Saturday, July 31, 2021

Checking pecan kernel development

     Its that time of year when I really start to notice the pecan crop hanging on my trees. The photo at right shows a cluster of Kanza nuts as they appeared 30 July 2021. At this point in the growing season, pecan nuts are in the phase of rapid fruit expansion  meaning that the nuts you see in the photo will almost double in size over the next 2 weeks.

   To check on the development of the kernel inside the nut, I took samples from several pecan cultivars and cut them open (photo at left). The kernels were less than one half expanded and still filled with liquid endosperm. Compared to previous growing seasons, this year's pecan crop is well behind schedule. An early maturing cultivar, such as Gardner, is usually at full water stage by the first week of August.  Since nut development is delayed this year, I expect pecan ripening (date of shuck-split) to be later than normal.

   If you remember back to earlier this Spring, we had a much cooler than average month of May. This lack of heat delayed the pollination season and slowed the embryo fertilization process. The net result has been that the normal biological clock for kernel development got a very late start.

   From a practical viewpoint, the delay in kernel development will impact the proper timing for crop load management and sprays for pecan weevil.  

Thursday, July 8, 2021

3-flap graft aftercare

     During the last week of June and the first couple of weeks of July, I try to visit every successful graft I made this year.  Pictured at right is a 3-flap graft made with a Kanza scion. The scion has made good growth but the rootstock below the graft has also sprouted several vigorously growing shoots. During this time of year, I like to prune off all rootstock sprouts and trim the scion down to a single shoot.

      Just by removing the rootstock sprouts, this graft looks to have made a good start towards growing into a strong central leader tree (photo at left). However, there remains a few more details that need attention.


    Earlier this Spring, the new shoot that sprouted from the scion terminated in a pistillate flower cluster (photo above left). The development of a flower cluster temporarily slowed the grow of the shoot but the terminal vegetative bud adjacent to the flower cluster eventually broke and started to grow. To promote the growth of that vegetative shoot, I pruned off the flower cluster (photo above right).

       In trimming the scion down to a single shoot, I made two additional cuts. The first was to remove a shoot developing from the secondary bud just below the main new shoot. And the second was to remove the stub above the new shot. By making an angled cut, I will encourage the rapid healing over of the cut at the top of the scion.

    To prevent the graft from becoming girdled by the grafting tape used to make a 3-flap graft, I remove all wraps from the graft at this time of year. Once the tape is removed you can easily see the flaps tightly attached to the scion (photo at right). You will also note white callus tissue growing in the cracks between the flaps. Also notice how this callus tissues causes the graft union to swell especially near the base of the graft. This is normal for 3-flap grafts. In a few years, the swelling at the graft union will disappear.

    Rapidly growing callus tissue is very susceptible to  sunburn and requires protection. To block the sun, I re-wrap the graft  union with aluminum foil and tie it on with grafting tape (photo at left). The grafting tape is tied just tight enough to hold foil in place so it can't be blown away by the wind.


    The final step in mid-summer graft care is to tie the new scion shoot to my tree training stake (photo at right). I use flagging tape to gently hold the shoot in place. Tying  the scion will prevent shoot breakage that can occur during strong summer storms.  The wire cage seen in the background of this photo will be placed over this young tree to prevent deer damage.


Saturday, July 3, 2021

Weather dictates disease and insect control measures


    During the last 5 days of June it rained every day for a total accumulation of over 5 inches. With all that rain, the Neosho river spilled over its banks and flooded my pecan grove. The excessive moisture provided excellent conditions for the spread of pecan diseases but I was forced to wait until the flood receded before starting up the sprayer. While waiting to spray a fungicide,  I also noticed several colonies of Japanese beetles (photo at left) starting to feed on pecan leaves. 
      Japanese beetle has been a pest in the US for also 100 years and has moved slowly westward across the continent. For SE Kansas, Japanese beetle is a new pest that I first noticed only 5 years ago. This year, the beetle population has grown large enough to present a significant threat to pecan foliage.
   The damage on pecan is easily spotted high in the tree's canopy. Beetles feed on foliage in large groups leaving areas of tree canopy with a lace-like appearance (photo at right). This photo was taken a few hours after an insecticide and fungicide application so the beetles are gone but evidence of their activity remains. I just wish I had a way to capture the wild buzzing of beetles around the tree when I hit them with the air-blast sprayer. While driving the sprayer a blistering 1.9 MPH, I was able to get a pretty good feel for the large number of beetles that had been feasting on my trees. 
   During the morning of spraying, I also noticed a single fall webworm colony (photo at left). The insecticide I used to control Japanese beetle will also kill the larvae inside this single web. However, the appearance of this webworm colony serves as a reminder that I will need to stay vigilant with my pecan pest scouting efforts.
    Starting at sunrise this morning (3 July 2021), I sprayed my orchard using Quilt fungicide and Mustang Maxx insecticide.