|
|
|
|
|
The Cottonwood Borer
(Plectrodera scalator) |
||
|
The adults generally appear in midsummer. The first adult specimens in Fern Bluff found in the current year were reported on June 4th. These photos are of a cottonwood borer found at the base of a Carolina Poplar in Fern Bluff on that date. After feeding briefly, they descend to the bases of host trees where the female digs into the soil. Note the claws shown in the photo below. She then gnaws small pits in the bark to serve as repositories for her eggs. Note the powerful jaws of this beetle, as shown in the photo at left.
Many of the Carolina Poplars (which are actually cottonwoods, and members of the Willow Family) that were damaged in the windstorm that struck this area on May 20th had been previously damaged by this borer. The potential for future damage, if control measures are not taken, is very great. If you have a willow or a poplar tree in your yard, annual inspections should be performed to determine if these beetles are infesting them. If they are, control measures should be begun at once to prevent additional damage. |
The cottonwood borer
is found throughout the eastern United States, but the highest populations and
greatest damage have been observed in the South. It is common in central Texas,
including the Round Rock and Austin area. It attacks cottonwood and willow
trees which, weakened by severe infestations, may collapse during wind
storms.
Adult beetles are 1 to 1½ inches (25 to 38 mm) long and about ½ inch (12 mm) wide. They are black with lines of cream-colored hair forming irregular black patches. The adults feed on the tender shoots of young trees, causing them to shrivel and break off.
The eggs hatch from 16 to 18 days later into small larvae which immediately bore downward into the inner bark. Usually they succeed in entering a large root of the tree before autumn arrives, where they feed and excavate galleries. Pupation occurs in the galleries from April to June and lasts about 3 weeks. The new adults chew exit holes through the sides of the pupal chambers and emerge through the soil, leaving round holes approximately 1/2 inch (13mm) wide. Some larvae complete development in 1 year, while others require 2 years. The immature beetles, or larvae. bore into the inner bark and wood at the root collar and tunnel downward into the roots. Light brown, fibrous frass is sometimes ejected from bark openings at or slightly above the ground line, accumulating in piles at the base of the tree. The root collar and roots of infested trees may be riddled by larval tunnels. |
|
