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Cutworm Pests of Crops on the Canadian Prairies: Identification and Management Field Guide

Authors:
  • Agriculture and Agri-Food Canada, Lethbridge, Canada

Abstract and Figures

This guide is intended to help producers identify and control oilseed and cereal crop cutworm pest species found on the Canadian Prairies. Included is general information on the biology and control of these pests followed by species-specific information. A list of registered cutworm chemical control products is not provided because available products frequently change. For this information, readers are instead directed to annual editions of provincial crop protection guides; links to updated online versions are listed in the Internet Resources section at the end of this guide. Also found in this guide are summaries of previous cutworm research, older control methods, and reasons why some control methods are no longer recommended. Information sources, many of which can be found online, are cited throughout the text. The historical context combined with current information helps identify knowledge gaps to direct future research. Keeping track of citations also simplifies updating the guide in the future.
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Content may be subject to copyright.
Cutworm Pests of Crops
on the Canadian Prairies
IdentIfIcatIon and ManageMent fIeld guIde
Cutworm Pests of Crops on the Canadian Prairie:
Identification and Management Field Guide
Cover photo: Armyworm cutworm larva and damage,
Mike Dolinski, MikeDolinski@hotmail.com
© Her Majesty the Queen in Right of Canada, represented by the Minister of Agriculture and
Agri-Food Canada (2017).
Electronic version available at www.publications.gc.ca
Catalogue No. A59-42/2017E-PDF
ISBN 978-0-660-08051-2
AAFC No. 12614E
This publication may be cited as follows:
Floate, K.D. 2017. Cutworm pests on the Canadian Prairies: Identification and management
field guide. Agriculture and Agri-Food Canada, Lethbridge, Alberta.
Paru également en français sous le titre Guide d’identification des vers-gris ravageurs des cultures
dans les Prairies canadiennes et mesures de lutte applicables.
For more information, reach us at www.agr.gc.ca or call us toll free at 1-855-773-0241
Cutworm Pests of CroPs on the Canadian Prairies i
Acknowledgements
Thank you to Dr. John Gavloski and Hugh Philip for comments on earlier
drafts and to Dr. Jeremy Hummel for his thorough technical review of the
final version. Erl Svendsen handled the editing, proofing, sourcing and
selecting of images and initial layout design, while Chennoa Tracey did
most of the heavy lifting on the graphic design of this guide. Thank you
also to the many photographers who made their images available for this
publication. Funding for preparation of this publication was provided by
the Canola Council of Canada (CARP Project No. 2012-1). This is an AAFC
Lethbridge Research and Development Centre contribution No. 387-
15019.
ii Cutworm Pests of CroPs on the Canadian Prairies
Table of Contents
Acknowledgements i
Foreword v
Introduction 1
Key Species and General Biology 1
Cutworm Outbreaks 6
Predicting Outbreaks 9
Scouting 12
Natural Enemies 16
Parasitoids 17
Predators 20
Pathogens 22
General Control Options 26
Biological 27
Chemical 29
Cultural 31
Species Specific Information 32
Army cutworm - Euxoa auxiliaris (Grote) 34
Armyworm - Mythimna unipuncta (Haworth) 36
Black cutworm - Agrotis ipsilon (Hufnagel) 40
Bristly cutworm - Lacinipolia renigera (Stephens) 42
Bronzed cutworm - Nephelodes minians (Guenée) 44
Clover cutworm - Anarta trifoli (Hufnagel) 46
Darksided cutworm - Euxoa messoria (Harris) 48
iii
Cutworm Pests of CroPs on the Canadian Prairies
Dingy cutworm - Feltia herilis (Grote), Feltia jaculifera
(Guenée), Feltia subgothica (Haworth) 50
Dusky cutworm - Agrotis venerabilis (Walker) 52
Glassy cutworm - Apamea devastator (Brace) 54
Pale western cutworm - Agrotis orthogonia (Morrison) 56
Redbacked cutworm - Euxoa ochrogaster (Guenée) 58
Spotted cutworm - Xestia c-nigrum (Linnaeus),
Xestia dolosa (Franclemont) 60
Variegated cutworm - Peridroma saucia (Hübner) 62
Western bean cutworm - Striacosta albicosta (Smith) 64
Winter cutworm - Noctua pronuba (Linnaeus) 68
Yellow-headed cutworm - Apamea amputatrix (Fitch) 70
Other Common Cutworms of Economic Importance 72
Black army cutworm - Actebia fennica (Tauscher) 72
Claybacked cutworm - Agrotis gladiaria (Morrison) 72
Strawberry cutworm - Amphipoea interoceanica (Smith) 73
White cutworm - Euxoa scandens (Riley) 73
Insects Commonly Mistaken as Cutworms 74
Leatherjacket (crane fly larva) 74
Millipede 75
White grub (scarab larva) 75
Wireworm 76
Internet Resources 77
References 78
Appendix A. Quick Guide Index - Cutworm adults 90
Appendix B. Quick Guide Index - Cutworm larvae 92
Cutworm Pests of CroPs on the Canadian Prairies
forward
v
Cutworm Pests of CroPs on the Canadian Prairies
Foreword
This guide is intended to help producers identify and control oilseed
and cereal crop cutworm pest species found on the Canadian Prairies.
Included is general information on the biology and control of these
pests followed by species-specific information. A list of registered
cutworm chemical control products is not provided because available
products frequently change. For this information, readers are instead
directed to annual editions of provincial crop protection guides; links to
updated online versions are listed in the Internet Resources section at
the end of this guide.
Also found in this guide are summaries of previous cutworm research,
older control methods, and reasons why some control methods are
no longer recommended. Information sources, many of which can
be found online, are cited throughout the text. The historical context
combined with current information helps identify knowledge gaps
to direct future research. Keeping track of citations also simplifies
updating the guide in the future.
- Kevin Floate
Stubble eld
C. Tracey, AAFC
forward
vi Cutworm Pests of CroPs on the Canadian Prairies
IntroductIon
1
Cutworm Pests of CroPs on the Canadian Prairies
Introduction
There are several pest cutworm species affecting Canadian Prairie
crops. Much of the time, their impact is negligible. However, from time
to time, outbreaks occur. These can be localized to small areas in a
field or widespread across a large region, they can last years and, most
importantly, can cause significant economic damage.
The key to successful cutworm management and limiting their impact is
by first correctly identifying the species causing damage. Then, through
an understanding of its biology, lifecycle, preferred habitats, behaviour,
influences of climate and weather, and interactions with natural enemies
and other factors, you can exploit its weaknesses by knowing when
to control (susceptible stage and time of day) and only when it makes
economic sense. Learning how to recognize damage, detect the species
(scouting), and take advantage of natural processes are additional
important elements in a management strategy.
Key Species and
General Biology
‘Cutworm’ is the common name given to the larva of several noctuid
moth species (Lepidoptera: Noctuidae). Of the 1,555 species of noctuid
moths in Canada (Zahiri et al. 2014), only a small number are considered
pests. Prominent species that attack crops on the Canadian Prairies
include army cutworm (Euxoa auxiliaris (Grote)), pale western cutworm
(Agrotis orthogonia (Morrison)), and redbacked cutworm (Euxoa ochrogaster
(Guenée)). Other pest species include armyworm (Mythimna unipuncta
(Haworth)), black army cutworm (Actebia fennica (Tauscher)), black
cutworm (Agrotis ipsilon (Hufnagel)), bristly cutworm (Lacinipolia renigera
(Stephens)), darksided cutworm (Euxoa messoria (Harris)), dingy cutworm
(Feltia jaculifera (Guenée)), and glassy cutworm (Apamea devastator
(Brace)) (Strickland 1923; Ayre and Lamb 1990).
Caterpillar (Cucullia sp.) on gumweed (Grindelia squarrosa)
C. Tracey, AAFC
IntroductIon & Key SpecIeS and general BIology
2Cutworm Pests of CroPs on the Canadian Prairies
The species that make up the cutworm pest complex vary in terms
of regional dominance, crops attacked, timing of different life stages
and feeding behaviour. For example, the pale western cutworm is
generally associated with drier regions and tends to be more dominant
in the southern portions of Alberta and Saskatchewan. In contrast, the
redbacked cutworm is less adapted to dry conditions and more often is
a pest in the northern parkland regions of these provinces. Excessive soil
moisture favours the black cutworm, which is more commonly a pest
in Manitoba and further east. Two or more species may co-occur in the
same field, which further adds to this complexity (Ayre and Lamb 1990).
Cutworms develop from egg to reproductive adult through a series of
lifecycle stages (metamorphosis); i.e., egg larva pupa adult.
The duration of each lifecycle stage varies with cutworm species (table,
p. 5). Eggs of some species may hatch within a few days of being laid
or they may overwinter in the ground, hatching after several months.
Eggs laid in autumn may
begin developing prior
to winter and then hatch
the following spring with
the onset of warmer
temperatures and after
the soil has thawed
(Jacobson 1962b). For
species that overwinter
as eggs, a period of cold
may be required before
the eggs hatch; e.g.,
redbacked cutworm,
pale western cutworm
(Jacobson 1962b) and
dusky cutworm (Ayre
and Lamb 1990). This
requirement prevents
the eggs from hatching in
autumn when there is no
food for the larvae.
The larvae of some species that hatch in early spring may survive without
feeding for two to three weeks, especially at cooler temperatures; e.g.,
10°C (Jacobson 1952). Some species may complete larval or pupal
Eggs 3
Pupa1
Adult moth 2
Larva4
(instar stages)
Lifecycle
of a
Cutworm
Cutworm lifecycle
1,3 cc-by 2.0 USGS Bee Monitoring Lab,
2 cc-by 2.0 Andy Reago and Chrissy McClarren
4 John Gavloski (Manitoba Agriculture)
Key SpecIeS and general BIology
3
Cutworm Pests of CroPs on the Canadian Prairies
development in four to six weeks, whereas species that overwinter as
larvae or pupae may require eight to nine months to complete these
life stages (table, p. 5). Larvae go through a number of developmental
stages called ‘instars’. Most cutworm species complete five or six
instars (Guppy 1961), but individual cutworms may undergo seven to
nine instars if parasitized (Byers et al. 1993), feed on poor quality food
(Santos and Shields 1998) or are exposed to low winter temperatures
(Breeland 1957). Cutworm larvae are generally smooth-skinned, hairless
caterpillars with a base colour ranging from pale to dark brown or nearly
black. They may be variously marked with lines or spots depending on the
species. The larvae have three pairs of thoracic or ‘true’ legs located on
the thorax (first three segments behind the head) and typically five pairs
of abdominal false legs called prolegs. They curl up when disturbed and
are roughly 3 to 5 cm long when mature. See Species-Specific Information
section for detailed larval descriptions of each important cutworm pest
species (also Crumb 1956).
Only cutworm larvae cause crop damage; adults, eggs and pupa have no
impact on crop productivity and yield. Cutworms exhibit three general
types of feeding behaviour: subterranean, above-ground and climbing
(table, p. 5 and Walkden 1950).
Subterranean cutworm larvae feed almost exclusively underground.
Larvae cut the main stem of young plants but are otherwise not
usually seen.
Black cutworm
cc-by 2.0 USGS Bee Monitoring lab (adapted by C.Tracey, AAFC)
Thorax AbdomenHead
Setae
Thoracic or ‘true’ Legs Abdominal Prolegs
Spiracles
Anal Prolegs
Ocellus
Key SpecIeS and general BIology
4Cutworm Pests of CroPs on the Canadian Prairies
Above-ground or surface-feeding cutworm larvae feed on foliage
during the night and hide in the soil or under leaf litter during the
day. Older larvae may cut the main stem of young plants at or near
the soil surface. Tunnelling cutworms are considered here to be a
subcategory of above-ground cutworms. Larvae hide in tunnels
during the day and emerge at night to remove bits of foliage from the
host plant that they then take back into their tunnels.
Climbing cutworm larvae climb up plants to feed on the foliage with-
out necessarily damaging the main stem.
Depending on the crop and larval stage, a cutworm species may exhibit
more than one type of feeding behaviour. These feeding differences
affect the effectiveness of insecticide applications. For example, foliar
insecticides are less effective against subterranean cutworm species.
Upon completing their final instar, larvae stop feeding and form an
earthen cell a few centimetres underground where they pupate. Adult
moths emerge from their pupal cases and feed on flower nectar. Moths
are inconspicuous and usually do not fly during the day. Wings are
coloured different shades of grey, brown or reddish-brown with silver or
whitish markings. Female moths typically mate once and preferentially
lay eggs in light-textured, dry, loose soils. However, some species (e.g.,
clover cutworm, western bean cutworm) oviposit on leaves. Depending
on the species, they may lay several hundred (e.g., pale western cutworm
(Jacobson 1965)) to more than a thousand eggs (e.g., darksided cutworm
(Cheng 1972)).
Some species may have just one
generation per year (univoltine)
while others may have two or
more generations (multivoltine)
(Guppy 1961; Ayre and Lamb
1990). Most of the pest cutworm
species in Canada overwinter
locally. However, some like the
armyworm and black cutworm
re-establish each year in Canada
when prevailing winds blow adults
northward from the USA (McNeil 1987).
Cutworm pupa in an earthen cell
Lloyd Harris
Key SpecIeS and general BIology
5
Cutworm Pests of CroPs on the Canadian Prairies
Approximate seasonal occurrence of lifecycle stages for different species of cut-
worms. Crop damage is caused by larvae. Chart originally compiled by J. Otani and
Gavloski, expanded and updated by K. Floate.
Key SpecIeS and general BIology
6Cutworm Pests of CroPs on the Canadian Prairies
cutworM outBreaKS
7
Cutworm Pests of CroPs on the Canadian Prairies
Cutworm Outbreaks
Almost all of the cutworm species that affect crops on the Canadian
prairies are native to North America and were present prior to European
settlement (Beirne 1971). The shift from native grassland complexes
to simpler agriculture ecosystems dominated by relatively few crops
and tilled soils increased the potential for these species to reach
high, economically damaging densities. The likelihood of any one or a
number of species achieving this potential in a given year and location
is influenced by a combination of factors. The most important is
weather, which affects the initial build-up of populations. However,
not all cutworm species respond in the same way to environmental
triggers. For example, successive dry years increase the potential for pale
western cutworm outbreaks; successive wet years favour black cutworm
(Walkden 1950).
Shorter term weather events moderate the ability of cutworm
populations to cause damage. For example, a large cutworm population
in autumn can be reduced by a harsh winter or wet spring to non-
economically damaging levels the following growing season. Natural
enemies (i.e., parasitoids, predators and pathogens; see Natural Enemies,
p. 16) can further reduce pest populations. Because outbreaks are largely
driven by climate cycles, they occur sporadically every five to thirty years.
Outbreaks can occur locally or be more widespread, lasting one to three
years before populations are reduced to pre-outbreak levels by weather
events or a buildup of natural enemies. Beirne (1971) describes the
history of outbreaks of different cutworm pests in Canada.
The extent of crop loss during a cutworm outbreak is highly variable.
