My primary research interest is in the ecological role of tree diseases. Specific aspects being investigated are the chemical ecology of tree/fungal pathogen/insect interactions, with some attention to effects of disease on the host signals (semiochemicals) utilized by insect pests to locate and select suitable feeding and breeding substrate as well as the host's defensive chemistry. Connected to this primary interest is a focus on systemic disease and insect resistance induced in trees by fungal pathogens. Chemical, biochemical, molecular, and anatomical approaches are used to dissect these phenomena in pines, with particular emphasis on the model system represented by Austrian pine and the shoot blight and canker pathogen Diplodia pinea.
A second major area of interest is on the effects of soil type and soil management regimes on mycorrhizal community structure of trees in simulated urban environments. We are investigating the effects of soil type and management regime, fertility, and mycorrhizal inoculants on tree resistance to drought stress and patterns of within tree carbon allocation, with special emphasis on allocation to defense mechanisms against pathogens and insects. Our model tree in this research is paper birch.
A third, increasingly significant involvement is in the area of emerging pathogens and insect pests of trees, or disease syndromes, with particular attention to the ecological consequences of pathogen and insect pest invasions. Several projects are currently under way: 1) A study in California on the use of chemical markers for genetic resistance of coast live oak to the sudden oak death (SOD) pathogen, Phytophthora ramorum; 2) a study in California on wood decay fungi associated with xylophagous insects that preferentially attack coast live oak infected with P. ramorum; 3) a comparative analysis of mechanisms of resistance to the emerald ash borer in co-evolved and nave ash species; and 4) an investigation into the etiology of a decline syndrome on white oaks recently discovered in SE Ohio. The lab is also in charge of a regional component of the national, US Forest Service-sponsored annual survey for the SOD pathogen. In 2004-2007 we conducted surveys and/or processed samples from Illinois, Indiana, Iowa, Missouri, Ohio, and Wisconsin.
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