Monday, January 26, 2015

Pecan nut casebearer's winter home

     Mid-winter is not the usual time to be thinking about pecan nut casebearer, an early-summer, nut-feeding insect pest (photo at right). But if you have been a regular reader of this blog, you will know that we spend a lot of time monitoring this insect during the months of May and June. I have even placed a special tab at the top of this blog so you can follow the progress of moth flight and first significant nut entry each summer. But have you ever wondered where and how the pecan nut casebearer overwinters?

    Yesterday, I was looking at a pecan twig under a dissecting microscope and I found the casebearer's winter home. Nestled at the base of a pecan bud was a small partially grown caterpillar wrapped in a protective case called a hibernaculum. In the photo at left, note how small the hibernaculum is compared to the dormant pecan bud and leaf scar. No wonder it is nearly impossible to spot hibernacula in the field.
    The larva will emerge from its winter home shortly after budbreak and begin feeding on the expanding new pecan shoot. Once the larva grows to full size it will pupate in the stem of the damaged shoot. An adult moth emerges from the pupal case in May and is part of the generation of moths we catch in pheromone traps. This generation of moths eventually lay eggs on nut clusters in early June.