Predicted wheat midge development

Wheat midge model simulations to August 8, 2021, predict that wheat midge populations should be in one of two larval stages. Where wheat midge is present, most larvae (55 %) will be in wheat heads, feeding on developing kernels. Development of this stage is predicted to be greatest across eastern Saskatchewan. Larvae that have completed development in wheat heads will be dropping to the soil where they will transition to larval cocoons (44 % of the prairie population). The occurrence of larval cocoons should be greatest across northwestern Saskatchewan and eastern Alberta. This stage will overwinter in the soil.

Figure 1. Percent of the wheat midge (Sitodiplosis mosellana) larval population that is predicted to be in wheat heads as of August 8, 2021.
Figure 2. Percent of the wheat midge (Sitodiplosis mosellana) larval population that is predicted to be in the soil (larval cocoons) as of August 8, 2021.

Monitoring: The window for scouting and application of the economic threshold for wheat midge (i.e., during the synchrony between wheat anthesis and midge flight period) has now drawn to a close for 2021. 

Wheat midge was featured as the Insect of the Week in 2021 (for Wk07). Be sure to also review wheat midge and its doppelganger, the lauxanid fly, featured as the Insect of the Week in 2019 (for Wk11) – find descriptions and photos to help with in-field scouting!  Additionally, the differences between midges and parasitoid wasps were featured as the Insect of the Week in 2019 (for Wk12).  Remember – not all flying insects are mosquitoes nor are they pests! Many are important parasitoid wasps that actually regulate insect pest species in our field crops OR pollinators that perform valuable ecosystem services!

Information related to wheat midge biology and monitoring can be accessed by linking to your provincial fact sheet (Saskatchewan Agriculture or Alberta Agriculture & Forestry).  A review of wheat midge on the Canadian prairies was published by Elliott, Olfert, and Hartley in 2011.  

Alberta Agriculture and Forestry has a YouTube video describing in-field monitoring for wheat midge.  

More information about wheat midge can be found by accessing the pages from the new “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and Field Guide”.  View ONLY the Wheat midge pages but remember the guide is available as a free downloadable document as both an English-enhanced or French-enhanced version.

Predicted wheat midge development

The continued warm temperatures have resulted in the rapid development of wheat midge populations. Where present, wheat midge populations are predicted to be predominantly in the egg stage across most of the prairies (Fig. 1). This is a substantial change from last week where only 12 % of the population was predicted to be in the egg stage. The initial appearance of larvae (in wheat heads) is predicted to be occurring (Fig. 2).

Figure 1. Percent of wheat midge (Sitodiplosis mosellana) population that is in the egg stage, across the Canadian prairies as of July 11, 2021.
Figure 2. Percent of wheat midge (Sitodiplosis mosellana) population that is in the larval stage (in wheat heads), across the Canadian prairies as of July 11, 2021.

The model was projected to July 27 to determine potential development at Regina (Fig. 3), Lacombe (Fig. 4), and Grande Prairie (Fig. 5) over the next two weeks. The model output suggests that oviposition will continue to increase over the next 5-7 days and should peak sometime this week. Larvae (Sm L1-2) are expected to complete development by the end of July. Macroglenes penetrans, a parasitoid of wheat midge, is active in wheat fields when wheat midge adults are present. Simulation runs indicate that the parasitoid has begun to appear in wheat crops in fields near Regina.

Figure 3. Predicted development of wheat midge (Sitodiplosis mosellana) near Regina, Saskatchewan as of July 11, 2021 (projected to July 27, 2021).
Figure 4. Predicted development of wheat midge (Sitodiplosis mosellana) near Lacombe, Alberta as of July 11, 2021 (projected to July 27, 2021).
Figure 5. Predicted development of wheat midge (Sitodiplosis mosellana) near Grande Prairie, Alberta as of July 11, 2021 (projected to July 27, 2021).

If not already underway, scout for wheat midge adults this week and especially in regions where higher densities are predicted to occur. It is especially important to be monitoring for adults at dusk in regions expected to be at high risk, based on the 2020 survey which is mapped here.

Monitoring: When scouting wheat fields, pay attention to the synchrony between flying midge and anthesis.  

In-field monitoring for wheat midge should be carried out in the evening (preferably after 8:30 pm or later) when the female midges are most active. On warm (at least 15 ºC), calm evenings, the midge can be observed in the field, laying their eggs on the wheat heads (Fig. 7). Midge populations can be estimated by counting the number of adults present on 4 or 5 wheat heads. Inspect the field daily in at least 3 or 4 locations during the evening.

Figure 7. Wheat midge (Sitodiplosis mosellana) laying their eggs on the wheat heads 
(Photo: AAFC-Beav-S. Dufton & A. Jorgensen).

