We have a post oak tree that is probably about 50 years old and last year we noticed a black looking sap accumulating at the base of the tree. It also lost its leaves last year in August. This year the tree came back with new leaves but were very sparse and not full. It has now in a matter of 4-5 days leaves have turned yellow, now brown and are dropping like it was fall here in Texas. Does anyone know what might be the problem and what can be done for the tree? We hate to lose the tree as it is the only tree we have in the backyard. Someone told us it might be borers and we have sprayed but has not helped.

Reply to post by Pat, on August 01, 2002 at 14:14:37:

can you post a picture or describe it better? black sap can be caused by borers or bacteria or phytophthora or...

Reply to post by Pat, on August 01, 2002 at 14:14:37:

Before the tree defoliated earlier than usual last year, were there problems with the leaves?
Where is the tree located? What has been the general condition of the tree during the previous few years?
What is the planting area like? (landscape, irrigation, etc.)
When the leaves grew back, were some of the branches completely without leaves?
Have you looked for borer exit holes?
Did the person who suggested borers identify any signs, such as "D" shaped holes from 2-lined chestnut borer?
Has the tree been subject to drought, injury, changes in the rooting area?

I must say that things don't sound good.The tree may have been attacked by more than one pest or pathogen.

Reply to post by Pat, on August 01, 2002 at 14:14:37:

Pat, let me hazard a guess towards a few factors and you let me know if I'm close, okay?

Your soil is a sandy loam, probably a substrate of clay/limestone a few feet below. You've experienced the loss of a select few variants of live oak (evergreen canopies), although not in the area of the post oak?

The new growth, before decline this year displayed a bit "yellower" or chlorotic than last year.

Rotting seemd intense on the upper reaches - meaning the dead limbs "droop" faster than your used to seeing before breaking off?

Sections of bark on both the trunk and higher limbs have fallen off, revealing smooth inner tissue?

This question requires a bit more examination but maybe you've sectioned a fallen limb by chainsaw - if so, the cross section might reveal a distinct discoloration including hues of red, pink, grey, and black peripheries alongside of "sponge"-type of decay in the heartwood or inner portions of the log?

If my suspicions are correct you may have an infection of hypoxylon, common in Central Texas and becoming epidemic in virulance - controllable only by cultural means (removal of infected host and peripheral stands). However decreasing inviting elements (high moisture then drying conditions at root zone) limiting organic contributions (manure, rotting leaves) and spiking the soil pH (sulfur applications, slight copper increases)and above-ground wound maintanence (sealing all cracks, cuts, and wind tears) have shown some remarkable turn-arounds here on the Plateau. There are no chemical controls for infected trees so don't listen to the county agent or extension forester, there are some programs being advocated here for treatments but none I've found therapeutic.

Waiting for your response,

Reed