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Reviewing pecan cultivar data

February 21, 2018, 8:15 am
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    On cold winter days, its always fun to pour over cultivar trial data. Below, I created a table of nut performance data for 43 pecan cultivars growing at the Pecan Experiment Field. For each cultivar, the table shows the number of years nuts were evaluated (N), the weight of a nut (average, maximum, and minimum), and the percent kernel (average, maximum, and minimum).
     The time period of this data set (2004-2017) represents some of the most extreme weather conditions our trees have survived. We've seen record floods (2007) and record drought (2012). We suffered a limb-breaking ice storm (2007) and late spring frosts (2007, 2014). It no wonder that over the course of 14 years we've recorded some wide swings in cultivar performance.   



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Dormant pruning last year's bark grafts

February 26, 2018, 3:06 pm
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    Finally, the sun came out and it was a great day to get outside.  I hopped into my UTV and drove down to the pecan grove to check on some of last year's bark grafts. The photo a right shows a Kanza graft that grew exceptionally well. The scion produced three strong shoots with the central leader growing over five feet in length in a single growing season.

   However, taking a closer look at the scion, just above the graft union, reveals that I've already got a tree with a narrow fork and a side limb that's growing way too close to the ground. So I grabbed my pruning shears and made a couple of much needed cuts.
    First, I removed the left side of the narrow fork. Then I pruned off the side limb growing out to the right (photo at right). This left me with a single central leader and a good shoot to develop into my main tree trunk.  After pruning, I moved down to the graft union and removed the plastic bag and aluminum foil from the tree.
    With the graft wraps removed, you can see that the graft union has callused over nicely. On the left side of the graft union you can still see the staples I used to attach the graft.   But notice the color of the bark that was once covered by the aluminum foil and plastic bag.  The chestnut brown color of the bark indicates that this bark is not used to being out in full sun and may be prone to sun-scald.
     At this point, I used some cheap latex paint to apply a sun block over the entire graft union (photo at right). I used white paint to mark the tree as being grafted to Kanza. By painting the graft unions, I can quickly see which trees are grafted and which cultivar is grafted on the tree. On my farm, white=Kanza, yellow=Lakota, green=Hark, etc.  It takes a little extra time and money to color code trees but its definitely worth it to help me keep tract of my grafting efforts. It easy to get lost in my pecan orchard because it is based on grafting volunteer seedlings that have popped up at random across the field. No nice straight rows to keep things in order.
   Once I replaced the deer cage over the tree, I noticed that the top of central leader had several small branches that had developed from stalked buds(photo at left).  All of these shoots would develop into narrow-angled branched with deep bark inclusions. So to prevent future problems with limb breakage, I pruned off each small shoot and any remaining stalked buds.
       After pruning the central leader, I was left with a single strong shoot (photo at right). When this tree starts to bud out this Spring, I'll need to return with my clippers to perform some directive pruning to help maintain good structure. Side shoots will  emerge this coming season and my new Kanza graft will start looking like a pecan tree.
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Thinning a Kanza Block:

February 28, 2018, 5:04 pm
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    Over the course of the last 6 years, I've documented how we have progressively thinned a 3-acre block of Kanza trees (photo at right). In 2012, I drew up a tree thinning plan and have removed trees only within areas of the orchard with tree crowding. Year after year the trees continued to grow. As adjacent branches started to touch, we cut more trees. You can review the history of our thinning plan and the progress we made removing trees over the past 6 year by checking out the links listed below. 
1. 2012, 2013, and 2014 tree thinning 
2. 2015 tree thinning
3. 2016 tree thinning
4. 2017 tree thinning

