Wednesday, September 30, 2015

Nut shape defines kernel characteristics

   The other day I was cutting pecans in half to check on kernel quality when I made a simple observation. Nut shape has a huge impact of a couple of important pecan kernel characteristics.
    As I walked down one of our tree rows, I came across three early-ripening cultivars; Faith, Gardner, and USDA 75-8-5. In cross-section,  Faith and Gardner have a similar nut shape--nuts are wide and seem flattened on the suture side (photo above). In contrast, nuts of USDA 75-8-5 appear narrow when viewing the nut from the suture side but are wide in the opposite direction.
    When kernels are extracted from these nuts Faith and Gardner kernels will appear much larger than the 75-8-5 kernels simply because they will be much wider. Now, look at the shell packing material that fills the space in the dorsal grooves of each kernel half. Note that the packing material forms a wide "V" shape in the Faith and Gardner nuts. In comparison, the USDA 75-8-5 nut has narrow fingers of packing material inside deep dorsal grooves.  Narrow dorsal groves often trap bits of packing material in kernel halves making the shelling process more difficult. The "V" shape of the dorsal grooves inside Faith and Gardner nuts will mean that all fragments of packing material will fall free from the kernels during nut cracking.

Tuesday, September 29, 2015

Pecan cultivars spliting shuck in late September

Waccamaw, 28 Sept. 2015
    Over the weekend six more pecan cultivars started to open their shucks. Pictured at right is a seedling cultivar of unknown parentage that originated outside of Golden City, MO. The tree's owner named the tree Waccamaw, after a native American tribe that once inhabited coastal South Carolina. The Waccamaw River flows from North Carolina into South Carolina running parallel to the eastern seacoast. The Waccamaw produces a nut slighty smaller than Pawnee and yields 54% kernel. Waccamaw is scab susceptible.
City Park, 28 Sept. 2015 

     Another seedling pecan we have under trial is "City Park". Years ago, we planted a Giles seedling in Chetopa's Riverside Park. Eventually, the tree started to bear nuts. I was so impressed by the size of nuts produced by this tree that I grafted scions from the original tree into field trials at the research station. The grafted trees of 'City Park' have now matured enough to allow us to get a good read on it ripening date--about the same time as Kanza.

Kanza, 28 Sept. 2015

    Speaking of Kanza, our heavy crop of Kanza nuts have begun to split shuck. Spotting shuck split on Kanza is a little difficult. The shuck separates down the sutures but remain fairly tight around the nut. It will take a killing freeze to really open up the shucks and release the nut inside.

Hark, 28 Sept. 2015

     Like Kanza, I have a strong suspicion that 'Hark' has Major as one of its parents. As a result, the shucks of Hark split down the sutures but the shuck remains tight around the nut until frost.

Posey, 28 Sept. 2015

      Posey has a very distinctive shuck that is characterized by a rough surface texture and prominent wings along the sutures. At this time Posey nuts are about 10% shuck split.

Yates 68, 28 Sept. 2015

   Yates 68 looks to be a Posey seedling and shares Posey's dark shell color and tendency for kernels to turn dark quickly after harvest.  Yates 68 was selected from a group of seedling trees planted by Ed Yates on his farm in Southern Indiana. 

Sunday, September 27, 2015

Scab on 'Mandan' pecan

    The cultivar release notes published when Mandan was first made available to the public claimed that nuts produced by this tree are resistant to pecan scab. Although not extremely susceptible to scab we have found Mandan shucks infected with the disease.
    This past season we applied a fungicide three times to our Mandan trees during the months of June and July. For the most part, we have kept the shucks mostly clean with only a few small scab lesions appearing by late summer (photo at right).

   However, where we didn't get good fungicide coverage on the nuts, I found several clusters of Mandan nuts covered with scab lesions (photo at left). Mandan also seems to be susceptible to powdery mildew.
    While taking this photo of scabby nuts, I found a crab spider resting on one of the nuts. Crab spiders are a common insect predator in pecan tree canopies with female spiders often hiding their eggs at the base of nut clusters.

Friday, September 25, 2015

More pecan cultivars ripen in late September

Colby, 25 Sept. 2015
    This morning I took a ride in our hydraulic lift so I could get up into pecan tree canopies to check on nut ripening. I found that 10 more cultivars had split shuck including; Colby, Gardner, Goosepond, Major, Mandan, Pawnee, Peruque, Witte and two USDA selections 63-16-182 and 64-11-17 (photos at right and below).
    Among the cultivars I photographed today only Major is resistant to pecan scab. While most cultivars in our trials received 3 fungicide applications, our Goosepond trees are located within a native grove and receive only a single spray. As a result, all the Goosepond nuts were covered with scab. What I found interesting was that many Goosepond nuts still split shuck and will release a smaller-than-normal but sale-able nut.
   Colby and Peruque nuts exhibited high levels of scab despite receiving 3 doses of fungicides. The difficulty we have controlling scab on Peruque and Colby is just one reason among others that these northern cultivars are no longer being grafted into new orchards.

