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Compiled by: John
Gavloski, extension entomologist, Manitoba Agriculture and Food,
Phone: (204) 745-5668
Abbreviations used:
The following abbreviations will be used in this document to indicate
the following agricultural regions in Manitoba; NW=Northwest,
SW=Southwest, C=Central, E=Eastern, I=Interlake.
Estimated acres:
Estimated acres grown in Manitoba in 2005 (shown in brackets under each
commodity title) are from the Manitoba Crop Insurance Corporations 2005
Variety Market Share Report.
Summary
Many of the
insects causing the most injury to crops in Manitoba in 2005 were
insects that do not overwinter well or at all in Manitoba, and where the
majority of the population in blown in on winds from the south.
Diamondback moth (Plutella xylostella) were noticed on traps as
early as April 18th, and were a concern on canola early in
the season. Populations declined as the season progressed, however, and
most of the control that was needed occurred early in the season.
Armyworms (Pseudaletia unipuncta) caused significant defoliation
to some cereal fields in the Central, Eastern and Interlake areas of the
province. Larvae of the painted lady butterfly (Vanessa cardui)
caused noticeable defoliation to Canada thistle in many areas of the
province, but populations were also high and insecticides applied to
control them in sunflowers, canola and borage.
Cutworms
were a problem in some cereal and canola fields early in the season.
Bertha armyworm, Mamestra configurata, was a problem on canola in
the Northwest region of Manitoba in August, resulting in significant
insecticide application.
cereals |corn
| canola | flax | sunflowers | forage crops |
field beans| peas | soybeans | canaryseed
(Wheat-2,593,130 acres; Barley-636,294
acres; Oats-526,513 acres; Rye-49,590 acres; Triticale-4,415
acres)
Cutworms:
Some cutworm damage to spring and winter wheat was reported, mainly from
the southwest, Central and Interlake regions of Manitoba.
Aphids
Aphids began appearing in cereal fields about mid-June, but did not get
to economical levels. No instances of cereal fields needing insecticides
to control aphids were reported.
Wheat midge (Sitodiplosis mosellana): No instances of insecticides being used
to control wheat midge were reported. However, several wheat samples
from the Southwest had high enough levels of midge damage to be
downgraded.
Armyworm (Pseudaletia
unipuncta): Armyworm populations were high and needed control in
some cereal fields in the Central, Eastern and Interlake regions of
Manitoba. Armyworm populations were controlled in fields in the Carman
(C), Roland (C), Homewood (C), Winkler (C), Lac du Bonnet (E) and Teulon
areas. High populations were not noticed until late July, and most of
the insecticide applications to control them occurred in late-July and
early-August. Prior to late-July larvae were small and went unnoticed in
most fields. Aside from the defoliation these caterpillars do, some
heads and panicles were being chewed off.
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(98,080 acres grain corn; 37,726 acres silage corn)
Cutworms:
Cutworms were a problem in a few corn fields in the Central and
Southwest regions. In one field near Arden (SW) corn next to forage was
treated to control glassy cutworm.
Wireworms
Some wireworm damage to corn was reported in the Altona (C) area.
European corn
borer
(Ostrinia nubilalis): Some corn in the Central region was sprayed
to control European corn borer, although few incidence of high corn
borer populations were reported. 59.2 % of grain corn was seeded to
Bt varieties, and 12% of silage corn was seeded to Bt
varieties.
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(Argentine canola-2,313,059 acres; Polish canola-1,743 acres; Mustard-3,470
acres)
Flea beetles
(Phyllotreta spp.):
Flea beetle populations in canola were much lighter than in 2004,
although there were still some flea beetle problems in some canola
fields in the Northwest, Southwest and Central regions of Manitoba. Some
spraying for flea beetles in canola occurred near Pilot Mound (C),
Somerset (C), Foxwarren (NW), and Gilbert Plains (NW).
