Monday, December 30, 2013

Evaluating new pecan cultivars: A look inside the shell

     2013 turned out to be a good year for evaluating new pecan cultivars. The above average rainfall we received this past summer meant that soil moisture would not be a limiting factor in terms of kernel fill. However, the 2013 growing season was significantly shorter and cooler than normal. Lets take a closer look at the kernels inside the shells of three cultivars to see how cooler temperatures can impact nut quality.

    Let's start by looking at an open-pollinated Giles seedling we originally planted in the Chetopa City Park.  On the outside, this nut is large and attractive. City Park is larger than its Giles parent but smaller than Mohawk (the possible male parent). At first glance the kernels look OK but on closer inspection I note a lack of plumpness and some shriveling towards the tip of each kernel half. I also spot some kernel fuzz on surface of the kernels.

    USDA 75-8-5 and USDA 75-8-9 are sibling cultivars that resulted from a cross of Osage and Creek. Both cultivars produced medium-sized pecans this year. The kernels are bright and attractive but upon closer inspection, both cultivars have a significant amount of fuzz on the surface of the nut meats. In a previous post, I found the USDA 75-8-9 had more scab on the shucks than USDA 75-8-5.  With more scab on the shucks, USDA 75-8-9 had poorer kernel fill than its sister clone. Note that USDA 75-8-9 has flatter, less-plump kernels.

     All three of the cultivars pictured in this post show kernel symptoms that point to a shortage of summer heat during the growing season. Even though all three cultivars split their shucks well before the first fall freeze, nut development was delayed by cool mid-summer temperatures and kernel filling process simply ran out of time as fall approached.

Tuesday, December 24, 2013

What happens when Lakota over-produces?

    As a pecan cultivar, Lakota has a lot of great attributes. Lakota produces large pecans with high quality kernels. The tree is precocious, high yielding, and scab resistant. However, Lakota is not the perfect cultivar. As the tree ages, Lakota can over-produce and slip into alternate bearing.   
    Our Lakota trees are now close to 30 years old and this past summer the trees were loaded up with pecans (photo at right). Lakota can produce large nut clusters often with six to seven nuts to a cluster. Although large cluster size looks impressive in mid summer, too many nuts in a cluster usually creates problems with kernel fill.

    In the photo above, the four kernels on the right side are examples of the excellent quality nuts  usually associated with Lakota pecans. The four kernel halves on the left side also came from Lakota nuts but illustrate the common kernel defects associated with crop over-production.  If you look carefully you will spot three indicators of poor kernel fill. 
    First, note that the kernels on the  left do not appear as plump as the kernels on the right. In addition, the poorly filled kernels have a light coat of fuzz on the surface of the kernel especially towards the apex. Turn the kernel over and you see that the underside looks hollow or depressed. All three of these symptoms are indications that the tree did not have enough available energy to fill every nut on the tree to maximum quality.
    The biggest problem with over-producing Lakota trees is the fact that a single tree produces both high quality and lesser quality nuts. This can create a marketing nightmare especially when selling directly to the consumer. Ultimately, over-production can be managed by thinning the nut crop in mid-summer using a trunk shaker. Shaking over-loaded trees during the water stage of nut development will reduce both the number of nuts per cluster and the number of nut clusters per tree. By reducing the crop load, the remaining nuts will fill to perfection and the tree will set a better crop the following season.      

Monday, December 23, 2013

Ice coats native pecan groves

    Last week we had 3 days of harvest-able weather conditions. All was going smoothly until our pecan tree shaker flew to pieces just as the weather was beginning to take a turn for the worse. Over the weekend we had a little over an inch of rain including a quarter inch of ice accumulation. This morning the sun finally broke through the clouds making our ice covered native pecan groves sparkle (photo above).

       We still have pecans to harvest (photo at left), but it looks like the ice won't be melting off the trees until Christmas day. After that,  the ground will need to dry before harvest can resume. While we wait for harvest conditions to return, we will be busy repairing the shaker (and trying to stay warm!).

Friday, December 20, 2013

Kanza production 2013

2013 Kanza Crop
     I've been recording the yield of a 3 acre block of Kanza pecan trees over the past several years. In 2013, we had a nice crop of good sized nuts with the yield bouncing back following two years of drought. The yield of for these trees over the past four years is given below.

