Symptom expression in conifers infected with Armillaria ostoyae and Heterobasidion annosum

Abstract

Crown symptoms and other aboveground variables were examined on 36 Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco.) (40–209 years old), 46 white fir (Abies concolor (Gord. & Glend.) Lindl.) (36–165 years old), and 97 ponderosa pine (Pinus ponderosa Dougl. ex Laws.) (64–220 years old) trees in northern New Mexico and southern Colorado. Root systems of all trees were excavated to determine extent of root disease. Symptoms observed on infected trees, including reductions in height growth, changes in foliage characteristics, and crown dieback, worsened as the number of infected roots increased. Trees with aboveground symptoms had a significantly higher (p < 0.05) number of infected lateral roots than trees without symptoms. In mixed conifer stands on the Archuleta Mesa, Colo., four qualitative crown symptoms were used to accurately detect Armillaria ostoyae (Romagn.) Herink and (or) Heterobasidion annosum (Fr.) Bref. infection of Douglas-fir (21/22, or 95%) and white fir (19/28, or 68%). Similarly, 61% (48/79) of the A. ostoyae infected ponderosa pine trees on the Jemez site, N.M., were detected using the qualitative Thomson vigor rating system. Discriminate analysis, using more thorough variables and analysis, resulted in correct infection classifications of 82%, 85%, and 78% for Douglas-fir, white fir, and ponderosa pine, respectively, suggesting that aboveground variables are reasonable indicators of root disease.

Armillaria species distribution on symptomatic hosts in northern hardwood and mixed oak forests in western Massachusetts

“…Additional studies have confirmed that relying on aboveground symptoms underestimates the incidence of root disease (Filip, 1986;Whitney et al, 1989). Yet, several studies have proven just the opposite, that aboveground symptoms are reliable indicators of root disease in both wet and dry forests (Shaw and Toes, 1977;Wallis and Bloomberg, 1981;Omdal et al, 2004). All of these aforementioned studies were performed in conifer forests where the most abundant Armillaria species (A. ostoyae) is predominantly root-infecting.…”

Wood production, wood technology, and biotechnological impacts

“…However, decay columns as long as 12 m have also been observed (Stenlid & Wästerlund 1986). In an advanced stage of infestation, some trunks have a bulged appearance by anatomical defence responses, resin exhudation might occur, crown deterioration is often observed, and fruiting bodies might form on the surface of roots and the base of stems (Greig 1998, Krekling et al 2004, Omdal et al 2004. If any of those symptoms are visible, one can be sure that the fungus has already reached an internal decay dimension as shown in Fig.…”

Vitality Assessment of Visually Healthy Trees in Estonia

“…Neighbouring trees can be affected by soil movement via mycelia [8,9] and rhizomorphs [10], but the mycelium of Heterobasidion is not able to spread freely in the soil. The disease may inhibit nutrient and water flow by damaging or killing the roots, which ultimately leads to tree mortality and decreases in forest ecosystem health, resilience, and productivity [3,[11][12][13]. The incidence of Heterobasidion root disease is higher in stands on former agricultural lands [14][15][16][17] and in stands growing in mineral soils with good water drainage and higher soil pH [18].…”