     Following the 2017 pecan harvest, we measured the diameter of each tree's trunk and plotted that data on the map pictured at left. Each tree in the orchard is designated by a green circle with the size of that circle directly proportional to the diameter of the trunk. As you can see from the map, the bulk of the trees that still need removing are located at the south end of the field. You will also note that the largest trees in this orchard are located in the northeast corner. If you review the history of our progressive thinning plan, you'll find that we started the thinning process in the NE corner of the orchard back in 2012.
   This year we completed the thinning plan by removing 23 tree from the orchard. The black dots on the map at left shows the location of the trees removed this winter.
  When this orchard was established from stratified seed in 1996, we set trees 30 feet apart in a square pattern. In 2000, we grafted all 144 trees to Kanza. Now that we have completed our thinning plan, we have 72 trees remaining spaced 42.4 feet apart. The trees are still arranged in a square pattern but the squares are now tilted 45 degrees from the original north-south orientation.
   It won't be too many more years until this orchard will need another thinning plan as the remaining trees continue to grow at the rate of 1/2 inch in trunk diameter per year. The next thinning plan will remove every other north-south row to carve out an orchard with trees 60 feet apart.
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Big native pecan tree weakened by wood rot

March 14, 2018, 2:10 pm
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    Last harvest season, I came across a tree (photo at right) that I was scared to shake. From a distance it just looks like is a big old native tree that bears the scars of the 2007 ice storm (numerous sprouts from chopped-off limbs). It was only when I went to clamp onto the tree that I noticed a large crack in the trunk. I carefully shook the tree in December  but made a mental note to remove the tree come late winter.

    The trunk of this native tree had a large crack running over eight feet in length (photo at left). I looked inside the crack and discovered a rotten cavity inside the core of the tree. This tree was a potential disaster waiting to happen so I decided to cut it down.

    Cutting down a hollow tree can be tricky. The structure of the tree is so weak that you can't predict when or how the tree will fall once you start cutting. I had cut only one quarter around the trunk, when I heard the sound of wood splintering and cracking. I pulled out my chainsaw and moved away from the tree to watch it come crashing down. It was not the prettiest way to fell a tree but at least this potentially hazardous tree was on the ground (photo at right).

    The way the tree split apart upon falling allowed me to photograph the internal structure of the wood. I've labeled the key portions of the tree trunk in the photo above. Starting at the far left is a very normal looking layer of bark. Inside the bark are multiple layers of white sapwood. The heartwood of this pecan tree is reddish brown. As I looked to the center of the tree I came across a portion of the heartwood that was riddled with the white hyphae of a wood-rotting fungus. Fungal decay of the heartwood caused it to become soft and lighter in color. The hollow core of the tree represents the portion of the wood that has been completely broken down by fungal activity.    

    Inside the hollow core of the tree, I found the fruiting body of the wood-rotting fungus (photo at right). This fungus is a member of a mushroom family commonly referred to as shelf fungi. The fruiting body of this mushroom is hard and feels woody. Rather than gills, the underside of the shelf fungus has numerous pores that release spores. The appearance of shelf fungi on a tree is sure sign of significant internal wood rot.
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Spring fertilizer application

March 20, 2018, 8:21 pm
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    Today, we made our spring fertilizer application. I like to time this application by carefully watching for the first sign of bud swell. With pecan, bud development starts when the outer scale splits open and the upper portion of that scale is shed (photo at right). It is almost like the bud is taking off its winter hat.
    The swelling of pecan buds is a good indication of when pecan roots are starting to grow. Actively growing roots aggressively mine the soil for nutrients so when fertilizers are applied at this time of year you can be certain your trees will get maximum benefit from applied fertilizer.
   As we have in the past, we applied a mix of Urea and Potash to our pecan grove (photo at left). Urea is white in color and we spread 150 lbs. of urea per acre. Potash is pink in color and it was spread at the rate of 100 lbs. per acre. In total, we spread 250 lbs./acre of fertilizer containing 69 units of nitrogen and 60 units of potassium.
    This fertilizer application follows the one we made last October when we applied 100 lbs. per acre of urea (46 lbs. N/acre).
   