Year   Tree age   Yield (lbs/acre)
-----  ---------  ----------------
2010      15         1050
2011      16          899
2012      17          810
2013      18         1028

    This winter, we will be thinning additional trees from this orchard according to our thinning plan.

Thursday, December 19, 2013

Finally! Pecan harvest resumes

    Over the past couple of days the pecan harvesters have been humming over the native pecan groves of Southeast Kansas. After weather delays due to rain and snow, soil conditions were finally favorable enough to pick pecans. Yields in the area are good, not great. Plentifully rain during midsummer of 2013 has meant that nut size and kernel fill are outstanding this year.
     Unfortunately, another winter storm is headed this way for the weekend. The weather man is promising rain, ice and snow. It looks like the 2013 harvest season will be stretching well into 2014.  

Thursday, December 12, 2013

Double-row pecans: Pecan yield at year eleven

   Earlier this fall I posted a photo of the trees in our double-row pecan planting (photo at right). A couple of weeks ago I harvested the nuts from these trees and recorded yields for each of the three cultivars in the trial. 
     In establishing this orchard, we grafted Faith, Gardner, and Lakota during the years 2005-2007 onto Colby seedling rootstock trees that had originally been planted back in the fall of 2002. Below is a chart of this year's average yields.

Cultivar      Lbs/tree    Std.Dev.
------------  ----------  ---------
Faith           8.16       1.24
Gardner        10.03       2.00
Lakota         20.01       3.18

   The trees in this trial are still young, averaging a little less than 4 inches in trunk diameter. The Lakota trees actually over-produced for their age resulting in less-than-stellar kernel quality. The 10 lbs. per tree yield produced by Gardner seemed just about right for this size tree. Both Faith and Gardner produced excellent quality nuts.
   On a total land area basis, the double-row planting plan has 27 trees per acre. Per acre yield for 2013 ranged from a low of 220 lbs/ac for Faith to a high of 540 lbs/ac for Lakota. 

Tuesday, December 10, 2013

Snow stalls pecan harvest

   A two inch blanket of snow fell on our pecan grove last night putting a halt to our pecan harvest. Weather delays are a part of pecan farming that I've come to accept. So instead of cursing the weather, I decided to enjoy the moment and take a few "artistic" photographs (below). There is no place on earth more beautiful than a pecan grove.


Saturday, December 7, 2013

Pecan: A standout among hickories

   There are eleven species of hickory native to North America and yet the pecan is the only member of the Carya genus that has been developed into a commercially viable orchard crop. Ever wonder why?  It's not all about taste. Sure some of the hickories produce bitter kernels, like the bitternut hickory (Carya cordiformis) and the water hickory (Carya aquatica). However, the shagbark hickory (Carya ovata) produces a sweet, oily kernel that has a delightful flavor.
    What makes pecan (Carya illinoinensis) stand out among all the hickories is a unique shell architecture that makes extracting the kernel much easier. To illustrate the major differences in shell characteristics between pecan and a typical hickory nut I'll be using photos of Kanza pecan and Fairbanks shagbark hickory (photos at right).
      I used a bandsaw to carefully slice through a pecan and hickory nut to reveal, in cross section, the relationship between kernel and shell (photo at left). The red arrows point to the portion of the nut's shell that protrudes into the dorsal grove of each kernel. Note that this protrusion in the hickory is basically an extension of the hard outer shell. In sharp contrast, the material that protrudes into the dorsal grove of the pecan is composed of loose packing material rather than shell material.
    This major difference in shell structure becomes obvious when cracking each nut. When a pecan is cracked the material inside the dorsal groove breaks free from the outer shell easing the extraction of kernel. When cracking a hickory, the shell's protrusions into the kernel remain firming attached to the outer shell and can trap portions of nut meat inside of shell fragments.
    The yellow arrows, in the photo above, point to the inner wall partition of each nut. Note that this inner wall in the hickory is composed of the same hard material as the outer shell. In pecan, the inner wall is softer packing material similar to the material found inside the dorsal groove. When a pecan is cracked the inner wall breaks free from the outer shell allowing both kernel halves to fall free of the shell. In contrast, the inner wall partition inside a hickory nut is not easily separated from the outer shell wall during the cracking process. Often, when cracking hickory nuts, the inner wall will trap one of the two kernel halves requiring a second crack to fully remove all the kernel.

