Twigs falling from pecan trees

    This afternoon I decided to trim up some seedling pecan trees growing along the south edge of my farm. These trees are growing in the worst soil on my farm, an eroded Dennis silt loam that is shallow and very prone to drought. However, I can't bear to cut down  these squirrel-planted pecan trees even if I'll never harvest a nut. I can still enjoy the shade.
    When I drove up to the trees I noticed the ground was littered with small branches that look like they had been cut from the tree with the leaves still attached. I picked up four of the fallen shoots and brought them back to the house to photograph (photo at right).

    If you look closely at the cut end of the branch you will note that the outer portion of the stem was cut smoothly but the center portion actually broke off in a gust of wind (photo at left). This type of limb pruning is caused by a long-horned beetle called a "twig girdler". You can see a photo of this beetle in a previous post.

     As I carefully inspected each of the four limbs I collected , I found one with a partially completed girdle (photo at right). I bet the insect got frustrated by constantly backing into that small branch just below and decided to try a different location. However, this partially completed girdle gives us a good idea how deep twig girdlers chew into pecan branches.

   Looking even closer at the twigs, I noticed a oviposition site at the base of old leaf scar (photo at left) . Twig girdlers carve a crescent shaped hole in the twig and deposit their eggs inside. Looking at the entire stem I found several oviposition sites, always placed just below a leaf scar.
    Twig girdlers adults are active in late summer (August-Sept.). They girdle pecan stems at this time of year so that all the carbohydrates created by the leaves can not be translocated down to the roots and end up accumulating in the stem above the girdle. Eggs laid in crescent-shaped scars hatch the following spring, with the resulting larvae feeding on the nutrient rich twigs.
    In commercial orchards, twig girdler is rarely a problem because sprays aimed at controlling pecan weevil during the month of August also control twig girdler. For non-sprayed pecan trees, twig girdler populations can reduced by picking up all fallen twigs during the winter months and burning them (thus killing the next generation of girdlers).  

Pawnee needs crop load management

    Pawnee is one of the most popular cultivars grown in our area (photo at right). The popularity of Pawnee is based on two factors; the nuts are big and they ripen early. However, Pawnee is a high maintenance cultivar. Pawnee is susceptible to pecan scab and the crop needs to be regulated to insure well filled nuts at harvest.
     Today, I collected a few Pawnee nuts from trees at the old Pecan Field Station. In previous years, I reduced the crop load of overloaded Pawnee trees by using a trunk shaker. Now that I've retired from the University, the field station has been abandoned and Pawnee was allowed to over-produce in 2018.

    I collected Pawnee nuts from two areas. The first was a mature orchard with nuts hanging from every terminal. Prior to 2018, these mature Pawnee trees received a good summer shake every year they loaded up with nuts. The second spot was in a young orchard, just starting to produce nuts. Like all young pecan trees, these Pawnee trees had not reached the age when over-cropping becomes a problem.  The young tree produced normal-sized Pawnee nuts while the over-loaded trees produced much smaller nuts (photo above). When I held those smaller nuts in my hands I could already tell the kernels inside were going to be shriveled.

    As I suspected, the kernels produced by the over-loaded Pawnee trees were smaller, poorly filled, and even darker in color. The two kernels on the far right in the photo above were so paper thin that they would be inedible.
   Pawnee is a cultivar that requires a high level of care but when treated right can produce beautiful pecans. Growing Pawnee profitably means adopting a good scab control program and shaking off nuts during the years when the trees set an over-abundant crop.     

Thanksgiving harvest

Harvesting native pecans near Chetopa, KS

  Thanksgiving is an American Holiday with a long tradition of family gatherings and roast turkey dinners. But here in pecan country, today's bright sunshine and dry soil conditions makes it the perfect day to pick pecans. By mid-morning, I could hear the familiar drone of pecan harvesters working in the native groves near my farm. I took a quick drive around the area and found that every grower was celebrating the Thanksgiving holiday the same way,  by picking pecans. I can't think of a better way celebrate the fall harvest season. 

