A week ago or so, my wife and I (and our two dogs) took a walk at Fountainbleu State Park in Mandeville, Louisiana. Along the way we came upon some branches on the ground — lots of small branches. Being a fruit and nut specialist I knew right away what was causing it. You can see what we saw in the photo below.
Girdled branches on the ground from a pecan tree
The culprit is the Twig Girdler (Oncideres cingulata). Twig girdlers are grayish-brown beetles, about 1/2 inch long, with reddish-brown heads and long antennae. They overwinter as eggs or grubs inside the branches that lay on the ground. The insect is an adult by August, when we start noticing the symptoms of their existence. Adults lay eggs in the tips of twigs and then girdle them. Their life cycle is generally complete within one year.
The adult twig girdler girdles pecan twigs beginning in late summer and moving into fall. The girdling causes the branch to break off and fall to the ground. Stems that are girdled by a twig girdler have beveled ends (see photo below), whereas those done by twig pruners (a different insect) have smooth cuts.
Twig Girdler damage on a pecan branch
Some great online resources on this insect (including photos) are below:
Texas A&M — https://insects.tamu.edu/fieldguide/bimg176.html
NCSU — http://www.ces.ncsu.edu/depts/ent/notes/O&T/trees/note96/note96.html
Auburn — http://www.ag.auburn.edu/enpl/bulletins/twiggirdler/twiggirdler.htm
Missouri — http://extension.missouri.edu/p/g7276
Kansas State — http://www.hfrr.ksu.edu/doc1736.ashx
Oklahoma — http://entoweb.okstate.edu/ddd/insects/twiggirdler.htm
Sanitation is important in controlling this pest. Destroy all branches that fall to the ground and that takes care of the eggs. By disrupting the life cycle one can reduce the population in the future.
It was fun to have a nice hike on a great, sunny fall day, but it was even better to be able to share this with my readers. One never knows what one will see on a hike in the woods (we also saw three different types of snakes!).