Twig Girdler/Twig Pruner
Contact: Eric Day, Manager, Insect Identification Laboratory
Publication 444-249, August 1996
Twig Girdler/Twig Pruner
Plants Attacked
Pecan, hickory, and oak are the most commonly
attacked, but persimmon, elm, poplar, gum, basswood,
honey-locust, dogwood, and some fruit trees can be damaged as
well.
Description of Damage
These beetles cause very conspicuous damage in late summer. The
leaves on large numbers of twigs and branches will be observed to
turn brown prematurely. These twigs and branches sometimes fall
from trees in great numbers and accumulate. On close
examination, the twigs have one of two kinds of damage. Twigs
damaged by the twig girdler are cut as neatly as by a knife. The
cut end has been gnawed almost straight across with a faint
rounding and is slightly roughened by the chewing. The twig
girdler is more commonly found on pecan and hickory. The twig
pruner causes a slightly different type of cut. The twig will be
observed to have a hollowed out space at the cut end filled with
sawdust like frass. The twig when split open will have a long
tunnel through most of its length. The twig pruner is more
commonly found on oak.
Twig pruner, adult, larva and damage
Identification
In the larval stage, both the twig girdler and twig pruner are
creamy white in color and up to 2 inches in length. They look
like typical roundheaded borers in that their heads and bodies
are cylindrical in shape and they have legs that are reduced to
very small claws. The adult twig girdler is about 5/8 inch long
and has a pair of long antennae. The color is brown with
irregular patches of fine gray hairs and the antennae are spines
on the segments closest to the head. The twig girdler, Oncideres
cingulata (Say), and the twig pruner, Elaphidionoides
villosus
(F.), are both in the order Coleoptera, family Cerambycidae.
Life History
The adult female twig girdler prepares twigs for egg laying in a
very distinctive manner. She selects a small twig with thin bark
about 3/8 inch in diameter and very carefully cuts a circular
incision through the bark and deep into the wood. In the section
of the twig above the girdle, a small hole is gnawed and the egg
is placed inside. The twig soon dies and will remain on the tree
for a period of time. Eventually, the twig falls from the tree.
The egg nevertheless hatches soon after being laid, and the larva
starts development in the late summer and fall and the partially
grown larvae overwinter in the twig. The larva development
continues again in the spring until the middle of the next summer
when it is completed and the twig is filled with fibrous frass.
This development cycle takes place even if the twig falls off the
tree. The larvae pupate in the twig and the adults emerge in
late summer.
Twig pruner eggs are deposited near the tip of the twigs in the
axial of a leaf. The young larva mines down the stem, increasing
in size as it goes. Late in the summer it severs the branch by
several concentric cuts from the center outward, leaving the
thin bark. Infested branches 1/4 to 2 inches in diameter break
with the wind and fall to the ground. In the fall, within the
stem the larva positions itself between two wads of fibrous
frass, where it pupates to the following spring or fall.
Control
Since the twig cutter larva is in the twig when it falls from the
tree, gathering and burning of the girdled twigs is the most
satisfactory means of preventing further damage. This control
works provided it is thoroughly done and extended some distance
in the surrounding area. This form of control, however, is of
limited value if the trees are growing adjacent to wood lots,
where these girdlers are abundant, but should still be practiced.
Spraying has not shown much promise for control of these species.
Remarks
Several closely related species of beetles damage twigs in a
similar manner but are less common. In Virginia mulberry bark
borers, oak stem borers, spined bark borer, and the mulberry
borer may all cause the same damage as the twig pruner and
girdler. Fortunately, control is the same for all species - pick
up fallen branches and burn them.