Evaluating nut samples

    Last week we had a light snow fall that covered the pecan grove with about two inches of wet snow (photo at right). The snow turned out to be only .16 inches of precipitation but the cold weather that followed meant that the orchard floor stayed snow covered and wet for several days. Wet soil conditions means that I was unable to finish harvesting my pecans. So, I parked the tractors and moved inside to start cracking nut samples I had collected from the pecan breeding block.
   At shuck split, I collected at least 25 nuts from each tree. I let these nuts air dry for several weeks then began the process of measuring, weighing, and cracking nuts.

    The first step in my evaluation process is to record the diameter size class of each nut in the sample. I do this because every nut ever brought to a shelling plant is run through a nut sizer in preparation for cracking. Pecans are sized by a series of steel cages with various size slots for nut to fall through. The sizes are recorded in sixteenth of an inch increments. A size 12 pecan falls through an opening 12/16 or 3/4 of an inch wide. I use a series of end wrenches (measured in 1/16 increments) to simulate the nut sizing process (photo above). In the photo, note a nut stuck in the 15/16 wrench. This same nut passed easily between the jaws of the 16/16 wrench (1 inch) and would be classed as a number 16 diameter pecan. By measuring every nut in a sample I can develop a size profile for each clone. The sample I was processing when I snapped these pictures was 50% size 15 and 50% size 16 nuts.

    The next step in my nut evaluation process is to weigh 10 randomly selected pecans. This weight will give me an average nut weight but can also be used to calculate average nuts/pound. I use a gram scale to weight the nuts (photo at right).  This sample weighed 101.97 grams. This nut averages 10.197g per nut and if you divide the conversion factor of 453.6 by the average nut weight in grams you'll find that this particular pecan averages 44.48 nuts/lb.

    With the inshell nuts weighed, I next use a hand cracker and shelling tool to extract the kernels from the shell. In cracking the nuts, I use a light touch because I take great care in trying to extract full kernel halves from every nut.

    Once all the kernels are removed from the ten nut sample, I weight the kernels. This sample had kernels that weighed 54.91 grams. By dividing the kernel weight by the nut weight and multiplying by 100, I can calculate the percent kernel for this nut sample. In this case the math works out like this:  (54.91/101.97)*100=53.85% kernel.
    In addition to the hard numbers that I record on nut size, weight and percent kernel, I take notes on kernel color, ease of extracting full halves, adherence of shell packing material, and any glaring kernel defects.
    As I collect this information year after year, I should be able to recognize those trees that produce quality pecans every year. Hopefully, that will lead to some new cultivars.
  

Hard freeze drops pecan leaves and kills green shucks

Kanza nuts right after a deep freeze

    Last night we received our first killing freeze as temperatures dropped to 15 degrees F (-9.4 C). For pecan trees, temperatures need to drop below 26 degrees F (-3.3 C) to kill green plant tissues. During the final days of Fall a hard freeze results in the hastening of leaf fall and killing still-green pecan shucks.

    Since the deep freeze forecast was made earlier in the week, I made plans to make a visual record of the impacts of sub-freezing temperatures on Kanza pecan trees. In the photo above, my Kanza tree was still holding a leaf crop up on November 9th. After a blast of cold weather, every leaf from the very same tree had dropped off by mid-afternoon.

    The photo above shows that Kanza shucks were still very green before the freeze but turned dark and water soaked after being subjected to temperatures below 26 degrees F. When green shuck tissue freezes, cell walls are destroyed by the formation of ice crystals. At first the shucks look water soaked but they will dry out and turn black in just a few days. As the shuck dries, it pulls back away from the nut and will finally open enough to allow the nut to fall free.
 

Comparing Kanza and Hark nuts

   This fall I have been taking a closer look at the performance of Hark as it compares to Kanza. Earlier this Fall I collected a nut sample from a Hark tree and an adjacent Kanza tree. I weighed out these samples and cracked the nuts to determine percent kernel.
   As you can see in the photo above, Hark produces a nut that is slightly larger than Kanza. The shell markings on the Hark nut are very similar to its Major parent. Both Major and Hark shells are covered with many small black speckles. In contrast, the Kanza nut shell is light colored and has few black markings. Even though Kanza has Major parentage the shell of Kanza is more reminisent of its other parent, Shoshoni.

