Tuesday, August 9, 2016

Mid-summer tree shaking to improve kernel quality

    As the pecans on our trees approach full size, it's a lot easier to see the crop load produced by each pecan cultivar. The photo at right shows a Pawnee tree with limbs already bending down with an over-abundance of pecans.  Left un-managed, this overloaded pecan tree will end up producing a lot of poorly filled nuts this fall and will struggle to produce female flowers next year. Today, I'm going to use my trunk shaker to remove a portion of the crop.

   The prime time for crop load management is during the water stage of kernel development (photo at left). At this point, the tree has invested only a minimum amount of tree energy into building a pecan fruit. In constrast, the kernel filling process and the creation of high-oil-content kernel requires a huge amount of energy.
    We wait until full water stage to thin the crop because the nuts are only now heavy enough to fall when the tree is shaken. 

     I used a tree shaker equipped with doughnut pads to shake off a portion of the crop from my over-loaded Pawnee trees.  In mid-summer, the cambium layer under the bark is still actively growing and can be damaged by improper tree shaking. In addition to using doughnut pads, I apply silicon lubricant between the outer rubber flap and each doughnut pad. The lubricant will allow the rubber flap to slide around when shaking the tree instead of vibrating off a portion of the tree's bark.

    Trees over-loaded with nuts shake easily. A couple of  short-duration, hard shakes will rain down plenty of green-shucked nuts (photo at left). Using a tree shaker to remove a portion of the crop has one disadvantage; nuts are not removed evenly throughout the canopy. After shaking, you'll find more nuts fall from the top of the tree and fewer nuts are dislodged  from low limbs. That's why I always look at the mid-portion of the tree's canopy to judge if I've removed enough nuts.
    The one thing you can't do while summer tree shaking is look at all the nuts on the ground. The typical human response to an orchard floor covered in green nuts is to start thinking about lost nut production. However, shaking off nuts in August actually means that you'll see far fewer poorly filled nuts blowing out of the pecan cleaner after harvest.