     There is one more difference between pecans and hickories that makes pecan easier to shell. In the photo at right, the red arrows point to cleft in the kernel of each species. This is the location of a  secondary inner wall partition that runs perpendicular to the main inner wall seen in the cross-section photos above. The secondary inner wall in hickory is quite prominent and extends deeply into the kernel. This secondary wall is also composed of hard outer shell material that can trap kernel fragments inside broken bits of shell during the cracking process. In pecan, this secondary wall is greatly reduced or not present at all. In cracking a pecan, the secondary inner wall partition may appear as a small sliver of packing material lodged in the tip of the kernel. However, this bit of inner shell material usually falls free of the kernel during commercial shelling. 

Monday, December 2, 2013

Cultivars that ran out of time to fill kernel

Maramec 2013
   The 2013 growing season in SE Kansas was shorter, wetter and cooler than average. While early-ripening, pecan cultivars have produced high-quality pecans this year, cultivars that ripen late in season are displaying some serious kernel quality issues.
    During this past summer, I posted photos of the development of Maramec pecans as compared to the earlier ripening cultivars Osage and Kanza. Now at harvest we can see the end results of Maramec simply running out of time to fill kernel (photo above).
    Both kernel halves in the photo came out of the same Maramec nut--a nut equal in size to the whole nut pictured next to the kernels. The kernel on the left looks normal but is only 3/4 the length it should have been. The kernel on the right is flat and misshapen. Both kernel halves have patches of fuzz attached to the surface. If you were to snap one of these kernels in half you would find air spaces inside the kernel. The kernels lack oil and taste like cardboard.
Stuart 2013
    Stuart also ran out of time to fill its kernel this year (photo at left). The kernels are short. The kernel halves are shriveled on the ends and the surface of the nutmeat is fuzzy. These are all symptoms of a Stuart nut that did not receive enough heat and length of growing season to properly develop a quality kernel.

Friday, November 29, 2013

Pecan shell geometry and kernel dorsal grooves

      Have you ever cracked open a pecan and gotten frustrated but the shell's inner packing material trapped in the grooves of the kernel (the dorsal grooves). It seems that some cultivars are more prone to this problem and the reason may be as simple as the shape of the nut's shell. I'm not talking about the length of the nut or how pointed the nut appears. When it comes to narrow dorsal grooves and trapped packing material, the important shape to observe is the shape of the shell in cross section. Not all nuts are perfectly round in diameter. In the photo below, I have arranged the nuts of three cultivars so you can see the how nut diameter can differ if measured 90 degrees from the shell suture (nut on left) or on the suture (nut on right). Below each pair of nuts I've listed the diameter ratio (diameter 90 degrees from suture/ diameter on the suture).  A nut that is practically round in cross-section, like Kanza, has a diameter ratio close to 1. Cultivars that produce "flattened" nuts, like Greenriver, have a diameter > 1.  Cultivars with a diameter ratio < 1, such as Chetopa, often appear narrow when viewed suture side up.

   So, what does all this have to do with packing material stuck in the dorsal grooves?  Its all about how kernels are oriented inside the shell. When you look at the shell's suture, underneath is a full kernel half. In other words, the inner wall partition between the kernel halves is oriented 90 degrees from the suture line. Lets look at the kernels of these same three cultivars (photo below).

   Cultivars, such as Chetopa, that have a diameter ratio < 1 typically produce long narrow kernels. The dorsal grooves on these narrow kernels are not only narrow themselves but they tend to flare outward into the kernel. The result of this kernel geometry is frequently trapped packing material.
    In contrast, round nuts or flattened nuts have broad kernels with wide dorsal grooves. These grooves also penetrate straight down into the kernel. The result of this geometry are kernels that fall free of all inner shell packing material.   

Monday, November 25, 2013

How long does it take until pecan trees bear a commercial crop?

