Manitoba Insect Pest Summary For 2003

December 31, 2003

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


Flea beetles in canola and cutworms in many crops were early season insect concerns. Grasshopper populations were high in Manitoba in 2003 and resulted in control measures being needed in many areas. Insecticide applications for grasshopper control started the first week in June in some locations. Some regions were dry as well, which reduced crop recovery from grasshopper damage. An annual program to assist rural municipalities with the cost of grasshopper control on public property was again administered. Aphid populations were at economically damaging levels in many crops, including peas, flax, cereals, canola and canary seed.


Flea beetles (Phyllotreta spp.):

Quite a few fields that were seeded with seed treatments containing low rates of insecticide for the control of flea beetles were in addition sprayed with a foliar insecticide for the control of flea beetles. Some of these fields received more than one foliar insecticide application. There were also some reports of fields with treated seed containing high rates of insecticide for flea beetle control, receiving in addition foliar insecticides for the control of flea beetles. Some noted that the flea beetle damage was worse on the earlier seeded canola. A possible explanation is that the time of seeding canola has been pushed back to the point where, because of cooler soil and air temperatures, it is taking longer for the canola seedlings to get to the more feeding tolerant 3-4 leaf stage. The insecticide in the seed treatment may thus be losing effectiveness while the canola is still in the younger, more susceptible stages.

There were 3 reports of canola fields in the Pilot Mound district being reseeded because of flea beetle damage. All three fields were planted with seed treated with insecticide for flea beetle control, and seeded in the first 4 days of May. Some reseeding of early-planted canola due to flea beetle feeding was also reported in the Somerset district.

There were some reports of feeding on canola stems at, or just slightly below, the soil surface. Our best guess was that this was feeding by flea beetles. This was seen mostly on canola that was planted early (April 24 to May 1) and there was also a fair amount of feeding on the cotyledons.

Heavy flea beetle populations were present in late summer with some spraying occurring in the southwest, northwest, central and interlake regions of Manitoba.

Cutworms: Some insecticide applications, and reseeding of canola, was necessary because of injury by cutworms.

Bertha Armyworm (Mamestra configurata): In the southwest, 2 of the pheromone baited traps used to monitor adults of bertha armyworm were above 1200 moths after the 6 week trapping period, indicating a high risk of larval feeding damage. The highest trap counts occurred in the southwest part of the province with counts being low in the eastern and interlake parts of the province. Some insecticide applications to control bertha armyworm in canola occurred in the southwest part of Manitoba.

Diamondback moth (Plutella xylostella): Some insecticide applications to control diamondback moth in canola occurred in areas around Deloraine and Gilbert Plains.

Grasshoppers: Some canola in western and central Manitoba was treated with insecticides to control grasshoppers. In some of these instances only the border of the canola field was sprayed.

Turnip Aphid (Lipaphis erysimi): Canola was treated with insecticide to control turnip aphid in several areas, including fields near Niverville (eastern region), Virden (southwest), and Gladstone (Central region). A canola field that was about 50% flowering in the Niverville area was reported to have aphid clusters on about 30% of canola stems in one part of the field, and clusters on about 10% of the stems in the rest of the field. The field was sprayed in the evening with a rate of dimethoate lower than recommended rate. One concern that was raised is that the rate of dimethoate registered for the control of aphids on canola is the same rate registered for grasshoppers on canola, and is at least twice the rate of dimethoate registered for the control of aphids in flax, peas, and small grain cereals. Considering that the main economic species of aphid in canola is one that clusters near the tips of the stems, the reason for having a rate this high was questioned. The fact that dimethoate is the only registered insecticide to apply for a pest that is often sprayed while canola is flowering is also a concern because of the potential for honeybee kills.


Cutworms: Several sunflower fields in the central region of Manitoba were sprayed with insecticides to control cutworms.

Sunflower Bud Moth (Suleima helianthana): Feeding by sunflower bud moth was noticeable in many fields again this year, but the overall level of injury to sunflower heads was less than in 2002.

Sunflower beetle (Zygogramma exclamationis): There was some insecticide applied to control sunflower beetles, but overall injury from sunflower beetles was not high in 2003.

Grasshoppers: Some control of grasshoppers was needed in sunflowers. On at least one farm, control was needed during the first week in June for grasshoppers feeding on young sunflower plants. Adult grasshoppers were also a concern on sunflowers later in the season.

Seedhead Insects

Banded Sunflower Moth (Cochylis hospes) and red sunflower seed weevil (Smicronyx fulvus): Although many processors are still sending their growers of confection sunflowers letters telling them to apply insecticides during the flowering stage of sunflowers to control seedhead insects, populations of banded sunflower moth and red sunflower seed weevil were very low this year. In many fields seed weevils could not be found at all. Only in 1 sunflower field in the southwest near Goodlands were red sunflower seed weevils reported at levels of concern. Some confuse the juvenile stage of the minute pirate bug for seed weevils. Minute pirate bugs, which are predators, are quite common on sunflower heads, and efforts are being made to make sure those scouting sunflowers know the difference.

Lygus bugs (Lygus spp.) High numbers of lygus bugs were found on the heads in many sunflower fields, and several sunflower fields in the central region were sprayed to control lygus bugs.


Cutworms: Some flax was sprayed in the Hamiota area to control cutworms, and some late seeded fields of flax in the northwest had problems with cutworms.

Grasshoppers: Insecticides were used to control grasshoppers in flax in the southwest, northwest, and central regions.

Potato aphid (Macrosiphum euphorbiae): Insecticides were used to control aphids in flax in fields near Russell, Shoal Lake, Minnedosa, and Gilbert Plains.