    Folks often ask how we spread our fertilizer. We rent a fertilizer spreader from our local fertilizer dealer and use it to broadcast the fertilizer over the entire surface floor of the orchard (photo at right).  It took me about half a day to fertilize our 80 acre pecan grove.  
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Young pecan trees need training

March 29, 2018, 3:33 pm
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    It seems like we've been waiting for Spring to arrive for a long time now. But lets look on the positive side, a late spring gives more opportunity to get some dormant pruning done.  I've written extensively about pruning and training young pecan trees in this blog and I'll provide links to some of those posts at the end of this article.
   The photo at right shows a young pecan tree with a well structured canopy. But this didn't happen by accident. This tree was summer pruned each year to train the tree into a strong central leader form with well-spaced, wide-angle lateral branches.

    Left to grow un-pruned, a young, open-grown pecan tree will develop a bushy top with no clear central leader (photo at left). If this tree had received a little selective pruning during previous years, the tree would have grown taller and straighter. Fortunately for owner of this seedling pecan tree, removing most of the top of this tree to place a bark graft on top would give him the opportunity to train the scion into a well structured tree.

    Unfortunately, many folks never get around to training their young pecan trees. The seedling tree pictured at right could have been grafted 15 years ago and the tree trained into a central leader. However, the tree remained a seedling and was never pruned. As a result, this tree has developed numerous narrow branch angles and after 20+ years produces only a few small, native nuts.
   Training trees when they are young will ensure a strong trunk and a healthy branch framework (photo at left). I have posted numerous discussions of pruning to this blog. If you need pruning advice just type "pruning" into the search bar on this page to find these posts. However, I'd also like to point out 3 key posts. Since we are currently still in the dormant season you can start with "Pruning dormant trees".  Most of the basic principles and practices of tree training can be found in my 6 part series entitled "Training young trees". And finally, check out my discussion on training a successful graft. Grafted trees tend to grow fast and unruly so proper pruning is a must for developing a strong central leader tree. Click on the titles below to see these pages.



Pruning dormant trees

Training young trees (a six part series) 

Summer pruning a young grafted tree 
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Pecan cultivar information updated

April 6, 2018, 7:36 pm
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Oswego Pecan 2017
    I just finished updating the pecan cultivars page of this website. I included new photos (example at right), additional cultivars, and additional nut data. So go check it out (press the Pecan Cultivars tab at the top of this page).
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Pecans survive cold snap

April 9, 2018, 2:24 pm
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    Over the weekend, a cold front swept across the plains and dropped our temperatures down to 22 degrees F (Saturday morning 7 April 2018). At that point in time, the buds on our pecan trees were just starting to swell and the outer scales of many apical buds had fallen off. The photo at right shows a typical pecan terminal.
    The terminal bud at the very top of the shoot has lost it outer bud scale. Likewise the upper bud on the right side of the shoot. The bud immediately to the left of the terminal bud is actually the secondary bud to the terminal bud and is still covered by its outer scale. Further down the shoot on the left side, a bud has split open the outer scale but its has yet to fall off.

    To check for cold injury, I removed the terminal bud for closer inspection (Photo at left). Once the outer scale falls from the tree, you can see that the bud is actually made up of three parts. In the center is a large vegetative bud that produces a new shoot that terminates in a pistillate flower cluster. On either side of the vegetative bud are two lateral buds that will produce only catkins.

     I sliced the bud in half to reveal the health of the bud (Photo at right). Again you can see the large vegetative bud in the middle flanked by the catkin-containing lateral buds. Fortunately all the tissues inside the bud a still green and healthy. A cold injured bud would have appeared black in color, two days after the deep freeze.
   I guess its a good thing pecan trees break bud late in the spring. The freeze on Saturday, did significant damage to my peach crop (trees were in full bloom).  Which is the main reason I have 20 acres of pecan trees and only 2 acres of peaches. Peaches are great when you have them but pecans are far more reliable.
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Spring cleaning

April 10, 2018, 9:59 am
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   Sunshine and warmer temperatures made for a great day to be out in the pecan orchard today. It was also a good time for Spring cleaning. Our first task was to burn all the piles of sticks we had raked up during harvest last fall (photo at right). Its best to get this mess cleaned up before the grass grows up and we lose tract of large chucks of wood in the tall grass. Hitting a heavy piece of pecan wood is hard on our orchard mowing equipment.