Damage may be limited to a few small patches in a field, requiring no
control effort. Elsewhere, the entire crop may be lost if the outbreak is
unmanaged. In the worst case, cutworm outbreaks can reduce crop yields
across a large geographic area for successive years resulting in high
economic losses. For example, damage by pale western cutworm was
first reported in 1911 and 1912 in Alberta (Mabee 1929). Subsequently,
widespread damage to cereal crops from 1918 to 1921 was observed in
Montana with yield losses exceeding $4.1 million [= $53.8 million in 2015
Historical cutworm damage in Leader, Saskatchewan (1946)
WB Fox, AAFC
cutworM outBreaKS
8Cutworm Pests of CroPs on the Canadian Prairies
dollars] (Mabee 1929). Between 1927 and 1933, pale western cutworm
damaged cereal crops from eastern Saskatchewan to western Alberta
and northward up to 500 km from the Canada/USA border (Seamans
1935); total crop losses for the region were estimated at about $19
million [= $336 million in 2015 dollars] (McMillan 1935).
Pale western cutworm outbreaks affected an estimated 100,000 ha
(250,000 ac) in southern Alberta in 1985. Based on insecticide sales at
that time, total losses were estimated at $8 million [= $16 million in
2015 dollars] (J.R. Byers, unpublished data). Army cutworm outbreaks
in 1990 affected more than 10,000 ha (25,000 ac) in southern Alberta
of which about 6,000 ha (15,000 ac) were sprayed with the remainder
reseeded without spraying (Jones et al. 1990 – cited in Byers et al.
1993). Outbreaks of glassy cutworm in fescue seed fields and pastures
in Alberta caused estimated losses of $5 million [= $6.6 million in 2015
dollars] in 2000 (Dosdall et al. 2000). More recently and varying with
region and crop, localized outbreaks in the Prairie Provinces have been
reported for army cutworm, armyworm, black army cutworm, bristly
cutworm, dingy cutworm, glassy cutworm, pale western cutworm,
redbacked cutworm and variegated cutworm (WCCP 2012; WCCP 2013).
Many local outbreaks go unreported.
Damage to eld caused by pale western cutworm
J. Robert Byers, AAFC
cutworM outBreaKS
9
Cutworm Pests of CroPs on the Canadian Prairies
Predicting Outbreaks
Early forecasting methods developed
in the 1920s and 1930s used
rainfall (‘wet days’) during the larval
development period (May and June)
to predict where outbreaks of pale
western cutworm would occur in the
following year (Cook 1926; Seamans
1935) – the fewer the ‘wet days,’ the
more likely an outbreak. When soils
are wet, this subterranean-feeding
species moves to the soil surface
where populations are reduced by
parasitoids (Seamans 1935) and
epizootics (Cook 1926). Seamans
(1935) reported that the method was
highly accurate during an 11-year period across southern Alberta and
Saskatchewan. However, this method was ultimately not adopted, likely
because of changes in farming practices and the increasing availability of
synthetic chemical insecticides.
More recent efforts have tried to forecast
cutworm outbreaks based on recovery
of adults. Cutworm populations of some
species can be roughly quantified (high,
medium, low) by the number of adult
moths recovered in traps baited with
sex pheromones or in light traps. Sex
pheromones are volatile chemicals that
are produced and released by females
to attract males. In a study in southern
Alberta, the total number of moths
recovered in pheromone traps baited
with a combination of sex pheromones
specific for darksided cutworm, pale
western cutworm and army cutworm
comprised more than 99% of these three target species (Byers and
Struble 1987). In contrast, light traps attract both pest and non-pest
Light Trap
R. Batallas, University of Alberta
Pheromone trap
R. Batallas, University of Alberta
predIctIng outBreaKS
10 Cutworm Pests of CroPs on the Canadian Prairies
species. This means that light trap catches first have to be sorted before
counting the species of interest (Ayre and Lamb 1990).
Unfortunately, predicting cutworm outbreaks based on adult numbers
generally does not work (Ayre and Lamb 1990; Turnock et al. 1993)
or is impractical. For most species, the cutworms that are damaging
crops in the current year have developed from eggs laid in the previous
year (table, p. 5). Thus, depending on overwintering mortality and other
factors, catches of moths in autumn may not reflect cutworm numbers
in the following spring. For example, catches of moths in a light trap
operated for 11 years in southern Manitoba did not correspond to
regional levels of damage caused by their larvae (Ayre and Lamb 1990). In
addition, maintaining a network of traps to develop regional forecasts can
be expensive. Furthermore, regional forecasts may not apply to individual
fields where factors such as soil type and crop type greatly influence
the risk of cutworm damage. Hence, timely scouting of individual fields
remains the best method to minimize cutworm damage (see Scouting, p.
12).
Western bean cutworm is an exception. Adults lay eggs in mid-summer
from which larvae hatch to feed on crops later in the same growing
season. Thus, for this pest, use of pheromone traps is recommended to
monitor adult numbers to assess the risk of subsequent crop damage by
the larvae.
Cutworm damage to cereal crop
© Western Australian Agriculture Authority
(Department of Agriculture and Food, WA: www.agric.wa.gov.au)
predIctIng outBreaKS
11
Cutworm Pests of CroPs on the Canadian Prairies
predIctIng outBreaKS
12 Cutworm Pests of CroPs on the Canadian Prairies
ScoutIng
13
Cutworm Pests of CroPs on the Canadian Prairies
Scouting
Producers need to check their
fields frequently in spring and early
summer for signs of cutworm
damage. Cutworms will sever
canola seedlings. Cereal seedlings
may be severed or have leaves
removed near attachment points.
In this latter case, the base of
the plant may be visible on closer
examination. For corn at growth
stage V2 or V3 (i.e., when the lower
two or three leaves, respectively,
have visible collars [aka collared
leaves]), cutworms may tunnel into
the plant from below-ground to
kill the inner whorl of developing leaves. The collared leaves remain alive
and green but little further growth will occur. Damage in peas is visible as
freshly cut or wilting plants within otherwise healthy stands. Sugar beet
seedlings may be severed, whereas older plants may have single leaves
removed.
Individual cutworms tend to feed within
the seed row, with movement between
plants aided by the loosened soil caused
by the seeding implement. When the
attacked plant dies, it leaves a gap in the
row. The length of the gap increases as
cutworms move down the row to feed
on the next healthy plant. When these
lengthening gaps occur in adjacent rows,
they form thinning or bare patches of
expanding size surrounded by healthy
young plants. Producers may attribute
these patches to poor germination, but
closer investigation will show dead and
dying plants with stems cut close to
Dying plants with stems cut
close to the ground
Canola Council of Canada
Corn at V2 (two leaves with collars)
cc-by-sa 3.0 Rasbak
Armyworm larva outbreak in wheat
Mike Dolinski, MikeDolinski@hotmail.com
ScoutIng
14 Cutworm Pests of CroPs on the Canadian Prairies
the soil surface. Cutworms are normally not visible: they typically shelter
underground during the day and feed at night. However, aboveground
activity may occur during daylight hours, particularly when conditions are
cool and wet early in the growing season.
It is important to confirm the presence and identity of cutworms before
deciding on a course of action. For example, damping-off disease can
cause wilting in seedlings that may be mistaken for cutworm damage. To
confirm the presence of cutworms, carefully search the top 2.5 to 5 cm (1
to 2 in.) of soil around the base of severed plants at the end of within-row
gaps or around the base of healthy plants at the end of these gaps. Also
search the soil at the base of healthy plants in the middle of bare patches.
To look for cutworms between rows with feeding damage, carefully
remove plant residue and soil clumps. Large numbers of seagulls or other
birds may be attracted to fields when cutworms are abundant (p. 21).
When large flocks are observed, closer examination of the field to assess
cutworm numbers may be warranted.
Depending on the size of the affected area(s), cutworm density, the
crop, crop stage and whether the cutworms are still voraciously feeding,
control measures may or may not be required (see General Control Options,
p. 26).
Black cutworm larval damage
cc-by 3.0 WM Hantsbarger, bugwood.org
ScoutIng
15
Cutworm Pests of CroPs on the Canadian Prairies
ScoutIng
16 Cutworm Pests of CroPs on the Canadian Prairies
natural eneMIeS
17
Cutworm Pests of CroPs on the Canadian Prairies
Natural Enemies
Mortality by natural enemies
(parasitoids, predators,
pathogens) can reduce the
severity of cutworm outbreaks.
Mortality by parasitoidism can
be determined by collecting
cutworm larvae in the field
and holding them indoors in
containers for the emergence of
parasitoids. During a redbacked
cutworm outbreak at Saskatoon, Saskatchewan, estimated average
parasitoidism ranged from 38 to 61% depending on the year (King and
Atkinson 1928). Average parasitoidism was estimated to be 32% during
an armyworm outbreak in Tennessee (Breeland 1957), and from 20 to
60% during an army cutworm outbreak in southern Alberta (Byers et
al. 1993). Recent surveys of cutworms recovered in south, central and
northern Alberta from 2012 to 2014 revealed about 20% parasitoidism
(Floate 2016).
Pathogens (i.e., nematodes and fungal, viral or bacterial diseases) add
further to this mortality. A black cutworm study in Ontario showed that,
while parasitoidism averaged 21%, pathogens were responsible for a
further 35% mortality (Bucher and Cheng 1971). Predators kill additional
cutworms, but this type of mortality is difficult to quantify.
A recent review (Gavloski and Hervet 2013) lists known natural enemies
that attack army, darksided and redbacked cutworms in North America.
Other lists of natural enemies that affect pest cutworms are provided by
Strickland (1923), Crumb (1929), Walkden (1950), Breeland (1957) and
Schaaf (1972).
paraSItoIdS
In a generalized insect parasitoid lifecycle, females lay eggs near, on or in
a host. The eggs hatch into larvae that then feed on the host’s tissues.
Emerging parasitoids
Vincent Hervet, AAFC
Bee y
Mike Dolinski, MikeDolinski@hotmail.com
natural eneMIeS
18 Cutworm Pests of CroPs on the Canadian Prairies
Once the larvae mature, they either pupate in their host or exit their
host and then pupate. After pupation, the new adult parasitoids emerge
to seek out new hosts. Unlike predators, which may be generalists,
parasitoids typically attack and develop inside only a small number of
closely-related species. Thus, two cutworm species in the same field may
be attacked by different parasitoids. During winter months, parasitoids
survive as immature stages inside a host.
Depending on the species, parasitoids
may lay one or many eggs per host,
may lay their egg(s) in the host’s
eggs or larvae, and have one or more
generations per year. The eggs of some
species require a period of time before
hatching; the eggs of other species
develop inside the female and hatch
almost immediately when laid (O’Hara
2008). Some parasitoid species only
have females while other parasitoid
species may have populations that are
all female and other populations that
contain both males and females (Hervet
et al. 2014). Cutworm parasitoids include
wasps (Hymenoptera), flies (Diptera) and
mermithid worms (Nematoda).
Parasitoid wasps of cutworms include braconid, encyrtid and
ichneumonid species. Braconid and ichneumonid wasps lay their eggs in
early-instar cutworm larvae. Parasitoidism by braconids kills the cutworm
larva; parasitoidism by ichneumonids generally kills the cutworm in the
prepupal or pupal stage. Encyrtid wasps have a particularly interesting
lifecycle. Female encyrtids lay their eggs in the host’s eggs. In a process
called polyembryony, an encyrtid egg will divide several times to become
many eggs. The development of the wasp larvae that hatch from these
eggs is delayed until the cutworm has finished feeding as a late-instar
larva. The wasp larvae then complete their development and pupate
within the host; at this stage the host is called a ‘mummy’. Army cutworm
studies have shown show that one egg laid by the encyrtid wasp
Copidosoma bakeri (Howard) may produce up to 2,500 adult offspring
from the body of the host (Byers et al. 1993).
P 
P 
Parasites and parasitoids
both spend part of their
life cycle developing in or
on a host organism. When
a parasite leaves its host to
complete development, the
host normally lives. When
a parasitoid leaves its host
organism, the host nor-
mally dies. A great deal of
research has been devoted
to the study of parasitoids
as natural enemies of pest
insects.
natural eneMIeS
19
Cutworm Pests of CroPs on the Canadian Prairies
Parasitoid flies of cutworms mainly include bombyliid and tachinid
species. Bombyliids (bee flies) lay their eggs on soil or vegetation where
host species are likely to occur. Bombyliid eggs hatch to produce first-
instar larvae with a specialized shape (planidium) adapted for dispersal.
The planidium actively locates and then, depending on the species,
attaches to or penetrates the host (Yeates and Greathead 1997).
Second- and later instar bombyliid larvae are sedentary with a stouter
shape. Development to the pupal stage for most species occurs on the
outer surface of the host, although the larvae of some bombyliid species
develop inside the host (Yeates and Greathead 1997). For tachinids,
different species inject eggs directly into the host, lay their eggs on or
near the host, or on vegetation with the eggs hatching only if they are
consumed by the host (O’Hara 2008). Tachinid larvae normally exit their
host to pupate nearby in soil or ground litter. Sarcophagid and muscid
flies have been reported as cutworm parasitoids (Crumb 1929; Cheng
1977), but these reports are rare and possibly suspect (Dahlem and
Downes 1996).
Mermithid worms have only rarely
been reported from cutworms
and are not an important source
of mortality affecting cutworm
populations (Schaaf 1972). Adults
lay eggs on land or in water.
Newly-hatched mermithid larvae
are free-living until they infect a
suitable host. They develop inside
and ultimate fill the body cavity of
the host until they emerge as free-
living adults.
Encyrtid mummy — redbacked cutworm parasitoidized by Copidosoma bakeri
Miles Zhang
Mermithid worm exiting from host
Paul A. Lenhart
natural eneMIeS
20 Cutworm Pests of CroPs on the Canadian Prairies
predatorS
Ground beetles (Coleoptera: Carabidae) are among the most important
cutworm predators in agro-ecosystems, with about 400 species on the
Canadian Prairies and upwards of 80 species present in any field (Holliday
et al. 2014 and references within). Normal densities range from about
10 to 50 beetles per m2 (8 to 42 beetles per yd2) (Thiele 1977; Brust et
al. 1986b), but are occasionally much higher (Holliday and Hagley 1979;
Floate and Spence 2015). Depending on the species, adults range in size
from less than 3 mm to 30 mm (< ¹/₈ to 1¹/₈ in.). Ground beetle larvae and
adults may be herbivores, scavengers, omnivores or predators.
Plant-feeding ground beetle species are unlikely to damage field crops,
but many reduce weed densities by feeding on seeds (Kulkarni et al.
2015).
Predaceous species are generalists and feed on a number of crop
pests in addition to cutworms including aphids (Hemiptera: Aphididae),
cabbage root maggot, (Delia radicum L.; Diptera: Anthomyiidae) (Finch
1996), Colorado potato beetle
(Leptinotarsa decemlineata (Say);
Coleoptera: Chrysomelidae)
(Alvarez et al. 2013), grasshoppers
(Orthoptera: Acrididae) (Songa and
Holliday 1997), slugs (Mollusca:
Gastropoda) (Pianezzola et al.
2013), wheat midge (Sitodiplosis
mosellana (Géhin); Diptera:
Cecidomyiidae) (Floate et al. 1990)
and wireworms (Coleoptera:
Elateridae) (Fox and MacLellan
1956), among others.
