The exotic, invasive
emerald ash borer (Agrilus
planipennis), or EAB, was
found infesting ash trees
in Nebraska in 2016.
However, a number
of native borers infest
ash trees, too, and treatment needs
differ depending on pest species.
Trees decline for many reasons, and
symptoms of decline are similar for
most pests. It is important to correctly
diagnosis the pest before making
management
decisions.
One of the most
common borers
of ash is the
native ash-lilac
borer (Podosesia
syringae), which
infests both
ash trees (Fraxinus spp.) and lilac
bushes (Syringa spp.). This insect is
a clearwing moth, not a beetle, and
the adult is often confused for a wasp.
Larvae are round and white, feeding
under the bark then tunneling into
the sapwood, unlike EAB larvae that
remain just under the bark.
The exit holes of the ash-lilac
borer adults are round and
1
⁄4 inch in
diameter, much larger than EAB's
1
⁄8-
inch D-shaped exit holes. The adult
moth will often
leave its pupal
skin stuck in the
exit hole as it
leaves the tree.
The banded
ash clearwing
(Podosesia
aureocincta) is a
closely related insect. However, these
adults emerge in the fall, while ash-
lilac borer adults emerge in spring.
Several round-headed borers are
known to infest ash trees, including
the redheaded ash borer (Neoclytus
acuminatus) and the banded ash
borer (Neoclytus caprea). The adult
redheaded ash
borer is
1
⁄2 inch
in length and has
a burnt reddish
color with distinct
yellow lines
across its back.
Adults emerge
in the spring and
lay eggs in bark
cracks.
The life cycle
of the banded
ash borer is very
similar; however,
the adult beetles
are darker in
color, with shorter
legs than the redheaded ash borer, and
have whitish bands instead of yellow.
Larvae of both species feed under the
bark before moving into the sapwood.
The adult exit holes of these borers are
round and larger than EAB exit holes.
Remember, not all borers are EAB,
and effective management requires
accurate diagnosis. ■
When It is Not an Emerald Ash Borer...
By Julie Van Meter
State Entomologist, Nebraska
Department of Agriculture
Presented by
WHITNEY
CRANSHAW,
BUGWOOD.ORG
GYORGY
CSOKA,
BUGWOOD.ORG
STEVEN
KATOVICH,
BUGWOOD.ORG
MARK
DREILING,
BUGWOOD.ORG
us
s
d
JULY 2017 • NEBRASKAland 21
