Manitoba Insect Pest Summary For 2002

December 9, 2002

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

Summary

Early season insect problems in canola in Manitoba included flea beetles, cutworms, and wireworms. Later in the season, lygus bugs had to be controlled in some canola fields. A lot of sunflower fields in Manitoba were sprayed to control seedhead insects, although proper scouting techniques and economic thresholds were not always used. Grasshoppers were the biggest problem in cereal crops in 2002 in Manitoba. Soybean aphid is now found on soybeans throughout most of the soybean growing area of Manitoba. Aphids were a problem in many canaryseed fields. At least 100 horses in Manitoba died from West Nile Virus, which is vectored by mosquitoes, in 2002.

Canola

Flea beetles (Phyllotreta spp.): Flea beetle feeding on canola was heavy across Manitoba in May and June. Some canola fields had to be reseeded because of flea beetle feeding. Foliar spraying of flea beetles was necessary in some fields; in some fields only the edges were sprayed, while in other instances the whole field was sprayed. Because of the slow development of canola this year, canola plants remained in the susceptible stages (below the 3 to 4 leaf stage) for quite long periods of time in some fields. Some fields had the edges sprayed multiple times for flea beetles. There were some instances of canola fields that had a seed treatment containing an insecticide still needing to be sprayed with a foliar insecticide to control flea beetles. Some flea beetle feeding on the buds of canola was reported. Flea beetle populations were also high in canola in late summer, and at least 1 field was sprayed to control late summer flea beetles.

Cutworms: Cutworms had to be controlled on canola in the southwest, northwest, and central regions. Some reseeding of canola due to cutworm damage was necessary in the Dauphin and Somerset areas.

Wireworms: A canola field in the southwest of Manitoba had to be reseeded because of wireworm damage.

Lygus bugs: Lygus bugs had to be controlled on canola in the Swan River, Somerset, Beausejour, and Niverville areas.

Bertha Armyworm (Mamestra configurata): In spite of the high levels of bertha armyworm adults in pheromone traps in some areas of Manitoba, populations of larvae were not high enough to warrant control. Over 1200 bertha armyworm moths in the pheromone baited traps over a 6-week monitoring period is considered a high risk of bertha armyworm larvae infesting a field. After 5 weeks of trapping, a trap near Waskada had captured 1441 bertha armyworm adults, and a trap near Melita had captured 1339 adults. After 7 weeks of trapping, a trap near Russell had 1204 bertha armyworm adults.

Sunflowers

Banded Sunflower Moth (Cochylis hospes): Some banded sunflower moth larvae were found, although not in high numbers. However, many of the fields of confection sunflowers in Manitoba were sprayed to control banded sunflower moth. Much of this spraying was the result of processors of confection sunflower seeds sending letters to growers indicating that they should be spraying for seedhead insects.

Wireworms: Some sunflower fields in the southwest and central regions of Manitoba were damaged by wireworms to the point where reseeding was necessary. There are currently no registered insecticides for wireworms in sunflowers.

Sunflower Bud Moth (Suleima helianthana): Damage by sunflower bud moth was quite noticeable in many sunflower fields this year. Some confused this with stem weevil. There is at least 1 incident in the province where insecticides were applied to try to control sunflower bud moth, but it is not likely that this was effective or economical.

Grasshoppers: Some grasshopper control was necessary in sunflowers in the Portage La Prairie area.

Sunflower maggot (Neotephritis finalis): Sunflower maggot pupae were abundant on many sunflower heads at the same time that sunflower fields were being scouted for insects that can cause damage to the seeds. Many were concerned that they were one of the insects that will cause seeds to be downgraded because of insect damage.

Cereal Crops

Grasshoppers: Grasshoppers had to be controlled in some cereal fields. Some grasshopper control was necessary in September in fall rye which was being established in the southwest region.

Wheat midge (Sitodiplosis mosellana): Populations of wheat midge were high in some areas of the southwest, although I am not aware of any spraying for wheat midge having occurred this year.