    The trees in our double-row intercrop block are starting to produce a lot of nuts (photo above). Earlier this fall we even planted a permanent ground cover in the space formerly dedicated to field crops.  Now, with the leaves off the trees, you can see why we needed to plant a ground cover to facilitate harvest--the trees are loaded with nuts.
    A lot of folks interested in establishing a new pecan orchard wonder how long it will take until the pecan trees start to bear nuts. This double-row orchard provides a good example. The orchard was established with contianer-grown trees. One-year-old 'Colby' seedlings were transplanted into the field during the fall of 2002.  The cultivars Lakota, Faith, and Gardner were grafted onto these rootstock trees during the grafting seasons of 2005-2007. The young trees started to set a few nuts by 2009. By  2012 we needed to use a trunk shaker to harvest our first machine-harvestable crop (ie. a crop big enough to justify the expense of running the equipment). The 2013 crop is even bigger and this year we will start collecting meaningful yield data.
    Here's the bottom line. The trees pictured above were started from seed in the nursery during the Spring of 2002. By the Fall of 2013, eleven years later, the trees have grown large enough to bear their first commercial crop.  

Sunday, November 24, 2013

Brown fuzz on pecan kernels

    Patches of a brown fuzzy material loosely adhering to the surface of pecan kernels are a common sight this fall (photo at right).  This is not a disease but simply some of the internal shell packing material that has become stuck to the kernel.
    During the 2011 and 2012 growing seasons, the brown fuzzy patches were caused by a summer droughts. This year the problem was just the opposite. The summer of 2013 was cooler and wetter than normal. In fact, nut development ran two weeks behind normal all season long. By the end of the 2013 season, many pecan cultivars ran out of time and heat to fully pack the inside of the shell with kernel.
    If the expanding kernel does not fully compress all the packing material tightly against the inside of the shell, some of that packing material can adhere to the kernel. Note that the brown fuzzy material is generally concentrated towards the upper end of the kernel half. This is the part of the kernel that fills last during nut development.  It seems that time simply ran out for kernel filling as shorter days and falling temperatures promoted nut ripening and shuck splitting. 

Monday, November 18, 2013

The problem with Witte

    The Witte pecan cultivar has been around for a long time (photo at right). It was discovered in the 1920's by J.H. Witte as a native pecan tree growing in the Mississippi River floodplain just outside of Burlington, Iowa.  This northern pecan cultivar ripens early, about 4 days before Colby. The tree produces a medium sized nut (6.6 g) with 51% kernel. Witte has a protandrous flowering habit and is moderately susceptible to pecan scab. From the outside, Witte looks like a fairly good choice for northern pecan growers. However, crack open the shell and you will discover Witte's fatal flaw--Dark ugly kernels.

     Witte kernels are dark even when harvested fresh off the tree (figure left). A few weeks after harvest the kernel color gets even darker. Witte kernels also have a wrinkled "old man" appearance that contributes to an illusion that the kernels poorly filled out.
    You can really see how dark the kernels of Witte are when you compared them to kernels of Oswego and Kanza (photo at right). When consumers are shopping for pecans they associate light kernel color with freshness. Dark kernels are avoided as being possibly rancid.
    Because Witte produces such unappealing kernels year in and year out, I wouldn't recommend this cultivar to any northern pecan grower.

Friday, November 15, 2013

Harvest 2013

     Its amazing how a hard freeze helps to kick the harvest season into high gear. Our pecans are opening up nicely and are drying out quickly. I've been taste testing nuts for a couple of weeks now and for the most part, the nuts have been rubbery and green tasting. Previously, the kernels had just too high of a moisture content. Today, I ate my first fully dry and great tasting pecan from this year's crop--a Faith pecan (photo at right).
    So far, our harvesting equipment seems to be working without any major problems (photo at left). Today, we moved the harvester into the Kanza block. Yields in this block of trees are once again impressive  judging from the number of full super-sacks that are being pulled out the field. However, I'm seeing indications that tree crowding has reduced nut production in sections of this block. Later this winter, I'll consult my thinning plan for this block of  Kanza trees and sharpen my chainsaw.

Wednesday, November 13, 2013

Deep freeze ends pecan growing season

    The temperature dropped to 18 F early this morning representing this Fall's first killing freeze. When I arrived at the pecan grove, leaves were dropping from the trees so fast they quickly covered the bed of my truck. Its impossible to capture the sights and sounds of such a quick leaf drop with a still photograph but I hope you can see the leaves raining down in the photo above (click on photo to enlarge).

    Last week I wrote about cultivars differences in preparing for dormancy.  By the time the freeze hit today, the cultivars I photographed with yellow leaves last week had already lost their leaves by this week (ie. Greenriver and Kanza). Stuart, on the other hand, was still holding on to green foliage as of yesterday. By one o'clock today, the ground under our Stuart trees was littered with green leaves knocked off the tree by cold temperatures (photo above, left).

