Making a second scab spray

    Last Sunday we had over 3 inches of rain. 2019 is turning out to be a wetter than normal year for us and it has made great conditions for the spread of pecan scab. Today, I walked over to the cemetery (across the road from my farm) to inspect nuts growing on unsprayed trees. It didn't take too long to spot some black scab lesions forming on a young pecan (photo at right).

    With this year's heavy rain fall pattern I knew it was time to make my second pecan scab spray. Despite the water soaked soil in the pecan grove, I started up the sprayer and sprayed the grove. Many farmers may criticize me for rutting up the field, but waiting for better field conditions may have been too late for keeping me  ahead of pecan diseases (photo at left). For this application, I used Flint fungicide.

Spraying pecans to prevent diseases

   I've been scouting pecans for pecan nut casebearer every-other-day but as of June 11, I haven't seen anything. What I have seen, is lots of pecans. Every native pecan tree in our area seems to have a nut cluster on every terminal. In addition, my improved cultivars have a great crop. So this year I've decided to change my pest control priorities and concentrate on preventing pecan diseases.

    The photo at right shows a typical cluster of Gardner pecans. Gardner is a scab susceptible pecan cultivar that produced high quality large pecans. Right now every nut in the cluster is clean; no casebearer and no scab. If all the nuts currently set on this Gardner tree stay perfect until August, I'll need to shake about half the crop off the tree to insure good kernel fill and a decent return bloom.
   A light infestation of casebearer would actually be beneficial in helping thin down the crop. In sharp contrast, there is no way I want to allow scab to get established on this year's nut crop.
   Looking at the weather predictions for the coming week it looks like we can expect several rainy days. With the rain comes high humidity and perfect conditions for scab to spread. So today, I sprayed my trees with a systemic fungicide that will work to prevent scab infection for the next 10 to 14 days.
   I sprayed the fungicide even on scab resistance cultivars such as Kanza, Hark, and Lakota because these cultivars are not resistant to all pecan diseases.  I've found that early season fungicide applications can help prevent pecan anthracnose and downy spot from creating serious late season problems during wet summers.
  I plan on making additional fungicide applications as the season progresses depending on rainfall patterns.  

Pruning a Kanza graft

    Flood waters covered my pecan grove for two weeks and the water just receded this past Monday. This week the soil had a chance to dry out and I was finally able to get out to look over some of my grafts. Today, I came across an especially vigorous growing tree (photo at right). It looks like I already had 2 feet of new shoot growth. However, upon closer inspection I found that some of the new shoots were growing from below the graft union.
   

     I had three shoots growing from the scion. The scion also produced catkins at each bud (photo left). It is not uncommon to see catkins on a new graft because these catkins actually formed inside pecan buds the previous summer while the scion was still part of a bearing Kanza tree.

   This scion also produced pistillate flower clusters at the terminals of each new shoot (photo at right). Obviously,  the Kanza scion I used for this graft was extremely fertile and ready to make pecans. A quick check of my mature Kanza trees revealed that they too set a big flower crop. So, I wasn't too surprised to find pistillate flowers on this graft.

   The first step in trimming this graft is to remove all stump sprouts (photo at left). Since the flood prevented me from trimming this tree earlier, one of the stump sprouts had already grown more than 2 feet in length. By trimming off all the stump sprouts, I'll be forcing all the tree's energy into growing vigorous scion shoots.

    My next step was to prune the scion down to one shoot (photo at right). Here I am selecting my new central leader--I want the tree to focus on growing a strong straight trunk.

   To keep the new central leader growing vegetatively, I used my clippers to snip off the terminal flower cluster (photo at left). The terminal bud just below the flower cluster will break quickly and I'll see rapid growth of the scion resume.

    To prevent possible wind damage to the tender new growth, I used green flagging tape to tie the scion shoot to the bamboo stake I had placed on the tree when I grafted over a month ago.  Before moving onto the next tree, I set a wire cage over the graft to prevent deer from browsing on the tender new shoot.

A bad case of pecan leaf phylloxera

    I have been scouting pecan trees for signs of pecan nut casebearer activity and have made a couple of important observations. I haven't seen any casebearer as of today, June 7th and every native pecan I've looked at is loaded with nuts. It looks like 2019 will be a year of over-cropping and it may beneficial to skip the casebearer spray and to allow casebearer to help thin the nut crop.

    During my rounds of looking at wild pecan trees for casebearer activity, I came across a tree with the worst case of pecan leaf phylloxera that I have seen in a very long time (photo at right). The pecan leaf phylloxera is an aphid-like insect that causes the tree to form galls around these plant sap-feeding insects. Note that the galls are confined to the leaf blades.
   

    Once the galls are formed, there are no control measures for this pest. Later this summer, all seriously gall infested leaves fill drop from the tree. 
    Insecticide treatments are effective for control of this pest but must be applied before galls form over the insect. For pecan leaf phylloxera, a single insecticide application made at leaf burst will control this pest. Mark infested trees this summer and plan on spraying those trees next spring.
    You can read more about the pecan leaf phylloxera in a previous post.

The mystery of pecan grafting

    Early this spring, I decided to top work a fairly large tree with the idea of creating a tree just to grow Pawnee scionwood. This particular tree had two main stems, each about 2.5 inches in diameter. I used my chainsaw to cut the top out of the tree and then placed two bark grafts on each of the cut stems (photo at right).  In normal circumstances, I top work a tree by placing just one graft on the central leader. However, because my goal was to produce scionwood, I choose to make multiple grafts to increase the number of new shoots produced.
   Three weeks after grafting, the buds on the scions started to show signs of life. To my surprise, bud break varied widely among the 4 scions. Now this was interesting. I had grafted 4 Pawnee scions onto the same tree using the exactly same grafting method but I achieved different results.

    The photo at left shows a pair of bark grafts growing from one of the main stems. Note that the graft on the left is more advanced than its companion on the right. Why the difference? I have no easy explanation.

   Moving over to  the other set of grafts (photo at right) you will note that one graft is starting to form new shoots while the other has only swollen buds. Again, why?
     For the time being, I'm going to just sit back and watch these 4 grafts as the season progresses. When I unwrap the grafts later this summer, I might spot an explanation for these differences in performance. However, sometimes the mystery of grafting success (or failure) forever goes unsolved.