The swede midge, Contarinia nasturtii (Kieffer) (Diptera: Cecidomyiidae), is invasive to North America, where it was first reported in Ontario, Canada. It is now established in eastern Canada and from eastern Minnesota in the Midwest to the northeastern seaboard of the United States of America. Swede midge is a serious pest of brassicaceous plants, including vegetable and oilseed crops. To ensure its early detection in the Northern Great Plains, a monitoring programme was established using pheromone traps located primarily along the edges of canola fields from North Dakota, United States of America, northwest to the Peace River region, in Alberta and British Columbia, Canada. In North Dakota, 117 trap sites were monitored between 2015 and 2021. In western Canada, monitoring occurred on a small scale from 2006 to 2011, and 521 trap sites were monitored from 2013 to 2021. Swede midge was not detected in canola grown in the Northern Great Plains between 2006 and 2021. Partners in North Dakota and western Canada intend to maintain the monitoring programme to support early detection of swede midge if it does continue to disperse northwestwards. The monitoring programme contributes to outreach activities and fosters farmer and agronomist participation in pest management (i.e., community science) in the Northern Great Plains.

This study recorded distribution and size of alfalfa weevil (Hypera postica (Gyllenhal); Coleoptera: Curculionidae) populations in Saskatchewan, Canada, from 2001 to 2014. The spread of alfalfa weevil across the province, originally southwest to southeast, was northward and westward during this time. By 2014, only northwestern and west central areas remained relatively alfalfa weevil free. From a minor pest in 2001, the alfalfa weevil increased to be the principal insect pest of alfalfa (Medicago sativa Linnaeus; Fabaceae) in 2014. The parasitoid Bathyplectes curculionis (Thomson) (Hymenoptera: Ichneumonidae) had a similar distribution. Other parasitoids collected included Oomyzus incertus (Ratzeburg) (Hymenoptera: Eulophidae) and Microctonus colesi Drea (Hymenoptera: Braconidae). Conservation of these parasitoids is an important step in maximising their effectiveness as alfalfa weevil biocontrol agents. Molecular sequencing of the DNA barcoding region of specimens identified morphologically as B. curculionis indicated moderately high levels of sequence divergence among specimens (up to 5.8%); however, interspecific genetic variation between other species of Bathyplectes Förster was also high. Therefore, we conclude that B. curculionis was the only Bathyplectes species collected in our study. An illustrated key to the described species of Bathyplectes in North America is provided, as well as DNA barcodes of most species, including five distinct barcodes in the Bathyplectes curculionis–B. exiguus (Gravenhorst) species complex.

This study examined the use of degree-day models to predict alfalfa weevil Hypera postica (Gyllenhal) (Coleoptera: Curculionidae) population development on the Canadian prairies. Air temperatures, alfalfa weevil abundance, and instar data were collected in 2013 and 2014 from 13 alfalfa (Medicago sativa Linnaeus; Fabaceae) fields across Alberta, Saskatchewan, and Manitoba. We coupled three alfalfa weevil population prediction models with three temperature data sources to determine which combination most closely aligned with results observed. Our objective was to find the best prediction of peak occurrence of second instar alfalfa weevils, the optimum time for management decisions. Of the parameters analysed, prediction model had the greatest effect on the accuracy of peak instar prediction, with Harcourt and North Dakota models better at predicting population peaks than the Guppy–Mukerji model. Interactions between temperature source and prediction model significantly affected prediction accuracy. The probability of accurate prediction of population peaks to within 3.5 days of actual occurrence using in-field and multiple-site temperature data sets, combined with Harcourt and North Dakota development models, was 0.45–0.70. Lower predictability was found from fields in the Mixed Grass Ecoregion than in other ecoregions. The use of the recommended models can assist growers in timing their monitoring activities and deciding if pest management action is warranted.

A new species, Contarinia brassicola Sinclair (Diptera: Cecidomyiidae), which induces flower galls on canola (Brassica napus Linnaeus and Brassica rapa Linnaeus (Brassicaceae)), is described from Saskatchewan and Alberta, Canada. Larvae develop in the flowers of canola, which causes swelling and prevents opening, pod formation, and seed set. Mature larvae exit the galls, fall to the soil, and form cocoons. Depending on conditions, larvae will either pupate and eclose in the same calendar year or enter facultative diapause and emerge the following year. At least two generations of C. brassicola occur each year. Adults emerge from overwintering cocoons in the spring and lay eggs on developing canola flower buds. The galls produced by C. brassicola were previously attributed to the swede midge, Contarinia nasturtii (Kieffer) in Saskatchewan; here, we compare and list several characters to differentiate the two species.

