Manitoba Insect Pest Summary For 2005

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 2005 (shown in brackets under each commodity title) are from the Manitoba Crop Insurance Corporations 2005 Variety Market Share Report.


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

Small Grain Cereals

(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.  


(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.

Canola and Mustard

(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.


(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.


(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.

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.

Peas (Field)

(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.

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.