Tuesday, June 27, 2017

Early signs of pecan scab infection

    We've had a fairly wet spring this year and along with the damp weather, pecan scab has made its early season appearance.  The photo at right shows a cluster of Giles nuts. Giles is a scab susceptible cultivar that must be protected with fungicide sprays in order to produce a harvestable crop.
   A quick look at the Giles nut cluster reveals just the smallest hint of scab infection, a very small black lesion on the upper left side nut. However, if you look at the leaf below the nut cluster you will numerous scab lesions appearing as black irregularly shaped spots.
   With plenty of scab spores up in the tree (coming from leaf lesions) we'll need a good fungicide program to protect the nut crop. We've sprayed once but additional sprays will be needed.

    On super scab-susceptible cultivars, like Hirschi,  the disease has already progressed to the nut crop. In the photo at left, a Hirschi nut (left nut) is already supporting a large scab lesion. You can also see scab lesions dotting the foliage. Historically we've had trouble controlling scab on Hirschi even with multiple fungicide applications. This year looks no different. Our Hirschi trees will receive the same spray schedule as the rest of the orchard but we'll probably lose most the nut crop from these tree due to scab.
   

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).

Friday, June 9, 2017

Training a tree using the 2-foot rule

    A lot of the trees I grafted last year are growing vigorously this year.  Unfortunately, most of the new growth seems to be sprouting from the very top of the tree. Left unchecked, I'll lose the central leader among a profusion of new shoots. In addition, the tree would become top heavy and eventually droop over under the weight of shoots and leaves. The photo at right shows one of many trees in my orchard that need pruning attention this Spring.
    The ladder in the photo is 6 feet tall which gives you a good idea how fast this tree has grown. The graft union is about 2 feet from the ground and is painted white. Last year (the same year I grafted the tree), I trained the tree to a single central leader. The new graft responded by putting on over 6 feet of new growth in a single growing season. This Spring, buds all along the central leader broke and new shoots began to develop.   However, growth has been most aggressive at the top of the tree.
  
    My first step in pruning this tree was to climb the ladder  and search out the very top of last year's growth (photo at left). I was amazed by how many new shoots had developed at the top of the tree. Not only did primary buds break and start growing into new shoots but many shoots had grown from secondary buds.  Its no wonder this tree was looking so top heavy.
    After parting the foliage, I identified one upward growing shoot to become my central leader. At that point, I removed all competing shoots at the top of the tree. Here's where I use the first part of the 2-foot rule. Measuring down from the apex of my new central leader I pruned off all lateral shoots within the top 2 feet.
    By just removing competing shoots using the 2-foot rule, I've thinned out the top of the tree and regained a strong central leader (photo at right). But I'm not done yet.
    To slow the growth of lateral branches and encourage diameter growth on both trunk and branches, I employed the second part of the 2-foot rule. All lateral branches were tip pruned to two feet in length.

  In tip pruning the laterals, I always make sure to prune to an outward growing bud (photo at left). When lateral branches begins to regrow in 3 to 4 weeks,  several buds will break along the length of each branch and the lower portion of the tree's canopy will begin to fill out.
   It took me less that 5 minutes to prune this tree into the proper shape. The before and after photos above really illustrate how a few simple pruning cuts made using the 2-foot rule can totally reshape a young pecan tree.
    For more detailed information on training young trees and the 2-foot rule click HERE to begin reading my six part series.


Thursday, June 1, 2017

Prevent stump sprouts from shading new pecan grafts

   Over the past few days, I've taken advantage of cool morning temperatures to revisit the grafts I made a month ago (photo at right). During my orchard walk-thru, I decided to photograph several Kanza grafts that I made all on the same day in late April. The main purpose for visiting these trees was to remove stump sprouts and promote the growth of the scion.  However, in working with my trees, I noticed wide variations in scion growth and the proliferation of stump sprouts.  
    In the photos below, you will see seven successfully grafted trees before (left) and after (right) pruning. As you look over the photos, take note of a few things. First, the sprouts that are growing from the stock below the graft union have leaves with a reddish coloration. In sharp contrast, the leaves growing from Kanza scions are light green in color. Red pigmentation of emerging leaves is characteristic of juvenile pecan tissue.  The leaves growing from the Kanza scions originate from sexually mature tissues in the bud stick and are fully green.
    The second thing I noticed about these trees is that vigorously growing stump sprouts seem to inhibit the growth of buds on the scion.  Trees 5 and 6 had so much rapid shoot growth coming from below the graft that the buds on the scion were barely sprouting. And remember, all these grafts were made on the same day using Kanza scions.
    The differences in scion growth we see in the field are most certainly due to the natural variation in seedling rootstocks. Some rootstock trees will callus over a scion faster than others. Better and faster callusing will allow the scion greater access the the rootstock's energy reserves resulting in enhanced scion growth.
    Some rootstocks seem to produce more stump sprouts than others. Rapidly growing shoots produce plant horomones that retard the growth of other buds on the tree. This is why it is so important to prune off stump sprouts.
    I grafted over 100 trees this year. Looks like I'll spend a few more days pruning off stump sprouts.    

