How to Test the Soil for Root Rot Fungi in a Red Oak Tree

Check the tree trunk for "conks." These are the basidiocarps, or fruiting bodies, of the fungus infecting the tree. Armillaria root rot forms brown mushroom clusters, while Inonotus dryadeus forms a large, spongelike conk with a cream-colored top. Inonotus dryophilus produces a vertical growth of shelf-like conks in a ladder-like formation up to 6 feet tall.

Choose a pathogen test kit that seems most likely to confirm which fungus is in the soil as evidenced by the type of conk formations you found, if any. Phytophthora and Pythium do not produce conks or other fruiting bodies visible to the naked eye.

Dig the soil away from the red oak's roots. Be careful not to injure the roots with the shovel or trowel.

Examine the exposed roots carefully. Black threads might form visible mats at or below the soil line if Armillaria fungus is present.

Take a small sample of soil from the area near diseased roots. If the test kit calls for a vegetative sample, cut or scrape off a small sample of a diseased root. Each kit has detector devices, test strips or other materials needed to perform the test. You will need a different test kit for each suspected fungus. Follow the manufacturer's instructions for using the kit to test your soil or vegetative sample and interpret the results.