The Rural Voice, 2003-06, Page 54Advice
European Chafer a big problem this spring
By Tracey Baute, Field Crop
Entomologist, OMAF - Ridgetown
and Dr. Art Schaafsma, Associate
Professor, University of Guelph -
Ridgetown College
Grub populations are very high
this spring, as last fall appears to
have been ideal for egg laying and
grub development. Numbers as high
as 10 chafer grubs per square foot are
being reported in some wheat fields.
Because chafer can tolerate cold soil
temperatures, feeding has been taking
place for over a month now.
Scouting wheat, forages and
potential cornfields is imperative.
Pay particular attention to the sandier
areas of the fields, especially the
knolls. Most of the grubs are
currently close to the soil surface but
some are still up to 3-4 inches deep.
Use a squared spade and turn over a
flat slice of soil about 3-4 inches
thick. Scatter the soil and break up
any clumps (some are still dormant in
their cells) and sift through the soil for
about 30 seconds and count the
grubs. Our best guess is that you
should take about five samples in each
area of the field you are sampling.
European chafer larvae are white
and C-shaped with an orange -brown
head and dark posterior. You can
distinguish them from other white
grubs by the Y-shaped pattern of anal
bristles known as "rasters" located on
the underside of the last abdominal
segment of the larva.
No thresholds have been
established yet but research
conducted out of Ridgetown College,
University of Guelph is showing
some indication that thresholds are
around four grubs per square foot. If
you are finding more than three grubs
per square foot, plant soybeans
instead of corn in that field. Soybeans
appear to be more tolerant to grub
feeding than corn or wheat. Replant-
ing in wheat fields might also be
necessary if grub levels are that high.
If you are planting corn into that
field, there are some treatments
available that can help to protect the
seed. Research plots out of
Ridgetown College indicate some
level of protection at corn emergence
when an in -furrow rootworm
50 THE RURAL VOICE
insecticide like Counter or Force, is
used in combination with the seed
treatment DL Plus. However, keep in
mind if an organophosphate
insecticide like Counter is used, a
sulfonylurea (SU) herbicide Should
Not be used. Postemergent
applications of a sulfonylurea
herbicide on. corn already treated
with a soil applied organophosphate
like Counter, Lorsban, Thimet and
Cygard may cause foliar and root
injury to your crop. Sulfonylurea
herbicides registered on corn include
Accent, Ultim, Ultimax, Elim EP,
PeakPlus, Broadstrike Dual, Striker,
and Fieldstar. The soil -applied
insecticide, Force 3G, a pyrethroid,
will not interact with SU herbicides
to cause injury to your crop.
Tilling up the soil a few days
before planting will also bring the
grubs up to the surface, where some
will die from being exposed to the
elements or will be eaten by
predators. Also, as for any soil insect
pest, planting in ideal soil conditions
is the best way to ensure the plants
will become well established and be
able to tolerate low to moderate pest
populations. Planting when the soil is
too cold and wet is like putting that
seed into a fridge; it will be too cold
for the seedlings to develop but will
be easily accessible to the grubs.0
Ridgetown plans
Diagnostic Day
The 9th annual Southwest Crop
Diagnostic Day will be held at
Ridgetown College on July 9 -10.
The Diagnostic Day is a "hands-
on" learning experience targeted to
seed, fertilizer and agri chemical
personnel and crop consultants. The
participants are broken into small
groups and they travel to six stations
across the campus as they seek to
improve on their problem -solving
skills.
The fee is $75 per person. For
further information, contact the
Ridgetown OMAF Resource Centre
at (519) 674-1690.0
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