Would anyone care to hazard an opinion as to the probable or possible causes of tree death mentioned in the report below? Perhaps a Phytophthora species? Fusarium?


All roots are dead. Bark at root crown and roots easily sloughs from wood beneath. Cambium is wet, black, somewhat stringy. Small (~3/16" long) reddish brown pupa found in this blackened tissue just above ground level. Wood is deeply stained grey-black (not red or brown). No white mycellium is present beneath the bark. No smell is detected (not sour or fermented). The tissues are dry and less darkly stained several inches above the ground. The bark is more firmly attached there. Various other very small invertebrates were seen beneath the loosest bark. There are no mushrooms present in the vicinity. No conks are on the trunk. No cankers or insect bore holes are visible on the trunk. Soil is moist, though rooting area has been reported to be without supplemental irrigation for several years. Other shrubs in the immediate area appear to be live and healthy. Tree declined noticeably over several years, with decreasing leaf and bud size, early defoliation, and finally dead leaves retained after normal leaf fall. A number of branches died the previous year, throughout the tree. There is evidence of some girdling roots. Concrete work and signage posts close to the tree (within 5 feet) indicate probable root disturbance.

Reply to post by Mark Goodwin, on March 13, 2002 at 14:59:26:

I forgot to mention:
The tree is Liriodendron tulipifera, about 10" DBH.
I assume summer water stress and probable mechanical root damage.
I wonder if the small pupae are fungus stain beetles, secondary (?) to tree death.
The location is Northern California interior valley, so tree is exotic.
Due to multi-story building and Coastal redwoods nearby, sun exposure was limited to mostly afternoon. It was not otherwise overgrown.
I don't know of any seasonal water drainage problems.

Reply to post by Mark Goodwin, on March 13, 2002 at 14:59:26:

While the description is thorough, it could describe any of several disease infections. It is possible that the symptoms you reported are the result of saprophitic fungi that have followed the primary infection (if any). A more thorough post mortem would be necessary to determine what diseases are present. On Liriodendron tulipifera, Armillaria is common, but so are other diseases. If the root system failed, the tree could die without the fungus even reaching the root collar. In this case, saprophytes could move into the root collar first.

If you really need to determine the cause, you should take several samples and have them identified by a lab.

Reply to post by Mark Goodwin, on March 13, 2002 at 14:59:26:

Mark

What you describe as being 'wet, black, somewhat stringy' doen not sound like a description of cambium but more likely phloem tissue.

It would be worth considering or investigating the possibility of anaerobic soil conditions resulting from either waterlogging or displacement of oxygen by escape from a gas main. The black staining you describe is a fairly good indicator for gas leaks when found beneath the bark of roots.

Reply to post by mike, on March 13, 2002 at 14:59:26:

Gas leak would have been my first guess too, but did Mark say the surrounding shrubs were unaffected?

Reply to post by Scott, on March 16, 2002 at 04:29:13:

Dependant on shrub genera/species, shrubs may be rooting significantly closer to the surface where perhaps gaseous exchange is less inhibited by the soil structure and depth. Particularly in a clay soil, the effects of gas leakage can be slow but persistent and progressive due to the gradual exclusion of oxygen. If my memory serves me correctly, anaerobic bacteria play a part in this syndrome.

Reply to post by mike, on March 16, 2002 at 06:14:33:

OK then. I agree. Mark should check for any evidence of gas leaks.

Reply to post by mike, on March 13, 2002 at 14:59:26:

Phloem, of course; you are right. I will see what I can find out about proximity of gas sources in the area. Thanks.