- -   AGRICULTURE CORE CURRICULUM  - -


(CLF7000)  Advanced Core Cluster:  PLANT AND SOIL SCINECE

  (CLF7600)   Unit Title:  PRUNING

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  (CLF7607)   Topic:  TREATING PRUNING        Time      Taught in Year(s) 
                      WOUNDS                 1 hour          3 AND 4       
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         Topic Objectives:  Upon completion of this lesson the student will 
         be able to:

         Learning Outcome #:

           (K-13)  -  Discuss when it is appropriate to treat pruning wounds 
                      and demonstrate the proper methods of treatment.

         Special Materials and Equipment: None

         References: Shigo, A. L.  (1986).  A NEW BIOLOGY: FACTS, PHOTOS, 
                       AND PHILOSOPHIES ON TREES AND THEIR PROBLEMS AND 
                       PROPER CARE.  p. 595

         Evaluation: Quiz by instructor

TOPIC PRESENTATION:  TREATING PRUNING WOUNDS

A.  If the tree is properly pruned and maintained, large pruning cuts will 
    be kept to a minimum.

    1.  Cuts need to be made close to the limb from which the branch arises.
        This will promote rapid healing.

    2.  Treatment of pruning wounds depends on local conditions.

        a)  In areas with fog or damp climates pruning cuts need to be 
            disinfected as soon as the wood is dry.

        b)  In areas where the air is dry, pruning wounds seldom need 
            disinfection.

B.  There still continues to be a controversy over the effect of treating 
    primary wounds.

C.  Very few compounds that are normally used have been found to give
    desired effects.

D.  Usually untreated trees do as well as those that have been treated with 
    the various compounds sold for this purpose.

E.  The common products sold for wound treatment usually are petroleum 
    emulsions and contain some fungicidal compounds.

F.  Trees respond to wounds by forming boundaries.

    1.  Boundaries defend the trees transport system, energy storage areas 
        and mechanical support systems.

    2.  They also resist the spread of fungi and other pathogens into the 
        wood.

    3.  To properly treat a mechanical wound as those caused by shaker 
        damage or breakage caused by wind or fruit load, remove injured 
        bark and wood but do not enlarge the wound.  Do not treat the 
        wounds.

    4.  When making large cuts do not make a flush cut.

        a)  Cut as close as possible to the limbs collar, but leave the 
            collar,

        b)  do not leave stubs, and

        c)  do not treat the cuts.

    5.  Flush cuts and wound dressings stimulate large callus that rolls 
        inward and prevents wound closure.

G.  There is increased concern over mechanical injury caused by shakers used
    to harvest almonds, peaches, prunes, walnuts, and some other fruit
    species.

    1.  Researchers are finding that this damage caused by current equipment
        can be reduced.  Some of their suggestions are:

        a)  Reduce clamping pressure (no more than 150 psi applied to a 
            tree trunk),

        b)  use proper size and type of clamp,

        c)  use one slightly longer shaking cycle instead of two or more 
            shaking cycles,

        d)  discontinue irrigation two weeks prior to harvest, and

        e)  train shaker operators to approach trees carefully.

    2.  New designs of trunk shakers that cause less tree damage are being 
        developed.

H.  Bleeding of grafting cuts can be heavy on walnut trees, grapevines, and 
    some ornamentals.

    1.  Bleeding of susceptible trees can be minimized if cuts are kept to 3 
        inches or less and made in the fall or early winter.


    2.  Bleeding is most likely when severe pruning is done just before 
        growth begins in the spring.

        a)  It is usually not harmful to the tree, and

        b)  if it is heavy and persistent, it can cause bark injury below 
            the pruning cut.

    3.  At grafting time, bleeding can often be so profuse that it will 
        float the wax off the grafted stub.

        a)  Kerfing (sawing) at the base of a grafted tree will help release 
            the pressure and help control the bleeding.

        b)  A cut should be made on both sides of the crown making sure that 
            it is deep enough to go through the cambium.

          __________________________________________________________
          ACTIVITY:  
                      
          1.  Demonstrate to the class the proper way of cutting
              a large branch.

          2.  Demonstrate to the class the proper method of treating
              a tree wound.

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7/25/90 sg

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