    Looking up into the Stuart tree, I found the green shucks had frozen and taken on a water-soaked brown appearance (photo at right). Starting today, the green shucks of Stuart or any other pecan that still had split green shucks will begin to dry, turn dark brown, and pull away from the nut.  Late ripening cultivars that had not begun the split shuck process by today will remain firmly enclosed within a blackened shuck; a condition commonly called stick-tights.
     Let the harvest begin!

Monday, November 11, 2013

Container grown pecan trees: Fall planting and overwintering potted trees

   For the past three weekends, I've been planting the pecan seedlings I started in containers this past spring. Fall is the perfect time for planting container grown trees (photo at right).  For the most part, the soil has just enough moisture to make digging the planting hole easy but is dry enough to allow you to back fill the planting hole with loose, friable soil. Fall planting also allows the roots of the young tree to begin growing out into the surrounding soil almost immediately, helping to decrease transplant shock.
      The trees I planted this fall averaged about 10 to 12 inches in height with an air-pruned root system only about 4 1/2 inches deep (photo at left).  The depth of the root system makes it very easy to transplant--one shovel full of soil and I've got a hole deep enough for the tree. I like to to plant these trees about an inch deeper than they had grown in the container, allowing the root ball to be fully covered with soil. Planting deep ensures that the soil-less media that still surrounds the root system is not directly exposed to drying winds and the tree doesn't desiccate.
     The photo at right gives you a good look at the type of root system that develops inside the bottomless container. The tap root has been air-pruned forcing the development of  a network of fine lateral roots. Once this tree is planted in the field, the air-pruned taproot will re-sprout often creating two or three new "taproots". Next year, my transplanted seedlings will put on just a few inches of new top growth but more importantly, they will be developing massive root systems designed by nature to ensure tree survival.
     I planted about 150 trees this fall but still had some trees left over. With winter's first blast of arctic air forecast for this week, I took some steps to protect my remaining potted trees from the big chill. Although pecan trunks and branches can stand temperatures down to -26 F, the roots of pecan trees will freeze at about +19 F.  This means I needed to take some steps to protect the roots of my remaining potted trees.
    I moved the trees from the nursery bench into my vegetable garden. The garden has two things that makes in perfect for overwintering trees. First, we have raised beds in the garden and the garden paths are just the perfect width for a flat of trees. With a raised bed on either side of the flat, it looks like the trees are partially buried in the soil (photo above).  The garden is also surrounded by a fence that will keep the trees safe from mid-winter rabbit feeding.
    To prevent root freezing, I used a thick carpet of hay packed around the tree flats to insulate and trap the soil's heat around the trees (photo below). 

Thursday, November 7, 2013

Scab at season's end

Giles, 4 Nov. 2013
    This past summer we ran some fungicide trials which included a "no spray" treatment. Not surprisingly, fifteen inches of rain in mid-summer helped pecan scab spread rapidly on susceptible cultivars. The photo at right demonstrates what scab can do to the Giles pecan cultivar. The nut the points downward and the nut that point towards the camera will end up in the reject pile as stick-tights. The nuts with open shucks on the right and left sides of the cluster will be harvestable but are smaller in size and not as well filled. All four nuts in this nut cluster were covered in black scab lesions.

Giles, 4 Nov. 2013
      Compare that to Giles nuts treated with three applications of fungicide over the course of the season (photo at left). We didn't get perfect scab control because you can see some scab lesions on nuts at left, but we controlled the disease enough to prevent a reduction in nut size and quality. All of the nuts pictured still had green shucks that had split shucks. Giles nuts tend to stay fairly "closed" after shuck split. After a hard freeze kills the green shuck, the shucks will open up fully. Unlike the scabby nuts pictured above, all of these nuts (at left) will be marketable.
    Scab control this past year was a little tricky. We ended up applying fungicides much later into the season than we even have in previous growing seasons. I was pretty happy with the scab control we achieved. This past season proved how important it is to stay in touch with nut development stage and to make pesticide applications according to the tree's time line rather than the calender date. 

