Monday, September 30, 2013

Pecan cultivars that matured by September 30

Canton, 30 Sept. 2013
     I spent this afternoon checking on the development of our 2013 pecan crop. This week I found some additional early-ripening cultivars with split shucks. Most of these are cultivars that have originated as seedling selections for northern pecan states. Two are USDA introductions. Osage is a USDA cultivar with very early ripening but can be injured by cold winter temperature. USDA 64-11-17 is early ripening but is not consistently productive and I would not recommend it further propagation.
    Cultivars I found ripe since last week are pictured at right and below.

Goosepond, 30 Sept. 2013

Lucas, 30 Sept. 2013

Norton, 30 Sept. 2013

Osage, 30 Sept. 2013

Shepherd, 30 Sept. 2013

USDA 64-11-17, 30 Sept. 2013

Wednesday, September 25, 2013

Early ripening pecan cultivars open shucks

Henning, 25 Sept. 2013
    This morning, I found three pecan cultivars had split their shucks; Henning, Mullahy, and Warren 346. Photos of ripe nut clusters for each of these cultivars  are found at right and below.
    Last year, I found these same three cultivars had opened their shucks by Sept 4th. That is three weeks earlier than this year. Of course most of you remember that last season (2012) we had an early spring and everything ran two weeks ahead of normal. This year we are running about a week later than normal.
Mullahy, 25 Sept. 2013

Warren 346, 25 Sept. 2013

Tuesday, September 24, 2013

Nut development: 24 Sept. 2013

    Each week I've been documenting the development of three pecan cultivars; early-ripening Osage, mid-season Kanza ripening  , and late-maturing Maramec. This week I found that Osage had quickly moved to develop shell color and create separation between shuck and shell (photo at right).
    This morning I pulled three Osage nuts from a tree and found some variation in the shuck dehiscence process. None of the nuts had split shucks but the nut on the left had fully developed shell color and was completely separated from the shuck. The nut in the center had fully separated from the shuck but was still developing normal shell color. The nut on the right was 3/4 separated from the shuck.
    Why such variation in nut ripening all from the same tree?  For anyone that has every searched for ripe fruit on a peach or apple tree, the answer is simple: location, location, location. The nut on the left was taken from the upper portion of the tree's canopy. The nut in the center was collected from a lower limb while the nut on the right was pulled from an interior limb. Just like fruit trees, sunlight exposure effects the speed of ripening of pecans. Nuts in the upper portions of the canopy will split shuck first followed by nuts on lower limbs. Nuts developing on interior branches will be the last to ripen.

    When I checked Kanza this morning, I found that the kernel was completely packed with kernel (photo at left). Although you can't see it, the kernel filling process continues all the way up to shuck dehiscence. At this point in kernel development, the tree is filling the firm kernel with the long-chain fatty acids (nut oils) that make pecans taste so good at harvest.
   Kanza had not started shuck dehiscence. I used my knife to cut into the shuck near the apex of the nut and found the shuck still firmly attached to the shell (photo above). Shuck dehiscence always starts at the tip of the nut and proceeds towards the base.

       I moved to Maramec next. This time I collected three nuts but with varying degrees of nut scab. In the photo at right I arranged the nuts by the degree of scab infection--from most (left) to least (right). Below each whole nut is a photo of the very same nut cut in cross section.
   Over all, you can see that Maramec is still trying to fill but doing a pretty poor job of packing the inside of the shell with kernel. You can also see the influence pecan scab has on nut size and kernel fill. The heavily scab infected nut is the smallest of the three and has the poorest filled kernel.

Thursday, September 19, 2013

How much scab is too much scab?

