Summary Of Insects On Crops In Manitoba In 2008

November 2008

Compiled by John Gavloski, Entomologist, Manitoba Agriculture, Food and Rural Initiatives, Crops Knowledge Centre, Phone: 204-745-5668; Fax: 204-745-5690

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 2008 (shown in brackets under each commodity title) are from the Manitoba Crop Insurance Corporations 2008 Variety Market Share Report. The symbol ↑ indicates an increase in acres from 2007, whereas ↓ indicates a decrease in acres from 2007.


Summary: In cereal crops, wheat midge populations were high in some areas in the western part of the province, resulting in some spraying of insecticides. Cutworms and grasshoppers were also concerns in some areas.

In canola, flea beetles, grasshoppers and lygus bugs were the biggest concerns. Cutworm populations were also high in some areas.

Cutworms were at damaging levels in many sunflower fields, particularly in the Central and Eastern regions. Levels of lygus bug (Lygus spp.) and banded sunflower moth were at levels of concern in some fields of confection sunflowers, resulting in controls being applied.

Soybean aphids reached economic levels in many fields in the soybean growing areas of the province.

Alfalfa weevil was a concern in many alfalfa hay and seed fields.

Small Grain Cereals

(Wheat (spring)-2,391,987 acres↑; Wheat (Winter)-615,670↑; Barley-686,550 acres↓; Oats-783,059 acres↓; Rye-57,227 acres↑; Triticale-2,147 acres↑)

Cutworms: Cutworm populations were at noticeable levels in some cereal fields. Two barley fields west of Cypress River were treated with insecticide to control cutworms.

Wireworms: No significant problems with wireworms in cereals were reported in 2008.

Aphids: No significant problems with aphids in cereals were reported in 2008.

Wheat midge (Sitodiplosis mosellana): Some regions in the western part of Manitoba reported high levels of wheat midge. Spraying for wheat midge is known to have occurred near Foxwarren (NW), Souris (SW), and Boissevain (SW).

Grasshoppers: Localized hotspots resulted in some grasshopper control in small grain cereals. Some field edge treatments were applied, and a field of wheat near Miami and oats near Cypress River were treated for grasshoppers.

Wheat Stem Maggot (Meromyza americana): After a year when high levels of heads damaged by wheat stem maggot was reported in 2007, there were no reports of high levels of heads damaged by wheat stem maggot in 2008.

Armyworm (Pseudaletia unipuncta): Armyworms appeared in noticeable levels in a few fields in the Eastern part of the province. In a couple of the fields levels may have reached economic importance but the problem was not realized until it was too late to apply any control measures.

Wheat head armyworm (Faronta diffusa): A farmer in the Killarney area was concerned after noting high levels of wheat head armyworm on the header of his combine while harvesting spring wheat. The wheat still ended up graded number 1. This is an insect that is generally not an economical concern in cereals but occasionally shows up in noticeable levels.

Wheat Curl Mites (Aceria tosichella): Incidents of wheat streak mosaic were fewer in 2008 than in 2007. Wheat streak mosaic was reported in 2008 from farms near Morris (C), Elie (C), Crystal City (C), Glenboro (SW) and Hamiota (SW).


(203,914 acres grain corn↑; 54,997 acres silage corn↓; 524 acres open pollinated↓)

Cutworms: Some cutworm feeding on corn was reported from the Red River Valley.

European corn borer (Ostrinia nubilalis): In 2008, 58.7 % of grain corn was seeded to Bt varieties, and 19% of silage corn was seeded to Bt varieties. There were no reports of economical levels of European corn borer in grain corn in 2008. There has not been a significant, widespread outbreak of European corn borer in Manitoba since the mid-1980’s.

Stink Bugs: A 70 acre field of corn near Arden (SW) had extensive damage, but the cause was difficult to diagnose. The damage did appear to be consistent with stink bug damage.

Canola And Mustard

(Argentine canola-2,977,632 acres↑; Polish canola-400 acres↑; Mustard-9,474 acres↑)

Flea beetles (Phyllotreta spp.): Use of seed treatments containing neonicotinoid insecticides to manage early-season flea beetle populations is common. However, development of canola was slow in some areas of Manitoba early in the season, extending the period where flea beetles could be of concern. Some fields, and many field edges were treated with foliar insecticides to control flea beetles. A field of canola near Starbuck was reseeded, mainly because of flea beetle feeding.

Cutworms: Cutworm populations were noticeable and at times economical in canola fields in the central region of Manitoba. Insecticides were applied to control cutworms in canola fields near MacGregor, Starbuck, and Carman.

Wireworms: A canola field in the Pilot Mound (C) area had areas of the field heavily damaged by wireworms. About 20 acres of the field had to be reseeded back to canola. The previous crop was alfalfa.