Monday, November 4, 2013

Northern pecan cultivars and fall foliage color

    Establishing early-ripening cultivars is critical for successful pecan growing along the northern edge of the pecan tree's native range. Over the past couple of months, I've photographed many cultivars adapted to northern pecan culture as they ripened this fall (25 Sept. 2013, 30 Sept. 2013, 9 Oct. 2013, and  21 Oct. 2013).  However, ripening date is not the only characteristic that is important for assessing the adaptability of a cultivar for northern pecan production.  
    Today, I photographed a Stuart tree growing next to a Greenriver tree. As you can see in the photo above,  the Greenriver tree has developed a nice yellow fall color while the Stuart tree is mostly still green with a touch of fall browning.   Greenriver, like most northern pecan cultivars, starts to shut down earlier in the fall than southern cultivars, such as Stuart.  This earlier entrance into winter dormancy means that Greenriver would be far more prepared to withstand a sudden blast of winter cold than the ill prepared Stuart tree.
Kanza, 4 Nov. 2013
Many of today's early-ripening cultivars represent hybrids of cultivars of northern and southern origins. That is why we see cultivars like Pawnee and Osage still holding on to their summer green foliage all the way into early November. Although early ripening, Pawnee and Osage act like their southern ancestors when it comes entrance into fall dormancy. This might explain why we have seen cold injury on Pawnee and Osage in some years. Kanza is also a hybrid of northern and southern ancestry, but look at our Kanza trees today (photo at right). Its no wonder that we have not seen winter injury on Kanza across KS, MO and IL. 

Sunday, November 3, 2013

Downy spot on pecan foliage

   Back in early October, I was collecting nuts samples from our breeding plots when I took a few minutes to photograph downy spot, a minor pecan disease not often seen in well tended groves. This disease popped up in the breeding plot for two reasons. First, we don't apply fungicides to the breeding block to enable us to check for scab resistance. And second, 15 inches of rain over 4 weeks in mid-summer provided great conditions for disease spread.
   By the time I photographed downy spot, the disease was in in advanced stages of development. Looking at the underside of a leaflet with the sun streaming from above, it is easy to see the irregular shaped lesions of downy spot. Each lesion appears yellow with dark patches at the margins and within the lesion (photo at right).  

   Viewed from the upper side of the leaf, downy spot appears as faint brown patches on the foliage (photo at left). An extensive downy spot infection causes early defoliation in the fall. Prior to early defoliation, this disease can reduce photosynthesis by up to 40%. 
   Downy spot is caused by the fungus, Mycosphaerella caryigena, which overwinters on fallen leaves from the previous season.

    Downy spot gets its name because the disease first appears on the underside of leaves as a faint light green spot that turns white and "downy" as the fungus begins to sporulate. As the season progresses, downy spot lesions grow upward through the leaf blade until they reach the upper leaf surface. At this point, spore production has ceased and the downy spot lesions appear brown in color, especially on the underside of leaves (photo at right).
    Downy spot is usually controlled when fungicides are applied for the control of pecan scab.

Wednesday, October 30, 2013

Leaf scorch caused by pecan anthracnose

   This fall you might have noticed pecan leaves with brown, crispy margins (photo at right). This past summer's rainy weather helped to promote the spread of this disease once known as "fungal leaf scorch". Now, during the month of October, this disease has caused the early defoliation of some pecan trees.
    Leaf scorch is actually just one symptoms of a late-season disease called anthracnose which attacks both pecan leaves and nuts. Pecan anthracnose is caused by the fungus, Glomerella cingulata, a common plant pathogen that causes diseases in many fruit and vegetable crops.
   On pecan leaves, anthracnose first appears as brown, irregularly shaped lesions along the edges of a leaflet. These lesions can spread rapidly over the entire leaflet ultimately causing early leaf fall. The advancing margin of the infection forms a distinctive dark brown line that separates healthy tissues from disease killed tissue (photo above).      

    Anthracnose infection of the nut can start as small sunken lesions on the shuck but the disease can spread to cover a large part if not the entire shuck (photo at left). Infections that cover the entire shuck by early August (water stage) can cause smaller nut size and prevent normal shuck split. Anthracnose infections that occur late in season seem to have little impact on the nuts other than to advance the shuck opening process.