    This year my Hark nuts yielded more percent kernel than my Kanza nuts (photo above). Hark kernels also appeared larger. However, Kanza kernels were lighter in color and appeared more attractive than the Hark kernels. For the first time, I noticed that the dorsal grooves on Hark kernels are narrow and can trap packing material. In fact, if you look closely at the left dorsal groove of the left Hark kernel you'll see some trapped packing material.
   Even though Kanza still remains my favorite cultivar, I plan to graft more Hark into my orchard. Hark is scab resistant and a good pollinator for Kanza.

Harvesting early maturing pecans

    One of my prime objectives in breeding pecans is to discover new early maturing pecan cultivars that will ripen in northern pecan growing areas. Because most of the clones in my pecan breeding block split shuck a month ago, I decided today was a good day to shake some trees and harvest pecans. For the most part, the nuts fell freely from the trees and I could use my new Savage pecan harvester to pick up the crop (photo at right).
    Harvesting pecans today was just as exciting as it had been for the past 37 years when I was working at K-State's Pecan Experiment Field. However, today's harvest was different. I was harvesting my own crop and I was handling every portion of the harvest process by myself.
    Today was my first day of harvest. I wanted to make sure all my equipment was working correctly and I wanted to get a feel for how many trees I can harvest in a day's time. I began the day by shaking 3 rows in the pecan breeding block. I then walked these rows picking up any large stick that had fallen during the shaking process. Once the orchard floor was clean, I used the harvester to pick up the nuts. This was a new harvester to me so it took a little while to find the proper ground speed and PTO rpm to pick up nuts cleanly.

   One drawback to harvesting early is that I ended up picking a large number of nuts with green husks still firmly attached (photo at left). After a hard freeze these green stick-tights would have turned black and dried hard. However, harvesting pecans before a hard fall freeze means that green stick-tights become mixed in with dry, ready-to- crack nuts. If green-hulled nuts are allowed stay mixed in with good pecans they will increase the moisture content of the good nuts and can even cause the entire batch of nuts to start heating up.
  So, in harvesting nuts today, I also made sure to leave enough time at the end of the day to run my crop through the pecan cleaner to remove all the green nuts. This way my good pecans would not pick up any unwanted moisture. As it turned out, the number of green stick-tights I removed from the cleaning table was far less that I had first thought. I bet some of those green hulls got scrubbed off by the scuffing wheel inside my pecan cleaner.
  Tomorrow's weather forecast is warm and sunny. As soon as the morning dew dries up I'll be back to harvesting. 

Fall planting of container grown pecan trees

   Every spring I stick a few stratified pecan seeds in pots and grow my own rootstock trees. Today, I took advantage of perfect weather (sunny, low 70's) and moist soil conditions to load up some potted trees in my utility vehicle and head to the field (photo at right). With just about 20 trees to plant, I used a shovel to dig the holes for the trees.

   When digging holes for container-grown trees, I only dig deep enough to hold the entire root system. I used tall pots to grow out my trees so the hole needed to be about 12 inches deep (photo at left).

    When I plant container-grown trees, I shake off all the loose potting soil from the root ball and then place the tree in the hole. I back fill the hole around the tree's rootsystem making sure to crumble the dirt clods as I go. In planting  trees, I always make sure that the entire root ball is covered with soil and it is firmly packed down (photo at right).

    To prevent deer from browsing on my newly planted trees, I always place a welded wire cage around the tree (photo at left). This cage is made from 6 feet of  2" x 4" welded wire and formed into a circle. The cage pictured here is five feet tall but after working with both 4 feet tall and 5 feet tall cages, I've found both heights prevent deer browse. The 4 foot tall welded wire is significantly less expensive so I won't be buying any more 5 foot tall welded wire in the future.

   In making wire cages, I tie the cages in a circle using polypropylene twine (baler twine) (photo at right). This makes removing the cages much easier if the tree grows though the wires of the cage. I tie the cage together in just two spots and can use my pocket knife to cut the cage open and pull the cage away from the tree. I use the same twine to tie the cage to a steel fence post. 

  When driving the fence post into the ground, I always make sure part of the T-post's paddle is showing above the soil (photo at left). By leaving the paddle visible, I ensure that no tree roots will grow over the paddle trapping the fence post under the rootsystem (making it impossible the pull out).
    Hopefully, all my efforts to plant and protect these new trees be successful.  With proper tree care, I expect these trees to be ready for grafting in 2-3 years time. My only problem will be in deciding which cultivars to graft.