Depending on their size, beetles may attack eggs, early- and late-instar
larvae, and pupae of cutworms (Frank 1971; Brust et al. 1986a; Frank
and Shrewsbury 2004). Walkden (1950) reported that one adult of the
ground beetle species Calosoma lugubre Leconte consumed 16 mature
corn earworm larvae (Helicoverpa zea (Boddie); Lepidoptera: Noctuidae)
before losing interest.
Calosoma beetle eating
a Bertha armyworm
Vincent Hervet, AAFC
natural eneMIeS
21
Cutworm Pests of CroPs on the Canadian Prairies
Other insect predators of cutworms include ants (Hymenoptera:
Formicidae), rove beetles (Coleoptera: Staphylinidae) (King and Atkinson
1928; Frank 1971)
and stiletto fly larvae
(Diptera: Therevidae)
(King and Atkinson
1928). Spiders capture
adult cutworms but not
in large numbers (Cheng
1973b). However,
spiders do feed on even
the largest cutworm
larvae and may at times
be important predators
(Schaaf 1972).
A number of vertebrate species also feed on cutworms. Birds (e.g., crows,
grackles, starlings, seagulls and hawks) eat large numbers of cutworm
larvae (King and Atkinson 1928; Walkden 1950; Cheng 1973b). Flocks of
seagulls following tractors during field operations can be a useful indicator
of cutworm outbreaks. Small rodents eat larvae and pupae in crops, and
a number of animals feed on army cutworm moths. Each summer, army
cutworm moths migrate in massive numbers from the prairies to the
mountains. At night, as
the moths feed on the
nectar of alpine and
subalpine flowers, they
are eaten by owls and
bats. During the day, the
moths aggregate under
rock formations where
they are discovered and
eaten by black bears,
grizzly bears, coyotes,
mountain bluebirds,
ravens and American
pipets. (French et al. 1994;
White et al. 1998).
Western bluebird eating a winter cutworm
Sylvia of Northern California
(courtesy of www.whatsthatbug.com)
Flock of gulls feeding on pests in a canola eld
Canola Council of Canada
natural eneMIeS
22 Cutworm Pests of CroPs on the Canadian Prairies
pathogenS
Pathogens that kill insects (i.e., entomopathogens) include bacteria, fungi,
nematodes and viruses. Collectively, these disease agents can cause high
levels of mortality (Walkden 1950). This has led to studies examining
the potential for these pathogens to be developed as commercial
microbial pesticides (aka biopesticides) (Ignoffo and Garcia 1979). And
while microbial pesticides have been identified and developed (van
Frankenhuyzen et al. 2015), none are registered for cutworm control in
Canada.
Ingested pathogenic bacteria kill their insect hosts by producing toxins
(Castagnola and Stock 2014). The toxins may attack the cells that line
the inside wall of the insect gut to cause starvation and eventual death,
or attack nervous tissue. Some groups of bacteria form spores that allow
them to persist outside of the host in the soil and on vegetation (e.g.,
Bacillus). Other bacteria cannot survive in the environment but live inside
as symbionts of nematodes that infect insects. The most widely studied
entomopathogenic bacteria is Bacillus thuringiensis (Bt), which produces
crystal (Cry) proteins with insecticidal activity. The bacterial gene that
produces Cry proteins has been incorporated into the genomes of various
plants to produce transgenic cultivars with insecticidal foliage (Shelton
et al. 2002). Different Bt isolates produce different types of Cry proteins
that vary in their toxicity to different insects. B. t. kurstaki (Btk) has been
commercialized as a pest control product for different Lepidoptera (moths
Metarrhizium-infected larva
Scott Johnson, Simon Fraser University
natural eneMIeS
23
Cutworm Pests of CroPs on the Canadian Prairies
and butterflies) species and B. t. israelensis (Bti) has been commercialized
as a Diptera (flies) control product. Btk-based products have been tested
in field studies against darksided cutworm, but were ineffective (Cheng
1973a). Bacteria pathogens isolated from cutworm pest species include
Achromobacter, Bacillus, Enterobacter, Klebsiella, Pseudomonas, Serratia and
Streptococcus species (Steinhaus and Marsh 1962; Cheng 1984).
Fungi attack insects by attaching as microscopic spores to the outer
surface of the host. The spores germinate and develop threadlike hyphae
that penetrate the insect’s cuticle (i.e., the insect’s outermost layer or
‘shell’) to colonize the body cavity. The fungal cells proliferate inside the
cavity and typically kill the insect. New spores are formed either inside
or on the dead host. Spore germination and the formation of new spores
require optimal temperatures and high humidity. Entomopathogenic
fungi recovered from cutworms
include species of Beauvaria,
Isaria, Metarrhizium, and
Sorosporella (Speare 1920;
Walkden 1950). Fungal
infections can cause appreciable
mortality levels in cutworm
populations but are not normally
a major source of mortality (King
and Atkinson 1928; Walkden
1950).
Juvenile entomopathogenic nematodes (e.g., Photorhabdus, Xenorhabdus)
infect insects by penetrating into their body cavity, usually through
existing opening (e.g., mouth, anus) or through thin regions of cuticle.
Once established in the body cavity, the infective juveniles release
bacteria that produce a toxin to kill the host. As the dead host begins to
liquefy, the nematodes (and bacteria) feed within, become adults and
produce successive generations. When the food quality of the decaying
host declines, the adult nematodes produce hundreds of thousands of
new juveniles that exit the dead insect to locate and infect new hosts.
The entire life cycle — from infection and host death to the release of
new infective juveniles — is completed within a few days. Nematodes
have been successfully commercialized as microbial pesticides for use
against insect pests (Georgis et al. 2006), and have been studied for
application against cutworms in laboratory and small-scale field trials
(Capinera et al. 1988; Morris et al. 1990; Ebssa and Koppenhöfer 2012;
Beauvaria-infected cutworm
Naomi DeLury, AAFC
natural eneMIeS
24 Cutworm Pests of CroPs on the Canadian Prairies
Mahmoud 2014). However,
no commercial nematodal
products for cutworms
control are available yet.
Viruses that infect insects
(baculoviruses) are ingested
by their hosts as occlusion
bodies (OBs). These OBs
contain one or more virus
particles surrounded by a
protein coat. The protein
coat protects the virus particles from temperature extremes and
ultraviolet radiation, allowing the particles to survive outside a host. The
virus particles are released when the protein coat of ingested OBs is
broken down by the combined action of the insect’s gut acidity (i.e., low
pH) and digestive enzymes. Once released, the particles enter the cells of
the insect and undergo numerous replication cycles. In the latter stages
of this replication process, virus particles reacquire the protein coat. The
replication process kills the insect host by causing cell wall breakdown,
which often given the insect a liquefied appearance. Dead insects contain
billions of OBs that are readily spread by wind and water. Because
baculoviruses have a narrow host range, they typically infect only one
or a few closely-related insect species. Large scale epizootics (i.e., an
epidemic non-human disease outbreak) of baculoviruses occur in pest
cutworm populations (Federici 1978), but are not normally a significant
cause of mortality. In Canada, baculoviruses have been reported in
redbacked cutworm and have been tested for their efficacy against
darksided cutworm. Initial results looked promising, but the study was
not completed (Cheng 1984).
Nematodes exiting dead host
in search of new victims
cc-by 3.0 Peggy Greb, USDA ARS, bugwood.org
natural eneMIeS
25
Cutworm Pests of CroPs on the Canadian Prairies
Once infected with a virus, the insect liquees internally and dies. The
outer covering of the insect body ruptures shortly after, releasing the
liqueed contents and spreading virus particles that infect other larvae.
Daniel A. Potter, University of Kentucky
natural eneMIeS
26 Cutworm Pests of CroPs on the Canadian Prairies
general control optIonS
27
Cutworm Pests of CroPs on the Canadian Prairies
General Control Options
Options for cutworm control include biological, chemical and cultural.
Effective use of these options relies on a strategy of integrated pest
management (IPM). As described in Philip (2015), the six key elements
of IPM are: i) implementing pest prevention strategies, ii) correct
identification and knowledge of potential pests, damage and their
natural enemies, iii) monitoring pests, damage, natural enemies and
weather conditions, iv) applying economic thresholds, v) suppressing pest
populations, and vi) evaluating results of control measures.
BIologIcal
The best option for the biological control of cutworms is to conserve
existing populations of their natural enemies (conservation biocontrol)
(see Étilé 2014 for conservation practices and strategies). This approach
employs farming practices that help maintain healthy populations of
parasitoids and predacious insects which are essentially an army of
unpaid employees working for the farmer to control pests. The most
effective way to do this is to minimize the use of insecticides (i.e., spray
only when necessary, apply products with high specificity, and limit
sprays to the affected area and a zone surrounding the affected area; see
‘Chemical’).
Maintaining field boundaries (e.g., roadside margins, fence lines) in a
semi-natural, undisturbed state with a diversity of flowering plants is
also beneficial. These boundary areas provide critical habitat to enhance
natural enemy overwintering survival. Plant species that flower at
different times provide a continuous nectar and pollen source for adult
parasitoids (and many pollinator species). Field boundaries also provide
habitat for alternate prey and host species to sustain predators and
parasitoids when cutworms are not present. Studies have repeatedly
shown that natural enemy diversity is higher in field boundaries than in
adjacent fields (Olfert et al. 2005).
Braconid wasp adult parasitizing beet armyworm
cc-by-nc 3.0 Debbie Waters, University of Georgia, bugwood.org
general control optIonS
28 Cutworm Pests of CroPs on the Canadian Prairies
Natural enemy populations also can be enhanced by increasing plant
diversity (and the availability of nectar and pollen) within fields (Altieri et
al. 1993). Intercropping may be an option in some cases. For example,
several studies have examined the effect of planting understories of
flowering plants in orchards or along orchard boundaries on pest species
and their natural enemies. A review of these studies shows that the
practice mostly reduces the pest species or has no effect; however, in a
few cases, pest numbers have increased (Simon et al. 2010). In annual
cropping systems, it may be possible to leave a low density or scattered
patches of flowering weeds without appreciably affecting crop yields.
A second option for biological control is to introduce natural enemies into
regions where they do not already occur. This is normally done to control
pest species that have originated elsewhere. In such cases, natural
enemies from the pest’s region of origin are relocated to where the pest
has become established (classical biocontrol). Care is required when
relocating natural enemies into new regions to avoid affecting organisms
other than the target species. Classical biocontrol programs normally
require many years of research and oversight by federal authorities (De
Clerck et al. 2006). Unfortunately, classical biocontrol does not provide
a good option for cutworm control for at least two reasons. First, most
of the main cutworm pest species are native to North America and their
general control optIonS
Diverse eld boundary/ditch
Tyler Wist, AAFC
29
Cutworm Pests of CroPs on the Canadian Prairies
natural enemies, effective or not,
are already present. Second, many
non-pest noctuid species could also
be attacked by non-native natural
enemies released against pest species.
However, on occasion, natural enemies
may find their own way into a region
(see sidebar).
The third option is to increase existing
populations of natural enemies
(augmentation biocontrol). In this
approach, large numbers of natural
enemies are mass-reared and then
released to seek out and attack the
target pest (Cranshaw et al. 1996).
One example of this approach includes
the mass-rearing and release of
parasitoids in greenhouses to control
aphids (Boivin et al. 2012). Another
example is the mass-rearing and
release of parasitoids in livestock
facilities to control filth-breeding flies
(Geden 2006). Purchasing biocontrol
agents is relatively expensive and it
may take days to weeks after release
before pest numbers decline. For these
reasons, augmentation biocontrol is typically only used to protect high
value crops that are under continuous attack by pest species. Because
cutworm outbreaks are sporadic and generally affect crops of relatively
low value, augmentative biocontrol strategies for cutworms have not
been developed.
cheMIcal
Registered insecticides for cutworm control change from year to year.
Consequently, specific products are not recommended here. For an
up-to-date list of available products, producers should contact the
appropriate provincial agriculture department/agency or search through
the Pesticide Management Regulatory Agency (PMRA) label database
(see Internet Resources, p. 77).
A N C
E A 
N A
Cotesia vanessae
(Reinhard)
is a parasitoid wasp native to
Europe and northern Africa.
It was rst recorded in North
America in 2009, when it
was reared from tomato
looper,
Chrysodeixis chalcites
(Esper) and cabbage looper,
Trichoplusia ni
(Hübner) in
southern Ontario. It may now
also be present in southern
Alberta (Hervet et al. 2014).
Laboratory studies show that it
develops well on alfalfa looper,
dingy cutworm, darksided
cutworm, army cutworm,
early cutworm and, to a lesser
extent, on redbacked cutworm
and Bertha armyworm (V.A.D.
Hervet, unpublished data).
e wasp may have arrived in
North America with overseas
shipment of plants.
general control optIonS
30 Cutworm Pests of CroPs on the Canadian Prairies
Pesticides should be used according to label instructions and only when
cutworm numbers exceed economic thresholds. Economic thresholds
vary by cutworm species, crop type, and stage of crop development (see
Species Specific Information, p. 32). Target applications only to infested
areas of the field and at the correct time-of-day for maximum efficiency.
For example, apply treatments to control night-feeding species (above-
ground cutworms, climbing cutworms) in early evening.
Target and non-target organisms are killed directly by exposure to the
insecticide at time of application and indirectly by contact with insecticide
residues. When options exist, use insecticides with a high specificity.
This approach reduces the harmful effects of applications to non-target
organisms including many natural enemies of not just cutworms but
also of other pest species (see Natural Enemies, p. 16). For example,
chlorpyrifos is an organophosphate and has a broad spectrum of activity.
When applied, care must be taken to avoid poisoning birds, wildlife,
fish, other aquatic organisms and honey bees (Brooks and Cutts 2016).
Deltamethrin is a synthetic pyrethroid and also has a broad spectrum of
activity. Soil residues of chlorpyrifos and deltamethrin are toxic to ground
beetles for at least one week after application (Floate et al. 1989).
Given the potential damaging effects of insecticides on non-target
organisms, producers should carefully assess the need for applications.
Control is most effective when cutworms are small/young (early instars).
Cutworms in the final instar have largely finished feeding and will soon
pupate (i.e., little further crop damage will occur). If most of the cutworms
are in this stage, insecticide application may be an unnecessary cost.
Depending on species, final-instar larvae may be about 25 to 50 mm (1
to 2 inches) in length. Furthermore, cutworm damage is typically isolated
to one or a few patches in a field. Depending on the size of the affected
area and potential for future damage, pesticide applications may not be
justified. If a decision is made to apply insecticides, spot-treat affected
areas plus a surrounding 10 meter (30 feet) wide buffer zone.
general control optIonS
31
Cutworm Pests of CroPs on the Canadian Prairies
cultural
There are few cultural control options. In the early part of the last
century, soil packing and the use of a drill press was shown to reduce
the movement of subterranean species. However, this practice did not
provide satisfactory cutworm control (Parker et al. 1921). Allowing
soils to build up a crust later in the season can reduce egg laying by
cutworm species that prefer to oviposit (i.e., lay eggs) in loose soils (King
1926; Sorenson and Thornley 1941). Cutworm-damaged fields can
be reseeded. However, if reseeded immediately without applying an
insecticide, cutworm larvae can survive to feed on the reseeded crop.
