Anatomy of a narrow branch angle

   Whenever I talk about pruning pecan trees, I mention the importance of avoiding narrow angled branches. The photo at right is an example of  pecan branches that have formed a narrow angle. Note the bark crevice where the two branches come together and the ridge of bark that extends down from the narrow angled crotch. After cutting these branches out of a tree with a chain saw, I was able to break these branches apart just like breaking a turkey wishbone.
     In the photo below, you can see why narrow angled branch connections are so weak. First, look at the bark that surrounds the exposed wood. Note that at the top of the branch connection, the bark is grey, the same color as the outside of  the branches. This was the area of the bark crevice we saw in the photo above. Along the sides of the exposed wood, the bark is tan indicating the portion of the bark that was split open when I broke apart the limbs.

    
    Extending downward from the bark crevice and into the wood is a dark area known as a bark inclusion. Bark develops inside the narrow angled branch connection in response to the opening between the branches (the bark crevice). Once a bark inclusion becomes well established, the only wood fibers that hold these branches together are long grain fibers found on sides of the branch connection.  Long grain fibers split apart easily, just like splitting firewood.
    Some pecan cultivars tend to produce more narrow angled branches that others. Removing stalked buds during young tree training can minimize problems associated with bark inclusions.

Pecan Nut Casebearer Trap Catch Data

    The table below represents the capture of pecan nut casebearer moths we have set out around the state of Kansas. The casebearer moth flight begins in southern most counties and works northward over time. Growers should start scouting their orchards for damaged nut clusters 10 days after the moth flight has begun. You should starting seeing larval activity 12 to 16 days after first moth capture. Control measures should begin when you see first significant nut entry (2-3% of nut clusters have larvae feeding on nuts).
    Check this post regularly for data updates including additional locations.  General information on casebearer can be found here.

Trapping Pecan Nut Casebearer

    The pecan nut casebearer is a major nut feeding pest. Shortly after the pollination season casebearer moths lay eggs near the tip of young nutlets.  The larvae that hatch from these eggs crawl down to the base of a nut and start feeding. The insect chews its way into the center of the nut, hollowing out the inside. You can identify casebearer feeding by the light strands of webbing the caterpillar uses to fasten nuts to the stem (so the damaged nut doesn't fall off) and by the pile of frass at the base of the nut (photo above).
     Each spring, we monitor the activity of the insect by using pheromone and orchard surveys.This year, I've enlisted the help of several growers around the state of Kansas to follow this year's casebearer moth flight using pheromone traps.

    Pheromone traps are easy to use as long as you can identify the target insect.  In the photo at left, two male casebearer moths have become stuck in a trap. The moths are grey, about 3/8 inch long, and feature a prominent ridge of scales across their wings. You can see other insects caught in the trap and even a fallen catkin, but casebearer moths will be the only insect that have a ridge across their backs.
    The spring 2011 flight has begun in the southern most areas of Kansas as of May 20.

Holes in pecan leaves

    If you walk through a pecan grove at this time of year, you are bound to find some new leaves riddled with irregularly shaped holes (photo at left).  These holes were created by the feeding of sawfly larvae.

    The sawfly is not a fly at all but actually a member of the wasp family. The green larvae of this insect are smalll (follow red arrow) and always feed on the underside of the leaf. Sawfly larvae look like caterpillars but have legs on every body segment (moth larvae have some body segments without legs).
     We monitor sawfly populations every spring checking for outbreak population numbers. In years past, sawfly populations have grown so large as to require a pesticide application. This year, the population numbers have remained relatively low and will not require treatment.