Wheat, Barley, Oats

Cutworms: Damage to small grain cereals by cutworms was quite evident early in the season, and some insecticide applications were needed. Barley near Oakville (central region), and oats near Arborg (interlake) were reseeded because of cutworm injury.

Wireworms: Some wireworm damage to wheat seedlings was noted in the Treherne area.

Grasshoppers: Headlands around some cereal fields were treated with insecticides in early June to control grasshoppers. Some headlands were sprayed multiple times early in the season. Later in the season, whole fields had to be treated for grasshoppers.

Wheat midge (Sitodiplosis mosellana): Populations of wheat midge were low enough that there was very little, if any, insecticide used to control wheat midge in 2003.

Aphids: Populations of aphids were high in some areas, resulting in some insecticide applications to wheat, barley, and oats.

Wheat Curl Mites (Aceria tosichella): Wheat streak mosaic, which is spread primarily by the wheat curl mite, was confirmed in a few fields in the southwest.


Cutworms: High populations of cutworms in corn were reported from the central and northwest regions, with some insecticides being applied.

Wireworms: Wireworm damage was reported from the edge of a corn field near Somerset.

Grasshoppers: Some edge spraying of corn fields for grasshopper control occurred early in the season. In late July a corn field was observed where the grasshoppers were feeding mainly on the weeds.

European corn borer (Ostrinia nubilalis): There were generally low populations of European corn borer in Manitoba in 2003. Most fields had 20-30% of plants attacked with some locally higher populations.


Aphids: Populations of aphids were above the economic threshold in some canaryseed fields in the eastern and central regions of Manitoba, resulting in insecticides being applied. Dimethoate and malathion are the only insecticides registered for aphid control in canaryseed, with the registration for malathion being for seed production only. Because dimethoate can not be tank mixed with the fungicide tilt, some canaryseed was sprayed with a tank mix of Matador and Tilt to control aphids and diseases. It was noted that when this was done, aphids were killed in the head, however aphids hidden between the sheath and the stem of the plant were not killed. Where aphids become clustered under the sheaths of canaryseed plants, the sheaths become brown and swollen.

Dry Beans

Cutworms: There was some spraying for cutworms in dry beans early in the growing season in the Winkler area.

Potato Leafhopper (Empoasca fabae): Populations of potato leafhopper in dry beans were high in some areas. Insecticides were used to control leafhopper populations in the area from St. Joseph to St. Jean (central region), and in the Carman area (central region).

Grasshoppers: Some spraying of field edges with insecticides to control grasshoppers occurred.


Pea aphids (Acyrthosiphon pisum): Populations of pea aphid were high in many areas. Insecticides are known to have been applied to control pea aphid in fields near Killarney, Hamiota, Shoal Lake, Melita, Sinclair, and Virden (southwest region); Foxwarren and Russell (northwest); and Somerset (central region).


Grasshoppers: Grasshoppers were controlled around the edges of some soybean fields, and in at least one field the population was heavy throughout the field. A soybean field near Morris was observed where a lot of the weeds were heavily eaten by grasshoppers, while the soybeans were not.

Soybean Aphid (Aphis glycines): Soybean aphids began to be noticed on soybeans in the eastern and central regions beginning around mid-August. Because of the late arrival of soybean aphid in Manitoba, and the low numbers being found, they were not at pest levels.

Forages And Forage Seed

Plant Bugs: Many alfalfa fields grown for seed were treated with insecticides to control plant bugs (Lgyus and Adelphocorus spp.). This is a common practice in Manitoba. Matador and Decis are currently the most common insecticides used for this purpose.

Grasshoppers: Some forage and pasture land was treated with insecticides to control grasshoppers. Some used foliar sprays, while others used Eco bran. As an example of how farmers are attempting to reduce the cost and non-target effects of grasshopper control, in a red clover seed field near Pilot Mound, Eco bran was applied using a modified version of the RAAT’s (Reduced Agent and Area Treatments) method.

Alfalfa Weevil: Damage by alfalfa weevil was noticeable in some areas of the southwest, although spraying for alfalfa weevil was limited. Many farmers notice evidence of alfalfa weevil once they start to cut hay.

White Grubs: Early in May, white grubs were found destroying plants in patches in a native hay field near Gladstone. Some of the dead patches were 50-60 feet.


Colorado potato beetle (Leptinotarsa decemlineata): There were relatively low populations of Colorado potato beetles in Manitoba in 2003, owing to widespread use of Admire (70-80% of fields).

Potato leafhopper (Empoasca fabae): There were very high infestations of potato leafhopper in the Portage La Prairie and Winkler areas. There were multiple applications for control in some cases, and some considerable losses.

Green peach aphid (Myzus persicae): Populations were low in Manitoba in 2003.


Lygus bugs (Lygus spp.): Lygus bugs remain a concern in buckwheat and research is ongoing. Some spraying occurs, but is discouraged.


Aster Leafhopper (Macrosteles quadrilineatus): Aster leafhopper remains a very serious concern. Population levels have been continually high over the past few years, with yield losses approaching 30%.


Heavy populations of forest tent caterpillar (Malacosoma disstria) were reported from the Swan River (northwest) and Sinclair and Turtle Mountain (southwest) areas. Spruce trees were sprayed to control yellowheaded spruce sawfly (Pikonema alaskensis) in the Elm Creek area. Likely due to the lack of other food sources, there was a report from the southwest of grasshoppers eating a Colorado blue spruce to the point where the owners were considering using insecticides to control the grasshoppers.

Introduced Insects

Two European earwigs (Forficula auricularia) were found on some peaches bought in the Fisher Branch area in early September. The earwigs were able to be caught.

For further information, contact your GO representative.