Gardner, 25 Sept. 2015

Goosepond, 25 Sept. 2015

Major, 25 Sept. 2015

Mandan, 25 Sept. 2015

Pawnee, 25 Sept. 2015

Peruque, 25 Sept. 2015

Witte, 25 Sept. 2015

USDA 63-16-182 ('Eclipse'), 25 Sept. 2015

USDA 64-11-17, 25 Sept. 2015

Tuesday, September 22, 2015

Early ripening pecan cultivars begin shuck split

Canton, 22 Sept 2015
   This morning I checked our cultivar trials for nuts with opened shucks. I found several of our early ripening cultivars had split shucks including; Canton, Norton, Osage, Faith, Shepherd and Surecrop (photos at right and below).
    Several years ago we grafted a selection from our breeding project, KT143, into a new field trial. Several young KT143 trees had good nut crops with roughly 50% shuck split (photo below). KT143 is a cross between Pawnee and Major but the shuck of KT143 behaves like its Major parent. The shuck separates along the sutures but remains fairly close around the nut. It will take a killing frost to fully open the shuck and free the nut inside. This "Major" habit of shuck opening is common among several Major progeny including Kanza and Hark.
   I found three USDA selections with split shucks (photos below). USDA 75-8-5 resulted from a cross of Osage and Creek. USDA 61-1-X and 61-1-15 share the same parents, Barton and Staking Hardy Giant.
    In looking over these nut cluster photos you will also notice that Canton, Faith, USDA 61-1-X, and USDA 61-1-15 all have light scab infections. We sprayed these trees three times for scab and had fair success in keeping the disease from impacting nut production.
     KT143 nuts were infected with powdery mildew but showed no signs of scab. The powdery mildew did not effect shuck opening and the nuts inside were fully packed with kernel. KT143 received only one early-season fungicide application in 2015.

Norton, Sept 2015

Osage, 22 Sept. 2015
Faith, 23 Sept. 2015

Shepherd, 23 Sept. 2015

Surecrop, 22 Sept. 2015

KT143, 22 Sept. 2015

USDA 75-8-5, 22 Sept. 2015

USDA 61-1-X, 22 Sept. 2015

USDA 61-1-15, 22 Sept. 2015

Wednesday, September 16, 2015

Impact of scab on Peruque pecan

    Peruque is an old pecan cultivar originating in the Mississippi floodplain outside of St. Charles, Mo. Unfortunately, Peruque is scab susceptible and this year scab was especially difficult to keep under control. This morning, I passed by a Peruque tree and noticed all the nuts blackened by the scab fungus. I pulled off an handful of nuts to show you how the severity of scab infection impacts nut size and kernel fill.

    The photo above shows a series of Peruque nuts with shucks infected by pecan scab. With increasing infection coverage of the shuck, nut size is reduced. Scab does not shrink full-sized nuts to a smaller size. Rather, scab infection that occurs during the early portion of the nut sizing period inhibits further fruit expansion. 

    Using the same five nuts, I cut each in half to reveal the kernels inside (photo above). Although all five nuts look like they have well developed kernels, scab did impact kernel fill. Look at the thickness of the inner wall partition in each nut. The nuts with the least amount of scab has thin, compacted partition. As the amount of scab increases, the thickness of the partition increases. In other words, increasing scab decreases the thickness (and plumpness) of the kernel halves. In the end, heavily scab infected nuts will have far less percent kernel.
    The key to controlling scab on Peruque is to start applying fungicides right after pollination and then continue making regular applications all during nut expansion  (late June through July). The early sprays are the most important. As you can see from the nut photos above, light infections caused by infections that start later in the season have far less impact on nut size and kernel quality than infections that got started earlier in the year and covered the entire shuck surface.

Friday, September 11, 2015

Pecan crop advancing towards shuck split

 This week, I drove through our field trials to check our earliest ripening pecan cultivars for signs of shuck split. Every year the order of ripening among cultivars is a little different and this year was no exception. The photo above shows four cultivars that had nuts completely separated from their shucks on September 10th. SWB617 and Henning were not only fully loose in the shuck but some of the shucks had started to open (see photos at the bottom of this post). In contrast,  I had to use a knife to remove the shucks on Warren 346 and Canton and did not find any nuts on the trees with split shucks. This photo also reveals that all four of these early-ripening cultivars needed additional drying time to develop their full shell color.

    This next group of four early-ripening cultivars had shucks that had separated from the nut's shell but required varying degrees of force to remove the shuck (photo above, right). Lucas was fully loose in the shuck and was similar to Warren 346 and Canton in terms of shuck dehiscence.
    Even though I was able to cut the shuck off the Mullahy nut, shuck was still tightly attached at the very base. Osage and Peruque had started the shuck separation process but the white coloration of the shell indicates these nuts have only recently separated from their shucks.