   Over the last several weeks, we've had several wind storms that has littered the pecan grove with even more dropped branches. While we burned last fall's piles, we raked up even more sticks to add to the fire (photo at left). We use a Rouse hydraulic hay rake to rake up the sticks.

    We weren't the only one cleaning up pecan groves. Our neighbors to the south were raking their groves and piling the brush with Stidsteer and attached grapple (photo at right).  With all the brush piles burning, the entire river bottom was covered in a smoky haze. By morning, the smoke will be gone and our orchard will be tidy.
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Signs of Spring

April 18, 2018, 8:10 pm
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    Our resident pair of Canada geese have returned from their winter habitat and are making enough noise to ensure we know Spring has arrived (photo at right). Canada geese mate for life and return year after year to the same nesting site. So far we've seen this pair raise at least six broods of goslings on our farm pond.

   Our pecan trees are still waiting for some warmer temperatures (especially warm night-time temperatures) before bursting out with a new crop of leaves. This year, pecan bud break is proceeding slower than normal. The buds have swollen but leaves have not yet emerged (photo at left). This slow bud development has been a blessing as we have experienced several hard freezes in early April and not suffered any cold injury.
    The pecan grafting season will start late this year. I like to see the first signs of leaf burst on stock trees before making any grafts. At this point, I probably won't carve a single scion until early May.   
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Freeze injury to pecan buds

April 21, 2018, 7:40 pm
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Kanza buds, 20 June 2018
    On Monday morning, April 16th, a strong cold front ushered in some very cold temperatures. We recorded 24 degrees F (-4 C) just after sun rise. Dormant pecan buds can easily handle 24 degrees but green pecan tissues freeze at around 26 degrees. Pecan bud development had not advanced much by April 16 but after the freeze many buds seemed to remain in a state of suspended animation (photo at above, right).

Kanza buds, 20 June 2018
     I decided to cut open some buds to see if I could spot cold injury (photo at right). Healthy buds should appear bright green. These buds darkened with dark brown streaks, sure sign of cold injury.









Kanza buds, 20 April 2018
     I cut open some more buds and found some were still green while others were black. It seems that this Spring's cold injury will vary widely both withing the canopy of a tree and between cultivars. One thing is certain, the 2018 pecan crop will be reduced.





    I looked at several cultivars and found shoots with damaged buds (no signs of further buds enlargement)  and shoots with nice green buds. The photo at left shows two shoots cut from the same Faith tree. The shoot on the left has emerging pecan buds that are plump and green. The shoot on the right has buds that look almost shriveled and have failed to "green-up" since the freeze. This kind of variation in damage seems very common among several pecan cultivars.
   
      I was encouraged to find that the two buds I cut open from Hark shoots looked healthy and not damaged (photo at right).
    We have suffered through late spring frosts in previous years with each episode causing different amounts of crop loss depending on the stage of bud development when the frost hit and the health of the trees. Back in 2014, we saw significant bud injury but the trees were able to produce pistillate flowers from buds lower down on the shoot. Come this May, I'll be evaluating pecan cultivars for their ability to produce female flowers following this freeze.
    Although I don't know the full impact this year's Spring freeze will have on nut production, I do know that the start of the Spring grafting season will be pushed back at least a week. I always like to see active green growth on my stock trees before I start grafting. 
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Bud break after early April freezes

May 2, 2018, 10:07 am
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    During the last week of April, we finally received some warm night-time temperatures that have stimulated the buds on our pecan trees to finally push open (photo at right). In my last post, I mentioned that I discovered some freeze damage to buds from the April 16th freeze. Now that the trees are finally starting to grow I can see the extent of that damage.
   The first thing I noticed was a wide degree of variation in bud break over the entire tree's canopy. With some trees, freeze damage was pronounced on lower limbs while higher in the canopy the buds were breaking normally. The photos above are examples of bud break on the same tree. In the lower portion of the canopy, terminal buds were killed and you can see green buds pushing out from the base of last year's shoot. Twenty five feet up in the air, bud break appeared normal.  The difference in damage due to height within the tree canopy is due to the fact that on April 16th we experience a radiation freeze. During these types of freezes, temperatures are coldest closer to the ground.

