When can I replant oak after Armillaria?
An old white oak in my front yard developed an Armillaria infection and eventually attracted Ambrosia beetles. An arborist confirmed that the although the tree was still leafing out, it would not last much longer so I had it removed last week. I would like to replace it, probably with another shade tree, perhaps even one of its offspring that is shooting up nearby. Do I need to wait for the Armillaria and/or other fungus to clear from the soil? I suspect there might have been other root rot earlier, perhaps from another fungus, since I noticed subsidence over a section of the lawn out towards the dripline of the tree -- but no mushroom growth -- maybe 15 years ago.
Montgomery County Maryland
You need to remove the stump, as the armillaria lives on dead wood. Keeping the stump helps armillaria remain in the area, because the stump is a good source. This fungus moved primarily by rhizomorphs (root-like structures under the soil).
Also have as much of the stump wood grindings removed off-site as is possible. Refill the hole with clean top soil.
You should not replant in the same hole. Plant your new tree about 30 feet away (or as far as possible.)
Your new shade tree can be an oak or other species, that will not matter as regards the armillaria. However, oaks are a premier species for encouraging wildlife (birds, etc.)
Thanks! The stump was ground down 4 to 8 inches below the surface and the hole filled with top soil from elsewhere. Unfortunately the yard is very small and the new tree will have to go within about 10 feet of the old one, if not even closer. I guess I should wait at least a year before planting anything? If no Armillaria clusters are seen through next summer, is that an indication that the area is clean enough?
Armillaria clusters may not come up until next fall. The farther away you can plant is best. However, 10 feet away is better than nothing. Young trees are less inclined to be infected and susceptible to problems. Depending upon what you plant, you do not have to wait a year. However, oaks transplant best in the spring.