For this reason, cultivate to remove living plants that may provide a food
source. Then wait 10 to 14 days before reseeding to starve the cutworm
larvae to death. Historically, this method was shown to be effective to
control pale western cutworm (Seamans and Rock 1945), but the practice
was not generally adopted as it required an additional field operation
and later-seeded crops are at greater risk to frost damage. Insecticide
application eliminates the need for a waiting period prior to reseeding.
Resistant crop cultivars may provide a future option to reduce cutworm
damage; unfortunately, none are currently available. And while pest
resistant cultivars have been successfully developed for some crops
for some pests (e.g., wheat midge resistant wheat cultivars (Vera et
al. 2013); genetically modified cultivars of several crops containing Bt
toxin genes (see Natural Enemies, p. 16), they are not a ‘silver bullet’ (i.e.,
insects routinely adapt to resistant plant cultivars (Tabashnik et al. 2013)).
This means that long-term cutworm control will continue to require a
comprehensive integrated pest management strategy.
general control optIonS
32 Cutworm Pests of CroPs on the Canadian Prairies
SpecIeS SpecIfIc InforMatIon
33
Cutworm Pests of CroPs on the Canadian Prairies
Species Specic Information
The following pages describe the economic pest cutworm species on the
Canadian Prairies, listed in alphabetical order by their common names. This
information has been extracted from scientific papers and government
reports, based mainly on research in Canada, but also in the USA.
The main heading of each page identifies the common and scientific
name that the species is currently known by. Other names that the
species may be known by also are provided. Each species is described
separately with two exceptions. Three species of Feltia with the same
common name (dingy cutworm) and similar life histories are combined in
one entry. Two species of Xestia with the same common name (spotted
cutworm) and similar life histories are also combined in one entry.
Information is provided to help identify species by both their adult and
larval forms. However, identification can be difficult, even for experts.
There are many species of noctuid moths that look similar to pest
species. Within a species, there may be different colour forms for adults
(e.g., redbacked cutworm moth) or larvae (e.g., bronzed cutworm).
Knowing when the species is present in the field as a larva or adult can
aid in correct identification.
Information on when different life stages are most likely to be
encountered in the field is provided in life cycle charts (see also table
on p. 5 and individual species descriptions). With minor exception (e.g.,
bronzed cutworm), the overwintering stage indicated for a given species
will be the same across Canada. However, the timing of when life stages
are present may vary by a few weeks depending on geographic regions
and year. For example, redbacked cutworm overwinters in Canada in the
egg stage. Egg hatch will occur sooner in warmer regions of the country
and in years with an early spring.
Information is also provided to help identify cutworm infestations when
they occur. Economic thresholds are provided when they are known.
Unless otherwise specified, the thresholds provided in this guide are from
Gavloski (2016) and Gavloski and Olfert (2016). Species Notes provide
additional information that may be of general interest or which may
further aid in pest control.
Redbacked cutworm larvae
John Gavloski, Manitoba Agriculture
SpecIeS SpecIfIc InforMatIon
34 Cutworm Pests of CroPs on the Canadian Prairies
larly common in arid regions.
lIfe cycle
Overwinters as half-grown
larvae in the soil before pupating
starting mid-May. Adults emerge
in early June and spend summer
in sheltered sites to escape heat.
Eggs are laid in or on loose soil late
in the season. One generation per
year.
hoStS
Wheat, oat, triticale, barley, canola,
mustard, flax, alfalfa, sweet clover,
pea, cabbage, sugar beet, various
weeds (notably stinkweed) and
grasses.
Army
Cutworm
Euxoa auxiliaris
(Grote)
o
ther coMMon naMe
Miller moth
french coMMon naMe
Légionnaire gris
IdentIfIcatIon
adultS: Forewings variable in colour,
but each with two prominent
spots, one round to oval, the other
kidney- or crescent-shaped. Wing-
span is 40-45 mm.
Mature larvae: Hairless; about 37-
40 mm in length. Body mottled
pale greenish-grey to brown with a
broad whitish dorsal stripe running
lengthwise. Head is light brown
with darker spots.
dIStrIButIon
Native to North America. Dis-
tributed throughout much of the
western part of the continent, east
to Michigan and north into the
Northwest Territories. It is particu-
Army cutworm larva
cc-by 3.0 Whitney Cranshaw, bugwood.org
Apr JunMay Jul Aug Sep Oct Nov
Overwintering Overwintering
Eggs Pupae
Adults
Larvae
arMy cutworM
35
Cutworm Pests of CroPs on the Canadian Prairies
feedIng daMage
aBove-ground cutworM: Young larvae
chew holes in leaves and notch
leaf margins while older larvae will
consume entire leaves.
MonItorIng/control
Monitor forage crops and pastures
closely in April and early May for
feeding damage. Count the num-
ber of larvae in a 50 cm by 50 cm
area of the crop; multiply by four
to estimate the number of larvae
per m2. Repeat this process 5 to 10
times at 50 m intervals.
Insecticide treatments may be
warranted if economic thresholds
are exceeded, but take steps to
minimize effects on natural ene-
mies; see General Control Options
(p. 26).
econoMIc threSholdS
cereal cropS: 5-6 larvae/m2.
canola: Thresholds not established;
however, a density of 5 larvae/m2
was reported to destroy a field of
mustard (Jacobson 1962a).
Army cutworm pupa
cc-by 3.0 Whitney Cranshaw, bugwood.org
noteS
When food is scarce, larvae will
move aboveground as a group in
the same direction to locate more
host plants. Hence the nickname
‘army’ cutworm.
Crops are at greatest risk to
damage by overwintered larvae
in early spring. Crops seeded later
in spring are at a lower risk of
damage; crops seeded in autumn
(e.g., winter wheat, winter triticale)
and alfalfa are at a higher risk of
damage in the following spring.
Larvae are similar in appearance to
armyworm (p. 36) and fall army-
worm.
Outbreak years are often preceded
by a year with an abnormally dry
July and wet autumn.
Most important as a potential
pest of crops in southern Alberta,
of lesser importance in southern
Saskatchewan, and only rarely of
importance in Manitoba (Beirne
1971).
Army cutworm adult
cc-by-nc 3.0 Mark Dreiling, bugwood.org
arMy cutworM
36 Cutworm Pests of CroPs on the Canadian Prairies
Armyworm
Cutworm
Mythimna unipuncta
(Haworth)
o
ther coMMon naMeS
Rice armyworm, true armyworm
french coMMon naMe
Légionnaire uniponctuée
IdentIfIcatIon
adultS: Forewings pale brown
with a single small white spot.
Wingspan of 40-50 mm.
Mature larvae: Hairless, about 38-
50 mm in length. Body greenish-
black with two alternating dark
and orange stripes along each side
plus a faint white line down the
back. Head has honey-comb like
markings.
dIStrIButIon
Global. Distributed throughout
the USA and southern Canada.
Present in parts of Europe, Asia,
Africa, Central America, and South
America.
lIfe cycle
Moths migrate into Canada
from the southern USA each
spring. Females lay white eggs
in batches of about 100 at the
base of host plants. Usually two
larval generations per year before
populations die off in the fall.
hoStS
Preferred hosts include native
grasses, oat, wheat, fall rye,
corn, barley, and forage grasses.
Secondary hosts include alfalfa,
bean, cabbage, onion, pea, sugar
beet, turnip and other species.
feedIng daMage
aBove-ground (clIMBIng) cutworM:
Larvae feed at night on leaf
margins and growing tips of host
plants. During the day, they hide
Immigrants
Apr JunMay Jul Aug Sep Oct Nov
Eggs Pupae
Adults
Larvae
arMyworM cutworM
Armyworm cutworm larva
cc-by 3.0 Joseph Berger, Bugwood.org
37
Cutworm Pests of CroPs on the Canadian Prairies
near the base of plants. Larvae
gradually move up the plants to
feed on the panicles and flowers,
stripping off awns and kernels.
MonItorIng/control
Monitor for larvae and feeding
damage from mid-June through
early-August. Count the number
of larvae in a 50 cm by 50 cm area
of the crop; multiply by four to
estimate the number of larvae per
m2. Repeat this process 5 to 10
times at 50 m intervals.
Preferentially sample locations
that are attracting birds. These
tend to be grassy, show signs
of lodging or areas with feeding
damage.
day tIMe MonItorIng: Remove ground
debris and count the exposed
larvae.
nIght tIMe MonItorIng: Beat the
plants to dislodge larvae and, using
a flashlight, count the number of
larvae on the soil. Check the backs
of larvae for eggs of parasitoids
(p. 39).
Control weedy stands of grass
in fields before the arrival of
adults to reduce egg-laying
opportunities and the risk of
subsequent infestations. Apply
foliar insecticides at night when
larvae are feeding; only treat areas
where larval densities exceed the
economic threshold.
Do not spray once larvae begin
to pupate or when the crop is
ripening.
Insecticide treatments may be
warranted if economic thresholds
are exceeded, but take steps
to minimize effects on natural
enemies; see General Control
Options (p. 26).
econoMIc threSholdS
cereal cropS (prIor to headIng):
40 small (<2.5 cm long) non-
parasitoidized larvae/m2.
cereal cropS (after headIng):
20 larvae/m2, if heads are clipped.
[Note: Wheat at the boot and
anthesis stages has been reported
to be able to sustain up to 75%
defoliation by armyworms with
the little loss in yield and with
negligible head cutting (Steinkraus
and Mueller 2003)].
forage cropS: 50 small (<2.5 cm
long) larvae/m2.
SeedlIng cropS: 20-30 small (<2.5 cm
long) larvae/m2.
Avoid insecticide treatments when
large numbers of parasitoidized
larvae are present.
Armyworm cutworm adult
cc-by-sa 3.0 Luis Miguel Bugallo Sanchez
arMyworM cutworM
38 Cutworm Pests of CroPs on the Canadian Prairies
noteS
First larval generation is most
damaging; second larval
generation can damage maturing
crops later in the summer.
When food is scarce, larvae will
move aboveground as a group in
the same direction to locate more
host plants; hence the nickname
Armyworm cutworm larval damage
Mike Dolinski, MikeDolinski@hotmail.com
‘armyworm. When armyworms
are observed migrating into the
field, treat a couple of swaths
in front of the infestation in the
direction of movement to form a
barrier strip.
Larvae are similar in appearance to
fall armyworm, army cutworm (p. 34)
and redbacked cutworm (p. 58).
arMyworM cutworM
39
Cutworm Pests of CroPs on the Canadian Prairies
arMyworM cutworM
Armyworm cutworm with three parasitoid eggs
cc-by-nc 3.0 Robert J. Bauernfeind
40 Cutworm Pests of CroPs on the Canadian Prairies
Black
Cutworm
Agrotis ipsilon
(Hufnagel)
o
ther coMMon naMe
Dark sword-grass cutworm
french coMMon naMe
Ver-gris noir
IdentIfIcatIon
adultS: Forewings long, narrow and
usually dark; tips lighter in colour
with three black dashes. Wingspan
of 38-50 mm.
Mature larvae: Hairless; about
35-45 mm in length. Upper body
nearly uniform in colour varying
from light grey to nearly black.
Head pale to dark brown.
dIStrIButIon
Native to North America.
Distributed throughout the USA
and southern Canada (Walkden
1950) and generally throughout
the world. More common in
moister regions of Canada; e.g.,
Manitoba and east.
lIfe cycle
Adults blow in (migrate) into
Canada from the southern USA
each spring; females lay eggs on
weed and grass hosts in fields
or margins. One or two larval
generations per year before
populations die off in the fall.
hoStS
Primarily corn, but also feeds
on alfalfa, clover, sunflower,
asparagus, bean, beet, cabbage,
lettuce, field pea, pepper,
potato, radish, spinach, squash,
strawberry and tomato. Favoured
weed hosts include bluegrass,
curled dock, lamb’s-quarters,
yellow rocket and redroot pigweed.
Black cutworm larva
cc-by 2.0 USGS Bee Inventory and Monitoring Lab
Apr JunMay Jul Aug Sep Oct Nov
Immigrants
Greatest Damage
Eggs Pupae
Adults
Larvae
BlacK cutworM
41
Cutworm Pests of CroPs on the Canadian Prairies
feedIng daMage
aBove-ground (tunnellIng) cutworM:
Larvae make burrows into which
they will drag their food. The first
larval generation is the most
damaging. Most larvae sever
young plants from roots near the
soil as they feed at the base of
the leaves; other larvae will feed
on the roots and underground
stems of cut plants. For corn at
growth stage V2 or V3 (i.e., when
the lower two or three leaves,
respectively, have visible collars
[aka collared leaves]), cutworms
may tunnel into the plant from
below-ground to kill the inner
whorl of developing leaves. The
collared leaves remain alive and
green but little further growth
will occur. One larva can kill many
plants before it pupates.
MonItorIng/control
Monitor germinating crop for
expanding thinned or bare areas.
In corn, examine ten plants in a
row at ten sites and estimate
the percent of dead or severed
plants. For sampling in cereals,
see pale western cutworm (p. 56).
Insecticide treatments may be
warranted if economic thresholds
are exceeded, but take steps
to minimize effects on natural
enemies; see General Control
Options (p. 26).
econoMIc threSholdS
cerealS: 3-4 larvae/m2.
oIlSeedS: 25-30% stand reductions.
peaS: 2-3 larvae/m2 in top 7 cm (3
in.) of soil (Philip 2015).
noteS
An occasional pest of golf course
greens and fairways (Frank and
Shrewsbury 2004).
Larvae cause damage out of
proportion to their numbers by
cutting plants without feeding on
them (Walkden 1950).
Avoid planting corn on newly-
broken sod or in fields that were
grassy or weedy the previous
summer. Corn is susceptible to
damage up to growth stage V3 (=
lower 3 leaves have visible collars;
see Scouting, p. 12). Use planting
practices to encourage rapid,
vigorous seedling development.
Black cutworm larval damage
cc-by 3.0 WM Hantsbarger, bugwood.org
Black cutworm adult
cc-by 2.0 Andy Reago and Chrissy McLarren
BlacK cutworM
42 Cutworm Pests of CroPs on the Canadian Prairies
Bristly
Cutworm
Lacinipolia renigera
(Stephens)
o
ther coMMon naMeS
Kidney-spotted minor moth,
bristly groundcat
french coMMon naMe
Ver-gris hérissé
IdentIfIcatIon
adultS: Forewings purplish-brown
with green patch. The green patch
on the lower half of each forewing
is kidney-shaped with a white
margin; above that is a distinct
black mark. Wingspan of 20-26
mm.
Mature larvae: Generally hairless,
but with short stout hairs
projecting from darkened warts;
about 25 mm in length. General
body colour is pale gray; a dark
band along the back is constricted
at regular intervals to form a chain
of diamond shapes.
dIStrIButIon
Native to North America. Widely
distributed from the southern USA
and north as far as the Northwest
Territories and east to Nova Scotia.
lIfe cycle
Overwinters as larvae. Two
generations per year (Walkden
1950) in Canada with more
generations in the southern USA.
Larvae pupate in earthen cells or in
flimsy cocoons spun in debris.