Fall fertilizing the pecan grove

    Today, I fertilized my pecan orchard (photo above). The soil had finally dried up enough so I could run over the orchard with tractor and fertilizer buggy without making tire ruts. In addition, the weather forecast calls for a light rain shower that should be perfect for melting fertilizer pellets into the soil.
     This fall I decided to start a new fertilizer program to help build the overall fertility of my orchard soil. Most of my pecan trees are growing in a Hepler silt loam. This soil is excellent for pecan trees but lacks the natural fertility I was accustomed to when caring for the trees growing on Osage silty clay at the Pecan Experiment Field. I applied a fertilizer mix that included not only nitrogen but also included phosphorus and potassium. In total, I spread 55 lbs./ ac. N, 23 lbs./ ac. P and 30 lbs./ac. K. The fertilizer mix I used was 2 parts urea, 1 part di-ammonium phosphate and 1 part potash.  I spread 200 lbs of this mix per acre.
     The amounts of applied P and K are fairly low but I'm thinking that over time, with repeated applications, I should be able build up the levels of these nutrients in my soil. A more fertile soil will provide a more optimum environment for pecan trees but will also increase the growth of ground cover plants. Since I mow the ground cover regularly, increased ground cover growth translates into increased  amounts of organic material added back to the soil. And, organic matter is critical for a healthy soil. Organic matter increases soil aeration, soil water retention, and micro-nutrient availability.

    A large part of my orchard was created by allowing volunteer pecan trees to grow up in an abandoned farm field. As these trees grew, I grafted them to northern pecan cultivars. As a result, I have a mixed-aged orchard that includes young, bearing trees along with newly grafted saplings (photo above). When it comes to fertilizing, I broadcast over the entire acreage. Sure, the small trees would probably grow just as well with a spot treatment of fertilizer but I go back my objective for fertilizing this Fall.  I am striving to build soil fertility and that means the fertility of the entire pecan grove.  

Cultivars splitting shuck in Mid-October

USDA 64-4-2, 8 Oct. 2018

  On my farm, I have tried to limit the number of pecan cultivars I have grafted. I have focused on cultivars with both scab resistance and outstanding kernel quality. Hopefully I've picked some cultivars that produce nut crops that will be enjoyed by customers that visit our roadside market.
   Four more pecan cultivars split their shucks on my farm in Mid-October. USDA 64-4-2 split shuck of Oct. 8th, Lakota split on Oct. 16th and Greenriver split on Oct. 19th. Oswego ripened at the same time as it parent, Greenriver, but I was unable to get a good photo because my neighborhood squirrels seems to prefer Oswego nuts (the tree is near a pine wind break which makes excellent cover for squirrels). Photos of these cultivars can be seen at right and below.

Lakota, 16 Oct. 2018

Greenriver, 19 Oct. 2018

Fall flooding delays fall fertilizer application to pecan groves

    In early October, I was trying to decide when to make my annual fall application of fertilizer to my pecan grove. At the time, daytime temperatures were still reaching the low 80's and the soil was dry. The combination of dry ground and hot temperatures is a sure way to lose soil applied urea (nitrogen fertilizer) to volatilization. So I waited for better weather conditions.
   It is now mid-October and the weather has turned wet and cool. Good conditions for fertilizing except for one thing. We've had a little too much rain and the Neosho River has spilled out of its banks (photo above). It is by no means a major flood. Portions of many pecan groves have anywhere from a few inches to a foot of water while other areas are just water soaked. 
    I am glad I waited to fertilize this Fall. If I had rushed to get the fertilizer on earlier this month, all my fertilizer dollars would have washed down the river. Now, I'll need to wait until the ground firms up before running a spreader over the grove. I definitely don't want to cut ruts in the orchard floor by dragging a fertilizer buggy over water-soaked soil.  
   Fall fertilization is an important part of my normal pecan management program. Applying fertilizer both Fall and Spring have helped to reduce alternate bearing in my grove. I'll be sure to post when I make this Fall's application including types of fertilizer and quantity applied.

Why is the date of shuck split important for pecans?