Cutworms:
Cutworms were controlled in some canola fields in the Central and
Interlake areas of the province. Only patches of fields, and not whole
fields, were sprayed in some instances. A 50 acre field of canola near
Manitou (C) needed to be reseeded because of cutworm damage.
Bertha Armyworm
(Mamestra configurata): Bertha
armyworm populations were high and insecticides applied to many canola
fields in the Benito/Durban area of the Swan River valley and areas
around Roblin. Some farmers sprayed their canola twice for bertha
armyworm, and losses as high as 50% were reported. About 14, 000 acres
were treated to control bertha armyworm.
Diamondback moth
(Plutella
xylostella):
Diamondback moth were noticed on traps as early as April 18th,
and were a concern on canola early in the season. Populations declined
as the season progressed, however, and most of the control that was
needed occurred early in the season. Heaviest feeding occurred in areas
around Winkler (C), Pilot Mound (C), Carman (C), Miami (C), Stonewall
(I) and Dugald (E).
Other Lepidoptera:
Some canola fields in the Swan River area were sprayed to control
thistle caterpillar (Vanessa cardui). High levels of alfalfa
looper (Autographa californica) were reported from a canola field
near Neepawa (SW) late in the season and had damaged some pods.
Thrips:
High levels of thrips were reported on canola in Northwest Manitoba in
mid-July.
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(Flax-346,988 acres)
Very few insect problems
were reported from flax in 2005. A survey of insect populations in
flax was conducted in late July / early August.
Potato aphid(Macrosiphum euphorbiae): Populations of Potato aphid(Macrosiphum
euphorbiae) were generally low, although in the survey of insect
populations in flax a field near Minnedosa (SW) had about 200 potato
aphids per 10 sweeps. There were no reports of control for potato
aphids in flax.
Lygus bugs
(Lygus spp.): High numbers of lygus bugs were noticed in
some flax fields in the survey of insect populations. About 150 and
100 lygus bugs per 10 sweeps were found in flax fields near St.Pierre
(E) and Neepawa (SW) respectively in early August. The majority of
lygus bugs were in the 1st to 3rd nymph stages
at the time of the survey. Lygus populations of 200-300 per 10 sweeps
were also reported from a field in the Selkirk district (I) in early
September. However, I am not aware of lygus bugs being controlled in
any flax fields.
Bertha Armyworm
The edge of a flax field
in the Swan River valley was treated with insecticide to control
larvae of bertha armyworm (Mamestra
configurata)
moving into the field.
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(153,131 acres non-oil;
31,913 acres oil)
Sunflower beetle
(Zygogramma exclamationis): There were few reports of economic
damage by sunflower beetle in 2005. One exception was a sunflower
field near Graysville (C) where insecticide was applied because of
heavy feeding by sunflower beetles, and 10-15 acres were reseeded.
Thistle caterpillar
(Vanessa cardui): Populations of thistle caterpillars, the
larvae of painted lady butterflies, were quite high in Manitoba in
2005, and a concern for some sunflower growers. Sunflower fields near
Melita (SW), Waskada (SW), Goodlands (SW), Gladstone (C) and Winkler
(C) were treated with insecticides to control thistle caterpillars.
Thistle caterpillars are very visible on sunflower plants, since they
are a relatively large caterpillar, produce a leaf-nest using silk
webbing in which they feed and in which their fecal pellets often
accumulates, and are often near the upper parts of the plant. Because
of this they are quick to get the attention of farmers and agronomists
scouting the field. When thistle caterpillar populations are high care
needs to be given to not over-reacting to the high visibility of the
caterpillars in the field, and only apply control measures when
economical damage is likely to occur.
Seedhead Insects
Banded Sunflower Moth(Cochylis
hospes) and red sunflower seed weevil (Smicronyx
fulvus): Populations of seed weevils were very low again this
year, and usually hard to find when scouting for insects on sunflower
heads. Although banded sunflower moth populations were noticeable in
some fields, I am not aware of any fields where high populations were
reported.