Thrips: Thrips were quite noticeable on wheat in June in the southwest and central regions of Manitoba, with heavy thrips damage to wheat being reported in the Gladstone area.

Canaryseed

Aphids: Many canaryseed fields in central and eastern Manitoba were sprayed with insecticides to control aphids.

Flax

Grasshoppers: Some flax fields were sprayed to control grasshoppers. Grasshopper feeding on flax bolls was reported.

Cutworms: Cutworm damage to flax was heavy in some areas.

Dry Beans

Seedcorn maggot (Delia platura): Some dry bean growers used dual purpose seed treatments to control seedcorn maggot and other early season pests of dry beans.

Cutworms: Some bean fields were treated for cutworms.

Grasshoppers: Some dry beans were sprayed to control grasshoppers near Elm Creek.

Lygus Bugs: Insecticides were applied to control lygus bugs in some dry bean fields. There is still a lot of uncertainty regarding what levels of lygus bugs are economical to control in dry beans. Alfalfa plant bugs were found in some of the dry bean fields as well, and there is still confusion over whether to group them with lygus bugs when determining economic thresholds, since no research has been done on what feeding, if any, alfalfa plant bugs are doing on dry beans.

Peas

Aphids: Insecticides were used to control aphids in some pea fields.

Soybeans

Grasshoppers: Some grasshopper control was necessary in soybeans in the Portage La Prairie area. There are currently no insecticides registered for grasshopper control in soybeans in Canada.

Soybean Aphid (Aphis glycines): Soybean aphid was found on soybeans throughout most of the soybean growing area of Manitoba. Control was not necessary in any fields. This is the second year that soybean aphid has been found in Manitoba. There are currently no insecticides registered for control of soybean aphid in Canada, although Ontario has submitted a minor use for matador for soybean aphids for all of Canada.

Forages And Forage Seed

Plant Bugs: Many alfalfa seed fields were sprayed with insecticides to control plant bugs ( lygus bugs and alfalfa plant bugs).

Grasshoppers: Some pastures and hayfields were treated to prevent damage by grasshoppers.

Alfalfa Weevil: Alfalfa weevil damage was noticeable near Somerset. Early cutting of hay provided adequate control.

Potatoes

Colorado Potato Beetle (Leptinotarsa decemlineata): Most growers applied two or three insecticide applications (two early season, one late) for control of Colorado potato beetles. Acreage treated with in-furrow Admire increased substantially. A small survey indicated widespread resistance to older chemistries, though which family was variable by location (and farm history).

Aphids: Green peach aphid monitoring program continued. Seed fields were sprayed twice each. Processing fields were sprayed once each and possibly twice, depending on local aphid populations.

Wireworms: Complaints were minimal, though more damage will be determined as shipments arrive at processors. There is a great deal of concern over the loss of Thimet (which will not be able to be used after 2004) and no replacement product.

Buckwheat

Lygus bugs: Some buckwheat in the central region of Manitoba was treated with insecticides to control lygus bugs. Whether lygus bugs damage buckwheat and what an economic threshold should be are still uncertain.

Livestock

Mosquitoes: At least 100 horses in Manitoba died from West Nile Virus in 2002, and at least 500 horses were infected with the virus. The southwest part of Manitoba was the hardest hit by West Nile Virus this year since this is where the most horses are. A vaccination program for horses to build immunity to West Nile Virus has been established. Culex tarsalis is the main mosquito being looked at as a vector of the disease, although other mosquito species are also involved. Aside from horses, a commercial goose flock near Winkler was infected and about 1,000 out of 3,000 geese died. There were also deaths in a research flock of mallard ducks at Delta Marsh (on the south shore of Lake Manitoba) because of West Nile Virus. Deaths due to West Nile Virus in these animals may be less next year since immunity would have been built up in many animals this year.

Beneficial Insects

Leafy Spurge Hawkmoth (Hyles euphorbiae): Larvae of the leafy spurge hawkmoth were frequently observed eating leafy spurge. Reports of it this year have come from as far north in Manitoba as Binscarth (near Russell). The only known release of this insect in Manitoba occurred near Morden in 1985.