A three-year field study in northeastern Saskatchewan, Canada, determined the effects of seeding date and seed treatment on feeding injury by Contarinia Róndani (Diptera: Cecidomyiidae) midges to canola, Brassica napus Linnaeus (Brassicaceae), and subsequent seed yield. Emergence cage monitoring indicated the presence of two generations of midges at the four locations observed. Intensity of midge injury to canola was low, but damaged plants were common. Field location and seeding date influenced probability of midge injury and canola growth stage. The wettest of the four locations had the greatest number of midges but low levels of probability of damage in two of three years. Early-seeded plots had higher injury probability than late-seeded plots, with the highest probability of injury occurring one to two weeks after flowering commenced. Seed treatment marginally affected midge injury ratings, suggesting that insecticide efficacy dissipated before the midges attacked. Seed yield was higher in early-seeded than in late-seeded plots in two of three years, despite the greater level of damage seen in early-seeded plots. Overall, the research showed that the agronomic benefits of early seeding outweighed the effects of the midge damage observed; therefore, producers in the Canadian prairie provinces should seed canola when conditions are most agronomically suitable.

To determine resistance of Brassicaceae field crops to Contarinia Róndani (Diptera: Cecidomyiidae) midge complex (Contarinia nasturtii Kieffer and Contarinia undescribed species), field trials of two different host assemblages were undertaken near Melfort, Saskatchewan, Canada in 2014 and repeated in 2015. In both years the first midge adults appeared in early July, when most plants were starting to flower, and a second generation occurred in mid-August, past the period of crop susceptibility. In a trial studying 18 lines of six brassicaceous species, the lowest probability of midge injury was found on Camelina sativa (Linnaeus) Crantz lines in both years. No differences were found in the probability of midge injury among any of the 13 Brassica Linnaeus species lines tested, including commercial glyphosate-resistant and glufosinate-resistant Brassica napus Linnaeus canola lines, Ethiopian mustard (Brassica carinata Braun), brown or oriental mustard (Brassica juncea (Linnaeus) Czernajew), or Polish canola (Brassica rapa Linnaeus) lines. Probability of midge injury on Sinapis alba Linnaeus yellow mustard lines reached levels between those on Camelina sativa lines and those on Brassica lines. A second trial examining 14 current commercial glyphosate-resistant Brassica napus canola cultivars found no differences in susceptibility to midge feeding among any cultivars tested. More plants were damaged in 2015 in both studies, and damage reached maximum levels earlier in 2015 than in 2014.

Flea beetle (Coleoptera: Chrysomelidae) species and numbers were determined from yellow sticky traps (n=11 180) set out in canola (Brassica Linnaeus, Brassicaceae) fields at 300 site years and 15 ecoregions across the Canadian Prairie provinces in each spring of 2007–2011 and in North Dakota, United States of America in 2010–2011. Peak numbers and relative species abundance varied with year, site, and ecoregion. Phyllotreta striolata (Fabricius) was most common in northern ecoregions, whereas Phyllotreta cruciferae (Goeze) dominated nearer the 49th parallel. The proportion of P. striolata in northern areas increased dramatically compared with surveys in the 1970s. Phyllotreta striolata displaced Psylliodes punctulata Melsheimer as the most common flea beetle in the Peace River Lowlands, displaced P. cruciferae as the most common flea beetle in the Aspen Parkland of central Alberta, Canada, and increased in proportion in central Saskatchewan and much of Manitoba, Canada. Once rare in southern ecoregions, P. striolata was found there in increasing numbers. Temperature was the most consistent weather parameter to predict occurrence of both P. cruciferae and P. striolata. Although P. striolata became more numerous over years in four of seven principal ecoregions, P. cruciferae remained the predominant species on traps with the highest numbers of flea beetles.