   Growers are seeing more pecan scab this year than they have in several years. Many were caught by surprise by blackened shucks that appeared after four weeks of unusually rainy weather in late-July through early-August. However, once the shuck becomes covered in scab lesions, there is literally nothing that can be done to "cure" this disease.
   The other day I was looking over some nut samples collected from 'Chetopa' pecan trees. The amount of scab I found on the shucks varied considerably (photo above). This made me wonder, "How much scab is too much scab?"
    In a previous post, I mentioned than scab infection can lead to a dramatic decrease in nut size and you can see that same effect in the photo above. But scab also impacts kernel fill and shuck opening.
    The three small nuts on the right side of the photo are completely covered by scab. These nuts may have some kernel inside but the shucks will never open at harvest. These 'stick-tights' will end up in the cleaner's trash  pile.
    The three nuts in the middle have more than 50% of the shuck's surface covered by scab but you can still see a little green. For these nuts, scab has reduced nut size somewhat but not as much as nuts that were completely covered by the disease. At harvest, the shucks of these heavily infected nuts will open but separation of shuck from nut might be incomplete. This can lead to a partial stick-tight  where part of the shuck remains firmly attached to the shell. Like full stick-tights, partial stick-tights are unmarketable. If the nut releases fully from the shuck, the kernel inside will be edible but percent kernel will be reduced.
    The three nuts on the left of the photo have scattered scab lesions on the shucks. This level of scab infection did not effect nut size and will have no effect on shuck opening or kernel fill. It seems pecans can tolerate a little bit of scab but once lesions start to cover more than 50% of the shuck's surface, yield losses from scab will be significant.

Tuesday, September 17, 2013

Nut development: 17 Sept. 2013

    After a month of dry weather, we finally received a nice rain shower both yesterday and today. The additional moisture will go a long way in helping early and mid-season ripening cultivars fill out their kernels. In the photo above, Osage kernel has fully filled the space inside the shell with only a hairline crack still visible between the dorsal and ventral sides of each kernel half. Kanza is nearly full but minor air pockets are still present inside the shell.
    This week, Maramec is definitely starting to show indications that time is running out for this late-maturing cultivar. The kernel has developed a small layer of translucent kernel since last week but major air pockets have opened up on either side of the inner shell partition. These air pockets indicate that Maramec kernels will never fill the inside of the shell and nut quality at harvest will be poor at best. Rain this week might help, but I'm already expecting to see most of our Maramec nuts on the burn pile this fall. 

Thursday, September 12, 2013

Double row pecans: From intercrop to covercrop

    In 2003, we planted a new pecan orchard using a double row planting plan that created a wider spacing for intercropping while maintaining adequate tree numbers to allow for early economic returns from nut production.
    Over the years, we had planted and harvested wheat, oats, and soybeans all during a time when our young pecan trees were just getting established.  But last summer, we noticed a change in the relationship between our trees and the intercrop. The tree's root system was starting to out-compete the intercrop for water and nutrients (photo at right). Then last fall, these same trees had their first commercial crop. And by commercial crop, I mean the trees produced enough nuts to require shaking and mechanical harvest. 

    This summer we allowed the previously cropped areas of the field to remain fallow. It was time to convert from field crop to cover crop. Over the summer, we chiseled the soil to help reduce weed growth.  Last week we worked the ground with a heavy disk (photo at left) then used a spring tooth harrow to prepare a fine seed bed.

     This week we planted a combination of perennial rye grass and redtop; two cool season grasses (photo at right). The perennial rye should produce a quick and vigorous ground cover. The redtop will be a little slow to take off but once established, it should provide us with a flood tolerant grass that provides an excellent surface for pecan harvest. Now all we need is a little rain to bring this new covercrop to life.

Tuesday, September 10, 2013

Black-margined aphids coat pecan leaves with honeydew

    Our pecan leaves are getting sticky with honeydew (photo at right). A late season outbreak of black-margined aphid is currently feasting on pecan leaf sap and the sticky exudate that aphids secrete is giving pecan leaves a shiny appearance.
    Black-margined aphids feed on the underside of pecan leaflets, mainly along the midrib of primary leaf veins.  In the photo at left you can see several immature (wingless) aphids feeding. Note that the insects appear in several sizes. The smallest aphids are newly born while the larger aphids are half-way grown towards adulthood. If you look carefully you'll see white, cast-off skins of aphids that have already molted. (Aphid nymphs grow larger by casting off their old small skin, or more accurately "exoskeleton", and growing a larger skin.)
    The photo at right shows a winded adult feeding on the midrib. The black markings on the outer margin of the adult's forewing is what gives this aphid its common name. The scientific name for this pecan aphid pest is Monellia caryella.
       The appearance of large amounts of honeydew on pecan foliage attracts large numbers of green and brown lacewings. These beneficial insect are voracious aphid predators. The larvae of lacewings are common known as aphid lions.
   The green lacewing lays its egg on a silken thread (photo at left). A single female produces 200 to 800 eggs and from the number of eggs I've found on our honeydew-covered trees, we've had plently of lacewing actively already. Unlike the green lacewing,  brown lacewings lay eggs directly on the underside of leaves or in bark crevices. Both species are important biological controls of black-margined aphid.
   At this late point in the season, I do not recommend trying to control black-margined aphid chemically. Eventually, lacewings and lady beetles will cause the aphid population to crash naturally. A good thunderstorm would also help in removing the honeydew from the foliage.  