Bristly cutworm adult
cc-by 2.0 Andy Reago and Chrissy McClarren
Apr JunMay Jul Aug Sep Oct Nov
Overwintering Overwintering
Eggs Pupae
Adults
Larvae
BrIStly cutworM
43
Cutworm Pests of CroPs on the Canadian Prairies
hoStS
Alfalfa, clover, corn, tobacco, turnip,
apple, grape, cottonwood, and
many other species of herbaceous
plants and grasses (Crumb 1956;
Wagner et al. 2011).
feedIng daMage
aBove-ground (clIMBIng) cutworM:
The larvae feed near the ground.
Rarely reported as a pest but local
outbreaks occasionally cause
economic damage.
MonItorIng/control
Among the most abundant of
cutworm species. Larvae cling to
stems when disturbed. In contrast,
many other cutworm species will
coil up when disturbed.
Bristly cutworm larva
(c) Rob Bercha, www.insectsofalberta.com
econoMIc threShold
None developed.
noteS
Cryptic/well-hidden or
camouflaged. When alarmed, the
larva can fully retract its head into
its thorax. Associated with boreal
and northern transition forests
(Wagner et al. 2011).
BrIStly cutworM
44 Cutworm Pests of CroPs on the Canadian Prairies
Bronzed
Cutworm
Nephelodes minians
(Guenée)
o
ther coMMon naMe
None available
french coMMon naMe
Ver-gris bron
IdentIfIcatIon
adultS: Forewings highly variable in
colour, ranging from gray-brown,
tan, or reddish brown; darker band,
running left to right across the
middle of the wings, outlines pale-
filled spots. Wingspan of 30-40
mm.
Mature larvae: Hairless; about 35-
45 mm in length. General body
colour dark brown to blackish
usually with a distinct bronzy
sheen; distinctly paler on its
underside. Three distinct pale
stripes extending entire length
of back. Head dark brown to
brownish gray. Early-instar larvae
are bright green, only turning dark
brown in later instars.
dIStrIButIon
Native to North America.
Distribution coast-to-coast
extending from the southern USA
north to central Canada.
lIfe cycle
Overwinter as larvae or
occasionally eggs (see Notes,
following page). Only one
generation per year.
Apr JunMay Jul Aug Sep Oct Nov
Overwintering Overwintering
Eggs Pupae
Adults
Larvae
Bronzed cutworm larvae:
rst, third, and sixth instar
D. Shetlar
Bronzed cutworM
45
Cutworm Pests of CroPs on the Canadian Prairies
hoStS
Primarily feeds on grasses and
cereal crops; also reported to feed
on fruit tree buds and leaves.
feedIng daMage
aBove ground cutworM: Can climb.
MonItorIng/control
Occasional pest of corn, hay crops,
pastures and turf grass; more so a
concern in eastern Canada and the
USA (Gibson 1915).
econoMIc threShold
None developed.
noteS
A portion of the eggs laid in late
summer will hatch prior to winter;
larvae will feed until soil freezes
and may even feed during winter
under snow cover. Remaining eggs
will not hatch until spring. Larvae
hatching from overwintered eggs
may not complete development
until mid-summer.
Bronzed cutworm adult
cc-by-nc 3.0 Mark Dreiling
Bronzed cutworm larva
cc-by 3.0 Whitney Cranshaw
Bronzed cutworM
46 Cutworm Pests of CroPs on the Canadian Prairies
Clover
Cutworm
Anarta trifolii
(Hufnagel)
o
ther coMMon naMe
Nutmeg moth
french coMMon naMe
Ver-gris du trèfle
IdentIfIcatIon
adultS: Forewings uniform
or mottle ashy-gray to pale
brownish-gray in colour. Wingspan
25-36 mm.
Mature larvae: Hairless; about 40
mm in length. Body velvety-black
(occasionally green) with three
narrow, broken white lines along
the length of the upper surface
and a broad yellowish-pink stripe
along each side. Head is light
brown.
dIStrIButIon
Native to North America. Wide
distribution from Mexico north into
Alaska, excluding south-eastern
USA.
lIfe cycle
Overwinters as pupae 5-16 cm
(2-6 in.) below the soil surface;
eggs laid singly on leaves. Two
generations per year. The first
generation is the most damaging.
hoStS
Canola, mustard, flax are major
field crop hosts. Other hosts
include cruciferous weeds, sugar
beet, clover, and some forages.
feedIng daMage
aBove-ground (clIMBIng) cutworM:
Young larvae feed on the
undersides of leaves. Early signs
of damage in canola and mustard
appear as areas of the field
becoming lighter green to white;
older larvae feed on all parts of
the plant. Damaged areas typically
have a patchy distribution in fields.
Apr JunMay Jul Aug Sep Oct Nov
Overwintering Overwintering
Eggs Pupae
Adults
Larvae
Clover cutworm larva
cc-by 3.0 Lo Troisfontaine
clover cutworM
47
Cutworm Pests of CroPs on the Canadian Prairies
noteS
A viral disease of larvae can reduce
populations through the summer.
Similar in appearance and size
to Bertha armyworm larvae.
However, the majority of clover
cutworm larvae will be green or
light brown with fewer velvety
black individuals than in a Bertha
armyworm population. Also, the
side band on a Bertha armyworm
is yellowish-orange versus
of yellowish-pink for a clover
cutworm.
MonItorIng/control
canola, vegetatIve through early
pod Stage: Shake the plants in a
50 cm x 50 cm (0.25 m2) area;
count the larvae on the ground
after removing leaves and debris
[multiply number by four to
determine number of larva per
square meter]. Repeat at 10 to 15
locations separated by at least
50 m following a zig-zag pattern;
calculate the average number of
larvae/m2.
Apply foliar treatments in early
morning or late evening when
larvae are feeding. Because of
the patchy nature of infestations,
spray only where pest pressure
warrants.
Insecticide treatments may be
warranted if economic thresholds
are exceeded, but take steps
to minimize effects on natural
enemies; see General Control
Options (p. 26).
econoMIc threShold
Not established. As a nominal
threshold in canola, use provincial
recommendations given for bertha
armyworm, Mamestra configurata
(Walker).
Clover cutworm larva
R. Underwood, AAFC
Clover cutworm adult
cc-by-nc-sa 2.0 Ilona Loser
clover cutworM
48 Cutworm Pests of CroPs on the Canadian Prairies
Darksided
Cutworm
Euxoa messoria
(Harris)
o
ther coMMon naMe
Reaper dart moth
french coMMon naMe
Ver-gris moissonneur
IdentIfIcatIon
adultS: Forewings grayish, each
with an oval and a kidney-shaped
paler spot with darker margins
among irregular dark lines.
Wingspan of about 35 mm.
Mature larvae: Hairless, up to 37
mm in length. Grayish in colour
with a prominent white stripe
along each side just above the
legs; upper surface with a reddish
background colour. Head is
orange-brown with darker spots.
dIStrIButIon
Native to North America.
Distributed from Atlantic to Pacific
coasts, north from the southern
USA into southern Canada.
lIfe cycle
Females lay up to 1000 eggs in soil
or under debris in cultivated fields.
Mature larvae enter a non-feeding
pre-pupal stage for about 30 days
before pupating. One generation
per year.
hoStS
Broad range of herbaceous and
woody hosts including vegetables,
cereals, canola, corn, tobacco, flax,
sunflower, vine, berry and tree
fruits.
Apr JunMay Jul Aug Sep Oct Nov
Overwintering Overwintering
Eggs Pupae
Adults
Larvae Pre-pup ae
Darksided cutworm larva
John Gavloski, Manitoba Agriculture
darKSIded cutworM
49
Cutworm Pests of CroPs on the Canadian Prairies
econoMIc threShold
cereal and oIlSeed cropS: 5-6 larvae/
m2 (Phillip 2015).
peaS: 2-3 larvae/m2.
dry BeanS and Soy BeanS: 1 small
(<2.5 cm long) larva/m of row or
20% of plants cut.
noteS
Larvae are similar in colour to
redbacked cutworm.
The most destructive pest of
tobacco throughout most tobacco
growing regions of Canada
(Cheng 1984). Can be particularly
damaging to buds of trees and
shrubs (Walkden 1950).
feedIng daMage
aBove-ground (clIMBIng) cutworM:
Larvae feed at night on the leaves
and stems of young plants causing
defoliation and death. Areas of
bare soil increasing in size soon
after crop emergence may indicate
cutworm feeding damage.
MonItorIng/control
Inspect bare patches and
surrounding margins for larvae,
which hide at the base of plants
during the day. Count the number
of larvae in a 50 cm x 50 cm area
of the crop; multiply by four to
estimate the number of larvae per
m2. Repeat this process 5 to 10
times at 50 m intervals.
Insecticide treatments may be
warranted if economic thresholds
are exceeded, but take steps
to minimize effects on natural
enemies; see General Control
Options (p. 26).
Darksided cutworm pupa
John Gavloski, Manitoba Agriculture
Darksided cutworm adult
cc-by-nc-sa 3.0 Phil Meyers
darKSIded cutworM
50 Cutworm Pests of CroPs on the Canadian Prairies
Dingy
Cutworm
Feltia herilis (Grote)
Feltia jaculifera (Guenée)
Feltia subgothica
(Haworth)
o
ther coMMon naMeS
Herald or Master’s dart (F. herilis)
Bentline dart (F. jaculifera)
Gothic or Subgothic dart
(F. subgothia)
french coMMon naMe
Ver-gris du terne
IdentIfIcatIon
adultS: Forewings are dark brown
with pale stripes and bean-
shaped markings. Feltia herilis and
F. subgothica are most similar while
F. jaculifera has more prominent pale
streaks. Wingspan of 35-40 mm.
Mature larvae: Hairless; about 25-
32 mm in length. General body
colour pale grayish-brown; broad
gray stripe down the back with
light gray V-shaped patterns and
four black spots on each segment.
dIStrIButIon
Native to North America. Feltia
jaculifera and F. herilis are distributed
from Atlantic to Pacific coasts,
north from the southern USA into
southern Canada; F. subgothica is
restricted to east of the Rocky
Mountains, but otherwise similar to
F. jaculifera and F. herilis.
lIfe cycle
Overwinters as young larvae that
complete development in the
spring. Females lay eggs in the
soil near host plants, especially in
weedy, moist areas of fields. Larvae
feed in fall before burrowing into
Apr JunMay Jul Aug Sep Oct Nov
Overwintering Overwintering
Eggs Pupae
Adults
Larvae
Dingy cutworm larvae
(F. jaculifera)
John Gavloski, Manitoba Agriculture
dIngy cutworM
51
Cutworm Pests of CroPs on the Canadian Prairies
the soil to overwinter.
hoStS
Sunflower, alfalfa, corn, flax,
canola, oat, barley, rye and wheat;
many other vegetable, grass,
ornamental and weed hosts.
feedIng daMage
aBove-ground cutworM, alSo clIMBS:
Crops at greatest risk in the spring,
when partially mature larvae
emerge to feed. Larvae feed
primarily above ground on leaves
and only rarely on stems. Areas
of bare soil increasing in size soon
after crop emergence may indicate
cutworm feeding damage.
MonItorIng/control
Inspect bare patches and
surrounding margins for larvae.
Larvae hide at the base of plants
during the day. Use a trowel or
shovel to count the number of
larvae in the top 2-6 cm of soil in
a 50 cm x 50 cm area of the crop;
multiply by four to estimate the
number of larvae per m2. Repeat
this process 5 to 10 times at 50 m
intervals.
Insecticide treatments may be
warranted if economic thresholds
are exceeded, but take steps
to minimize effects on natural
enemies; see General Control Options
(p. 26). As with other climbing
cutworms, apply necessary foliar
treatments in the evening just
before larvae begin to feed.
econoMIc threShold
cerealS: 3-4 larvae/m2.
oIlSeedS: 25-30% stand reductions
peaS: 2-3 larvae/m2 in top 7 cm (3
in.) of soil (Phillip 2015).
noteS
Control of weed hosts in fallow
fields and post-harvest will reduce
attraction of females for egg
laying. Spring and fall cultivation
will expose larvae to predation by
birds and predatory insects.
The common name ‘dingy
cutworm’ is generally applied
to three closely-related species
that are similar in appearance,
distribution and life cycles (Crumb
1956; Ayre and Lamb 1990).
Dingy cutworm adult (F. jaculifera)
see p. 90 for photos of
F. herilis
,
F. subgothica
adults
Carl D. Barrentine
dIngy cutworM
52 Cutworm Pests of CroPs on the Canadian Prairies
Dusky
Cutworm
Agrotis venerabilis
(Walker)
o
ther coMMon naMe
Venerable dart moth
french coMMon naMe
None available
IdentIfIcatIon
adultS: Light to medium dark gray-
brown forewings with indefinite
markings. Wingspan of 30-36 mm.
Mature larvae: Hairless; about
40-43 mm in length. Body colour
nearly uniform, varying from dull
grayish to nearly black with pale
flecks; traces of pale lines along
back. Head pale brownish with
heavy black markings that are
much broader along the back.
dIStrIButIon
Native to North America. Coast-
to-coast in southern Canada,
throughout the USA and south to
Mexico (Crumb 1956).
lIfe cycle
One generation per year. In the
USA, overwinters as larvae (Crumb
1929). In Canada, overwintering
may occur as eggs in the top 1 cm
of soil, with completion of larval
development in June, pupation in
late July and then emergence as
adults in September (Ayre and
Lamb 1990).
hoStS
Pasture grasses, oat, corn, alfalfa,
clover, tobacco, chickweed,
dandelion and other roadside
weeds (Walkden 1950).
Apr JunMay Jul Aug Sep Oct Nov
Overwintering Overwintering
Eggs Pupae
Adults
Larvae
Dusky cutworm adult
cc-by-nc-sa 2.0 Ilona Loser
duSKy cutworM
53
Cutworm Pests of CroPs on the Canadian Prairies
feedIng daMage
aBove-ground (tunnellIng) cutworM:
Larvae hide in tunnels during
the day. They emerge at night to
remove pieces of foliage from the
host plant which they consume
back in their tunnels (Walkden
1950).
MonItorIng/control
Common, but rarely a crop pest
(Rings et al. 1976; Ayre and Lamb
1990). May damage turf grasses
when abundant; a minor pest of
gardens.
Dusky cutworm larva
© Canadian National Collection
econoMIc threShold
None developed.
noteS
Mature larvae enter a prolonged
non-feeding dormant stage during
summer months before pupating
in late summer or autumn (Crumb
1929).
duSKy cutworM
54 Cutworm Pests of CroPs on the Canadian Prairies
Glassy
Cutworm
Apamea devastator
(Brace)
o
ther coMMon naMe
None available
french coMMon naMe
Ver-gris vitreux
IdentIfIcatIon
adultS: Long grayish-brownish
body; forewings with several dark
spots. Wingspan of 35-40 mm.
Mature larvae: Hairless; about
35-40 mm in length. Body semi-
translucent, greenish-white or
gray; no prominent markings. Head
bright reddish-brown.
dIStrIButIon
Native to North America.
Distributed from east to west
coasts, north from Mexico to
Alaska.
lIfe cycle
Overwinters as young larvae that
resume feeding in the early spring.
