Q: My elm tree has dropped hundreds its tips and they are all under the canopy. What could be causing this?
A: This is a common question during the fall from both homeowners and commercial sites – no one is immune. More than likely it is the result of a long-horned beetle called a twig girdler. Twig girdlers are important long-horned beetles. The grayish-brown adult females (1 1/16 inch long) are active from September to November. Twig girdlers are difficult to spot on the bark of trees as they have perfect camouflage coloring. The hard outer wing coverings may display interesting and distinct patterns. Their damage occurs primarily from egg laying. They girdle limbs by chewing a V-shaped groove entirely around twigs, branches or terminals.
Eggs are inserted into the bark on the girdled part of the branch away from the tree. Girdled limbs eventually break and fall to the ground. This is the reason you have seen so many small branches cut off and lying on the ground. Larvae cannot develop in healthy sapwood. Damage can disfigure a young tree and leads to secondary branching, especially if the terminal is attacked. Oak, persimmon, hickory and pecan are common hosts. The best control method is to pick up the small branches which have fallen to the ground, bag or burn them. If you have a young budding entomologist at home, they could leave some of the twigs in the shade and cut into the wood every week or so to measure the growth in the larva. Ultimately, they may be able to see a full grown adult. Be sure to have a camera ready to document each event and use the metric system when taking measurements. This would make a great classroom project. Attached is a website with other information on a variety of tree borings commonly found in Florida. http://edis.ifas.ufl.edu/mg007