Tree 1




Tree 2




Tree 3




Tree 4



Tree 5



Tree 6



Tree 7

Tuesday, May 30, 2017

Pistillate flower strength and pecan nut set

  I was checking on the development of the 2017 pecan crop last week and made some interesting observations about pecan flowering and nut set.  Whenever I look at pistillate flower clusters that are fully receptive and ready to be pollinated, I become extremely optimistic about the current season's nut crop. A cluster of five nutlets with bright red stigmas just looks so impressive (photo above, right).

   However, rarely do all the pistillate flowers in a cluster turn into harvestable pecans. When a pecan tree creates an pistillate flower cluster, the flowers at the end of the pedicel are often smaller or ill-formed (photo at left). Its like the tree just runs out of gas at the end of the flowering stalk.  
     Weak or poorly formed flowers may capture pollen but these flowers don't have the strength to produce a fertilized nut. This is why you might find that terminal flowers turn brown and eventually fall off the tree (photo at right). What the casual observer might blame on poor pollination, is actually weakly formed pistillate flowers being shed by the tree. 

    Pecan tree will only hold on to nuts that have become fertilized. The developing seed produces a plant hormone that sends a signal to the rest of the plant that basically says-- "hold me and feed me". The photo at left illustrates how a pecan tree shed unwanted unfertilized pistillate flowers. At first the weak flower turns brown (labeled A). The tree responds by forming an abscission layer between the flower and the pedicel. The location marked B once held a pistillate flower that has since aborted. If the pedicel does not contain a single fertilized nut, the entire pedicel will be removed from the tree. You can see an abscission layer forming at the base of the pedicel (marked C). 
     Without an actively growing nut cluster, you will note that the buds just below the pedicel are starting to swell. A second flush of vegetative growth  will soon appear on this branch terminal.


Friday, May 19, 2017

Checking on pecan pollination

    Yesterday, I wandered through our pecan cultivar trials to check on the progress of pecan pollination.  At this point, we are half way through pollination. All of the protogynous cultivars are releasing pollen and the protandrous cultivars have receptive pistillate flowers. Pawnee is a protandrous cultivar that is now displaying large, red stigmas on the ends of pistillate flowers (photo above).  The catkins on Pawnee shed their pollen a while back and have now dropped to the ground.

     The pistillate flowers of Kanza are fully pollinated (photo at left). Stigmas of female flowers dry up and turn black once they become pollinated.
    Kanza, being a protogynous cultivar, has late pollen release. Yesterday, Kanza catkins were releasing millions of pollen grains into the warm springtime winds.

    One thing I noticed about pecan flowers is that pistillate flowers of protogynous cultivars are smaller than pistillate flowers of protandrous cultivars.  In the photo above, you can see this size difference. Posey is protogynous while Pawnee is protandrous. By the end of the growing season the nuts of these two cultivars will be roughly the same size.


    While inspecting pecan flowers, I was also reminded that the color of receptive stigmas can vary from green, to orange, to bright red. The photo above illustrates some of this color variation. Both Major and Waccamaw had fully receptive pistillate flowers yesterday. Major displayed green stigmas while the Waccamaw stigmas are bright red. Since pecan trees are wind pollinated, stigma color has zero impact on pollination success. However, stigma color can sometimes be used to help identify certain cultivars. 

Wednesday, May 17, 2017

Finishing up the grafting season

   Last weekend, I finally finished grafting pecan trees in my orchard. After the flood receded, it seemed like I spent a week in rubber boots wading in the mud to finish up making bark, arrowhead, and 3-flap grafts. I've been grafting pecan tree since late April this year and those first grafts I made are starting to break bud (photo at right). Now it was time to finish up.
   Not every tree is cooperative with the grafting process and the last tree that I needed to graft this year turned out to be a graft failure from 2016 (photo at left).  Its a good thing that I had strong trunk sprouts grow up last summer to provide a perfect spot for grafting this Spring. My first step was to remove the failed graft and trim the tree down to a single trunk.
    I choose to keep the larger of the two sprouts for my new central leader. I trimmed off the old failed graft and the smaller trunk sprout with one cut using a chainsaw. I made the cut at about a 45 degree angle to aid in rapid wound healing.
    I cut the remaining portion of the tree at about 2 feet above ground level. At this point, the tree was about one inch in diameter--somewhat small for a bark graft. I selected a small diameter scion from my cooler and held it up to the stock. This is how I search for a flat spot on the stock wide enough to suit my scion (photo above right).

