P1253037225OmKfj

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Field Testing a Simple and Efficient Trap for
Sampling Arboreal Populations of Forficula
auricularia L.
Jesse Benbow, Richard Hilton and Sally Basile,
Oregon State University - Southern Oregon
Research Extension Center, 569 Hanley Road,
Medford, OR
Introduction The European Earwig (Forficula
auricularia L.) plays a significant role in many
orchard systems in the Pacific Northwest, both as
pest and beneficial insect, depending on crop.
Beating tray sampling is commonly used to monitor
arboreal insect populations but the nocturnal
nature of earwigs makes this method inadequate
for monitoring effects of pesticides or cultural
practices on earwig populations. We undertook to
find a simple, effective, and repeatable method
to determine relative numbers of earwigs in the
tree.   Results Trap Material Earwigs are
nocturnal foragers that typically seek a small,
secure crevice in which to hide during the day.
We determined that the small shelters created by
a rolled tube of corrugated material would
provide an attractive space for earwigs seeking
shelter during daylight hours. We found three
types of suitable material Corrugated cardboard
from recycled paper material, clear corrugated
plastic material used for growing tubes for young
trees, and an opaque corrugated plastic material
with a white flat surface and black corrugations.
All three materials were cut to 10 cm x 25 cm
and rolled into a tube 10 cm wide and
approximately 4 cm diameter (pictures at left).
The traps were attached to the trunk or major
scaffold limbs of pear trees in an organic pear
orchard, using plastic flagging tape to tie them
to the tree (pictures at right). Traps were
placed in individual trees in pairs of each
combination of different type of trap, and with
all three traps in the same tree. Earwigs showed
a clear preference for the cardboard roll,
occupying it in much higher numbers than either
of the plastic rolls (Fig. 1). We also observed
much more consistency in the number of earwigs in
cardboard rolls than in either of the plastic
rolls. Earwigs occupied the opaque plastic roll
in higher numbers than the clear
plastic. Location of Trap in Trees Cardboard
rolls were placed in different location within
trees in an organic pear orchard. Traps were
placed either high ( 2 m on a scaffold branch),
mid (1.5 m on a larger scaffold), or low (1 m on
the trunk or major scaffold), or in all 3 places
(picture at left). The traps were collected
after one week and the earwigs in each trap were
counted (Fig. 2). There were no statistically
significant differences in the numbers of earwigs
collected from traps placed in the different
locations, either in different trees or the same
trees. While the average number of earwigs per
trap was lower for trees with multiple trap
locations, total counts from trees with multiple
trap locations (6 traps total) were considerably
higher than counts from trees with only one trap
location (2 traps total). Length of Cardboard
Traps Cardboard rolls of 10 cm width and various
lengths were attached to the trunk or major
scaffold of pear trees in an organic pear
orchard, at approximately 1 m from the ground.
The traps were collected after 2 weeks and the
earwigs in each trap counted. Number of earwigs
caught was generally proportional to the length
of the trap, with the shortest containing fewer
insects and the longer containing more (Fig. 3).
The shortest trap length caught the second fewest
insects, but had the highest efficiency in
containing more earwigs per cm of length. Using
Cardboard Traps to Monitor Seasonal
Population Cardboard traps 25 cm in length were
placed individually in pear trees in a block
treated only with selective materials for codling
moth. Traps were collected weekly, and new traps
were placed in a different tree. Earwigs in each
trap were recorded by stage of development (Fig.
4).   Summary Rolled, corrugated cardboard tubes
can be used as an inexpensive, yet efficient
trapping device to monitor earwig populations in
the field. The traps are simple to construct and
easy to place and retrieve. Insects can be
counted and sorted while living, if populations
are low, or the traps and their contents frozen
for a short period to provide for easier sorting
and counting. European earwigs were by far the
most common species captured in the traps, with
various spiders and adult and larval insects,
including codling moth larvae and pupae, also
found frequently.
B
C
D
A
Fig. 1 Number of earwigs captured in rolled,
corrugated traps placed in mature pear trees in
an organic orchard. Traps were paired at 2 per
tree (A, B, C) or 3 per tree (D) and attached to
the trunk of the tree within 1 m of the ground.
Data was analyzed with Fishers LSD, p-values
are shown for each comparison.
Fig. 3 Earwigs captured in corrugated cardboard
traps of various lengths. Traps were placed one
per tree in mature trees in an organic pear
orchards.
B
A
Fig. 4 Average weekly European earwig trap
catch in rolled, corrugated cardboard traps in a
pear orchard in 2005. Insects were sorted by
development status.
Fig. 2 Earwigs captured in rolled, corrugated
cardboard traps placed at different locations in
mature pear trees in an organic orchard. Trapping
efficiency was compared with traps placed in
their respective locations in separate trees (A),
or in the same tree (B).