Friday, March 23, 2012

Splits in pecan twigs

    I had this photo emailed to me from Missouri (love the duct tape). The red arrows point to splits in the bark of one-year-old pecan twigs. The numerous splits made collecting high quality pecan scions difficult. What caused this damage? The answer is directly related to the emergence of large, noisy insects that appear only every 13 years.
    In 2011, parts of Missouri were treated to the emergence of 13 year cicadas. These insects spend most of their life cycle (13 years) under the soil slowly feasting on tree roots. Adults emerge in mid summer, mate, and then females gouge a split in the bark in which they lay their eggs.  Besides pecan, cicadas lay eggs in the twigs numerous species of hardwood trees. Once the eggs hatch, the nymphs fall to the ground, tunnel into the soil and feed on tree roots.

     You may not be familiar with the looks of the 1.5 inch long adults (photo at left) but I'm sure you've heard the loud mating calls on hot summer nights (a shrill sound the rises to peak before slowly fading). There are hundreds of species of cicada with life cycles that range from 1 to 17 years. Last year's emergence of the 13 year cicada flooded the forests of Missouri with a cacophony of cicada calls and caused immense damage to tree twigs.
    Tree twigs will heal over in time, especially if your pecan trees receive plenty of water and nutrients during the upcoming growing season. Look at the photo of the twigs above, and you can see that the tree has already formed callus tissue around each bark split.