Yates 68, 5 Oct. 2018

   Every fall I have spent a lot of time in a hydraulic lift inspecting pecan cultivars for their date of shuck opening. Over the years I've created a photographic record of this important event for dozens of cultivars. Just today, I noted that the cultivar Yates 68 had just split open (photo at right).
    But why is nut maturity date such an important cultivar characteristic? In northern pecan areas, only cultivars that split shuck before the average date of first fall freeze should be grown. Too often, I have come across folks in the Midwest that plant pecan cultivars advertised in flashy nurseries catalogs that never reveal that a cultivar requires a much longer growing season to ripen their nuts. It is only after 15 years of tree growth that they discover their tree only produces black stick-tights every fall. (Desirable and Western are two prime examples of cultivars not adapted to northern pecan areas).

KT255, 24 Sept. 2018

   Now that I've retired from Kansas State, my focus has shifted from taking notes on established cultivars to recording maturity dates for the trees in the breeding project. In breeding pecans for our northern area, maturity date is of prime importance. And we have found some early ripening clones. KT255 and KT307 both ripened by Sept. 24th this year. That's really not surprising since both of the trees are the results of a cross between Pawnee and Greenriver. In addition both clones have good nut size, high percent kernel and are not prone to pecan scab infections.

 Please Note.  These clones are still under test and I am not in the position to supply scions at this time. When the time comes for a new cultivar release, I'll announce it on the blog.

KT307, 24 Sept. 2018

   

When is shuck split?

   While looking over trees in my orchard, I came across a young tree grafted to USDA 64-4-2. This is the third year after grafting and this tree was already setting on nuts. So I pulled down some lower limbs in the hopes of determining a shuck split date for this clone. However, I found two clusters in very different ripening stages. One cluster was fully open and appeared to be well on the way to shuck drying and nut release (photo above). Another cluster just one foot away on the same trees had not yet split shuck. Now, I was curious. Which cluster is more typical for the clone USDA 64-4-2?

USDA 64-4-2 not split yet

   I drove down to the old experiment station to check on the development of this clone on a more mature tree. On this tree, the shucks had yet to open (photo at left). I used my pocket knife to peel off the shuck and found that USDA 64-4-2 is very close to popping open. Last year this clone ripened just 2 days after Kanza. This year it will probably be closer to 4 days after Kanza.
   My observations on USDA 64-4-2 this fall confirms my long held belief pecan trees need to gain a little maturity before their true phenological characteristics become consistent and typical for that cultivar.

Pecan cultivars ripening by October 1

Kanza, 1 October 2018

    On the first day of October I found three cultivars on my farm with split shucks. The first cultivar I checked was Kanza (photo at right). When Kanza splits shuck, the green shucks just barely pull open. Kanza will remain held in these green and split shucks until a hard freeze kills the all green tissues. Once the shucks are killed, Kanza finally opens up fully and the nut can be easily shaken free.

Hark, 1 October 2018

     Hark was also ripe by October 1 (photo below, right). Hark mimics Kanza in how shucks barely split open then remain green and closely cupping the pecan. I first noticed this type of shuck opening years ago on the old northern pecan cultivar, Major. Both Kanza and Hark have Major parentage.

Jayhawk, 1 October 2018

    The final pecan I found ripe today was Jayhawk (photo below right). Jayhawk is a Giles seedling but has the advantage of pecan scab resistance. Unfortunately, Jayhawk produces pecans with mottled kernels which is the reason that I have only one Jayhawk tree on my farm.

Early ripening cultivars split their shucks

USDA 61-1-X, 22 Sept 2018

     This year I'll be making a photographic record of pecan shuck-split just as I have every fall since starting this blog. However, this year, the photos will be limited to the cultivars I have bearing on my farm. The first grafted cultivar to split shuck was a USDA clone numbered 61-1-X. This clone was the result crossing Barton with Staking Hardy Giant way back in 1961.

Faith, 25 Sept 2018

   Today, I found that Faith and Gardner had split open. These two cultivars are very similar to Pawnee in terms of ripening date, nut size, and nut appearance. So, if I had any Pawnee on my farm (I don't), I'd expect it would be shuck-split also.

Gardner, 25 Sept. 2018

    Over the past couple of weeks I've been collecting nut samples from trees in my breeding block. As each tree ripens their nuts, I collect a sample and record the shuck split date. So far this year, two trees ripened on Sept. 17, two ripened on Sept. 20 and 14 ripened ripened on Sept. 24. Among the trees that ripen before Pawnee several look promising.

