Squirrels feeding on young tree bark

      When nut growers think about squirrel damage, they usually imagine their crop eaten by the fuzzy-tailed bandits. However, the other day I spotted a different kind of squirrel damage that can be equally as damaging, especially to young trees. When their normal food supply runs low, Squirrels will strip the bark from smooth-barked pecan trunks and/or limbs to feed on the tree's nutrient rich cambial layer (photo at left).

    Squirrel bark stripping is an especially troublesome problem on young grafted trees. If the bark is removed around the entire diameter of the tree, the upper portion of the tree will eventually die. Hopefully a bud above the graft union but below the girdled area will break next spring and grow into a new trunk.

    After seeing squirrel damage on several young trees, I decided it was time I did my part to help feed the squirrels.  I set out some conibear traps baited with one of last season's pecans (photo at right). Directions for trapping squirrels can be found HERE. 

    It turns out my local squirrel population was still hungry and couldn't resist a nice large pecan. That's one down and dozens more to go.

Time for nut crop thinning

     This year, my Kanza trees have set way too many nuts to be able to produce high quality kernels come this Fall. To remedy this problem, I need to remove a portion of the nut crop to allow the remaining nuts to pack the inside of every shell with kernel. The most efficient way to reduce pecan crop load is to shake the trees when the nuts reach the water stage of nut development. So, ever since the first of August, I've been cutting open Kanza nuts to check on their kernel development.  

    Today, the nuts hit the water stage (photo above, right). It was time to shake trees.

   For summer tree shaking I use a 3-point hitch tree shaker equipped with doughnut pads (photo at left). When shaking trees in mid summer it is important to use a doughnut pad shaker to help prevent shaker damage to the bark. I also lubricate the inside of the rubber flap that covers pad with silicone lubricant. The goal is to allow the rubber flaps to slip and not the bark off the trunk of the tree.

     Shaking trees for crop load regulation is somewhat of an art. The duration and intensity of the shake largely determines how many nuts are removed. Starting on the first tree, I shake only lightly. Getting off the tractor, I visually inspect how much I've removed. I never look at the nuts on the ground only the nuts left in the tree. If I haven't removed enough, I'll shake the tree again. My goal is to get between 60 and 70%  of the terminals bearing nuts. 

    Once I've shaken a few trees. I get the feel for how much to shake the rest of the trees in the orchard. This year, I was somewhat surprised how easy it was to remove nuts. I had to make sure to use a light touch on the throttle or else I would remove too many nuts. Shaking my entire Kanza block (10 acres) took just a couple of hours.

Pecan bark graft - The first year in pictures

25 April 2020, Bark graft set

   This year, I decided to photograph the growth and training of one bark graft that I made this Spring. I'll be adding to this post as the season progresses so you can see every step I take in training the scion and pruning back the under-stock. The process began this year with a bark graft placed on a young tree on April 25th (photo at right).

17 May 2020, Bud swell

Three weeks after grafting, buds on the scion start to swell and green up (photo at right). This is a good sign for graft success. However, remember that there is often enough stored energy within the scion itself to push buds open even if the scion and stock haven't made a strong, growing connection. It is only when I see leaves expanding,  do I known the scion and stock have united fully.

  

25 May 2020, Leaf Expansion

    Four weeks after grafting, leaves are expanding on the new shoots growing from the scion (photo at right). At this point I am confident I have a successful graft.

1 June 2020, Shoot elongation

    With warm summer temperatures, the new shoots growing from the scion start elongating rapidly (photo at right).  Successful bark grafts usually grow 4-6 feet in height during the growing season.


















8 June 2020, Graft training

    By the first week in June the graft has grown to a point where it is time to select one shoot to become the new central leader. In the photo at right, you can see that the scion has developed two strongly-growing shoots that are competing for dominance.
    At this point, I will begin the tree training process to promote the growth of the scion, limit the scion to a single growing shoot (new central leader), and install a larger tree-training stake. These steps are illustrated in the photos below.

Prune back growth below the graft to push scion growth, June 8th

Prune to one scion shoot, trim off top stub to promote healing. June 8th.

Remove tape to prevent girdling, June 8th.

Install 1 x 2 training stake, tie new growth with flagging tape to prevent wind damage. June 8th.