   In choosing a flat spot to insert the scion, I also took into account the locations of buds on the stock. Each bud has a bud trace or small branch of wood that grows up into the bud. If you try to insert a scion right under a bud on the stock, the scion might get hung up on the bud trace. I found two buds on the stock tree that I needed to avoid. In the photo above, the red arrow points to a bud at the very top of the stock. This location looks like a nice flat spot, but the bud trace could create a problem for inserting the scion.  I found a second bud in the grafting zone (yellow arrow) and I chose to avoid this bud also. Ultimately, I decided to place the graft in location of clear bark that seemed just wide enough for the scion (the scion in the photo hovers above that location).
  
    The way I carve my scion for a bark graft means that I always place the scion on the left side of the split in the stock's bark. Keeping that in mind, I made the downward slice in the stock's bark on the very right side of the area I had identified for scion placement. I proceeded to carve the scion and staple it in place (photo at left).

    This year's grafting season for me ended up the same way as always--covering a graft with aluminum foil and plastic bag, then attaching a bird perch. For me the end of the grafting season means the beginning of the directive pruning season, especially on trees grafted in 2016.

Monday, May 15, 2017

Cages protect young pecan trees from deer browse


    A picture may be worth a thousand words but the two photos above teach a valuable lesson. The photo on the left shows an unprotected seedling pecan trees that has been heavily browsed by deer. The tree on the right is enclosed by a cage constructed of welded wire fencing. This tree has a full canopy of leaves and has already made over ten inches of new shoot growth.

    Although browsing doesn't kill the tree, the removal of new growth ultimately stunts the growth of the tree.  The photo at right shows the terminal of the tree that was browsed. The yellow arrow points to the stub of this year's new growth left behind after a deer bit off the top of the tree. You can tell it this stump  is from the spring flush of new growth because of its green color.  Once the deer removed the first flush of new growth, its taken the secondary buds a couple of weeks to start breaking.
    The lesson I've learned is that tree cages are now necessary for every young tree on my farm.  I use 2 x 4 inch welded wire to build the cage. I've used both 4 foot and 5 foot tall wire but find that 4 tall works just as well in curtailing deer browse. I've used both light gauge and heavy gauge wire but find that the greater expense of the heavy gauge wire is offset by the cage's greater durability. As the trees grow above browse height, I'll remove the welded wire cage then re-use the cage to protect newly planted trees.

Thursday, May 11, 2017

Training last year's bark graft

    When grafting a vigorously growing tree with a bark graft I often produce a tree with 5 to 7 feet of new growth on the scion during the first summer. I achieve that kind of growth by meticulously  pruning to preserve a strong central leader. But by the end of the growing season, I usually find that I've created nothing but a tall, branchless tree. When the one-year-old graft breaks bud the next spring it seems like all the new growth is confined to the very top of the tree (photo above, right). How am I going to promote lateral branch formation with a tree like this?  All it takes is some careful directive pruning.

   In pruning this tree I start at the very top then work my way down.The photo at left shows the cluster of new shoots that have developed at the very top of the tree. If I were to leave all these shoots in place, I would quicky lose my central leader and the tree would be topped by a sprawling assembly of branches pointing in every direction but straight up. In addition, allowing the tree to grow freely at the very top of the tree will create a top-heavy tree that causes the tree to bend over under the weight of the foliage.

     My first pruning cuts were made to encourage the growth of a single new leader. Here's where I use the 2-foot rule in tree training. In the photo at right, you can see that I removed all the the new shoots in the area of the trunk two feet down from the apex of the shoot that I have choosen to become the new central leader.

   When pruning off all the lateral shoots that are directly competing with the new central leader, I was careful to leave all secondary buds in place (photo at left). A few of the secondary buds had started to push and that's OK. The just-emerging shoots from secondary buds won't be able to catch up with the strongly growing central leader. In addition, shoots that develop from secondary buds form lateral branches with wide crotch angles (a good thing). 

    After pruning the top of the tree using the two-foot rule, the top of my tree has a single central leader and has lost its bushing appearance (photo at right). My next pruning task was to work my way down the stem and thin out the dense array of lateral branches that I found growing there (photo at right). There is no way the tree could support that many lateral branches all within about 18 inches of trunk.

    I removed more than one-half of the lateral branches that had formed on this portion of the trunk. In pruning lateral branches, I was careful space out the remaining branches both up and down  and around the trunk (photo at left).  After pruning, the entire tree no longer appeared so top heavy with foliage
    Thinning out lateral branches near the top of the tree has an additional advantage. Buds lower down on the trunk will be stimulated to grow and form branches along the entire length of the last year's scion growth.

    Stepping back from the tree that I just pruned, I could see that the new shoots and foliage were now better distributed along the main trunk (photo at right). The ladder in the photo is 4 feet tall to give you a better idea of the size of the tree I was pruning. With lots of lateral shoots developing already this year, my single shoot graft should turn in a well bushed out tree by the end of its second growing season. Maybe by year three, I'll be producing a few nuts on this tree.