Pecan Nut Casebearer

 

    Every year pecan growers watch and wait for pecan nut casebearer. We have been monitoring casebearer nut entry for over 35 years and have achieved a pretty good feel for when the first nut damage will appear. The first thing I look for is the shedding of catkins from the latest pollen shedding tree in the grove.  Nut entry by casebearer larvae usually starts three to five days after the last catkin falls from the the latest pollen shedding native pecan tree.
  
    The second thing I look for in scouting my trees for casebearer is the position of the sepals on the pollinated nutlets. Sepals are the small leaf-like projections that are attached to the nutlet just below the black stigma (photo at right). During pollination, the sepals spread outwards away from the stigma. When the nut becomes fertilized and begins growth, the sepals fold upwards and curl over the stigma. Casebearer damage will not occur until the nuts are fertilized and the sepals are pointing upwards. Note the position of the sepals on nuts pictured below.

    When most of the sepals on our pecans have turn upwards and even curl over the stigmas located at the end of the nut (photo at right), pecan nut casebearer damage should start.
   Casebearer damage is easy to spot. The larva always enters at the base of the nut and creates a pile of brown frass in the narrow axis between the pedicel and nut (photo at left). You will also note some fine silken threads that span between the nut and pedicel. When pecan nuts are damaged early in the growing season they quickly drop from the tree. Casebearer larvae create this webbing to tie the nut onto tree so it can attack a second nut in the cluster without fear of falling from the tree. A single casebearer caterpillar will eat an average of three nuts before pupating inside one of the nuts.