        I discovered that most cultivars suffered only limited cold damage. On many trees, bud break on lower limbs appear almost normal, except if you look closely, the terminal buds are stunted and not growing normally (photo above). Buds just below the terminal are growing new shoots.This type of damage becomes obvious when you compare the lower shoot to one growing higher in the tree. Note that the terminal buds on the upper shoot are growing strait up from the terminal of last year's growth, just like they should.
    Since the vast majority of nuts are produced in the upper portion of the tree's canopy the impact the the April 16th freeze will be minimal. However, we won't know for certain until pollination season rolls around later this month.
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Pecan pollination habit revealed at budbreak

May 4, 2018, 12:53 pm
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     While I was checking pecan budbreak, I cut shoots from two popular pecan cultivars (photo at right). These two cultivars represent the two flowering types pecan cultivars can exhibit. Kanza is a protogynous cultivar, meaning that female flowers become receptive before pollen is released. Hark is protandrous which means that pollen is shed before pistillate flowers become receptive. These two cultivars will pollinate each other. The early pollen shed by Hark will pollinate the early female flowers set by Kanza. Later in the pollination season, Kanza pollen will be released just in time to pollinate the late female flowers on Hark.
    During bud break you can already see clues to the flowering habit of any cultivar. The catkins of protandrous cultivars will be large and fat right at bud break. In contrast, the catkins on a protogynous cultivar at this time of year will be small and thin. One close up look at the photo and you can easily see the difference. Remember, you can click on any photo in this blog to get a larger image of that photo.
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Bark grafting tips

May 9, 2018, 8:23 pm
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    This year Spring arrived late but our trees are finally bursting with new leaves. This also means it is time to get grafting.
 I've been grafting for several days now so I decided to stop and take a few photos to relay a few grafting tips.
    For me, the grafting process begins by sizing up a young sapling pecan tree and deciding which grafting method is best suited for that particular tree. The photo at right shows a small tree that is the perfect size for a bark graft. For a detailed description of the bark grafting technique I use, click HERE for one of my previous posts on the subject.
     I like to be aggressive in preparing the stock tree for grafting. I start by removing any basal sprouts and very low limbs. I then remove much of the remaining top growth to leave a single stem to accept the scion. The height of this cut was chosen because it is a comfortable height for me to work on when sitting on my cooler full of scions (photo at left).  By removing over  2/3 of the top of this tree, I'll be forcing the tree to put all it root energy into sprouting the buds on my scion. 



    If the stock tree has a lot of rough bark, I use a wood rasp to smooth the bark in the area where I plan on placing the scion. Smoothing off the bark makes the remaining bark more pliable and allow for a tighter fit over the scion.  Use the rasp with light touch. Shave off to much and you can cause the bark to tear when the scion is inserted.

   I inserted the scion in my usual way. Note that the bark is already forming around the scion (photo at right).

    Once the scion is fully inserted I always check for gaps between the scion and the stock. In photo "A" above, the yellow arrow points to an air gap between the wood of the stock and the scion. Using my fingers to apply pressure, I can close that gap ("B" above). Air spaces between scion and stock always lead to graft failure. So I use a staple gun to hold everything tightly in place ("C" above).


    Once I cover the graft with aluminum foil and a plastic bag, I always count the number of exposed buds on the scion. If I find more than two buds, I prune the scion down so only two remain (photo above).  I like to limit the number of buds on the scion so that the remaining shoots will grow more vigorously.

