Summary Of Insects On Crops In Manitoba In 2009

November, 2009

Compiled by:

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

Horticultural and Forage Crops, Brent Elliott, Entomologist, Manitoba Agriculture, Food and Rural Initiatives, Crops Knowledge Centre, Phone: 204-745-5669; 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 2009 (shown in brackets under each commodity title) are from the Manitoba Crop Insurance Corporations 2009 Variety Market Share Report. The symbol ↑ indicates an increase in acres from 2008, whereas ↓ indicates a decrease in acres from 2008.


Aphids and thrips were the main insect problems in cereal crops. Cereal leaf beetle was found in Manitoba for the first time.

In canola, flea beetles and cutworms were the biggest concerns. A few canola fields had to be reseeded because of cutworm feeding. Cutworms were at damaging levels in many sunflower fields, particularly in the Central and Southwest regions.

Peas aphids were controlled in several fields of field peas in the Southwest and Central regions.

Alfalfa weevil was a concern in many alfalfa fields.

Small Grain Cereals

(Wheat (spring)-2,616,602 acres↑; Wheat (Winter)-462,090↓; Barley-583,141 acres↓; Oats-468,232 acres↓; Rye-87,389 acres↑; Triticale-1,022 acres↓)

Wireworms: Wireworm damage was noted in wheat fields in the Teulon (I) and Dauphin (NW) areas.

Aphids: High populations of aphids were noted on wheat, barley and oats, with some fields being sprayed with insecticides. High populations began to be noticed in late-July and aphid populations continued to be a problem in some areas into the third week of August. Cereal crop development was delayed because of cool weather, so crops took longer than normal to reach the less susceptible stages of soft dough and beyond.

Thrips: Thrips were a problem on barley in many fields in the southwest part of Manitoba. Reports of high populations extended as far east in Manitoba as Somerset. Most of the concern was during mid-July, with insecticides being applied to some fields.

Wheat midge (Sitodiplosis mosellana): Emergence of wheat midge appeared to start in the second week of July. There were few reports of high levels of wheat midge, although it was reported that wheat midge was present in a few fields in the Northwest at levels which will likely affect grade more than yield.

Grasshoppers: Localized hotspots resulted in some grasshopper control in small grain cereals. There were some concerns over grasshoppers feeding on fall seeded cereals.

Cereal Leaf Beetle: Cereal leaf beetle was found in some cereal fields in the northwest. This is the first year that cereal leaf beetle has been found in Manitoba.


(167,524 acres grain corn↓; 54,070 acres silage corn↓; 751 acres open pollinated↑)

Wireworms: Some wireworm damage was noted on corn in the Dauphin area.

European corn borer (Ostrinia nubilalis): In 2009, 56.3 % of grain corn was seeded to Bt varieties, and 17.6% of silage corn was seeded to Bt varieties. There were no reports of economical levels of European corn borer in grain corn in 2009.

Canola And Mustard

(Argentine canola-3,092,323 acres↑; Polish canola-1,642 acres↑; Mustard-10,412 acres↑)

Flea beetles (Phyllotreta spp.): Use of seed treatments containing neonicotinoid insecticides to manage early-season flea beetle populations continues to be common. However, development of canola was slow in some areas of Manitoba early in the season due to cool weather and frost. This extended the period where flea beetles could be of concern. Some fields which had insecticide treated seed were additionally treated with foliar insecticides to control flea beetles.

Cutworms: Cutworms populations were high and at times economical in canola fields in the central and southwest regions of Manitoba. Insecticides were applied to control cutworms in some canola field. Some reseeding of canola because of cutworm feeding was done in fields near Austin (C), Mariapolis (C), Bruxelles (C), Clearwater (C), and Baldur (C).

Grasshoppers: There were some reports of grasshoppers feeding on pods and needing to be controlled in canola fields.

Root Maggots (Delia spp.): Root maggots were at noticeable levels in fields near Foxwarren (NW), Snow Flake (C), and Carman (C).

Bertha Armyworm (Mamestra configurata): Pheromone-baited traps to monitor adult moths of bertha armyworm were set up at 78 locations in Manitoba in 2009. The monitoring period was June 8 to August 3. Cumulative moth counts suggested populations were at low risk of being problematic in all regions of Manitoba in 2009. Highest trap counts for 2009 were from fields near Hamiota (292), and Russell (274), both in the low risk category. Peak trap catches occurred in most traps during the weeks of July 6-12 and July 13-19, later than in many years.

There were no reports of insecticides being applied to control bertha armyworm in Manitoba in 2009.

Diamondback moth (Plutella xylostella): Pheromone-baited traps for adult moths were set up at 80 locations in Manitoba in 2009. The monitoring period was generally from May 18th to July 5th. Counts were generally low. The highest cumulative counts were 53 from a trap near The Pas (NW), 36 near Landmark (E), and 30 near Carey (E). The highest single week count was 30 near Carey (E) during the week of June 15-21.