They pupate in soil cells. Females
lay their eggs in the soil near host
plants.
hoStS
Primarily grasses; occasional
damage reported to cereals and
corn.
feedIng daMage
SuBterranean (Below-ground)
cutworM: Larvae feed underground
on plant crowns and roots, or, in
the case of bunch grasses, within
the crown and rarely come to the
surface. They often clip off more
leaves than they can consume.
Overwintering
Apr JunMay Jul Aug Sep Oct Nov
Overwintering
Eggs Pupae
Adults
Larvae
Glassy cutworm larva
cc-by 3.0 Joseph Berger, bugwood.org
glaSSy cutworM
55
Cutworm Pests of CroPs on the Canadian Prairies
In corn at growth stage VE (= 2
leaves visible, none with collars),
clipped plants die and remain
upright. Outbreaks can last 2-3
years.
MonItorIng/control
In the fall and early spring, check
for larvae in fields by examining
the roots, crowns and nearby
soil of plants showing browned
or clipped leaves or slow growth.
In corn at growth stage VE (= 2
leaves visible, none wiapameath
collars), look for sections of dead
and upright plants within rows.
econoMIc threShold
None developed.
noteS
Newly broken land and summer
fallow with grassy weeds should
Glassy cutworm adult
cc-by-nc-sa 2.0 Ilona Loser
be well cultivated in August to
prevent new growth suitable for
egg laying and larval feeding.
Corn planted in fields seeded to
wheat in the previous year may be
at particular risk.
Apply insecticide using a high
water volume (200 L/ha) to
ensure the product reaches the
larvae beneath and within the
plant foliage. Apply insecticide
just before rains or irrigation to
improve control.
May co-occur with other cutworm
species, including lined Quaker
moth (Apamea inficita), thoughtful
apamea moth (Apamea cogitata),
plus dingy, pale western,
redbacked, variegated and yellow-
headed cutworm.
glaSSy cutworM
56 Cutworm Pests of CroPs on the Canadian Prairies
Pale Western
Cutworm
Agrotis orthogonia
(Morrison)
o
ther coMMon naMe
None available
french coMMon naMe
Ver-gris orthogonal
IdentIfIcatIon
adultS: Light gray forewings with
indefinite markings. Wingspan of
about 38 mm.
Mature larvae: Hairless; about 40
mm in length. Body pale gray
to greenish gray in colour. No
distinguishing markings except for
the yellow-brown head which has
two distinct vertical black dashes.
dIStrIButIon
Native to North America. Largely
restricted to arid and semi-arid
regions. Common in Canada on the
southern prairies in Alberta and
Saskatchewan.
lIfe cycle
Overwinter as eggs in the top 1 cm
of soil. Larvae pupate in earthen
cells. One generation per year.
hoStS
Cereals preferred, with greatest
damage observed in wheat, oat
and barley. Other hosts include
canola, mustard, flax, corn, sugar
beet, field peas and other legumes,
and certain weeds.
feedIng daMage
Below-ground cutworM: Newly-
hatched larvae feed on the surface
of newly-emerging shoots and
furled leaves of young plants
causing small holes. Older larvae
sever plants just below the soil
surface. They occasionally pull and
eat severed plants underground.
Apr JunMay Jul Aug Sep Oct Nov
Overwintering Overwintering
Eggs Pupae
Adults
Larvae
Pale western cutworm larva
cc-by-nc 3.0 John Capinera
pale weStern cutworM
57
Cutworm Pests of CroPs on the Canadian Prairies
econoMIc threSholdS
cerealS: 3-4 larvae/m2. [Note: pale
western cutworm at 8.4 larvae/m2
caused 25% loss in wheat and a 30
larvae/m2 caused 100% loss]
flax: 4-5 larvae/m2.
canola: 4-5 larvae/m2.
pea: 2-3 larvae/m2.
dry BeanS and Soy BeanS: 1 small
(< 2.5 cm long) larva per meter of
row, or 20% of plants cut.
noteS
Weed-free uncultivated fields in
August to mid-September are
less attractive to females for egg
laying.
If volunteer cereals show signs
of feeding damage in the spring,
cultivate the soil and keep it
black for 10 days before seeding
to starve young larvae (Salt and
Seamans 1945).
MonItorIng/control
Check for the presence of gaps
within rows. Monitor germinating
cereal crops for expanding thinned
or bare areas, especially on sandy
hilltops and south-facing slopes.
Examine the top 5-7 cm of soil in
a 30 cm x 30 cm (0.1 m2) area for
larvae at a minimum of 10 sites
along the edges of an affected
area. Multiply average by 10 to
calculate number of larvae per
square meter.
Insecticide treatments may be
warranted if economic thresholds
are exceeded, but take steps
to minimize effects on natural
enemies; see General Control
Options (p. 26).
Apply insecticides to infested
areas in late evening when larvae
begin feeding. Larvae that do
not contact residues on the soil
surface will be exposed when
they feed on treated leaves
pulled underground. Infested
fields should be sprayed before
reseeding.
Pale western cutworm damage
cc-by-nc 3.0 Phil Sloderbeck
Pale western cutworm adult
Van Truan, bugguide.net
pale weStern cutworM
58 Cutworm Pests of CroPs on the Canadian Prairies
Redbacked
Cutworm
Euxoa ochrogaster
(Guenée)
o
ther coMMon naMe
None available
french coMMon naMe
Ver-gris à dos rouge
IdentIfIcatIon
adultS: Forewings variable in colour,
ranging from light yellow-brown,
orange-brown, or red-brown
with a pale brownish-yellow
kidney-shaped spot pale. Tips of
forewings for all colour-forms have
a dark gray band. Wingspan of
about 40 mm.
Mature larvae: Hairless; about 38
mm in length. Broad reddish-
brown stripe extending down
the back with a dark center line
bordered by a dark band on each
side.
dIStrIButIon
Native to North America; globally
present in most of the northern
hemisphere in dry open habitats.
lIfe cycle
Overwinters as eggs in the top
1 cm of soil. Larvae pupate in
earthen cells. One generation per
year.
hoStS
Cereals, flax, canola, corn,
mustard, sunflower, sugar beet,
forage legumes, vegetables and
many other crops.
Apr JunMay Jul Aug Sep Oct Nov
Overwintering Overwintering
Eggs Pupae
Adults
Larvae
Redbacked cutworm larvae
John Gavloski, Manitoba Agriculture
redBacKed cutworM
59
Cutworm Pests of CroPs on the Canadian Prairies
Insecticide treatments may be
warranted if economic thresholds
are exceeded, but take steps
to minimize effects on natural
enemies; see General Control
Options (p. 26).
Apply insecticides to infested
areas in late evening when larvae
begin feeding. Larvae that do
not contact residues on the soil
surface will be exposed when they
feed on treated leaves. Infested
fields should be sprayed before
reseeding.
econoMIc threSholdS
cerealS: 5-6 larvae/m2.
graIn corn: 5-6 larvae/m2.
flax: 4-5larvae/m2.
canola: 4-5 larvae/m2.
pea: 2-3 larvae/m2.
dry BeanS and Soy BeanS: 1 small (<
2.5 cm long) larva per meter of
row, or 20% of plants cut.
noteS
May co-occur with pale western
cutworm (p. 56), black cutworm
(p. 40) and other species.
Uncultivated fields with broadleaf
perennial and winter annual
weeds attract egg-laying females.
Therefore, keep uncultivated fields
weed-free from late July to the end
of September. If volunteer cereals
show signs of feeding damage in
the spring, cultivate the soil and
keep it black for 10 days before
seeding to starve young larvae
(Salt and Seamans 1945).
feedIng daMage
aBove-ground cutworM: Newly-
hatched larvae feed on the surface
of newly-emerging shoots and
furled leaves of young plants
causing small holes. Plants
damaged in this manner may or
may not recover. Older larvae
move along rows cutting off leaves
and sever plants just below the soil
surface. They occasionally pull and
eat severed plants underground.
MonItorIng/control
Monitor germinating cereal crops
for sections within rows of dead
or dying plants; adjacent rows
with this damage may be visible
as thinned or bare areas. Examine
the top 5-7 cm of soil in a 30 cm
x 30 cm (0.1 m2) area for larvae at
a minimum of 10 sites along the
edges of an affected area. Multiply
average by 10 to calculate number
of larvae per square meter.
Redbacked cutworm adult
John Gavloski, Manitoba Agriculture
redBacKed cutworM
60 Cutworm Pests of CroPs on the Canadian Prairies
Spotted
Cutworm
Xestia c-nigrum
(Linnaeus)
Xestia dolosa
(Franclemont)
o
ther coMMon naMeS
Lesser black-letter dart moth,
Setaceous Hebrew character
french coMMon naMe
Ver-gris tachete
IdentIfIcatIon
The two species are indistinguish-
able to the layperson.
adultS: Forewings reddish brown
(males) or purplish gray (females)
with a pale ochre V-shaped mark
at the costa (p. 61). The base of the
wing is purplish gray in both sexes.
Wingspan of about 35-40 mm.
Mature larvae: Hairless, about 35
mm in length. Upper body mottled
light to dark brown or gray with
darker dorsal-lateral chevrons; the
lower side of the body is distinctly
paler in colour with a yellow or
orange tint, and may be bordered
by an irregular wavy black line.
Head white or pale brown with
black submedian arcs (p. 61); fine
interlaced black to rust-coloured
markings along body.
dIStrIButIon
Xestia c-nigrum has broad
distribution across the northern
hemisphere. In North America,
it occurs from Mexico north
throughout the USA (uncommon
or absent in drier regions and
southern states) and Canada into
Alaska (in the west) and James Bay
(in the east). Xestia dolosa is known
from northcentral to northeastern
USA and southeastern Canada.
lIfe cycle
Overwinter as larvae; emerge the
following spring to complete the
first and then a second generation.
May complete a third generation in
Apr JunMay Jul Aug Sep Oct Nov
Overwintering Overwintering
Eggs Pupae
Adults
Larvae
Spotted cutworm larva
cc-by-sa, Hsuepe
Spotted cutworM
61
Cutworm Pests of CroPs on the Canadian Prairies
southern regions of its distribution
(e.g., Tennessee).
hoStS
Broad host range; includes many
agricultural (alfalfa, clover, corn,
oat, pea, sunflower, tobacco,
wheat) and horticultural (apple,
beet, cabbage, carrot, cauliflower,
celery, maple, pear, peppermint,
rhubarb, tomato, turnip) crops.
Other hosts include ferns, Canada
thistle, chickory, chickweed,
currant, goldenrod, gooseberry,
violets and grasses.
feedIng daMage
aBove-ground (clIMBIng) cutworM:
Larvae feed on leaves, sever
seedlings and eat roots.
MonItorIng/control
Commonly reported as pests
during outbreaks, particularly in
vegetable gardens.
econoMIc threShold
None developed.
noteS
‘Spotted cutworm’ is the common
name that has been generally used
for two closely-related species
that are similar in appearances
and lifecycles, and which have
overlapping distributions
(Franclemont 1980).
In the Maritimes, larvae are
reported to pupate in late April
and May, with the first flight of
adults in mid-May/early June
(Gibson 1915). In Ontario, the
first and second flights of adults
are reported to occur in May
and September (Rockburne and
Lafontaine 1976).
Spotted cutworm larva (early
instar)
cc-by-sa 2.5 James Lindsey
Spotted cutworm adult
George F. Hampson (ed.) adapted
by Dysmorodrepanis
Pale V-shape at costa
Spotted cutworm larva (submedian
arcs labelled)
Tina Schulz
Black submedian arcs
Spotted cutworM
62 Cutworm Pests of CroPs on the Canadian Prairies
Variegated
Cutworm
Peridroma saucia
(Hubner)
o
ther coMMon naMe
Pearly underwing
french coMMon naMe
Ver-gris panaché
IdentIfIcatIon
adultS: Forewings are yellow or
brown with a pale oval marking
near the wing edge, adjacent to
a darker kidney-shaped marking.
Wingspan of 45-50 mm.
Mature larvae: Hairless, about 35-
40 mm in length. Body pale gray
or light brown mottled with dark
brown. Larvae have four to seven
pale yellow spots along their back
with a large black followed by a
large yellow spot on the last (8th)
segment. They also have a narrow
orange-brown stripe along their
side.
dIStrIButIon
Broad global distribution. In North
America, it occurs in Mexico,
throughout the USA and across
southern Canada.
lIfe cycle
A study from Manitoba concluded
that variegated cutworm does
not overwinter in Manitoba, and
moths of this species are blown in
from the south in the spring (Ayre
et al. 1983). Two or three larval
generations per year depending on
weather conditions.
hoStS
Broad host range that includes
corn, bean, alfalfa, cereals, sweet
clover, potato, soybean, garden
crops, trees, vines, grasses,
ornamentals and greenhouse
plants.
Variegated cutworm larva
cc-by-nc 3.0 James Kalisch, bugwood.org
varIegated cutworM
Apr JunMay Jul Aug Sep Oct Nov
Eggs Pupae
Adults
Larvae
Immigrants
63
Cutworm Pests of CroPs on the Canadian Prairies
econoMIc threShold
None specifically for this pest; for
other cutworms 2-4 larvae/m2
can cause significant injury or loss
depending on crop (Philip 2015).
noteS
Eggs laid on host plants in clusters
averaged about 130 eggs (Wadley
1921); each female may lay up to
2000 eggs.
Fields free of weeds and volunteer
crop hosts are less attractive for
egg laying.
feedIng daMage
aBove-ground (clIMBIng) cutworM:
Larvae climb up plants at night to
feed on foliage, flowers, buds and
fruits.
MonItorIng/control
Adults can be detected with
pheromone-baited traps. When
cutworm damage is suspected:
daytIMe: Examine the top 3-6 cm of
soil around the plants for larvae.
nIghttIMe: Use a sweep net on
foliage to catch feeding larvae.
Insecticide treatments may be
warranted if cutworm numbers are
high, but take steps to minimize
effects on natural enemies; see
General Control Options (p. 26).
Apply insecticides to infested
areas in late evening when larvae
begin feeding.
Variegated cutworm adult
cc-by-nc 3.0 Mark Dreiling, bugwood.org
varIegated cutworM
64 Cutworm Pests of CroPs on the Canadian Prairies
weStern Bean cutworM
Western Bean
Cutworm
Striacosta albicosta
(Smith)
o
ther coMMon naMe
None available
french coMMon naMe
Ver-gris occidental du haricot
IdentIfIcatIon
adultS: Forewings are mainly
grayish-brown in colour with a
broad white margin along leading
edge (costa). On each forewing,
there is also a small spot above a
kidney-bean shaped surrounded
by a white margin. Wingspan of
35-40 mm.
Mature larvae: Hairless and
generally smooth (no bumps or
warts); about 35-40 mm in length.
Body tan or pinkish in colour; two
distinct black ‘rectangles’ located
on the segment immediately
behind the brown-coloured head.
Apr JunMay Jul Aug Sep Oct Nov
Eggs Pupae
Adults
Larvae
Western bean cutworm larva
Laboratoire de diagnostic en phytoprotection,
Ministère de l’Agriculture, des Pêcheries et de
l’Alimentation du Québec,
www.iriisphytoprotections.qc.ca
dIStrIButIon
Native to North America. Historical
occurrence on the Great Plains,
extending from northern Mexico
northward to the southern Prairie
Provinces (Crumb 1956; Michel
et al. 2010). Since about 2000, its
range has rapidly expanded east
and north to include southern
Ontario and Quebec and the
northeastern United States (Michel
et al. 2010). Although damage by
this pest has not been reported
in the Prairie Provinces, corn and
dry bean producers are advised to
be aware of the potential for such
damage.