 This last group of cultivars (photo at right) illustrate the very early stages of shuck separation. The Shepherd nut was about 3/4 separated from the shuck while James and Colby had only just begun the process at the very tip of the nut. Like the nut filling process, shuck dehiscence starts at the apex of the nut and works it way down to the base.

   This is the first year I have caught SWB617 at the point of 50% shuck split (Photo at left). I knew this seedling ripened early but I never got around to actually seeing how early. Even though this seedling is mildly susceptible to pecan scab, the extreme earliness of SWB617 makes this a special tree to watch.

    Historically, Henning has been the earliest ripening cultivar in our trials (Photo at left). On September 10th, Henning was about 10% shuck split. Our Henning trees are located near the boundary of our research station. By next week, I better get a nut sample collected before the squirrels harvest every last Henning on the farm.

Wednesday, September 9, 2015

Fall Webworm outbreak

   The white webs are everywhere. Street trees, yard trees, and trees along the highway all seem to be covered by numerous colonies of the fall webworm. Last month, I photo graphed some fall webworm egg masses and predicted that we would be seeing an severe outbreak of this pest this fall. And sure enough, if you didn't spray your trees back in August, your trees are probably covered with webs.
    The photo at right shows a young tree in covered with webworm colonies. When I look at this picture, two questions pop into my mind : 1) Will webworms cause long term damage to this tree? and, 2) Why do the webs look so much bigger than usual?
   Fall webworm larvae can totally defoliate a young tree by mid-September. However, branches and dormant buds are untouched by the caterpillars. This means that limbs, defoliated in early fall, will typically remain in a dormant condition until next spring. The true long-term impact of webworm defoliation is a little harder to see.
    Losing leaves 6-8 weeks early means less time to build carbohydrates via photosynthesis and ultimately less stored energy for budbreak the following spring. The result is a weaker spring flush of growth and a slow down of tree growth rate. Fortunately, trees can overcome this lag in growth rate by supplying trees with ample soil nitrogen in early spring. 

    This fall's webworm colonies appear larger because the colonies actually have more caterpillars within each web. Over the years, I've looked at a lot of fall webworm egg masses and they always seem to be roughly the same size. This would mean the size of a colony's  web should also be about the same size each year. However, this year, there were so many egg masses laid that sometimes two egg masses appeared on a single leaflet (photo at left).  When two egg masses hatch in close proximity, caterpillars eventually coalesce and become like one big colony.  This year, I've seen young trees totally covered by webs in what looks like one huge webworm colony. However, what I'm actually seeing is the result of multiple webworm colonies competing to consume every last bit of green leaf tissue from the tree.  

Tuesday, September 1, 2015

How full are pecan kernels today?

    The first day of September was a good day to check on the development of the 2015 pecan crop. I collected nuts from 14 different pecan cultivars ranging from the very early ripening Warren 346 to the late ripening (late for SE Kansas) Mohawk. I cut a nut from each cultivar in half so I could look at kernel development. Remember to click on each photo and you'll get a much larger view of the nuts in cross section.

   The photo above shows five early-ripening cultivars. Warren 346 is fully packed with kernel with all the internal packing material compressed to a orange-brown color. Shepherd and Colby nuts are largely filled with kernel but the light color of the packing material indicates that nut fill is still progressing. The Osage nut has a kernel that still has several air gaps. However the color of the packing material indicates that kernel fill is nearly complete and we might be left with a poorly filled nut meat. Faith is typically an early maturing cultivar however this nut has a long way to go in filling out the inside of the shell.

  This second group of cultivars (photo above) includes nuts that typically ripen during the first 10 days of October. Posey, Yates 68, and Surecrop kernels have filled all the space inside their shells except for a fine line down the middle of each kernel half. Major and Kanza have a lot of kernel filling to go. These two cultivars have developed only a thin layer of kernel. It looks like Major and Kanza may ripen later than normal this year.

     The final group of cultivars represent pecans that typically ripen during the last two weeks of October. Mohawk is still in the water stage with only the slightest evidence of kernel deposition. Mohawk is also the latest ripening cultivar among these four pecans. Greenriver was still mostly water but the nut has developed a visible layer of kernel just inside the seed coat. Both City Park and Lakota have a visible layer of white kernel and a prominent layer of "gel" inside. This gel layer will soon solidify and become solid white kernel. 

    A pecan enters the final stages of nut maturation when the shuck begins to separate from the shell. This process starts at the apex of a nut and works towards the base. Of all the nuts I collected on September 1st, only Warren 346 showed the first signs of shuck separation (photo at right). Over all, nut development this year seems behind schedule. This is probably due to the cooler than normal summer we have experienced in 2015. However, plentiful rainfall during August should guarantee excellent kernel quality at harvest.