Pecan Nut Casebearer 2016


  


    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. On May 31st of this year one of our big native trees still held on to its catkins (photo at right). 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.

    By Monday June 6th, most of the sepals on our pecans have turned upwards and even curled over the stigmas located at the end of the nut (photo at right). Pecan nut casebearer damage should start any day now.
   We recorded 1% damage to nut clusters on Wednesday June 8th. At the very beginning of the casebearer season, a larva will have damaged only a single nut with a nut cluster (photo at left). With a prediction of warm temperatures (90 F) for the next several days this year's casebearer population should develop quickly. We plan to apply an insecticide treatment starting June 9 or 10.
   Casebearer update 22 June 2016:    Looking over the data for the 2016 it looks like our "unsprayed" pecan orchard was mistakenly sprayed when our neighbor treated his grove using an aerial applicator service on June 12th. Damage levels stopped increasing following the June 13 cluster counts. This is not the first time a pilot has sprayed the our trees in error. It makes taking meaningful insect data a real challenge. On the bright-side, we now have additional evidence that a single, well-time insecticide application can keep pecan nut casebearer populations in check.    









2016 Average Cluster Size and 
Observed Casebearer Larval Damage

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Date     Nuts/     % Damaged   Mean number nuts
        Cluster    Clusters    damaged/infested 
                               cluster
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27 May   3.51         0           0
31 May   3.20         0           0
3 June   3.22         0           0
6 June   3.14         0           0
8 June   3.32        1.00        1.00
10 June  3.18        1.67        1.20
13 June  3.16        3.00        1.33 
15 June  3.19        2.00        1.83 
17 June  2.96        3.00        1.44 
20 June  3.00        3.00        2.33
22 June  2.95        2.33        2.14 
24 June  2.99        4.00        2.00
end of survey 

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Results based on counts from 10 unsprayed trees, 30  randomly selected nut clusters per tree