OverwinteringOverwintering
65
Cutworm Pests of CroPs on the Canadian Prairies
weStern Bean cutworM
Western bean cutworm adult
Jocelyn Smith, University of Guelph
lIfe cycle
Mature larvae typically drop from
the host plant to the ground by
early November and tunnel into
the ground to overwinter within a
soil chamber. Pupation occurs in
the spring with adults emerging
in mid- to late summer. Eggs are
laid in masses of 5-200 eggs on
leaves of the host plant and hatch
in about a week. One generation
per year.
hoStS
Primarily a pest on corn,
secondarily on dry beans, pea,
squash, cucumber; it is not a
soybean pest. A generalist feeder
on many herbaceous species
with a preference for legumes. In
addition, it has a high survival on
red root pigweed, nightshade and
lamb’s quarters (Smith et al. 2011).
feedIng daMage
aBove-ground (clIMBIng) cutworM:
In corn, eggs are laid on the
upper leaf surface of typically the
youngest 3 to 4 leaves; cultivars
with upright leaves are preferred.
Newly-hatched larvae feed on silks
and tassels; older larvae tunnel
into the ear to feed on kernels.
Mature larvae are most often seen
feeding on the tips (occasionally
on the side) of mature ears.
Larval feeding damage makes
the ear prone to fungal infection,
mycotoxin accumulation, and
attack by secondary pests.
Pretassel corn fields are preferred
by egg-laying females. Females
may shift to oviposit in nearby
fields of dry beans when cornfields
have begun to shed pollen.
In dry beans, eggs are typically laid
on the underside of leaves deep in
the canopy. Newly-hatched larvae
feed on leaves and flowers, but
don’t cause economic losses. Older
larvae hide on the soil surface
during the day and feed at night
on the outside of pods, or tunnel
into the pod to feed on developing
beans. Damaged pods have an
increased incidence of bacterial
and fungal diseases.
66 Cutworm Pests of CroPs on the Canadian Prairies
weStern Bean cutworM
Western bean cutworm adult
and egg mass
Jocelyn Smith, University of Guelph
MonItorIng/control
Summarized from Michel et al.
(2010) and OMAFRA (2013):
Use western bean cutworm (WBC)
pheromone traps starting in late
June to monitor adult activity.
Begin scouting fields for eggs
and larvae when trap counts are
nearing peak flight. Peak flight in
Ontario tends to occur in late July
to early August. Infestations are
more difficult to detect once eggs
hatch — newly-hatched larvae eat
their empty egg shells while older
larvae are hard to find in corn once
they enter whorls or tunnel into
ears.
corn: Examine the youngest 3-4
leaves of 20 plants at a minimum
of 5 scattered locations in the field.
Give preference to pretassel corn
fields or individual plants that will
soon or have just begun to shed
pollen. Because infestations are
patchy and the egg-laying period
may extend for several weeks,
repeated visits to fields may be
necessary.
It is critical that foliar insecticides
be applied to coincide with egg
hatch. After egg hatch, larvae
enter the corn ear where they
are protected from insecticide
applications. If only whitish eggs
are seen on plants, mark the
plants and return in 3-4 days. If
eggs have begun to turn purple,
they will hatch in 1-2 days.
dry BeanS: Place one WBC
pheromone trap on either side of the
field, along the field’s edge; monitor
trap catches regularly starting in
late June and keep a running tally of
the cumulative catch per trap. Peak
flight is reached once numbers begin
to decline from the previous week’s
total.
Focus scouting efforts in the field
approximately 10–20 days after
peak moth flight when pod feeding is
likely to occur; search for early signs
of feeding damage. Scouting for egg
masses in adjacent cornfields (which
are easier to find than in dry edible
beans) can also help determine local
WBC populations.
67
Cutworm Pests of CroPs on the Canadian Prairies
weStern Bean cutworM
Western bean cutworm larval
damage in corn
Jocelyn Smith, University of Guelph
Western bean cutworm larval exit
wounds on bean
Jocelyn Smith, University of Guelph
Insecticide treatments may be
warranted if economic thresholds
are exceeded, but take steps
to minimize effects on natural
enemies (see General Control
Options, p. 26).
econoMIc threShold
corn: Eggs or small larvae detected
on 5% of scouted plants. If the eggs
have hatched, spray at 95% tassel
emergence; if tassels are already
emerged, spray when most of
the eggs are expected to hatch.
Select insecticides that have some
residual activity during the moth
flight/oviposition period.
dry BeanS: If WBC has reached a
threshold in the neighbouring corn
field, then adjacent dry edible bean
fields are likely at risk, especially
if the corn fields have passed the
pre-tassel stage. If entry holes are
observed in the pods prior to R6
stage, an insecticide application is
necessary. Select insecticides that
have some residual activity, and pay
attention to pre-harvest intervals.
noteS
Overwintering survival is favoured
in sandy soils where larvae can
tunnel to greater depths that
protect from soil tillage and cold
temperatures Deep tillage may kill
overwintering larvae.
Larvae from the same egg mass
may move 2–3 m to feed on
different plants.
Transgenic Bt corn hybrids
containing Vip3A protein are
reported to provide nearly 100%
control. Transgenic Bt corn hybrids
containing Cry1F protein may
provide some protection, although
WBC appears to be developing
resistance in the USA and Ontario
(Ostrem et al. 2016).
68 Cutworm Pests of CroPs on the Canadian Prairies
Winter
Cutworm
Noctua pronuba
(Linnaeus)
o
ther coMMon naMeS
Snow cutworm,
Large yellow underwing moth
french coMMon naMe
Fiancée
IdentIfIcatIon
adultS: Forewings brown with
prominent small black dots near
tip; hindwings bright yellow-
orange with a black marginal band.
Wingspan of 50-55 mm. Distinct
from other species.
Mature larvae: Hairless; about 35-
40 mm in length. Body typically
olive brown, occasionally green
or with a reddish-hue. Each body
segment has a distinct black and
cream-coloured dash on either
side of the dorsal mid-line. Head
tan in colour with two thick black
lines that form a ‘V’ extending out
from the ‘neck’ of the larva.
dIStrIButIon
Non-native; broad distribution in
Eurasia. In North America, it occurs
throughout most of the USA and
southern Canada.
lIfe cycle
Information is unavailable for
Canada. In Idaho, it overwinters
as partially or nearly mature
larvae. Adults require 4-6 weeks
to mature before laying egg
masses and are active into early
October (Bechinski et al. 2009).
Typically one generation per year,
although three to four may occur
in warmer climates (Passoa and
Hollingsworth 1996).
hoStS
Broad host range. Feeds on
alfalfa, oat, rye, wheat, and grass
Overwintering
Apr JunMay Jul Aug Sep Oct Nov
Overwintering
Eggs Pupae
Adults
Larvae
Greatest Damage Greatest Damage
Winter cutworm larva
cc-by-nc-sa 3.0 Malcolm Storey
wInter cutworM
69
Cutworm Pests of CroPs on the Canadian Prairies
econoMIc threShold
None developed.
noteS
First reported in North America in
Nova Scotia in 1979; now present
in all provinces and often common.
Larvae will feed during mild winter
days (temperatures of about 7°C
and above). Hence, the common
name of ‘winter’ or ‘snow’
cutworm.
There are no reports of crop
damage by this pest in Canada.
This may be because the species
is a relatively new arrival to North
America, or because our colder
weather prevents it from reaching
high densities.
hay. Vegetables hosts include
carrot, onion, potato, spinach,
rhubarb, sugar beet and tomato.
Other hosts include strawberry,
hawkweed, dandelion, plantain,
grape, marigold, chrysanthemum
and others.
feedIng daMage
clIMBIng or SuBterranean (Below-
ground) cutworM, dependIng on hoSt
SpecIeS: At night, winter cutworm
will climb into the canopy of some
host species to feed on leaves,
buds and open flowers. They
will also sever young plants near
ground-level. During the day, they
hide under crop residue or clumps
of soil. For other host species (e.g.,
root crops), they will feed in the
crown and on roots.
MonItorIng/control
Common pest of gardens. Damage
to field crops has been reported
in alfalfa and rye (Michigan) and
winter wheat (Idaho) (Bechinski et
al. 2009). No research has been
done on managing this species as
an agronomic pest.
Winter cutworm adult
cc-by-nc 4.0 Ken-ichi Ueda
Winter cutworm larva
cc-by-nc 4.0 Judith Lopez Sikora
wInter cutworM
70 Cutworm Pests of CroPs on the Canadian Prairies
Yellow-
headed
Cutworm
Apamea amputatrix
(Fitch)
o
ther coMMon naMeS
None available
french coMMon naMe
Ver-gris á tête jaune
IdentIfIcatIon
adultS: Variable multicolored dark
red-brown to chocolate brown
forewings with a row of white
or ochre spots along the kidney-
shaped spot. Wingspan of about
40 mm.
Mature larvae: Hairless, about
30 mm in length. Body dull
greenish-white and somewhat
semitransparent; sides wrinkled
in appearance. Reddish head with
black mandibles. Each segment
with a few very small brownish
dots, each dot with one fine
brownish hair.
dIStrIButIon
Native to North America.
Widespread, excluding parts of
southeastern USA and much of the
Great Plains. Present across the
Prairie Provinces.
lIfe cycle
Overwinters as an early instar
larva. One generation per year.
hoStS
Broad host range that includes oat,
wheat, triticale, corn, pea, potato,
cabbage, currant, grape, lettuce,
rose, spinach, and turnip.
Overwintering
Apr JunMay Jul Aug Sep Oct Nov
Overwintering
Eggs Pupae
Adults
Larvae
Yellow-headed cutworm larva
Roxanne S. Bernard
yellow-headed cutworM
71
Cutworm Pests of CroPs on the Canadian Prairies
feedIng daMage
SuBterranean (Below-ground)
cutworM: Feeds on roots and can
sever young plants below the soil
line.
MonItorIng/control
Not usually considered a pest of
economic importance, although
local outbreaks have been
associated with crop damage.
econoMIc threShold
None developed.
noteS
Identified as Septis arctica, Knutson
(1944) reports that larvae of the
yellow-headed cutworm feed
mainly underground on the roots
of cereals, grasses and corn.
Secondarily, it is reported to feed
on shoots of vegetables and
shrubs.
Other sources identify it as an
above-ground feeding cutworm,
and it is indicated as such in the
table on p. 5.
During local outbreaks, larvae may
climb into hardwood shrubs to feed.
Yellow-headed cutworm adult
cc-by-nc-sa 2.0 Ilona Loser
yellow-headed cutworM
72 Cutworm Pests of CroPs on the Canadian Prairies
Other Common Cutworms of
Economic Importance
BlacK arMy cutworM
Also called the Finnish dart
moth, Actebia fennica (Tauscher)
is a common boreal species that
occurs across North America and
south into the northern tier states.
Adults somewhat resemble those
of redbacked cutworm. Larvae are
hairless and black with wavy white
bands along either side of the
body. There is one generation per year, with larval-feeding completed by
the end of May or early June.
Huckleberry (Vaccinium spp.) is the common host plant, and larvae have
become an economic pest of blueberries in northeastern North America.
During outbreaks, larvae will feed on many other species and may
defoliate conifers.
clayBacKed cutworM
Also called the Swordman
Dart moth, Agrotis gladiaria
(Morrison) is generally
distributed east of the
Rocky Mountains. It is
most often associated
with grasslands in the prairie region. Adults are patterned with various
markings with a light-coloured fringe along the tip of the wings. Larvae
are hairless with a broad dorsal reddish-tan stripe divided lengthwise
by a mid-dorsal line. Winter is passed as partly grown larvae with one
generation per year.
Larvae feed on garden, berry and field crops. They have been reported
to be quite destructive at times in parts of their range. On the prairies,
populations can reach high numbers on pastures and in alfalfa, but do
not normally cause economic damage (Walkden 1950).
Black army cutworm larvae
John Gavloski, Manitoba Agriculture
Claybacked cutworm larva
cc-by-nc 3.0 James Kalisch, bugwood.org
other coMMon cutworMS of econoMIc IMportance
73
Cutworm Pests of CroPs on the Canadian Prairies
StrawBerry cutworM
Also called the Interoceanic Ear Moth,
Amphipoea interoceanica (Smith) occurs
across Canada from Nova Scotia and
west into Alberta. The forewings of
adults are light reddish-brown with
darker brown wavy lines and circles,
and each a prominent whitish spot near
the foremargin. Larvae are hairless
with a yellowish-brown head. The body
is cream-coloured with a broad dorsal
band and narrower subdorsal bands,
each coloured purplish-brown. Winter
is passed in the egg stage, with larvae
feeding from May into July. There is one generation per year.
Larvae feed on grasses and sedges and on the leaves, stems and fruits
of strawberry, for which they can be economically-important pests of
commercial fields (Ayre 1980).
whIte cutworM
Euxoa scandens (Riley) is a common species of climbing cutworm widely
distributed throughout Canada east of the Rocky Mountains. Adults have
light grey or gray-brown (rarely pink) forewings and white hindwings.
Larvae are hairless, whitish in colour with a brown head. Larvae can be
found starting in late July and overwinter. There is one generation per
year.
Larvae are occasionally reported to cause economic damage to various
vegetable crops and to fruit trees, the latter by feeding on buds and
leaves. Larvae also have been reported in sweet clover, and from around
the base of dock (Rumex spp.) and among willow sprouts along irrigation
ditches.
White cutworm larva
Canadian National Collection, AAFC
Strawberry cutworm adult
cc-by-nc-nd 2.0 Seabrooke Leckie
other coMMon cutworMS of econoMIc IMportance
74 Cutworm Pests of CroPs on the Canadian Prairies
Insects Commonly
Mistaken as Cutworms
By the time crop damage is detected, cutworms may range in size from
about 1-2 cm (0.5-0.75 in.) before reaching their final instar size of
about 3-4 cm (1.25-1.5 in.). Organisms that are occasionally mistaken as
cutworms include leatherjackets, millipedes, white grubs and wireworms.
leatherjacKet
Leatherjacket is the common name for
crane fly larvae (Diptera: Tipulidae). Adult
crane flies resemble large mosquitoes,
with a similar body shape and delicate
long legs. They feed on nectar and are not
pests. In contrast, the larvae of some crane
fly species can cause extensive damage
to grass and forage crops (Jackson and
Campbell 1975) and can be remarkably
similar in size, shape and colour to
cutworms. However, cutworms have
a distinct head capsule and legs which
leatherjackets lack.
Early cutworm larvae (left) vs. craney larvae (right)
Vincent Hervet, AAFC
Crane y larva (Tipula sp.)
