A laboratory method for mass rearing the orange wheat blossom midge, Sitodiplosis mosellana (Diptera: Cecidomyiidae)

Orange wheat blossom midge, Sitodiplosis mosellana (Géhin) (Diptera: Cecidomyiidae), has been successfully reared in the laboratory for more than 20 years in Winnipeg, Manitoba, Canada. The rearing method has been developed to the point where it efficiently produces large numbers of wheat midge continuously under laboratory conditions for use in experiments on wheat midge biology and for screening wheat lines for crop resistance. Adult survival was extended by providing high humidity, and oviposition was increased by simulating natural dawn and dusk conditions and by supplying preflowering spring wheat to adults. Preventing desiccation of the wheat midge larvae in the wheat spikes before overwintering in soil and providing optimal cold conditions for a long enough period to break larval diapause enabled successful adult emergence. We provide data to facilitate the coordination of timing of wheat midge emergence from diapause with the wheat susceptible period. The method can be readily scaled up for screening many lines for resistance or scaled down for small experiments. Here, we report details of the rearing method so that others can implement it for research on the management of this internationally important pest.

Diversity, rate, and distribution of wheat midge parasitism in the Peace River region of Alberta, Canada

Wheat midge, Sitodiplosis mosellana (Géhin) (Diptera: Cecidomyiidae), is a major pest of wheat (Poaceae) that was first reported in the Peace River region of northwestern Alberta, Canada in 2011. Although parasitism is an important factor of mortality in wheat midge elsewhere, little is known about the prevalence, species, or distribution of wheat midge parasitoids in the Peace River region. To address this knowledge gap, we conducted a survey of wheat midge parasitoids in commercial wheat fields across the region in 2016 and 2017. For a given field, parasitism of wheat midge larvae ranged from 36 to 71%. All but one parasitoid (n = 2167) were identified as Macroglenes penetrans (Kirby) (Hymenoptera: Pteromalidae). The exception was a specimen in the genus Inostemma tentatively identified as I. walkeri Kieffer (Hymenoptera: Platygasteridae). These findings identify parasitism as an important factor that is suppressing populations of wheat midge in the Peace River region, provide the first report of Inostemma walkeri for North America, and provide the first report of this species as a parasitoid of S. mosellana.

Seasonal emergence patterns of Sitodiplosis mosellana (Diptera: Cecidomyiidae) in the Peace River region, Alberta, Canada

Wheat midge, Sitodiplosis mosellana Géhin (Diptera: Cecidomyiidae), is an invasive pest of wheat, Triticum spp. (Poaceae), in North America and is found in all wheat-growing regions of the world. Wheat midge biology, particularly post-diapause emergence of adults, varies with geographic region. The biology of wheat midge has not previously been examined in the northernmost area of its range in Canada – the Peace River region of Alberta. Wheat midge adult emergence was compared in situ to two phenological models of wheat midge emergence developed in other geographic regions. In-field adult emergence did not match the published phenological models. In the Peace River region, adults emerged later than are predicted by both models and precision for both models was low. With the Saskatchewan model, accumulated rainfall that was more than 110 mm in May and early June delayed emergence, whereas accumulated rainfall that was less than 43 mm during that period caused earlier than predicted emergence. Multiple peaks of wheat midge emergence, up to 20 days apart, were observed at some sites, supporting the Jacquemin model depicting “waves” of emergence. Including differences in soil temperature accumulation related to precipitation and optimising the model temperature thresholds would improve accuracy of the current Canadian phenological model in the Peace River region.

Modelling the tri-trophic population dynamics of a host crop (Triticum aestivum; Poaceae), a major pest insect (Sitodiplosis mosellana; Diptera: Cecidomyiidae), and a parasitoid of the pest species (Macroglenes penetrans; Hymenoptera: Pteromalidae): a cohort-based approach incorporating the effects of weather

This paper describes a tri-trophic analysis of the ecological dynamics of a crop, an insect pest, and a natural enemy of the insect pest. Worldwide wheat (Triticum Linnaeus) (Poaceae) production in 2018–2019 was estimated at over 700 million metric tons in 2018–2019. Wheat midge, Sitodiplosis mosellana (Géhin) (Diptera: Cecidomyiidae), a serious insect pest of wheat, is widely distributed in many parts of the world where wheat production occurs. Macroglenes penetrans (Kirby) (Hymenoptera: Pteromalidae), a parasitoid of S. mosellana, has successfully established in most wheat midge-infested areas. Mechanistic, or process-based, population models were used in this study to assess the interactive population dynamics of the three species, based on their respective life cycles and meteorological factors. The models were validated with survey data from multiple sites over numerous years (1991–2016). These simulation models helped to detail our understanding of the tri-trophic population dynamics and will help guide pest management decisions both prior to the growing season and until wheat heading, when wheat is no longer susceptible to S. mosellana. The associated models also help identify gaps in system knowledge, provide a foundation for evaluating future innovative management options, and evaluate the potential impact of a changing climate.

