Monday, September 21, 2020

Bark graft snaps in the wind

 


    One of the bark grafts I made this past Spring died suddenly (photo at right). The graft was still standing up straight and tall but all the leaves had turned brown. This warranted closer inspection.

 


    I immediately focused in on the graft union (photo at left).  Even though I had painted the graft union white, I could see that the scion had been broken right at the very top of the stock. I carefully stake every bark graft but is obvious that I did not secure the stake tight enough to the tree to prevent the scion from rocking back and forth in strong winds. I had used black tape to secure the stake to the tree but upon inspection I found that I could wiggle the stake just enough to allow the breakage observed to the scion. In the future, I'll need to start bringing a cordless impact driver and wood screws to the field when installing stakes on bark grafts. Two screws placed through the stake and into the stock tree should help hold things rigid. 


     The breakage of this one graft encouraged me to start looking at other bark grafts I made this year. I was especially interested to see how each scion grew at the very top of the stock. The photo at right is typical. This scion appears to be trying to creep over the top of the stock. You can also see how  new tissue is forming up from the cambial layer of the stock to grab onto the side of the scion. At this point, the scion can still break easily unless it is help firmly in place with a strong stake and plenty ties.

   


     I noted that bark grafts applied to 1 to 1.5 inch diameter stock trees can close over the grafting wound very quickly. The tree pictured at left was grafted this year and has nearly grown completely over the stock wound. 

    I've been grafting pecan trees for 40 years now. Every year presents a new set of challenges to overcome and lessons to learn. It is a good thing I've got plenty of young seedling trees coming along to teach me even more lessons about pecan grafting in the future.

    

Tuesday, September 15, 2020

Waiting for pecan shuck-split


     One of the cultivar traits important to northern pecan growers is ripening date. I judge pecan ripening date by recording when at least 50% of the nuts on a tree have split shucks. 

    I always start scouting my orchard starting in mid-September and pay particular attention to the trees in my pecan breeding plot. One tree, a cross of Pawnee and Greenriver, is always the first to shuck split. Over the previous 4 years, the tree I've labeled 'KT337' has ripened on 19 Sept 2016, 20 Sept 2017, 17 Sept 2018, and 13 Sept 2019.  This year, I first checked this tree yesterday (14 Sept 2020) and found some nuts shuck-split (photo above) but the tree had not yet achieved the 50% shuck-split level.


    I pulled several nuts off the KT337 tree to show you the variation in ripening you can find on a single tree (photo above).  The nut on the far right was pulled from fully split shucks, while the nut next in line was loose in the shuck but I had to forcibly peel back the shucks. You will note that the shell of nut #2 is still partially white, indicating that the nut was not yet fully mature. Nuts #3 and #4 illustrate how the shuck splitting process proceeds. The first sign that pecan ripening has begun is when the shuck starts to pull away from the shell near the tip of the nut. In time, shuck separation moves downwards towards the base of the nut. As the shuck separates, the shell starts to develop cinnamon-colored markings on its white shell surface. These markings will turn jet black and the shell a rich brown when the nut is fully mature.   

Update: 18 Sept 2020

 

     By Friday, September 18th, KT337 had reached over 50% shuck-split (photo above). This selection remains the earliest ripening pecan in my pecan breeding block.



Thursday, September 3, 2020

Spraying to control pecan weevil


      It has been hot and dry most of the summer in extreme SE Kansas. The lack of rainfall has effected nut size (smaller nuts than normal) and has delayed the emergence of pecan weevil.

    During most years pecan weevil adults emerge from the soil starting in early August (male and female weevils pictured above). However, during periods of drought, soil hardness prevents adult weevils from tunneling out of their subterranean pupal cases.

   We finally received 3/4 inch of rain last Saturday which should have been just enough moisture to soften the ground and allow weevil emergence. I was all ready to start up the sprayer on Sunday, but then I looked at the weather forecast. More significant showers were predicted for my area on Monday, Tuesday, and Wednesday. To avoid wasting insecticide by spraying one day and getting it washed off the next, I decided to wait until the danger of heavy rain was past. 

    Turns out, we never did get any heavy rainfall earlier this week, just plenty of cloud cover and fog. So I decided to make an application of Sevin insecticide today.  My orchard does not have a history of heavy weevil infestation but I have a neighbor that has un-managed native trees. When and if I get weevil damage, it is usually a result of weevils migrating into my grove from the adjacent property. Hopefully, today's spraying will keep visiting weevils from getting established in my grove.


Thursday, August 13, 2020

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.