John Gavloski, Manitoba Agriculture
InSectS coMMonly MIStaKen aS cutworMS
75
Cutworm Pests of CroPs on the Canadian Prairies
whIte gruB
White grubs are the larvae of
scarab beetles (Coleoptera:
Scarabaeidae). There are many
scarab beetle species. Adults
of some of these species are
commonly called June beetles or
Chafer beetles. Depending on the
species, larvae may feed in dung,
rotting vegetation or on plant
roots. Larval feeding by some
species is a common cause of
damage to turf on golf courses
(Smitley et al. 1998). Crop damage
by scarab beetle larvae on the prairies is uncommon. Fields that have
composted manure incorporated or have recently been converted from
pasture, meadow or rangeland may be at particular risk.
Similar to cutworms, scarab larvae have a head capsule and three pairs
of true legs on the thorax (p. 3). Unlike cutworms, scarab larvae lack
abdominal prolegs, are whitish in colour and typically rest with their body
Millipede
cc-by-nc-sa 3.0 Jeorg Spelda
White grub larva (scarab beetle)
(Chilothorax distinctus)
K.D. Floate, AAFC
InSectS coMMonly MIStaKen aS cutworMS
Millipedes have hard, long and
cylindrical bodies that may reach
30 mm for species found in
Canada. Each body segment has
two pairs of legs with usually more
than 20 segments per millipede.
They feed on a wide variety of
plant material, but tend to prefer
decaying plants and are not
considered crop pests. Although
they have a head capsule, the
presence of more than three
pairs of true legs immediately
distinguishes them from
cutworms.
MIllIpede
76 Cutworm Pests of CroPs on the Canadian Prairies
curved in a ‘C’ shape. The abdomen
of scarab larvae is distended with
an obvious swollen appearance
and often appears darkish, due to
digested material in the gut. The
maximum larval body length for
white grub species most often
reported from crop land (i.e., from
scarab subfamily Aphodiinae)
is unlikely to exceed 5 mm.
Larger species (Phyllophaga spp.;
subfamily Melolonthinae) with a
maximum larval size of 2-4 cm
may occasionally be encountered at sub-economic levels.
wIreworM
Wireworms are click beetle larvae
(Coleoptera: Elateridae). The larvae
of many click beetle species feed
underground on seeds, roots
and other below-ground plant
parts of different types of plants
and can cause significant crop
damage when present at high
densities. Pastures, meadows and
rangeland can have high densities
of wireworms. When these lands
are converted to annual cropping,
crops in the first or second year
following the conversion may be at
particular risk.
Both cutworms and wireworms have a cylindrical body shape with a head
capsule and three pairs of true legs on the thorax. However, wireworms
have a hard body, range in colour from pale yellow to reddish-brown,
have a distinct notch in the tail segment, and do not have abdominal
prolegs. Cutworms, on the other hand, are soft-bodied, lack a notched tail
segment, and have abdominal prolegs.
Wireworm (click beetle larva)
John Gavloski, Manitoba Agriculture
White grub adult (scarab beetle)
(
Chilothorax distinctus
)
K.D. Floate, AAFC
InSectS coMMonly MIStaKen aS cutworMS
77
Cutworm Pests of CroPs on the Canadian Prairies
Internet Resources
praIrIe peSt MonItorIng networK
Regional risk maps, in-season weekly updates, monitoring protocols, insect
of the week, etc.
www.prairiepestmonitoring.blogspot.ca/
peStIcIde ManageMent regulatory agency (pMra) peStIcIde laBel Search
View product information and full labels. The pesticide label search is also
available as a mobile app (iPhone and Android)
http://pr-rp.hc-sc.gc.ca/ls-re/index-eng.php
crop protectIon guIdeS
Alberta
http://www1.agric.gov.ab.ca/$Department/deptdocs.nsf/all/agdex32
Saskatchewan
http://www.saskatchewan.ca/business/agriculture-natural-resources-
and-industry/agribusiness-farmers-and-ranchers/crops-and-irrigation/
crop-protection/guide-to-crop-protection
Manitoba
www.gov.mb.ca/agriculture/crops/guides-and-publications/#gfcp
InSect guIdeS
Canola Council - Canola Encyclopedia - Insects - Cutworms
www.canolacouncil.org/canola-encyclopedia/insects/cutworms
Canola Watch - Cutworm Management Tips
www.canolawatch.org/2011/05/26/cutworm-management-tips/
Cutworms in field crops - Manitoba Ministry of Agriculture, Food, and Rural
Development
www.gov.mb.ca/agriculture/crops/insects/cutworms-field-crops.html
Field Crop and Forage Pests and their Natural Enemies in Western Canada -
Identification and Management Field Guide
http://publications.gc.ca/site/eng/9.630050/publication.html
Guide des ravageurs de sol en grandes cultures (Soil crop pests guide –
French only):
www.agrireseau.net/grandescultures/documents/guide%20des%20
ravageurs%20du%20sol_dec%202012.pdf
Western Forum on Pest Management – guidelines for insect pest control in
cereal grains, oilseeds, forage crops, pulse crops, tree fruits, turf, and wood
and timber structures
www.westernforum.org
Internet reSourceS
78 Cutworm Pests of CroPs on the Canadian Prairies
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1. cc-by-nc 3.0 Mark Dreiling, bugwood.org
2. cc-by-sa 3,0 Luis Miguel Bugallo Sanchez
3. cc-by 2.0 Andy Reago & Chrissy McClarren
4. cc-by 2.0 Andy Reago & Chrissy McClarren
5. cc-by-nc 3.0 Mark Dreiling, bugwood.org
6. cc-by-nc-sa 2.0 Ilona Loser
7. cc-by-nc-sa 3.0 Phil Meyers
8. cc-by-nc-sa 2.0 David Reed
9. Carl D. Berrentine
10. cc-by-nc-sa 3.0 Phil Meyers
Quick Guide Index — Cutworm adults (Appendix A)
Black cutworm
page 40
32
Armyworm cutworm
page 36
1
Army cutworm
page 34
Dingy cutworm
page 50
8
F. herilis F. jaculifera
9
Bristly cutworm
page 42
4
Bronzed cutworm
page 44
5
F. subgothica
10
7
6
Darksided cutworm
page 48
Clover cutworm
page 46
appendIx a - cutworM adultS
91
Cutworm Pests of CroPs on the Canadian Prairies
Spotted cutworm
page 60
Pale-western cutworm
page 56
Redbacked cutworm
page 58
1514
13
Variegated cutworm
page 62
11. cc-by-nc-sa 2.0 Ilona Loser
12. cc-by-nc-sa 2.0 Ilona Loser
13. Van Truan, bugguide.net
14. John Gavloski, Manitoba Agriculture
15. cc-by-sa 2.5 Olaf Leillinger
16. cc-by-nc 3.0 Mark Dreiling, bugwood.org
17. Jocelyn Smith, University of Guelph
18. cc-by-nc 3.0 Paoloa Mazzei, bugwood.org
19. cc-by-nc-sa 2.0 Ilona Loser
Dusky cutworm
page 52
11
Glassy cutworm
page 54
12
Winter cutworm
page 68
Yellow-headed cutworm
page 70
16 17
1918
Western bean cutworm
page 64
17
appendIx a - cutworM adultS
92 Cutworm Pests of CroPs on the Canadian Prairies
Quick Guide Index — Cutworm larvae (Appendix B)
1. cc-by 3.0 Whitney Cranshaw, bugwood.org
2. cc-by 3.0 Joseph Berger, bugwood.org
3. cc-by 2.0 Bee Inventory and Monitoring Lab
4. R. Bercha, www.insectsofalberta.com
5. cc-by 3.0 Whitney Cranshaw, bugwood.org
6. cc-by 3.0 Lo Troisfontaine
7. John Gavloski, Manitoba Agriculture
8. © Canadian National Collection
Army cutworm
page 34
1
Armyworm cutworm
page 36
2
Bronzed cutworm
page 44
5
Clover cutworm
page 46
6
Black cutworm
page 40
3
Bristly cutworm
page 42
4
Darksided cutworm
page 48
7
Dingy cutworm
page 50
8
appendIx B - cutworM larvae
93
Cutworm Pests of CroPs on the Canadian Prairies
Dusky cutworm
page 52
9
Glassy cutworm
page 54
10
Spotted cutworm
page 60
13
Variegated cutworm
page 62
14
9. © Canadian National Collection
10. cc-by 3.0 Joseph Berger, bugwood.org
11. cc-by 3.0 Frank Peairs, bugwood.org
12. John Gavloski, Manitoba Agriculture
13. cc-by-sa Hsuepe
14. cc-by-nc 3.0 James Kalisch, bugwood.org
15. Ministère de l’Agriculture des Pêcheries et de
l’Alimentation du Québec
16. cc-by-nc-sa 3.0 Malcolm Storey
17. Roxanne S. Bernard
Pale western cutworm
page 56
11
Redbacked cutworm
page 58
12
Yellow-headed cutworm
page 70
17
appendIx B - cutworM larvae
Western bean cutworm
page 64
15
Winter cutworm
page 68
16
94 Cutworm Pests of CroPs on the Canadian Prairies
Notes
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Cutworm Pests of CroPs on the Canadian Prairies
Cutworm Pests of Crops
on the Canadian Prairies
identi fiCati on and ma nagemen t field gu ide
... Most cutworm species that attack our field crops are native to North America (Beirne 1971). Examples of economically important species found in pulse crops in United States and Canada include army cutworm (Euxoa auxiliaris (Grotel)), black cutworm (Agrotis ipsilon (Hufnagel)), darksided cutworm (Euxoa messoria (Harris)), dingy cutworm Feltia jaculifera (Walker), pale western cutworm (Agrotis orthogonia (Morrison)), redbacked cutworm (Euxoa ochrogaster (Guenée)), spotted cutworm (Xestia c-nigrum (Linnaeus), X. dolosa (Francelmont)), and western bean cutworm (Striacosta albicosta (Smith)) (Floate 2017). ...
... Size is variable depending on species and wingspan can range from 32 to 38 mm. Moths are most active during the evening hour, and feed on pollen or nectar (Floate 2017). Some examples of noctuid moths of pulse crops are described below. ...
... Some examples of noctuid moths of pulse crops are described below. Selection of these cutworm species is based on these species being common pests in pulse crops of the northern Great Plains of the United States and Canada (Floate 2017 ...
Article
Full-text available
Wireworms (Coleoptera: Elateridae) and cutworms (Lepidoptera: Noctuidae) are significant soil insect pests of pulse crops including chickpea (garbanzo bean) (Cicer arietinum L.), field pea (Pisum sativum L.), and lentils (Lens culinaris Medikus). Integrated pest management strategies established for pest monitoring and nominal thresholds can be used for making management decisions. However, producers continue to rely on chemical control as their main strategy to reduce economic populations. Cultural strategies, such as crop rotation and tillage, and biological control agents, such as predators, parasitoids, nematodes, and entomopathogens, help mitigate wireworm and cutworm populations, but are usually not adequate for management of economic populations. Future research needs for wireworms and cutworms in pulse crops should concentrate more on developing improved economic thresholds, and integrating multiple management strategies, especially biological control and host plant resistance, to reduce the reliance on chemicals.
... In the vast majority of cases, the larval stage of Lepidoptera pests is the harmful stage. For example, cutworm larvae are the only life stage that causes crop damage, and the rest of the life stages (egg, pupa, adult) have no impact on yield (Floate 2017). This is typical of pest Lepidoptera in agricultural settings (although exceptions exist), and larval feeding is the most common cause of economic damage. ...
... For example, in Ostrinia nubilalis (Hübner) (Lepidoptera: Crambidae), young larvae are leaf feeders on corn plants and cause damage by defoliation, and in later instars larvae burrow into stalks and can feed on silks, kernels, and cobs (e.g., . Xestia c-nigrum (Linnaeus) (Lepidoptera: Noctuidae) is a gregarious feeder with respect to plant part and can attack buds and fruit, resulting in direct damage to yield, as well as behaving as defoliators or cutting young plants (Capinera 2001, Floate 2017. Depending on the circumstances, the pest guild of each of these species may be leaf-mass consumer, turgor reducer, fruit feeder, or all three, and X. c-nigrum may also function as a stand reducer. ...
... Cutworms cut the stems of young plants at or below the soil level, and certain species of climbing cutworms defoliate plants (Floate 2017, Knodel andShrestha 2018). Three main feeding behaviors in cutworms have been documented: subterranean, above-ground or surface-feeding, and climbing (Walkden 1950, Floate 2017, Knodel and Shrestha 2018. Subterranean feeders, such as Apamea devastator (Brace) (Lepidoptera: Noctuidae), are active below the soil surface and cut the stems of young plants. ...
Article
Full-text available
The pest status of insects in agricultural settings is human-defined based on behaviors that may negatively impact the yield of susceptible crops. As such, both the insect behavior and the affected crop play a part in determining pest status. One helpful means of understanding pest status involves using pest injury guilds, which distinguish different pest groups based on similar kinds of injury to comparable plant tissues. Pest injury guilds defined in the literature are reviewed and then applied to agriculturally significant Lepidoptera. More specialized Lepidoptera behaviors which are economically relevant, such as leaf-rolling or stem-boring, are examined within their respective injury guilds. In this review, fruit-piercing moths are discussed within the context of pest Lepidoptera behaviors and are highlighted due to their unique means of causing economic damage. Unlike other Lepidoptera in agricultural settings, fruit-piercing moths are harmful as adults rather than larvae, and directly injure fruits using a specially adapted proboscis. The ecology and systematics of fruit-piercing moths, as well as current control options, are also discussed.
... Many species are generalists that only occasionally contribute to yield losses in pulses and legumes (e.g., grasshoppers and wireworms). Cutworms are an exception, as larval feeding activity directly reduces plant stands by cutting plant stems near the soil surface (Floate 2017). There are no Prairie-wide monitoring programs for soil-dwelling cutworms, but adults (moths) of some species are occasionally monitored in some provinces using pheromone traps (e.g., western bean cutworm). ...
... While the Prairie herbicide-resistant weed surveys and post-harvest resistance surveys provide estimates documenting the increased incidence of herbicide-resistant weed biotypes in the Prairie region of Canada, the testing of grower-submitted samples is required to identify novel biotypes before they become a problem across broad acreage. Strategic collaboration between AAFC and diagnostic labs with other organizations like SMA continue to provide an avenue for early discovery of novel herbicide-resistant weed biotypes which rely on diligent scouting efforts and sample submission by growers and agronomists (e. g., 2017;. ...
Article
Full-text available
Crop production had dominated the Canadian Prairies for the past century, and has been constantly challenged by various pathogens, insects, and weeds. An effective biovigilance program to manage these crop pests requires continuous, timely, and detailed pest surveillance, to understand how pest populations are changing over time. Many of these pests have been managed through surveillance and various mitigation strategies, combined with follow-up analyses. Pest surveillance activities have been documented in the Canadian Prairies for over 100 years and analysis has progressed from determining the pest species involved, to understanding the damage they cause, their biology, spread, over-wintering strategies, reproduction, pesticide resistance, and genetic diversity. This research has generated a continuous history of the pest populations for crops in western Canada. Detailed virulence analysis has revealed pathogen evolution and adaptation to overcome some of the deployed host resistance genes. Some weed, insect, and plant pathogenic fungal species have evolved to become resistant to pesticides. Integration of pest surveillance activities will help to build a more responsive, robust, and reliable biovigilance program to manage crop pests in the Canadian Prairies.