Lygus bugs
(Lygus spp.): Lygus bug populations were high in some sunflower
fields during flowering, resulting in some spraying in fields of
confection sunflowers.
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BEANS (Dry Edible)
(192,319 acres: White pea (navy)-95,919 acres,
pinto-57,435 acres, kidney-15,832 acres, black-13,292 acres,
cranberry-2,793 acres, red Mexican-1,471 acres, other dry ebible-5,577
acres)
Very few insect
problems were reported from fields of dry edible beans in 2005.
Seedcorn
maggot (Delia
platura): Seedcorn maggots damaged beans in a field south of
Carman (C). Damage from the larvae feeding resulted in a thinning of
the stand of beans.
Potato
Leafhopper (Empoasca
fabae): Populations of potato leafhopper became noticeable in some
fields of dry edible beans around mid-June. Leafhopper damage to beans
was reported from the Portage la Prairie area in early-August, however
I am not aware of any insecticides being applied for leafhopper
control in 2005.
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(120,570
acres)
Very few insect
problems were reported from field peas in 2005.
Pea aphids (Acyrthosiphon
pisum): Some populations of pea aphid around
economic threshold were reported from the western part of the province
around mid-July. I am not aware of any insecticides being applied for
aphids in peas in 2005, however.
(100,457
acres)
Thistle caterpillar
(Vanessa cardui): There were several reports of thistle
caterpillar feeding on the leaves of soybeans, with populations as
high as 1 per plant reported. I am not aware of any insecticides
applications for thistle caterpillars in soybeans, however.
Soybean Aphid
(Aphis glycines):
Soybean aphids started to be noticed in soybean fields about mid-July,
but numbers remained well below levels that could do economic damage.
(9,705 acres)
A
few fields of fababeans in the Dauphin (NW) area were sprayed to
control lygus bugs (lygus spp.) and aphids.
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FORAGES AND FORAGE SEED
Plant Bugs:
Insecticide were applied in many alfalfa seed fields in the Eastern
and Interlake regions of the province in late-June and early-July to
control lygus bugs (lygus spp.) and alfalfa plant bugs (Adelphocoris
lineolatus).
Alfalfa Weevil
(Hypera
postica):
Alfalfa weevil was a concern in several alfalfa seed fields in the
Eastern and Interlake regions of the province, with some control
measures being applied.
Glassy cutworm
(Apamea
devastator): A pasture (brome and quack grass) south of Neepawa
(SW) was sprayed with insecticide in early June to control glassy
cutworm, which had damaged patches of the pasture.
(75,695 acres; 69,309
acres processing potatoes, 6,386 acres table potatoes)
Colorado Potato Beetle
(Leptinotarsa decemlineata): It is estimated that about 75-80%
of potato acres were treated with imidacloprid at planting (either
seed treatment or in-furrow). Overall, Colorado potato beetle pressure
was low.
Potato leafhopper
(Empoasca fabae):
Potato leafhopper was
present in high numbers in many locations this year and insecticide
was used in August to prevent crop damage.
Potato Flea Beetle
(Epitrix cucumeris):
Potato flea beetles were
observed in some areas, but did not raise as much concern as they have
done in the past. However, if the crop was in good shape, the grower’s
interest in controlling this pest may have been greater.
European corn borer
(Ostrinia
nubilalis):
European corn borer was observed in potato vines starting in late
July. By the end of the season, European corn borer was found in most
locations, but at a very low incidence. There is some concern that
this may become a potato pest in
Manitoba, however growers have been cautioned not to panic, as this
may be a result of the poor conditions and the staging of the
Manitoba corn crop earlier
in the year.
Aphids: An aphid
monitoring program was in place again this year as a joint program
between Agriculture and Agri-Food Canada in
Brandon and Manitoba Agriculture, Food and Rural Initiatives. Nine
locations were monitored, and aphid numbers were on the high side
compared to previous years. Aphid numbers were higher in the western
part of the province.
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