There were no reports of diamondback moth larvae approaching economic threshold levels in canola fields in 2009.

Aphids: Some high levels of aphids clustering on tips of canola was reported from fields near Dominion City (E).

Lygus bugs (Lygus spp.): Levels of lygus bugs in canola were generally low, and there were no reports of populations near or at economic threshold.


(Flax-287,727 acres↑)

Potato aphid (Macrosiphum euphorbiae): There were no reports of potato aphid being at economical levels in flax in 2009.

Grasshoppers: Grasshoppers were reported to be at high levels and clipping bolls in a flax field near Arnaud (E).


(118,363 acres non-oil↑; 31,528 acres oil↓)

Wireworms: There were no reports of wireworm damage to sunflowers in Manitoba in 2009.

Cutworms: Cutworms were at damaging levels in many sunflower fields, particularly in the Central and Southwest regions. There were reports of sunflower fields near MacGregor (C), Austin (C), Holland (C), Treherne (C), Sanford (C), and Waskada (SW) being sprayed with insecticide to control cutworms. A sunflower field near Sanford had to be reseeded because of cutworm damage. 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. A couple of sunflower fields near Elm Creek (C) were treated with insecticide in June to manage sunflower beetles.

Seedhead Insects Many fields of confection sunflowers were treated with insecticides during early flowering to control mainly banded Sunflower Moth (Cochylis hospes) and Lygus bugs (Lygus spp.). Populations of Red sunflower seed weevil (Smicronyx fulvus) were very low again this year, and usually hard to find when scouting for insects on sunflower heads.

Pheromone-baited trap for banded sunflower moth were placed in sunflower fields at 6 locations: fields near Winnipeg (C), Altona (C), Kalieda (C), Treherne (C), Souris (SW), and Waskada (SW) 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. Highest cumulative trap counts from Manitoba were from the western areas of the province; 517 at Waskada, 471 at Souris, and 352 at Treherne.

The plant bug Chlamydatus associatus was often common on sunflower heads. What it is feeding on and whether it can cause damage to sunflowers is not known.

Beans (Dry Edible)

(140,232 acres↓: White pea (navy)-38,378 acres↓, pinto-64,971 acres↑, black-14,877 acres↓, kidney-13,739 acres↓, cranberry-1,246 acres↓, small red-1,809 acres↓, other dry ebible-5,212 acres)

Seedcorn maggot (Delia platura): High levels of seedcorn maggots were noted in some fields of dry beans west of Altona.

Grasshoppers: There were a few reports of fields or edges of dry bean fields being treated for grasshopper control in the Central region.

Peas (Field)

(76,642 acres↓)

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


(441,938 acres↑)

Soybean Aphid (Aphis glycines): Soybean aphids were not noticed in Manitoba until the second week in August in 2009. Although populations did increase throughout August, they did not reach economic levels.


(5,414 acres↓)

Blister beetles: A demonstration of 0-tannin fababeans near Melita had heavy feeding from the ashgray blister beetle (Epicauta fabricii).


(2,027 acres↑)

Aphids: High levels of aphids were noted on some lentils in the southwest.


(15,391 acres↓)

Aphids: A few fields of canaryseed in the Central region were treated with insecticides to control aphids.


(4,878 acres for grain↑)

No economical insect concerns were reported from hemp in 2009.

Forages And Forage Seed

Plant Bugs: Lygus bugs (generally Lygus lineolaris and L. borealis in alfalfa) were nearly notable in their absence. It appears as though Lygus may have had only a single generation rather than the usual two generations experienced in Manitoba. There was an occasional late season complaint about “outbreaks” in September though this is likely just the adults that will overwinter congregating on whatever was green. Work on fall populations of Lygus in buckwheat and alfalfa grown for seed in Manitoba has indicated that little feeding damage occurs at this time of year.

Alfalfa plant bug (Adelphocoris lineolatus): Numbers were by contrast up in some alfalfa fields sampled, notably one organic field.

Alfalfa Weevil (Hypera postica): The key pest in alfalfa (for seed and hay) remains the alfalfa weevil. Sweep net sampling was carried out on a weekly basis in nine separate fields (100 – 180o sweeps per field) for weevils beginning in early May and carried through until early September. Weather conditions proved to be less than ideal for sweep net sampling and as a result detection of populations was difficult. Samples often returned few or no weevils, presumably because the weevils were very low in the canopy in response to the rainfall and below seasonal temperatures. No weevils (adults or larvae) were picked up in samples until June 22, much later than expected. Numbers peaked, depending on the field, between June 29 and July 13. As these were commercial fields, growers applied control measures upon learning of substantial populations, and populations dropped to near zero. Larvae and occasional adults continued to be collected through the season with the last positive sample occurring on August 25 (adults and larvae collected).

