Friday, June 23, 2017

What happened to my pecan tree's central leader?

    When I drove by my pecan grove the other day, I noticed a tree with a branch that had broken out in the wind (photo at right). At first glance , it looked like the central leader had snapped and I lost the top of the tree. So, I got out my 8 foot tall orchard ladder to take a closer look and the make some pruning cuts.
   Once I climbed up the ladder I could get a good look at the branch structure of this tree (photo at left). To my surprise the broken branch was not the central leader. What was once the central leader was bent over under the weight of an excessively bushy top.
  
     My first step in pruning up this tree was to remove the broken limb (photo at right). Next I needed to straighten up the leader (red arrow). At the same time, I needed to thin out the number of limbs that branched out from the trunk at nearly the same spot on the trunk. Rather than attach a training stick to the tree, I decided to use a lower branch (yellow arrow) to help retrain the tree. I chose this limb because it was leaning out in the opposite direction of the leader.
     I held both these limbs upright and taped them together using electrical tape (photo at left). I now had my leader pointing in the right direction. However,  I also had a training branch pointing in the same direction and in direct competition with the leader.

    I pruned off the top of the training branch just above the electrical tape (photo at right). This pruning cut immediately gave a sunlight advantage to the leader. However, the training branch would soon sprout new shoots so,  I decided to try a little old fashion trickery.
   At the base of the training branch, I girdled the branch (photo at left). I removed the bark from the branch from the point the branch attaches to the trunk upward for about 3 inches. Girdling a branch will not kill it immediately but will inhibit the movement of nutrients into the branch and seriously hamper shoot re-sprouting. However, the wood in the girdled branch will remain strong enough to provide support for the leader. After a year's time, the leader should gain in diameter and strength and  I can cut out the girdled branch completely.
   Next I turned my attention to the leader.  Each spring, a pecan tree will sprout 3 to 5 new branches from the terminal portion of last year's growth. This forms a growth pattern commonly known as a "crows foot". The photo at right shows that the leader of this tree grew a crows foot in both 2016 and 2017 (red circles). This growth pattern produced such a mass of foliage that the leader became top heavy and bend over from the weight.
    To make sure the leader would develop into a strong, upright-growing trunk, I needed to prune off all the side branches in this portion of the tree.
   

   In pruning the top of this tree, I removed both the 2016 and 2017 crow's feet (photo at left).  Suddenly, I've reclaimed a single central leader.

    Once I got through with redefining the top of the tree, I turned my attention to the side branches. I found that the lateral branches had sprouted so many new shoots this past spring that I needed to prune off some excessive leaf weight. I did that by first removing any new shoots sprouting straight upwards from a lateral limb. Next I headed back any new lateral shoot that had grown more than 2 feet in length.
    My biggest problem in making these pruning cuts is that I needed my 8 foot orchard ladder for every cut.  I guess that is the price I pay for grafting onto a fairly large rootstock tree and witnessing 5-7 feet of new growth each year. 
   

    It took me about 15 minutes to prune my tree with a broken branch. It seems most of my time was spent moving the ladder and climbing up and down. This fall (late Oct.) I'll prune out my training branch.
    

Tuesday, June 20, 2017

A new pecan graft can flower

    In grafting pecan trees, we take a piece of one-year-old wood collected from a mature pecan tree and place it on a seedling rootstock tree. If the scion was collected from a vigorous and healthy tree, that small piece of twig will be programed to produce both catkins and pistillate flowers.
   The photo at right is a Kanza graft I made this spring.  Hanging down over the plastic bag, that I use to wrap the graft union, are catkins produced by the scion. At the very top of the scion's new shoot growth is a cluster of female flowers.
  Whenever I see pistillate flowers forming on a new graft I usually pinch them off immediately. At this point in the tree's life, I want to encourage maximum vegetative growth. Female flower production on a new graft only serves to slow shoot growth. 

Monday, June 19, 2017

Spraying for scab

Spraying pecans (view from the tractor seat)
   With over 3 inches of rain falling over the weekend, it is high time we quit waiting on pecan nut casebearer and start concentrating on controlling pecan scab.  Today we fired up the sprayer and applied some Quilt Xcel fungicide. We sprayed the grove with our air-blast sprayer that applies roughly 100 gallons of water per acre of trees.  That makes figuring out how much chemical to put in the tank pretty easy.
    Read any chemical label and you'll find the rates of application given in amount of product per acre. Our sprayer has a 500 gallon tank or enough water to cover 5 acres. To determine the amount of product to be added to the spray tank, I just simply multiply the per acre rate by 5.  The recommended application rate is for Quilt is 14 oz. per acre. In filling our sprayer, I added 70 oz of Quilt to the spray tank.
   One word of advice abound spraying fungicides. Good disease is only achievable when the fungicide covers all plant surfaces. To get good spray coverage I always spray each tree from both sides. You should not assume that your air-blast sprayer is powerful enough to penetrate the entire canopy from just one side of the tree. 
   We did include a insecticide in with our fungicide spray. We added Govern insecticide to the tank to control this summer's first hatch of fall webworm (photo at left). In scouting the orchard, we have found several colonies of first instar larvae. At this point in the webworm's live cycle they have done a minor amount of defoliation or have yet to hatch. Spraying an insecticide now should keep this insect out of our orchard until the second generation arrives in mid-August.   

Friday, June 16, 2017

This is why scouting for pests is so important

   For the past week, I've been expecting to see damage from pecan nut casebearer start to take off.  In fact, I have my sprayer filled with water and ready to go. The problem is, we can't find enough casebearer damage to justify spraying
   Three times per week we scout our orchard for signs of insect damage (photo at right). The results of each of our scouting runs can be found by clicking on the Pecan Nut Casebearer tab (The tab is located just below below this blog's header). We have yet to find more than 1% damage.
   In a normal year, we apply a fungicide to control pecan scab at the same time we apply an insecticide to control casebearer. Its now mid-June and we still haven't applied any pest control chemicals. So starting next Monday (June 19th) we are going to start spraying a fungicide to protect our pecans from scab.  If the casebearer population stays low, we won't be including an insecticide with this spray.
   In late June, we might see fall webworm or walnut caterpillar move into the grove. If these insects appear, we will include an insecticide in the spray tank when we make our second scab spray (around July 1).