Tuesday, October 21, 2014

What's up in pecan tree canopies

    While I'm hand harvesting nut samples using a hydraulic lift, I often spot interesting and unusual things up in the tree's canopy that I wouldn't notice with my feet firmly on the ground.

    We have all noticed nut shells on the ground a harvest time that have been chewed by mice. You can see the gnaw marks on the shell and a hole chewed large enough to allow easy access to the kernel inside. But I never realized that mice would actually climb up the tree and start feeding on nuts long before they drop to the ground. The photo above shows two pecans neatly cleaned out by a hungry mouse. Since this was the only nut cluster I found like this, its likely that red-tailed hawks find tree-climbing mice an easy catch.

    In the canopies of unsprayed trees, I find lots of nuts infested with hickory shuckworm larvae. The small white caterpillar with a red head tunnels through the shuck of the pecan and can cause the shuck to stick to the shell (photo at left). 
      Hickory shuckworm larvae eventually pupate inside one of their tunnels before turning into an adult moths. But have you ever though about how the moth gets out of the shuck. The photo at right shows a shuckworm pupal case partially shoved out a hole created at the end of a tunnel. Still trapped in its pupal case, this shuckworm moth managed to wiggle out of the shuck until it could break free outside. I've seen several of these pupal cases and every time the case emerges from the shuck tail-end first. I guess makes sense. The moth could use the force of spreading wings to crack open the case then simply back out.  

    In one tree, I found nuts with unusually shaped shucks (photo above). The nuts appeared flattened with a distinctive crease down the middle. Although these nuts had not yet split shuck, the shuck had separated from the shell and I could easily peel out the nut. What I found inside was a small nut with a kernel that had grown too big for its shell. 
    This condition occurs when nut size and final shell dimensions are determined during a dry period in late July. A lack of soil moisture during the nut sizing period causes the creation of smaller-than-normal nuts.  Later, ample rain fell during the kernel filling process in late August which, in turn, promoted rapid kernel expansion to such an extent it popped open the shell.  What is interesting to see is how the shuck reacted to the over-expanded kernel. The crease in the shuck is located directly above the crack in the shell. Fortunately, not all the nuts on this tree appeared like this. Most nuts had normal shucks and already shuck split.

    Every fall, I enjoy taking photos of ripe pecans on the verge of falling out of their shucks. This year, I found a nut that was not only ready to fall but one that tickled my fancy (photo at right). Almost like a Rorschach diagram this pecan reminded me of something totally unrelated to pecans. Can you see the helmet, eye slits, and open mouth with pecan falling out?  Or maybe I have an overactive imagination!