any recent construction near these trees???

ken

Maybe drought stress from last year?

No construction and if there was a drought, would it not have affected the 3 right beside it? THERE have been a lot of woodpeckers, big ones... could they have damaged the tree in question? But the woodpeckers have pecked ALL the trees in the area. Hmmmm...
Okay, just remembered, the cable company came out with a trencher and ran a machine through the yard, may have gone under the pecan trees, but not exceptionally close to the one in question...

And just remembered last year this one in question did not produce even 1 nut, but it may have been its off-year.

Nut production typically falls off when trees are planted too close together. Typically, 35' is cited as minimum distance between trees. Once the branches are touching one another, the trees are too close to one another and nut production will begin to fall off. At this point the experts recommend removal of one of the trees in commercial production. A common soil deficiency here in Texas for pecans is zinc. Perhaps a soil test would point out if there are deficiencies in your soil for pecan tree. From what I see in your picture, I would guess that the other trees are out competing the weak tree and that your trees are too close together.

They for sure are planted too close together but have been producing nuts perfectly as long as we have been here. It seems very sudden that this one appears weakly. Would the others compete out this one so suddenly? BTW I wrote in my original post that the tree on left was one in question...obviously...it is the one on the RIGHT that appears weakly.

maybe root girdling cutting off circulation of other roots of the tree.

Arborist could tell by blowing away some of the soil to examine roots, if so they cut away the problem roots.

click on the link

Here is a link that might be useful: link

Thank you all so much for the advice & information. Before I call an arborist, do you think it would help any to give it a shot of fertilizer? I doubt it could hurt?

hi dinajean,
On the left is a branch from my pecan tree at the normal stage of leafing out. On the right is my 'Kanza' pecan which I planted last year. I really don't know why 'Kanza' is so slow to wake up this year but am confident it will catch up and be fine.
{{gwi:354652}}

If you went thru drought stress, it may have weakened/stressed the tree in question to the point that it is now in trouble. The record heat and drought suffered here in 2011, weakened some trees such that they croaked in 2012, and others are still suffering. The affects of it were variable. Perhaps you are seeing something similar.
I lost 3 out of 30 pecan saplings. Had another 10 that lost the upper grafted portion, but came back from the root-stock.
Perhaps you can try Howard Garett's sick tree treatment on it to help strenghen it. One thing he recommends is first check for root flare. If all your other trees are doing fine, is there anything different about the other trees vs this tree?

Here is a new picture of trees that look healthy & one in question. Maybe that will give me more answers from y'all who are AWESOME!!!