Root Maggots (Delia spp.): There were some concerns over root maggots in the Manitou (C) area. Crop damage which caused severe thinning was reported.

Bertha Armyworm (Mamestra configurata): Pheromone-baited traps to monitor adult moths of bertha armyworm were set up at 78 locations in Manitoba in 2008. The monitoring period was June 9th to July 27th. Cumulative moth counts suggested populations overall had decreased from previous years. No regions of the province were rated at high risk of economical populations in 2008. Highest trap counts for 2008 were from fields near Virden (994), in the moderate risk category, and Minitonas (739) and Brookdale (555), both in the uncertain risk category. Peak trap catches occurred in most traps during the weeks of July 7-13th or July 14-20th, later than in many years.

There were no reports of insecticides being applied to control bertha armyworm in Manitoba in 2008.

Diamondback moth (Plutella xylostella): Pheromone-baited traps for adult moths were set up at 66 locations in Manitoba in 2008. The monitoring period was generally from May 5th to June 29th. Counts were generally low. The highest cumulative counts were 56 from a trap near Stonewall (I), 48 near Steinbach (E), and 46 near Emerson (C). The highest single week count was 44 near Stonewall (I) during the week of June 16-22.

There were some reports of levels of diamondback moth larvae approaching economic threshold levels in canola fields near Emerson, Altona, and Brandon late in July. There were no reports of insecticides being applied to control diamondback moth in canola in 2008, however.

Lygus bugs (Lygus spp.): Economical populations of lygus bugs in canola and some spraying to control them were reported from the Eastern region of Manitoba. Insecticide application for lygus bug control were reported for canola fields near Beausejour, Whitemouth, and Lac du Bonnet.

Grasshoppers: There were reports of grasshoppers needing to be controlled in canola fields near Otterburne (E) and Cypress River (C).

Aster Yellows: Incidence of aster yellows were low and not of concern to farmers in 2008.


(Flax-263,576 acres↑)

Potato aphid (Macrosiphum euphorbiae): Aphid levels were high and insecticides applied to control them in localized areas, mainly in south-central Manitoba. About 800 to 1,000 acres of flax was treated with insecticide to control aphids in the Crystal City, Clearwater, Pilot Mound area. Aphids were also above economic threshold and controlled in a flax field near Emerson.


(113,054 acres non-oil↑; 68,850 acres oil↑)

Wireworms: There were no reports of wireworm damage to sunflowers in Manitoba in 2008.

Cutworms: Cutworms were at damaging levels in many sunflower fields, particularly in the Central and Eastern regions. There were reports of sunflower fields near Carman (C), Graysville (C), Portage la Prairie (C), Westbourne (C), and MacGregor (C), being sprayed with insecticide to control cutworms. A sunflower field near Miami had to be reseeded because of a combination of cutworm and planting depth issues. Dingy and redbacked cutworm were the dominant species reported in many sunflower fields.

Sunflower beetle (Zygogramma exclamationis): Sunflower beetle populations were generally below economic threshold, with a few exceptions in the Central region where some fields were sprayed with insecticide.

Sunflower Bud Moth (Suleima helianthana): Sunflower bud moth feeding damage was very noticeable in many sunflower fields again this year. Although there are no management options, it causes concern for many growers and agronomists. A survey was undertaken this year to quantify plants that contained sunflower bud moth larva, look at distribution in the field, and look for possible influences of planting date.

Seedhead Insects

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. There were no reports of high populations of sunflower seed weevils in Manitoba in 2008.

Banded Sunflower Moth (Cochylis hospes): Banded sunflower moth populations were at levels of concern in some fields, and were the main target of some insecticide applications to confection sunflowers in the Central Region.

A pheromone-baited trap for banded sunflower moth was placed in a sunflower field north of Carman as part of a program to monitor the emergence and relative abundance of banded sunflower moths in sunflower growing areas of Canada and the U.S. From mid-July to late August a total of 1,159 adult banded sunflower moths were caught in the trap.

Lygus bugs (Lygus spp.): Lygus bug populations were also at levels of concern in many fields of confection sunflowers in the Central and Eastern parts of the province, resulting in spraying in some fields. No insecticides are registered for lygus bugs on sunflowers in Canada. Research on insecticides and management strategies for lygus bugs in confection sunflowers is needed.

Beans (Dry Edible)

(143,164 acres↓: White pea (navy)-61,384 acres↓, pinto-43,320 acres↓, black-15,245 acres↑, kidney-14,069 acres↑, cranberry-2,940 acres↓, small red-2,163 acres↓, other dry ebible-4,043 acres)

No insect concerns in dry edible bean fields were observed or reported in 2008.

Peas (Field)

(102,175 acres↑)

Pea aphids (Acyrthosiphon pisum): There were some pea fields in the Southwest region that had insecticides applied to control aphids in mid-July.