    The deer herd in my area seem to have developed a fondness for the flavor of newly emerging pecan leaves. So to prevent any deer browse on my new grafts, I always cage the tree in 2 inch by 4 inch welded wire (photo at left).
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Decisions in making a 3-flap graft

May 16, 2018, 8:32 pm
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    Every morning I've been grafting the volunteer pecan seedlings that have sprouted on my farm. Since these "pasture" pecan trees have been mowed over at least one time in the past, most of these seedling trees have multiple stems. I prime example is pictured at right.

    In grafting this tree, I started by cutting off the small spindly shoot below ground level (photo at left).

   The two remaining shoots were perfect candidates for making a 3-flap graft. I selected the largest diameter scion I had in my cooler and held it up to each shoot to judge the locations were scion and stock were roughly the same diameter. The stem on the left was slightly larger (in diameter) that the stem on the right. I soon discovered that a 3-flap graft applied to the left-hand shoot would sit much higher up the stem than one placed on the right-hand shoot (photo above).  

   Given a choice, I have found that cutting off more of the stock tree increases scion growth rate once the scion calluses.  I decided to place my graft on the right-hand shoot and prune off the left-hand shoot (photo at right). Again, I cut off the stem as low as possible.
  You might be wondering why I didn't graft both stems. I find that wrapping the graft becomes a problem when you have another stem in the way. It hard to concentrate on pulling the grafting tape hard enough to compress the bark flaps against the scion when you keep bumping into another pecan shoot.
    Once I cut out the competing stem, I held up my scion to find just the right spot to place the graft (photo at left).

   I always look to avoid making a 3-flap graft on a stem with a pronounced "dog-leg". In the photo above, the yellow arrow points to the spot I plan on cutting the stock tree.  Above the arrow, the stem zigs and zags. However, below the arrow the stem is nice and straight. I always cut the stock tree off at a location that maximizes the length of straight stem.  It is so much easier to create three, even-sized flaps when working with straight wood.

    Once I choose the spot to make a graft, the rest of the grafting procedure was completed using the typical 3-flap grafting method. The photo at right shows the completed graft along with an attached bamboo stake that I'll use for training the scion this summer.
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Pecan pollination season

May 19, 2018, 7:26 pm
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Faith female flower cluster 2018
   I finished up all my grafting projects last week just in time to record the flowering habits of all the trees in my pecan breeding plot. On Saturday, all the protandrous cultivars had already shed their pollen while pistillate flowers on these trees were only now becoming receptive. In contrast, trees with the  protogynous flowering habit had pollinated female blooms with catkins that were still not releasing pollen.







    Lets look at two cultivars to see the differences between protandrous and protogynous cultivars.  I'll start will Kanza, a protogynous cultivar. The photo at left shows a cluster of Kanza female flowers. Note that the stigmatal surface of each flower is tinged black. This is the first indication that these flowers are already pollinated.
    Kanza catkins, the male flowers, are still green (photo at right). Catkins will turn yellow in color just before each pollen sac opens up to release pollen into the air. These catkins will be opening up sometime this week.
     Hark is a protandrous cultivar. In the photo at left, Hark catkins have turned fully brown indicating that pollen sacs have already opened and pollen has been released. Look closely at the catkins and you'll see that each pollen sac is split open and the catkin is almost ready to fall from the tree.
   
Hark pistillate flowers are not very showy, but as a wind pollinated crop, it doesn't need colorful flowers (photo at right). These Hark female flowers have not yet started to glisten with stigmatal fluid. When a female flowers becomes receptive to pollen the stigma produces a fluid to help capture pollen from the air.
   It takes trees with both flowering habits to ensure a successful pollination season. A protandrous cultivar like Hark was shedding pollen when a protogynous cultivar like Kanza had receptive pistillate blooms. In a few days, Kanza will start to release pollen just in time to land on receptive Hark female flowers.
   Pecan trees  have developed this flowering dichogamy to ensure cross pollination and preserve hybrid vigor within the species. 
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Nut set after a late spring freeze.