Monday, September 9, 2013

Nut development: 9 Sept 2013

   We've had another week of hot and dry weather and our pecans continue to fill out their kernels. Osage looks much the same as it did last week. A good rain shower would really help pack even more kernel inside the shell of Osage.
    Kanza has changed the most since last week. A week ago, Kanza kernel deposition had barely started. This week much of the inside of the shell is packed with kernel. Kanza, like Osage, still has discernible air spaces inside in the kernel, indicating that the kernel filling process is not yet complete.
   This week, Maramec has developed just a hint of kernel deposition. Note the thin layer of translucent green kernel that appears just on the inside of the seed coat of the kernel.  It also looks like our Maramec nuts will be smaller than normal this year. Scab has been difficult to control on Maramec this year and small nut size is only one of many negative affects pecan scab has on nut growth and development.

Saturday, September 7, 2013

Flat headed apple tree borers make a mess.

   I was mowing the other day when I spotted what looked like a long steak of mold growing on the bark of one of my young pecan trees (photo at right). Oh no! Is this something new I need to worry about? Am I going to lose this beautiful, well-shaped tree? I finished mowing, put up the tractor, then came back for a closer look.

   Upon closer inspection, I found several trees with prominent stains on the bark,  usually centered around the upper side of a branch connection (photo at left). The stain appeared water soaked (dark brown) on the outer margins and fuzzy light-grey near the center. It definitely looked like I had an actively growing fungus on the surface of the bark.
   It all became clear when I looked at the other side of the tree and found a neat pile of insect frass in the crotch of the tree (see red arrow, photo at right). Now I know whats going on here. I don't have a strange new disease on my trees I simply have some actively working flat-headed apple tree borers.
   These common wood boring insects are often found in young pecan trees, especially in orchards that have yet to receive regular applications of insecticides aimed at controlling nut feeding pests. However, the staining on the outside of the bark is not normally associated with apple tree borers.
   The stains are a result excessive sap flow that occurred in response to the heavy rains we experienced from July 21 to August 12 (> 15 inches). Sap flowed into the wood borer's tunnel then spilled out onto bark surrounding the branch crotch. Since tree sap contains several forms of carbohydrates, the sap-soaked bark combined damp weather conditions provided an excellent environment for the growth of the common grey mold fungus.
    Since mid-August, the weather has turned off hot and dry. No new sap is flowing from wood borer tunnels and the grey mold fungus has stopped growing. However, the stains have remained and will remain until winter rains scrub the bark clean.
   One final note. Apple tree borers do only slight damage to the tree and rarely require chemical control.

Friday, September 6, 2013

Rainfall and pecan weevil emergence

Pecan weevil larva feeding on pecan kernel tissue
   A large part of being a successful pecan grower is learning how to adapt to changing weather conditions. This year nut development was delayed by a cool spring and has remained at least two weeks behind normal all season long. But this summer we also experienced  above average rainfall in late July and early August that promoted early pecan weevil emergence.
    Late developing pecans. Early weevils. This year's weather patterns have created a unique pest control challenge. In the chart below, I've recorded both rainfall and weevil trap catches. We had over 15 inches of rain from July 21 until August 12. Since that time, the rain has completely stopped and at this point things are starting to look dry again.
    We captured our first weevil on July 31 with emergence peaking from August 5 to August 21.  As our soil has started to dry out the number of weevils we have captured dropped off dramatically.


     The combination of early weevil emergence and late kernel development has meant that, for the entire month of August, adult weevils could not find a place to lay eggs. However, pecan weevils are patient creatures. They simply feed on developing pecans (causing nut drop!), while they wait for the pecans to start creating kernel.  Because of the large number of weevils that emerged in early August, we sprayed our pecan grove starting August 14. Now I'm wondering, when it rains again this month, will we get a second flush of weevil emergence? Late emerging weevils will find plenty of places to lay eggs now that our pecan crop has started to fill kernel. And I certainly don't like finding weevil larvae in my cracked pecans at harvest time. This year, we'll be checking our weevil traps well into October.