Late season aphids

    After a week of above average temperatures, our pecan trees seem to be infested with aphids and covered in honeydew (photo at right). Every surface of every leaf is sticky with honeydew and numerous flies and wasps are busy collecting the sugary substance.
    We seem to get a late season aphid outbreak almost every year and I usually recommend not trying to control these insects because the cure often increases the problem in the long run.

   One interesting observation I've made about aphids this year is how weather conditions can influence their populations. Back on August 13th I photographed the first aphids I found (photo at left). At that time, the population of black-margined pecan aphids had reached high enough numbers where you could easily spot drops of honey dew on the leaves. But then the weather changed and we received more than 7 inches of rain over a 5 day period. Both the honeydew and most of the aphids disappeared, washed from the leaves by the heavy rain.

    The weather dried out over the next week and I noticed just a few aphids on the underside of  the leaves of my pecan trees (photo at right).  But then the clouds rolled in again and dumped enough rain to cause localized flooding. The heavy rain was again enough to knock down the aphid population.

   Over the past two weeks, the weather has been dry and unseasonably hot. And now we have an explosion in aphid populations (photo at left). Every leaflet seems to have at least a dozen aphids feeding on the sap of the pecan tree.
   A large aphid population usually crashes on its own but the rain predicted for this weekend may serve to hasten the crash.
   I certainly hope we get enough rain to wash the foliage clean of honeydew and aphids. Lately, I've been getting covered in honeydew as I collect nut samples from the pecan breeding project. Its driving me crazy to get sticky plant sap stuck in my hair.

Checking for pecan shucksplit

    The official first day of Fall is just around the corner so, today, I thought it would be a good idea to check on the progress of pecan shuck-split among the trees in our breeding program. To find out if the shuck is beginning to separate from the shell of a pecan, I use my pocket knife to slice down through the shuck until I hit shell. I give the knife a quick twist to see if I can easily pop off a portion of the shuck. Separation between shuck and shell begins at the apex of the nut and works downwards toward the base. So my first cut is always about 1/4 of the way down the nut. If the shuck pops off, I make a second cut about 1/2 the way down the nut. In the photo at right, you can see that the shuck separated from the shell at the 1/4 cut line. Note the beginnings of the shell markings near the tip of the nut. Then with my next cut the shuck stayed firmly attached to the shell. This pecan was only starting the journey towards shuck split. 

    Moving on to another tree, I found pecans that were further along in the shuck-split process.  I used the same process of cutting through the shuck 1/4 of the way down the nut then repeating at 1/2 and 3/4 of the way down. The photo at left shows a nut after I made the 3/4 cut. Here I found that the shuck was completely separated from the shell but the shuck had not yet split open. I then decided to peel off all the shuck to take a good look at the nut within.

    The nut was easily extracted from the shuck but had yet to develop the even brown shell color we usually associate with mature pecans (photo at right). To develop normal shell color, the nut needs to be exposed to the air and begin the drying process. This will start when the shucks split open.

    The splitting open of shucks is another process that occurs over time. Each pecan cultivar seems to split shuck just a little differently. In the photo at right, the shuck has begun to open along the suture right in the middle of the nut.

   In the more common case, the shuck opens at the tip of the nut and works towards the base (photo at right). The nuts pictured here are from our earliest ripening clone. Last year I recorded shuck-split for this tree on Sept. 20. This photo was taken today (17 Sept. 2018).

   One other observation I have made when recording shuck-split data. With many cultivars, shucks open uniformly over the entire tree. While other trees seem ripen over a couple of weeks. The nut cluster pictured at left shows a pecan clone that splits shuck one nut at a time over a  7-10 day period. In a cluster of 3 nuts, one is fully open while the others are still held firmly inside the shuck. Looking over the entire tree, I noticed just a few open shucks randomly within the canopy. Most nut were still tight in the shuck.
   

   Over the next month, I'll be watching for shuck-split among tree in the breeding project and the trees I've grafted on the farm. As of today, I found no movement towards shuck-split on my Kanza, Hark, Gardner, and Faith trees. (Gardner and Faith ripen the same time as Pawnee).
    The photo at right is from another tree in the breeding project. This nut may be early ripening but it is not a very impressive pecan.