Pecan Nut Casebearer 2017


  


    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.
  
    We found one nut damaged by casebearer on June 9th.
    One percent of nut clusters had been attacked by pecan nut casebearer on June 12th.
    Damage from casebearer was still very low on June 14. We won't be spraying the grove until we see the damage levels start to increase.
    On June 16, we are still finding only <1% damage from Pecan nut casebearer. We are now one week past our average date for spraying for this pest. I'm getting the feeling that we may not have to spray for this insect this year. However, we'll keep scouting until the first of July.
    On June 19th, we found 5 clusters out of 300 damaged by casebearer (1.67% damage). Also of note is that, on average, larvae have entered their second nut in the cluster. We may be looking at a record low casebearer population this year.
    Our casebearer counts on June 26th confirmed that 2017 will go down in history as the year casebearer never showed up. All during the month of June, we never found more than 2.67% damage. This represents the lowest damage level ever recorded since we began counting nut clusters in 1981.







2017 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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2 June   2.72         0           0
5 June   2.89         0           0 
7 June   2.89         0           0
9 June   2.77        0.33        1.0
12 June  2.96        1.00        1.0
14 June  2.83        0.67        1.0
16 June  2.65        0.67        1.0
19 June  2.63        1.67        2.0
21 June  2.60        2.66        1.8
23 June  2.45        1.00        2.0 
26 June  2.75        1.33        2.0
28 June  2.51        2.66        2.6 
30 June  2.31        1.33        3.0


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