May 24, 2018, 7:30 pm
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     Between rain showers this week, I took a closer look at pistillate flower production on many of the cultivars in our collection. Back in early April, we experienced some some late Spring frosts that caused a lot of damage to terminal buds. The photo at right illustrates the typical response our trees have made following the April deep chill. The terminal buds on last-year's-wood were killed and never opened (red arrow points to dead buds). However, primary buds have grown from the mid-portions of the shoot and some of those have terminated in a cluster of female flowers (inside yellow circle).

     I looked at about 15 cultivars including short-season northern cultivars as well as full season southern cultivars. I found the same type of growth and flowering patterns among all cultivars. Trees are producing nut clusters on shoots that originate from mid-shoot primary buds. However, the number of nuts in a cluster seems fewer than normal; 2 or 3 nuts rather than the usual 4 to 5 (nut cluster in yellow circle at right). I also noticed that many new shoots did not produce pistillate flowers at all. Then end result of this year's late Spring freeze will be a below average nut crop come this Fall. 
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New grafts breaking bud

May 26, 2018, 8:03 pm
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    This year, I started grafting pecan trees in early May. Today, three weeks later, most of my scions have broken bud (photo at right). For me, the grafting process now shifts towards efforts to train and prune the young grafted tree. Starting today, I took steps to ensure that the scion continues to grow rapidly and does not become overwhelmed by stump sprouts that form below the graft union.
   Whenever  I see that I have a successful graft, I prune off all stump sprouts. At this point, stump sprouts are still small and easily remove by just ripping them off the trunk with my hand (photo at left).
    More stump sprouts will probably appear later this summer, but for now, all the tree's energy will be focused on growing scion shoots (photo at right). I like to visit my new grafts every three weeks during the summer to prune off stump sprouts and to train the scion to form a new central leader. 
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Summer prune young pecan trees

June 1, 2018, 7:46 pm
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    I drove by a young pecan tree in my orchard and it had turned into what I call a "lolly-pop tree" (photo at right). The tree had a nice central leader but was topped by bushy ball of leaves. The ball on top was actually four new shoots that had sprouted from the top of last year's terminal. This growth pattern is normal for pecan but is the leading cause for a tree to lose its central leader. I've discussed this growth pattern in detail in a previous post HERE.
    At this point in the growing season, a couple of quick snips with the pruning shears will quickly re-establish a dominant central leader while encouraging lower buds to grow and form lateral branches.  The photo at left shows my "lolly-pop tree" after I cut off three of the new shoots growing from the top. I left the one strongest shoot to form a new central leader. This entire process took only a few seconds and will save me from having to make corrective pruning cuts next winter.
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Galls on pecan leaves: Pecan leaf phylloxera

June 5, 2018, 8:30 pm
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    This is the time of year when folks seem to notice bubble-like galls on the blades of pecan leaves (photo at right). These galls are caused an insect called the pecan leaf phylloxera. At this point during the growing season, the small aphid-like phylloxerans are feeding on plant sap from inside the gall. The seasonal life cycle of the phylloxera starts at leaf burst when spring crawlers emerge from the bodies of over-wintering females and crawl to rapidly growing new leaf tissues. As these wing-less females feed on the leaves, they secrete a growth regulating substance that causes the tree to grow a gall around the insect. Once inside the protective gall, female phylloxera give birth to hundreds of young.  

   Flip a phylloxera infested leaf over and you might find that some of the galls have developed an opening that almost looks like an exploded volcano (photo at left). A new generation of winged adults will emerge from this hole. The winged adults will mate and impregnated females will migrate to a hiding spot in pecan bark. The phylloxerans will remain dormant until next spring when a new generation of crawlers emerge from the body of the overwintering female. 

    I cut open a couple of galls with the hopes of photographing phylloxerans inside (photos above). However, what I found in each case was a syrphid fly larvae working to devour all the phylloxerans inside the gall. In photo "A", the syrphid fly larva had cleaned out the gall completely. In photo "B", there were just a few phylloxerans left.  Syrphid flies are probably the reason why pecan leaf phylloxera is only a minor pest of pecans. 
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