Summary
Wireworms and cutworms are currently the 2 biggest
insect problems in field crops. Some headlands are being
sprayed with foliar insecticides for control of flea
beetles.
Recent Insects of Concern
Wireworms
Recent Observations: Damage from wireworms has been showing up, primarily
in cereal crops, in several areas. The highest
concentration seems to be in the southern Interlake.
Several wheat fields in the area have quite high levels
of wireworms and wireworm damage to plants. Wireworm
feeding has also been reported at significant levels
from fields near Cypress River (barley), Neepawa
(wheat), and at noticeable levels near MacGregor
(sunflowers).
Scouting Tips: Soil sieves can be used to detect wireworms; but
if you do not have soil sieves, placing a few
trowels full of soil into a tray or container with a
large surface area and shaking it to level out the
soil often makes it possible to find the wireworms.
Just don’t put too much soil in at a time.
Management Tips:
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Wireworm larvae never come above the ground to
feed. Thus rescue treatments of insecticide are not
an option. Insecticides for wireworm control are
only available as seed treatments, or in some crops
as insecticides applied at seeding. If a field or
portion of a field needs to be reseeded because of
wireworm damage, check the Guide to Crop Protection
for possible seed treatments.
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As the soil warms up and dries out, wireworms
will move deeper into the soil and become less of an
issue, they are primarily an early season concern.
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Cutworms
Recent Observations: Localized
heavy populations are showing up. Personal observations
are that redbacked and dingy cutworm seem to be the 2
dominant species. Both will come above the ground to
feed on young leaves and cotyledons as well as clipping
plants. About 40 acres of canola in the Fannystelle area
was reseeded because of cutworm feeding. A couple of
canola fields in the Killarney area were sprayed
recently for cutworms. Levels of concern were also
noticed in canola in the Landmark area, and earlier in
the season in a pea field in the Glenboro area.
Management Tips:
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Cutworms will come out at night to do their feeding; so
if it is determined that insecticides would be economical,
spraying as late in the day as possible is recommended.
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Cutworm populations can often be in patches in a field,
so spraying whole fields is not always the most economical
method of control.
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When deciding whether cutworm control would be
economical, consider the stage of the cutworms. Some species
that overwinter as larvae, such as dingy or army cutworms,
may be fully grown larvae or starting to pupate already. If
this is the case, control is not likely to prevent enough
yield loss to make it economical. Species that overwinter as
eggs, such as redbacked cutworms, may still be small enough
that if there are high enough levels in the field, control
would prevent enough yield loss to be economical.
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Dingy cutworms found near Carman |
Flea Beetles on Canola
Recent Observations: Some headlands of fields have had
applications of foliar insecticides for flea beetle control in
the Hamiota and Shoal Lake/Rossburn areas. In some of these
fields, insecticide treated seed was used, but appears to have
lost its effectiveness before the plants got to more resistant
stages.
Leaf Rust Found in Winter Wheat
Recent Observations: We had two independent reports today from Emerson and from
the Killarney area where field scouts had found low levels of
rust pustules on lower leaves of winter wheat. This is just a
heads-up for others who may be scouting. The USDA’s last Cereal
Rust Bulletin reported a similar finding from southeastern North
Dakota on May 25th so it’s quite conceivable that these
infections came via airborne uredospores.
Surveys and Forecasts
Diamondback Moth: Traps counts have been coming in
since the week of May 20–26, and so far counts have been low;
the highest count so far is 9 from a trap near Ethelbert.
Wireworm Survey: A survey of the species of wireworms
is being conducted across western Canada. The purpose is to
determine the dominant species of wireworms in different
regions. Wireworms is a term that refers to the larvae of a
family of beetles known as click beetles, of which there are
many species. Knowing the dominant species of wireworms in a
region could have implication for how they are managed.
How to Send Wireworm
Samples: When you send wireworms,
you can send them live, in a small container with soil. An ideal
container is a film roll canister (if you still have some of
these) although any container will do as long as it will not
break or open in transit. You can put a few wireworms in a
container filled with soil, but some species do eat each other,
so I wouldn’t put more than 5 in a container. There is no need
to put holes in the lids for air, or to moisten the soil; just
send them in whatever soil they were found in, as it provides an
idea of what soils they prefer.
Where to Send Samples: The entomologists doing the
identification are based in Agassiz, B.C. Samples can be sent to
Dr. Bob Vernon, Pacific Agri-Food Research Centre, P.O. Box
1000, 6947- #7 Highway, Agassiz, BC V0M 1A0. If it is more
convenient, samples can be dropped off to me, and I can send
them in with samples I will be submitting. If you are aware of
fields with high levels but have not collected any, please let
me know and I can try to have some collected.
Insect Identification Quiz
Question: You are digging in the soil and notice this
larva. When disturbed it starts wiggling in a very quick and
erratic way to escape. You note it is white and has no legs at
all. What is it?
Answer: If you said cutworm or wireworm you are wrong.
This is the larvae of a fly known as Therevid or Stiletto flies,
of which there are different species. These are predators of
other insects, including wireworms. Don’t confuse them with
wireworms. Aside from colour differences, if you look closely at
the front end of a wireworm you will notice small legs; therevid
larvae have no legs.
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