In an investigation of Camelina sativa (Linnaeus) Crantz (Brassicaceae) and five common insect pests of canola (Brassica napus Linnaeus) (Brassicaceae), little feeding damage to the plant was inflicted by crucifer-feeding specialist flea beetles (Phyllotreta Chevrolat species) (Coleoptera: Chrysomelidae), Delia Robineau-Desvoidy (Diptera: Anthomyiidae) root maggots, or diamondback moth (Plutella xylostella Linnaeus (Lepidoptera: Plutellidae)). In choice tests, diamondback moths laid fewer eggs on C. sativa than on B. napus leaves. Diamondback moth larvae consumed less C. sativa leaf tissue, and tended to have a longer developmental period on C. sativa. Larvae of the polyphagous bertha armyworm (Mamestra configurata Walker (Lepidoptera: Noctuidae)) had similar feeding levels on C. sativa and B. napus plants. However, there was a longer developmental period from larval to pupal stage and pupae weighed less when fed on C. sativa foliage, suggesting that C. sativa contains antibiosis factors against bertha armyworm. Two strains of aster yellows phytoplasma, 16SrI-A and 16SrI-B, were identified in C. sativa and in Macrosteles quadrilineatus (Forbes) (Hemiptera: Cicadellidae). Differences in incidence of aster yellows and abundance of M. quadrilineatus were observed among lines of C. sativa. The findings confirm that C. sativa is unlikely to support high populations of these insect pests on the Canadian prairies.

Sweetclover, Melilotus Miller, was planted in a field near Saskatoon, Saskatchewan, to determine the effects of species and cultivars on early season feeding by the sweetclover weevil, Sitona cylindricollis. The wild annual species M. infesta Guss. was consumed less than were cultivars of M. alba (Desr.), which were generally consumed less than cultivars of M. officinalis (L.). The amount of feeding injury by the weevil among nine sweetclover entries was not significantly correlated with nitrate levels in cotyledons, unifoliolate, or first trifoliolate leaves. Weevils fed equally well on entries with high and low coumarin levels. Results from greenhouse cultivar trials generally paralleled those from the field. In an experiment in which different levels of ammonium nitrate fertilizer were broadcast prior to seeding of M. officinalis cultivar Norgold, levels of nitrate ion in the foliage were significantly correlated with fertilizer regime, but not with damage indices of the weevil. These experiments suggest that the nitrate ion in isolation is not the principal factor in the deterrence to sweetclover weevil feeding in M. infesta, and that elevating nitrate levels in sweetclover leaves would not confer resistance to this insect.

A 4-year field cage study was conducted to determine what effects feeding of alfalfa plant bug, Adelphocoris lineolatus (Goeze), late in the season had on alfalfa seed yields. When zero, one, two, or four alfalfa plant bugs were placed in sleeve cages containing stems of alfalfa at the green pod stage of growth, there was a significant decrease in the number of pods per cage and per raceme, the number of healthy seeds, and the weight of seeds with two or four bugs per cage. Increasing the duration of infestation resulted in significant increases in the number of damaged seeds per cage. An insecticide field trial was conducted in north central Saskatchewan in 1988 to determine what effects the occurrence of plant bugs had on seed yields of alfalfa. Alfalfa plant bug, lygus bug (Lygus spp.), pea aphid [Acyrthosiphon pisum (Harris)], and beneficial arthropod populations were monitored from 23 June to 1 September 1988. Seed yields were significantly greater in plots that were treated with trichlorfon in June and in June and August than in plots that were treated in August alone. The implications of a large alfalfa plant bug population late in the season to alfalfa seed production in the area are discussed.

A 5-year survey of Saskatchewan alfalfa (Medicago sativa L. sensu lato) seed fields was undertaken to determine the level of infestation by the alfalfa seed chalcid, Bruchophagus roddi (Gussakovsky). Seed samples were taken from commercial seed fields, hay fields, and roadsides just before pod maturity. From sample lots of 250 pods, the numbers of healthy, chalcid-damaged, and frozen or immature seed were determined. Later, producers were questioned about the attributes of and management practices employed in their fields. Seed yields and infestation levels were correlated with temperature, precipitation, and degree-day data from the year of and the year preceding seed collection. Alfalfa seed chalcid infestation level was correlated most closely with the temperature and rainfall in July and August of both years. The proportion of damaged seed was highest the year following warm, dry summers. Alfalfa cultivar also influenced infestation levels; winter-hardy cultivars that became dormant early in the autumn had lower levels of chalcid-damaged seeds than less hardy cultivars which maintained growth later in the season. Management practices such as the use of insecticides (for plant bug and aphid control), fertilizers, and herbicides, size or age of field, soil type, and application of irrigation water did not affect the proportion of seeds injured by chalcids.