Thursday, August 30, 2018

Pecan kernel filling

    I cut open a Kanza nut today and captured the kernel filling process in progress. The first thing I noticed when slicing the nut in half is that the shell was completely hard. In the photo above, the arrow marked "S" points to the shell. At this point in time, the outer shell of the nut is fully formed and light tan in color.
    The arrow marked "K" points to newly formed pecan kernel. The white creamy color is what we expect pecan kernel to look like. However, inside the white kernel layer is a translucent layer I've marked "J". This is rapidly forming kernel tissue that has yet to fully differentiate into its final solid white state.  The translucent appearance of this not-yet-fully-formed kernel tissue is the origin of the term "gel stage".
    When I first started working with pecans I was given the impression that kernel development progressed from water stage, to gel stage, to firm kernel. It was almost like the water turns to gel then solidifies into kernel. This is not how it works.
   New kernel tissue develops starting from just under the pecan seed coat. As new kernel tissue develops, the water inside the nut is absorbed back into the tree. The amount of "gel" that can be seen inside the nut is dependent on the speed of kernel formation.  The rate of kernel deposition is influenced by weather conditions and cultivar. This is the most "gel" I've ever found inside a Kanza nut. In past years, the gel layer was much thinner.  
   Kernel deposition is not the only pecan tissue I've seen with this translucent appearance. Back during grafting season, I noticed several stock trees with a layer adjacent to the cambium that had a water soaked or gel type look. This was obviously new wood tissue being formed that hadn't fully solidified. 
     Now when I think about pecan kernel development, I think of it in two stages. The first is "ovule expansion". Ovule expansion occurs during the first half of the growing season as pecan fruit grow rapidly in size. The culmination of this stage occurs when the nut achieves its full size and the inside of the nut is filled with water.  The second stage is "kernel deposition". Kernel begins to develop on the inside of the seed coat and works it way towards the center. Kernel deposition continues until the shuck starts separating from the shell (shuck split).

Tuesday, August 21, 2018

Making a pecan weevil spray

    After a week of showers it was time for me to make an insecticide application for pecan weevil. So, I attached my sprayer, put the tractor in 4-wheel-drive, and slogged my way over saturated ground to apply Warrior II insecticide to protect my nut crop (photo at right). It has been 12 days and nine inches of rain since I last sprayed (mainly for stinkbugs). This time my objective was to kill all weevils in the grove before they can lay eggs inside the nuts.
   I'll need to wait to see how things go during the last part of August and early September before deciding whether or not to make a second weevil spray in a few weeks.

Monday, August 20, 2018

The new pecan cultivar, 'Hark', looks promising

    We've had 9 inches of rain over the past week and I've found it hard to get out in the grove to look at pecan trees and take photos. Fortunately, the sun popped out today and I was able to take a quick look around a portion of my orchard. The nuts on most cultivars are fully sized with Kanza and Hark at full water stage. My oldest Hark tree has a trunk about 7 inches in diameter and has developed a nice full canopy (photo at right). This tree is located right next to a couple of Kanza trees so its easy to compare these two scab resistant cultivars.
    As a young tree, Hark is easier to train than Kanza. Hark seems to have a more naturally spreading growth habit and produces fewer stalked buds than Kanza. As you know, stalked buds grow into narrow-angled branches that are prone to wind breakage. Although Kanza is not a terribly hard tree to train, I do need to keep a close look out for stalked buds during the early years of tree development. 

    The 2018 crop load on Hark appears to be very similar to my adjacent Kanza trees. The nut yield won't be limb breaking but the 2018 crop appears "good" on both these cultivars. In fact, Kanza and Hark have the best nut set of any cultivars growing on my farm this year. Hark set nuts mainly in clusters of three (photo at left). This cluster size is similar to Kanza and to Major, a parent of both Kanza and Hark.
   With plenty of moisture available to fill out kernels, I'll be anxious to compare the nut quality of Kanza and Hark this coming Fall.

Thursday, August 9, 2018

Mid-summer training of a bark graft

     I've been making my way through the orchard, trimming grafts, removing stalked buds, and controlling weeds. This week I came across a prime example of a bark graft I made back in late April. The graft was pruned to one shoot growing from the scion back in June and I tied the new growth to a bamboo training stick (photo at right). The scion has grown nearly 5 feet in height. It looks impressive but this tree needs some care to keep the tree well balanced and to strengthen the central leader.
    The graft union of this tree is growing so rapidly that the new growth has split open the aluminum foil I used to wrap the graft union (photo at left). During the month of August,  I like to remove the plastic bag and aluminum foil then paint the graft union with white latex paint (to prevent sun scald). This tree appears to be more than ready to shed all graft wraps.
    Once the grafts wraps are removed you can see how the tree is healing over the graft union (photo at right). Note that the area where the scion was inserted under the bark has expanded dramatically. In contrast, the trunk on the opposite side of the scion has remained roughly the same size as when the tree was grafted. It is clear from this photo that the tree is putting all its energy into growing the scion.