   To determine the influence of anthracnose on nut quality, I collected nuts with infected shucks, peeled them out, then cut them in half to check kernel fill. The nuts that appear in the photo at right represent a range of anthracnose disease severity--from less disease on the left to the most severe on the right. The nut that came out the the shuck appears directly below the nut-in-shuck photo. Below each nut is that same nut cut in cross-section.
    The first thing I notice in the photo is that all 4 nuts are well filled with kernel. Looks like this year's anthracnose infection on nuts will have little effect on kernel quality. However, the nut on the far right was smaller than the others and the shuck did not peel off very easily. In this case, anthracnose probably got an earlier start on colonizing this particular nut.
    Even though the kernel inside the nut on the far right looks good, this nut would probably not survive the nut cleaning process. Judging from the force I needed to apply to remove the shuck, this nut would probably be discarded off the cleaning table as a stick-tight. If anthracnose causes enough stick-tights, this disease can lead to significant yield losses.
    Anthracnose can be controlled with fungicides and is largely suppressed when we spray fungicides to control pecan scab. However, this year's unusual weather patterns hit just right to promote an outbreak of anthracnose after we finished making fungicide applications aimed at controlling scab.  

Monday, October 28, 2013

Nut development: 28 Oct. 2013

   Each time I checked the development of Maramec nuts this summer, I wondered if they would have enough time to split shuck before the first killing freeze. Well, I got my answer today. I found the shucks split open on our scab-covered Maramec nuts (photo at right).
   Splitting shuck before the first freeze is important but  remember, Maramec was having a hard time filling out its kernel ever since mid-September.  So I collected a few Maramec nuts to check kernel quality. Since scab was also an issue with Maramec this year, I harvested nuts with varying amount of scab infection on the shucks.
     The photo above shows four Maramec nuts arranged by severity of scab infection. Below each nut is a photo of that same nut in cross section. Nut "A" had the least amount of scab and achieved normal size for a Maramec. A look inside nut "A" reveals less than perfect kernel fill with air pockets both within the kernel and near the inner-shell partition. The poor kernel fill observed inside nut "A" was a result of this cultivar running out of time and heat to fill the seed. In this case, scab infection was not severe enough to negatively affect kernel fill.
     Nut "B" is about the same size as nut "A" but total disease coverage on the shuck of nut "B" has caused even poorer kernel fill.  The earlier in the year scab covers the shuck, the greater effect the disease has on nut size.  Nuts "C" and "D" are examples of the how nut size can be affected by scab. Early scab infection had the greatest impact on nut "D" decreasing size and severely limiting kernel fill.

Thursday, October 24, 2013

Pecans ripe but not ready

Gardner, 9 Oct. 2013
   Two weeks ago I posted this photo of the 'Gardner" pecan cultivar (photo at right). By October 9th the shuck of Gardner had split and this pecan fruit was botanically ripe. However, if you were to remove the nut from the husk at this time and immediately crack open the shell you would find a white, rubbery kernel inside. And the nut meat would taste nothing like the sweet, oily kernel you normally associate with fresh pecans.

Gardner, 23 Oct. 2013
   Two weeks later, the shucks on Gardner look about the same as they did before. The shucks might be slightly more dry along the split-open sutures but the hull is still green and covering the nut (photo at left). I pulled a nut from the husk and shelled it out. The kernel was not at all dry and still hadn't developed its normal golden color (photo above). Two weeks after "ripening" this Gardner was still not ready to eat.
    The bottom line is that the green shuck traps moisture in the nut, preventing it from fully curing. Under natural conditions, our trees will experience a hard freeze, killing the green tissues in the shuck and allowing both shuck and nut to fully dry before harvest.
     For those not patient enough to wait for a killing freeze, the nuts can be physically removed from the shuck (by hand or with a mechanical deshucker). Once the nuts are removed from green shucks, they are still full of moisture and will need to be dried.  I've see all kinds of methods to air dry pecans. Nuts can be placed in mesh bags and hung from the rafters in the garage. Pecan can also be spread onto drying racks built from 2x4s and 1/2 inch hardware cloth. If you use drying racks, make sure to allow for free air movement from both above the rack and below the hardware cloth bottom. Don't use heat to dry pecans but a simple box fan is useful for keeping air moving around the nuts.
     On a larger scale, I've seen growers use a "peanut" wagon to dry pecans. A peanut wagon is basically a large drying rack on four wheels. A grain drying fan (no heat!) is attached to the wagon to keep air moving around the nut crop and promote drying.
     Personally, I prefer to allow nature to dry my pecan crop. Natural drying is a heck of a lot less work and doesn't require the purchase of additional equipment or electricity