Assessment of Available Tools for Monitoring Wheat Midge (Diptera: Cecidomyiidae)

Wheat midge, Sitodiplosis mosellana Géhin, is an invasive pest of wheat, Triticum aestivum L. (Poaceae) throughout Canada and the United States. The applicability of available monitoring tools, including sex-pheromone baited traps, yellow sticky cards, and soil core sample surveys, in the northern-most agroecosystem of its invasive range has not been assessed. In this study, the attraction of male wheat midge to two Delta traps (green and orange) baited with one of three pheromone lures (a flex lure and two red septa lures from different sources) were compared. The efficacy of three yellow sticky cards (7 × 12 cm, 14 × 18 cm, and 14 × 18 cm rolled into a cylinder) for capture of male and female midge was assessed. Larvae were extracted from wheat heads sampled at the same sites to determine relationships with earlier adult trap capture. More male adult midges were captured in pheromone-baited traps with a greater surface area and in traps baited with the Scotts flex lure than the Great Lakes IPM septa lure, which had higher and more variable pheromone release rates. The smaller yellow sticky cards captured more male and female midges than the larger yellow sticky cards, regardless of shape. The number of female midges captured on yellow sticky cards predicted the number of larvae in wheat heads. The number of male midges captured in pheromone-baited traps did not predict larval density. Relationships were found between the number of overwintering cocoons recovered in soil core samples and emerging midges the following spring.

Glencross hard red extra strong spring wheat

Glencross is a hard red spring wheat (Triticum aestivum L.) adapted to the wheat-growing regions of the Canadian Prairies, particularly where orange blossom wheat midge is a production constraint. Glencross was evaluated in the High Yielding Red Wheat Cooperative Test in 2004, 2005, and 2006. Glencross had grain yield similar to the Canada Western Extra Strong (CWES) checks, Glenlea and CDC Rama, as well as the Canada Western Red Spring check, Superb; however, Glencross was significantly (P < 0.05) earlier maturing than all checks by 3 (Superb) to 4 (Glenlea and CDC Rama) days. Glencross had plant height and lodging scores similar to the CWES checks, Glenlea and CDC Rama, but was significantly taller and had significantly higher lodging scores compared with the CWRS check, Superb. Glencross was moderately resistant to moderately susceptible to leaf rust but was highly resistant to stem rust and loose smut. Glencross showed an intermediate reaction to common bunt and was similar to the susceptible checks for Fusarium head blight. Glencross is the first CWES cultivar with resistance to the orange blossom wheat midge (Setodiplosis mosellana Géhin). Glencross demonstrated end-use quality suitable for all grades of the Canada Western Extra Strong wheat class.

Phenological matching drives wheat pest range shift under climate change

Shifting geographical ranges of crop pests and pathogens in response to climate change pose a threat to food security (1, 2). The orange wheat blossom midge (Sitodiplosis mosellana Géhin) is responsible for significant yield losses in China (3), the world’s largest wheat producer. Here we report that rising temperatures in the North China Plain have resulted in a mean northward range shift of 3.3° (58.8 km per decade) from the 1950s to 2010s, which accelerated to 91.3 km per decade after 1985 when the highly toxic pesticide hexachlorocyclohexane (HCH) was banned (4). Phenological matching between wheat midge adult emergence and wheat heading in this new expanded range has resulted in greater damage to wheat production. Around $286.5 million worth of insecticides were applied to around 19 million hectares in an attempt to minimize wheat midge damage to crops between 1985 and 2016. Despite use of these pesticides, wheat midge caused losses of greater than 0.95 million metric tons of grain during this period. Our results demonstrate the potential for indirect negative impacts of climate change on crop production and food security, and constitute the first large scale example of plant pest range shift due to global warming.

Evaluation of Sitodiplosis mosellana (Diptera: Cecidomyiidae) infestation and relationship with agronomic traits in selected spring wheat cultivars in northwestern Montana, United States of America

The wheat midge, Sitodiplosis mosellana Géhin (Diptera: Cecidomyiidae), is a serious pest of spring wheat in North America. Currently, most commercial cultivars in the state of Montana, United States of America are susceptible. A study was conducted to assess the variability of adapted spring wheat cultivars to wheat midge infestations. A secondary objective was to determine the relationship between wheat midge infestation levels and spring wheat agronomic traits, including yield, test weight, grain protein, plant height, and heading date. This relationship was determined by evaluating 16 hard red spring wheat cultivars over a six-year period at the Northwestern Agricultural Research Center, near Kalispell, Montana. Levels of infestation had a negative impact on grain yield and test weight. Overall, the average infestation level was 40 larvae/spike with the lowest being observed with “Reeder” and the highest for “Thatcher”. Concurrently, “Reeder” had the highest yield, whereas “Thatcher” had the lowest yield and the highest grain protein, demonstrating that wheat midge infestations were positively associated with grain protein. Heading date had a positive association with midge density with higher infestations associated with later maturing cultivars. The economic injury level was estimated at 12 and 20 midge larvae/spike for a market price of USD $0.27 and USD $0.16/kg, respectively.