In comparison to 2008, a single insecticide application (in most cases Matador due to proximal timing of bee release) in 2009 provided adequate control of weevil populations, where there were reports in 2008 of multiple applications. A better understanding of timing by growers probably reduced the number of applications more than any population shifts in the weevil.

Numerous larvae (approximately 10,000) appeared to be parasitized and samples were turned over to the University of Manitoba for examination at a later date. During the initial years of the weevil infestation in the Interlake region of Manitoba, populations were very high and in some fields quite devastating. This is likely due to an absence of the alfalfa weevil’s normal parasitoid guild during the first years of infestation in this region.


(66,679 acres↓; 55,933 acres processing potatoes (irrigated)↓, 6,540 acres processing potatoes (dry)↓,4,206 acres table potatoes↑)

Colorado potato beetle (Leptinotarsa decimlineata): Colorado potato beetles were deemed by growers to be “low” in 2009. Field sampling however showed that populations were at normal levels, but the cool, wet weather suppressed activity considerably giving the impression that populations were lower. Damage was less significant than would be expected in a normal year weather wise. Samples of adult populations were sent to Jeff Tolman at London AAFC for testing for resistance to imidacloprid and other insecticides. Thus far the Manitoba population has shown no resistance to imidacloprid.

Aphids: Aphid populations were moderate to high depending upon the field. Potato aphid (Macrosiphum euphorbiae) was the most dominant species though considerable populations of green peach aphid (Myzus persicae) moved into fields in late August and early September. Populations of aphids in Western Manitoba in September were high enough for occasional formation of “aphid holes” – areas where the canopy collapses due to feeding pressure from high numbers of aphids.

Wireworms: Wireworm populations remain relatively low in potatoes and presumably continue to be prairie wireworm species.

Potato leafhopper (Empoasca fabae): Potato leafhopper was negligible in 2009. The general expectation of potato leafhopper populations is for there to be significant levels only once in every five to seven years as this is a migratory pest from the Gulf States whose migration trajectory tends to take it to the east of Manitoba. We always have some low level populations but control measures are required only in high pressure years.

Potato flea beetle (Epitrix cucumeris): Potato flea beetle populations were extremely low in 2009, probably owing to the cool, wet weather that did not favor their survival.

Carrots, Cole Crops, And Other Vegetable Crops


Aster leafhopper (Macrosteles quadrilineatus) populations were very low throughout the majority of the growing season. Weekly sampling by sweep net (100 – 180o sweeps per field) was carried out in several fields and populations did not reach economic levels until early-September after temperatures had increased substantially relative to what was experienced prior in the season, coupled with strong south winds for a considerable period of time. While aster leafhopper may overwinter to some degree in Manitoba, the numbers of these overwintering leafhoppers are generally insignificant from an economic standpoint and remain that way unless a sizeable migratory population arrives from the south as well. It was a considerable surprise to see the numbers jump so significantly in September, but most carrot fields needed treatment with insecticides at that time.


No formal sampling for Swede midge (Contarinia nasturtii) was carried out, other than visual inspection in a number of fields scouted on a regular basis and no evidence of the pest was found. No complaints from growers were received though they may either still not know what they are looking for or may be reluctant to mention they have the pest.

Imported cabbageworm (Pieris rapae) numbers appear to be rebounding to some degree. After a significant outbreak several years ago, the population crashed and had remained remarkably low in the interim. Through August, adults were numerous and the resultant larval populations required control.

Berry Crops

The primary complaint in strawberries, as is common, was tarnished plant bug (L. lineolaris) though visits to farms turned up remarkably few insects in samples. It was quite likely the catfacing of the berries that was reported and attributed to tarnished plant bug was a result of the poor weather conditions and negative impacts on pollinators that has the same resultant physical appearance on the berries.

Trees And Shelterbelts

At least one species of ash plant bug (Tropidosteptes amoenus) and possibly a second caused considerable impact on ash trees in Manitoba with leaf drop being a common complaint. Numerous aphid species were abundant and a regular complaint received as well. Defoliators were also broadly represented during extension calls.

Several reports of emerald ash borer (Agrilus planipennis) were investigated throughout the summer, all of which proved to be negative. Given the relative proximity of the latest find (St. Paul, MN; approximately 500 miles south) and the propensity for U.S. citizens to carry firewood with them, it is expected that emerald ash borer will be within the province relatively soon. Pessimistic estimates place it at 1-2 years; optimistic estimates give us 5 years.

Insects In Stored Grain

In general, stored product insect pest discoveries are again higher than normal.

Rusty Grain Beetle (Cryptolestes ferrugineus) continues to be the most common insect found in stored grain. Discoveries have been greatest in stored wheat and barley.

A large proportion of cereals harvested in the prairies this year were put into storage at temperatures over 30ºC. It is important that producers prepared bins properly before storing grain, and use aeration techniques (aeration fans or grain turning) to lower and standardize the grain temperature. Lowering grain temperature below 15ºC as soon as possible reduces the risk of insects feeding and reproducing.