(312,518 acres↑)

Cutworms: A soybean field northwest of Elm Creek (C) had to be reseeded because of cutworm feeding. Redbacked cutworms were the main cutworm species present in the field.

Grasshoppers: A few soybean fields in the Eastern and Central regions were treated with insecticides, or had the edges treated, for grasshoppers.

Alfalfa weevil (Hypera postica): A soybean field in the eastern part of the province was treated with insecticides for alfalfa weevil.

Soybean Aphid (Aphis glycines): Soybean aphids reached economic levels in many fields in the soybean growing areas of the province. Insecticide use was widespread, and there were also some reports of levels of beneficial insects being high.


(6,048 acres↓)

No insect problems were reported from fababeans in 2008.

Forages And Forage Seed

Plant Bugs: Insecticide was applied in some alfalfa seed fields to control lygus bugs (lygus spp.) and alfalfa plant bugs (Adelphocoris lineolatus). There were reports from the Interlake of some applying their insecticide for plant bugs earlier than normal because of fields also containing high levels of alfalfa weevil.

Alfalfa Weevil (Hypera postica): Alfalfa weevil was a concern in many alfalfa hay and seed fields across the province. High populations of alfalfa weevil were reported from fields near Lac du Bonnet (E), Teulon (I), Riverton (I), Fisher Branch (I), Bagot (C), Minnedosa (SW), Sandy Lake (SW), Virden (SW), Rossburn (NW), Dauphin (NW), Rorketon (NW), Winnipegosis (NW), Alonsa (NW) and Swan River (NW). Insecticides were applied to many alfalfa fields, and early cutting was also used as a control option in some hay fields. In at least a couple of instances, a second or third application of insecticide was used to try to get good control. An alfalfa seed field near Fisher Branch was sprayed 3 times for alfalfa weevil. Some alfalfa fields in the Interlake were reported to be damaged to the extent that they were “not even good enough for hay”. In some instances second cut stands were significantly damaged by alfalfa weevil.

Spittlebugs (Cercopidae): High populations of spittlebugs occurred in some fields of birdsfoot trefoil and alfalfa in the eastern part of the province. Feeding by spittlebugs alone is not usually considered economical on forage and forage seed crops in Manitoba.

Spider mites: There was some concern about spider mites in a field of seed alfalfa north of Ashern.


(68,525 acres↓; 56,661 acres processing potatoes (irrigated)↓, 7,681 acres processing potatoes (dry)↓, 4,183 acres table potatoes↓)

Cutworms: There were some problems with cutworms in potatoes. Insecticide was applied to a potato field southwest of Portage la Prairie to control cutworms.

Colorado Potato Beetle (Leptinotarsa decemlineata): The population levels of Colorado potato beetles were generally considered to be low to normal in most cases as the neonicotinoid seed treatments seem to be continuing to work well. The generation timing of the beetles was normal, with ‘spring’ adults emerging through June and peak populations in late June, early July. Fall adults were observed in early August and some egg-laying did occur.

Potato Flea Beetle (Epitrix cucumeris): As is the usual case, potato flea beetles were locally abundant, typically more so in the Portage la Prairie area than in other regions. Some spraying was done to control populations though there remains debate as to whether this is necessary or not. The literature indicates that for the potato flea beetles to have a significant impact it must be coupled with significant early season defoliation by the Colorado potato beetle. In the absence of that early defoliation, the literature indicates that even dramatic populations of potato flea beetles will not have a significant impact.

Potato leafhopper (Empoasca fabae) and Aster leafhopper (Macrosteles quadrilineatus): Neither species of leafhopper was noticeably abundant in Manitoba. Aster leafhopper populations were negligible and potato leafhopper was only rarely locally abundant.

Aphids: Aphid numbers were slightly higher than in 2007, though were generally low overall. Some fields had relatively high populations of green peach aphid. Soybean aphids were a concern given their high numbers within soybean fields in close proximity to potato fields. Soybean aphids can potentially be vectors of PVY, but no potato fields were sprayed to control soybean aphid.

Sweet Corn, Carrots, Cole Crops, And Other Vegetable Crops

In Manitoba, populations of insect pests were lower than they have been in recent years. Many Lepidopterous pests of cruciferous crops were present, but only at levels well below economic thresholds. These included diamondback moth, cabbage looper and imported cabbageworm. Aster leafhopper populations were negligible due to a very low (if any arrived at all) migratory population. Populations of aster leafhopper did not reach economic thresholds at any point during the year, though some were present.

Populations of European corn borer in sweet corn were generally low again this year.


(1,475 acres for grain↓)

Heavy populations of stink bugs were noted in some hemp plots near Gilbert Plains (NW) late in the season.