Tuesday, September 3, 2013

Nut development: 3 Sept 2013

     The calender says its September, but nut development looks more like August. Even after the return of summer temperatures (lows in the 70's, highs in the 90's) pecan devlopment is very late this year.
      Since last week, Osage has really packed in the kernel (photo at right). If you look at last week's post you'll find that Osage had just started to lay down kernel tissue. This week much of the interior of the nut is filled with kernel with only a few air pockets remaining. For Osage, the kernel filling period is not over but is nearing an end.
    This week Kanza has started to lay down a thin, translucent layer of kernel (photo at left). Compare this photo to the photo of Osage taken last week and you'll see how similar they look. Will Kanza nuts fill out most of their kernel over the course of this week. The forecast for continued summertime weather bodes well for rapid kernel fill.
    The kernel cavity of Maramec has enlarged since last week but kernel deposition has yet to begin (photo at right). The average date of first fall freeze in our area is October 25. Will Maramec develop in time? Will have to wait and see.

Sunday, September 1, 2013

Notes on planting pecan trees: Reality vs. expectations

   A couple of years ago when record prices were paid for pecans, growers got very excited about planting new trees. The thinking at the time was, "If I can move the large seedling trees I already have growing in fence rows, I can fill in some orchard gaps and increase production in no time at all."  Over the winters of 2011 and 2012, hundreds of 1 to 2.5 inch diameter trees were moved with a truck-mounted tree spade in the Chetopa, KS area.
    Unfortunately, many of these transplanted trees have suffered serious dieback (photo at left). Two summers of drought (2011 & 2012), the total lack of weed control, and no irrigation has caused most of these transplanted trees to die back to the ground. These tree are not completely dead, you can spot a few new pecan shoots sprouting up from the base of the tree.
     In the photo at left, a red arrow points to the basal sprouts that have emerged this summer (A response to this year's much needed summer rains).  This tree is struggling to get back to a sustainable balance between roots and shoots. Initially, the tree spade cut off a large amount of the tree's lateral root system. Then the drought caused even more root loss. Without an adequate water supply supplied by the roots, the top of the tree simply burned up. Two years later, the surviving roots are trying to re-establish leaves and stems to provide  the photosynthetic energy necessary for tree survival.
   A lot of time and money was spent to move big trees in an effort obtain quicker nut production. Now two years later, the transplanted trees are just barely surviving. The moral for this story is: If you spend a lot of money to transplant large trees, expect to spend even more time and money in keeping them alive. Weed control and water, lots of water, are essential.

    At the Pecan Field, we decided to transplant one-year-old container-grown trees out into the gaps of our orchard (photo at right). I have always felt that the younger a tree is when transplanted, the better that tree will handle transplant shock.
    We learned a valuable lesson last year, when transplanting container grown trees out into the field. The deer seem to love destroying nursery grown trees. So, now we cage each tree right after transplanting.
    We have watered these trees during dry periods and tried our best to suppress the weeds (looks like some crab grass is coming in). Despite all of our best efforts to minimize transplant shock, I notice that most of these seedling trees have sprouted basal shoots--an indication that the tree is readjusting itself to a new growing environment. In our heavy clay soil, its not until the third year after transplanting that these seedling trees start to take off.

    The best way to avoid transplant shock is to never move a pecan tree in the first place. On my farm, I've gotten very good at spotting pecan seedlings amongst the weeds and grass from the seat of a tractor while brush-hogging. I carefully mow around the seedling then come back with a weed-eater to release the young tree from surrounding vegetation (photo at left). Once the tree is standing tall above the closely mowed grass, I carefully use a herbicide to kill all weeds in a seven foot circle around the tree.
   Letting nature plant your trees has the advantage of avoiding transplant shock but results in a completely random distribution of trees across the field. Since I've spent most of my career around native pecan groves, weaving around randomly positioned trees to mow, spray, and fertilize seems only natural. However, the total lack of straight rows would drive others completely crazy.
   When mowing around naturally occurring seedlings, I leave the most vigorous growing seedlings I find. These trees will make good rootstocks for my grafting efforts. I allow 30 to 40 feet between trees using my 10 foot brush-hog as a rough guide.  I allow the trees to grow to about 1.5 to 2.5 inches in diameter before applying a bark graft.