   My first step in addressing the graft union is to cut away some of the dead tissue at the top of  the stock. This tree was small enough in diameter that I could use my hand clippers to make a 45 degree cut (photo at left).  Making this angled cut will help the tree heal over the wound on the stock must faster.
    Once I cut the angle, I use white latex house paint to cover the graft union (photo at right). The paint protects the graft from sun burn and serves as a simple method to mark which trees in my grove have been successfully grafted.  I use a paint brush to apply a good solid coat of paint to the area that was formerly covered by the grafting wraps.
   Next, I moved my attention to the top of the tree. I noted that the tree had developed numerous stalked buds with one already growing as a small lateral branch (photo at left). To prevent the development of narrow branch angles these stalked buds need to come off.
   I first attacked the largest stalked bud that had developed into a shoot. I needed my clippers to remove this shoot (photo at right).
    Most of the stalked buds were still small and I could just tear them off the tree. The bud scar left after stalked-bud removal is seen inside the red circle in the photo at left.  
   As I mentioned earlier, this scion is growing at a rapid pace. In fact, the scion is growing much too tall for the diameter of the central leader.  Tall skinny trees have a tendency to bend over under their own weight or snap off in a wind storm. To slow height growth and to promote diameter growth of the stem, I trimmed of the top 10 inches from the tree's central leader (photo at right).
    To look at the tree after I was done trimming and training, it doesn't look much different than when I first approached the tree. Sure, you notice the white paint at the graft union but the top of the tree looks almost identical to the tree before I trimmed it. But that's the point, a few simple steps taken now will go a long way in developing a strong, trouble-free pecan tree. Ignore these training tips now and you will probably be faced with making major corrective pruning cuts later in the tree's life.

Wednesday, August 8, 2018

Spraying for stinkbugs and weevils

   Today, I made an application of Warrior 2 insecticide to my pecan grove (photo at right).  This insecticide application was made primarily to keep stink bugs in check and to kill any early emerging pecan weevils that might have migrated into my grove from the neighbor's un-managed native pecan grove.
    At this point in the growing season, my Kanza nuts are approaching full water stage. It is too early for weevils to lay eggs but both stink bug and weevil feeding can cause serious nut drop. With our below average nut set this year, I definitely want to prevent any potential nut loss.

    My grove was established by grafting volunteer seedlings to cultivars such as Kanza, Hark, and Lakota. As a consequence, the orchard looks like a native grove with trees growing at random locations. Since the trees are not planted in rows one question often comes up: "How do you keep track of which trees have been sprayed?".  Since I use a Savage sprayer, I take into account that it is most efficient to spray in one direction at a time. I usually spray to the right side of the tractor (as pictured above). I start on the edge of the grove and spray inwards. When I get to the end of the field. I turn the tractor so that I'm 40-50 feet away from my initial path through the orchard.  Still spraying towards the right side of the tractor, I end up spraying the other side of the trees sprayed during my initial pass. When I weave through the orchard, I keep track of where I am by looking for the tire impressions I made in the tall, wet grass 40-50 feet to my right.  Once I get to the other end of the field, I turn around and retrace the tire marks I just made (the second pass through the orchard). Driving in the opposite direction on the same path and spraying to the right means I'll be spraying trees not yet receiving insecticide treatment. In the photo at left, look at the ground-cover  carefully, you can see bent over blades of grass that mark the trail I took through the grove.  I know its hard to see in the photo, but from my tractor seat I can see it clearly. By sticking to this travel pattern, I'm certain to cover every tree n the grove.
     A couple more notes on spraying. I like to spray early in the morning. The high humidity and calm winds at that time of day helps the sprayer deliver the pesticide to the entire canopy. Since I'm using a late model tractor to spray the grove, I have a digital reading of ground speed. With my 12 speed tractor, I drive in 3rd gear and average 1.9 miles per hour.  I operate the fan at full throttle.      

Thursday, August 2, 2018

Getting ready to battle pecan weevils

    When the calendar turns to August, I immediately think about controlling pecan weevils. If the soil contains enough moisture, male weevils  will start emerging in late July. By early August, females will appear. Both sexes migrate to pecan nut clusters in the hopes of finding a suitable mate (photo above).
    During this courtship phase, male and female weevils will feed on nuts causing nuts, that are still in the water stage, to drop from the tree. Female weevils will continue to probe nuts until the pecan kernel inside the nut starts to firm up. Once a female finds solid kernel they will lay 5-7 eggs inside the nut.  Our job, as pecan growers, is to prevent females weevils from laying eggs.
   Today, I walked over to a Kanza tree to check on nut development. With recent rainfall, the nuts are growing rapidly (photo at left). This is the time of year when nut clusters are clearly in the tree's canopy and I start looking forward to a successful harvest season.
    I pulled off a Kanza nut and cut it open to determined the stage of kernel development (photo at right). At this point, Kanza is about 3/4 water stage. It will be mid-August before Kanza kernels will start to firm up and become susceptible to weevil oviposition.
    In my orchard, the weevil population is very low so I'm not overly anxious to start spraying for weevil. However, I am planning to spray for stinkbugs next week and that spray should take care of any early emerging weevil adults. My biggest concern is that fact the my neighbors native pecan grove doesn't appear to have a crop this year. That means, any weevils that emerge across the fence will probably migrate over to my orchard. 
    From past experience, migrating weevils are not captured in trunk mounted traps. So this year, I'll be making a weevil spray as soon as my Kanza nuts enter the dough stage in an effort to stop migrating weevils from becoming established in my orchard.
    If you want to monitor pecan weevil emergence in your grove, I'd suggest that you build some Circle pecan weevil traps. Step by step instructions for building traps can be found HERE.