Scion 2 feet tall on 15 June 2020

15 June 2020, Remove stalked buds

    With all the tree's energy focused on a single shoot growth rate is rapid. At this point,  the scion shoot is nearly 2 feet in length. However, rapid shoot growth promotes the formation of stalked buds which lead to the formation of poorly attached lateral branches. My goal in training this scion is to maintain a single, branch-less shoot during this first year of growth. I remove all stalked buds on the scion shoot as they appear during the summer months. The photos below illustrate the appearance and removal of stalked buds.

Stalked buds form on rapidly growing scion (red arrows), 15 June 2020

Scion shoot nearly 3 feet tall on 1 July 2020

1 July 2020,  More tree training

    By the 1st of July, the scion shoot is nearly 3 feet tall. New, upright-growing shoots have sprouted from the lower support limbs that can compete with the scion for light and nutrients. To maintain the tree's focus on growing the scion, I will prune off all upright-growing shoots competing with the scion and prune back the support limbs. To further train the scion shoot, I remove all newly-formed stalked buds and tie the new growth to the training stake. These steps are illustrated below.
  

Remove newly developed stalked buds from the upper portion on scion shoot. 1 July 2020.

Remove all new shoots that are competing with scion. 1 July 2020.

 Prune back support limbs to encourage more scion growth. 1 July 2020.

3 August 2020 scion shoot is now 5 feet tall

3 August 2020, Graft union painting and tree training

    During early August, I like to remove all the wrappings that cover the graft union and paint that area with white latex paint. By removing the plastic bag and aluminum foil, I can clean out any ant nests that have formed under the protection of the plastic. I use white paint for two reasons. First, to prevent sun-scald on a portion of the tree that has been covered since late April. And second, to mark the site of the graft union for easy identification for years to come.
    While I was attending to the graft union, I also pruned off any and all lateral shoots on the scion that have developed from stalked buds.  I also made just a few pruning cuts to the support limbs to remove low hanging branches. At this point in the season, I limit the pruning back of the support limbs to allow the scion shoot to start slowing down its growth rate. I don't want rapid growth to continue into the fall because that can lead to winter injury of the scion. 

All coverings removed from the bark graft.

Graft union painted white

Lateral shoots growing from primary buds on the lowest portion of the scion shoot will be removed

Stalked buds have developed and sprouted on the upper portion of the scion. These will all be removed.

Bark grafted tree before and after painting and training

 
 

Kanza will need crop load thinning

   By the first day of August, pecans have gained enough size to be clearly visible on the tree. Looking at my Kanza trees, I could already see limbs weighted down with an immense crop (photo at right). More than 80% of the Kanza tree's terminals are supporting a nut cluster with each cluster containing 4 to 6 nuts. Left alone until fall, these trees will produce a huge crop of poorly filled nuts and will not be able to produce a sufficient number of pistillate flowers next year. It is a lose - lose situation. Poor quality nuts in the Fall and no crop next year.

   To avoid these problems, I plan to shake my Kanza trees this summer to significantly reduce the crop load. As you may recall, I  thinned the nut crop on all my Kanza tree last year and had great results.

    Crop load regulation works best when the nuts achieve between 3/4 and full water stage. At that point in nut development, the nuts are heavy enough to be removed by shaking but have not yet invested a lot of tree energy into filling the kernel.

   As the pecan near full size, I start cutting open pecans to check for nut development. Pictured at right is a Kanza nut I pulled from the tree today. The nuts seem smaller than usual this year, most likely due to the extended dry spell we suffered through the months of June and July.

   To check on nut development, the nut must be sliced open in a very specific manner. First, hold the nut so that you are looking at the stem end. Note that the stem scar is oval in shape.  (photo at left)   

   Place a knife across the short width of the oval (photo at right) and slice the nut open the entire length of the nut. As you cut, liquid endosperm will leak out of the nut.   

 

   Once the nut is opened you should be able to see the two sides of kernel (photo at left). They appear as empty voids because all the liquid endosperm has dripped out. As of August 1, my Kanza nuts are a little more than 1/2 water stage. That's not quite full enough to start shaking. I'll check again in a few days. Since I can shake all my Kanza trees in one day, I'll wait until full water stage to start this summer's nut thinning.