167) mortalities that where associated with 0% armillaria root disease (Figure 3) and 0-30 cm 30-60 cm 60-90 cm 90-120 >120 cm determined the relationship mortality had cm with the size of the tree.(Figure 2) Once Douglas-fir these species where determined we The percent mortality based off of the woody stem calculated and mapped the crown radius size. The numbers above the graph in parentheses of each trees based off their dbh using Acer circinatum shows the total number of trees in that size class. the equation and parameters of table 3 in Abies amabilis Betchtold. If a species was not in the Taxus brevifolia table we substituted the parameters from Tsuga heterophylla a similar species. We set the estimated Other coarse root radius equal to the radius of Map of the estimated infected area based on root interactions with the crown. After mapping the root radius trees known to be infected. The probability of infection decreases with 996 tree mortalities are associated of each tree we then mapped trees distance from the infected tree. Orange Circles represent known with Armillaria. This graph shows whose mortality data showed an infected trees, Purple represents high probability of infection, red is a the distribution of mortality by tree association with Armillaria and mapped lower possibility of infection and green circles represent no infection. species. any root systems that where touching an Conclusion: REFERENCES: • Bechtold, W. A. 2004. Largest-crown-width prediction models for 53 infected tree and expanded out from all Determining the total infected area in the plot for Armillaria is very difficult. The total infected area infected trees in 5 meter groups to show species in the Western United States. Wes. J. App. For. 19(4): cannot be determined solely from mortalities associated with Armilliaria because a tree may still be 245-251. the probability of the area being infected infected and has yet to die. Using the estimated coarse root we determined that the infected area is (Figure 1).The area for The total root • Edmonds, R. L., J.K. Agee, and R.I. Gara. 2001. Forest health and a lot greater than thought in the Wind river forest dynamics plot. This new information will help us protection. Long Grove, IL: Waveland Press. 280-288. system, known infected area and the develop a model to predict the growth of the infection. An accurate model of the disease and its predicted total infected area where spread will allow conservation efforts to be made more effectively and also can help in many • Lutz, J.A., A.J. Larson, J.A. Freund, M.E. Swanson, K.J. Bible. 2013. calculated. The importance of large-diameter trees to forest structural industries such as lumber and farming. heterogeneity. PLoS ONE 8(12): e82784.