Clearing Cedars around Pecan trees kills the Pecan trees

[Rehoboth Ranch]

We moved to this farm north of Greenville 12 years ago. Our soil type is deep sandy loam with a lot of river bottom land and hillsides that are mostly clay loam. There are many large native pecan trees that are grown up inside the drip line with eastern red cedars so thick the pecan nuts can not be gathered easily. We have cleared, with chainsaws, the cedars out from underneath about a dozen of these groves of pecan trees. None of them have done well. Most of the cleared out pecan trees have died. It was not done with a dozer, just chain saws. The cedars were cut off at the ground level and then the ground level stumps died, as is characteristic of eastern red cedars. The death of the pecan trees takes anywhere from one to three years. We have not given the pecan trees the sick tree treatment because the logistics and the volume of spray makes that impractical. Besides, the pecan trees were not sick before we cleared the cedars. The clearing was mostly accomplished during the winter months. I have observed the same situation on other properties, but no one has any idea why removing the cedars would kill the pecan trees. Anybody else have experience with this? Anybody know of a way to clear cedars from under pecan trees without killing them? With the hundreds of pecan trees, there should be commercial potential to harvest pecans annually, but so far all we have done is worked hard and killed the pecan trees. We are 100% organic.
Robert Hutchins
Rehoboth Ranch

[Tree Dude]

How big were the pecans and eastern redcedars? I am guessing that if redcedars were bigger than pecans or so dense that when you removed them, the pecans had a "lightshock." But then that's one powerful light blow :shock: !
It was grove of pecans correct, not an orchid? How many pecans were there? Was there more cedars than pecans?

With all this questions, you'd better get an arborist or call DD.

Tree Dude

[Rehoboth Ranch]

Answers to your questions:
Cedars and pecans have been roughly the same diameter, which means the pecans are much older and have been engulfed by the cedars over the past 10-20 years. I have considered light shock, but could not imagine how that could kill the pecan tree. The places we have cleaned out were just native groves of pecan trees, not planted orchards. All pecan trees are still natives. No grafting has been done. I have already asked DD about it, and he had no explanation. It is almost as if when you cut down the cedar, the remaining root stock releases a toxic chemical that kills the pecan trees.
Any ideas would be appreciated.
Thank you.

[Dirt Doctor]

Robert - sorry, I don't remember talking about this. The roots of trees do fuse, even different species. The remaining trees are always stressed when some neighbors are removed. The remaining ones usually rebound later so this is a curious thing - and maybe a big thing. Cedar has its negatives - pulling too much water out of the soil for one thing and John Ferguson has told me that that cedar mulch in the acid soils of Houston doesn't work very well as it does here in the black and white soils. There could be something toxic from the cedar roots but I doubt it. The answer is probably that there was just too much clearing done at one time. Any other ideas are certainly welcome.