REMEMBER that in-field counts of wheat midge per head remain the basis of the economic threshold decision.  Also remember that the parasitoid, Macroglenes penetrans (Fig. 8), is actively searching for wheat midge at the same time.  Preserve this parasitoid whenever possible and remember insecticide control options for wheat midge also kill these beneficial insects who help reduce midge populations.

Figure 8. Macroglenes penetrans, a parasitoid wasp that attacks wheat midge, measures only ~2 mm long.  (Photo: AAFC-Beav-S. Dufton).

Economic Thresholds for Wheat Midge:
a) To maintain optimum No. 1 grade: 1 adult midge per 8 to 10 wheat heads during the susceptible stage.
b) To maintain yield only: 1 adult midge per 4 to 5 heads. At this level of infestation, wheat yields will be reduced by approximately 15% if the midge is not controlled.
Inspect the developing kernels for the presence of larvae and larval damage.

Wheat midge was featured as the Insect of the Week in 2021 (for Wk07). Be sure to also review wheat midge and its doppelganger, the lauxanid fly, featured as the Insect of the Week in 2019 (for Wk11) – find descriptions and photos to help with in-field scouting!  Additionally, the differences between midges and parasitoid wasps were featured as the Insect of the Week in 2019 (for Wk12).  Remember – not all flying insects are mosquitoes nor are they pests! Many are important parasitoid wasps that actually regulate insect pest species in our field crops OR pollinators that perform valuable ecosystem services!

Information related to wheat midge biology and monitoring can be accessed by linking to your provincial fact sheet (Saskatchewan Agriculture or Alberta Agriculture & Forestry).  A review of wheat midge on the Canadian prairies was published by Elliott, Olfert, and Hartley in 2011.  

Alberta Agriculture and Forestry has a YouTube video describing in-field monitoring for wheat midge.  

More information about wheat midge can be found by accessing the pages from the new “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and Field Guide”.  View ONLY the Wheat midge pages but remember the guide is available as a free downloadable document as both an English-enhanced or French-enhanced version.

Predicted wheat midge development

The recent warm temperatures have resulted in rapid development of wheat midge (Sitodiplosis mosellana) populations. Dry conditions in the Peace River region have contributed to delayed development of larval cocoons with 30-75 % of the population not expected to emerge this growing season. Unlike the larval cocoon stage (located in the soil), development of pupal, adult, egg and larval stages (in wheat heads) is not dependent on moisture. Development of these stages are dependent on temperature.

Where present, wheat midge populations should be entering the adult stage across most of the prairies (Fig. 1). This is a substantial change from last week where less than 10 % of the population was predicted to be in the adult stage. Oviposition is predicted to be occurring across most of the prairies and the initial hatch is now expected for southern Manitoba and southeastern Saskatchewan (Figs. 2 and 3).

Figure 1. Percent of wheat midge (Sitodiplosis mosellana) population that is in the adult stage, across the Canadian prairies as of July 4, 2021.
Figure 2. Percent of wheat midge (Sitodiplosis mosellana) population that is in the egg stage, across the Canadian prairies as of July 4, 2021.
Figure 3. Percent of wheat midge (Sitodiplosis mosellana) population that is in the larval stage (in wheat heads), across the Canadian prairies as of July 4, 2021.

The model was projected to July 20 to determine potential development at Regina (Fig. 4), Lacombe (Fig. 5), and Grande Prairie (Fig. 6) over the next two weeks. Output suggests that oviposition will rapidly increase over the next 10 days and wheat crops near all three locations may be susceptible for the next two weeks. Based on the predicted occurrence of adults and eggs, development is most rapid where populations were predicted to be greatest in 2021 (based on 2020 fall survey).

Figure 4. Predicted development of wheat midge (Sitodiplosis mosellana) and wheat development near Regina, Saskatchewan as of July 4, 2021 (projected to July 20, 2021).
Figure 5. Predicted development of wheat midge (Sitodiplosis mosellana) and wheat development near Lacombe, Alberta as of July 4, 2021 (projected to July 20, 2021).
Figure 6. Predicted development of wheat midge (Sitodiplosis mosellana) and wheat development near Grande Prairie, Alberta as of July 4, 2021 (projected to July 20, 2021).

Macroglenes penetrans is a parasitoid of wheat midge that is active in wheat fields when wheat midge adults are present. Model simulations indicate that the parasitoid has begun to appear in wheat crops in fields near Regina (Fig. 7).

Figure 7. Predicted occurrence of wheat midge (Sitodiplosis mosellana) and Macroglenes penetrans adults near Regina, Saskatchewan as of July 4, 2021 (projected to July 20, 2021).

If not already underway, scouting for wheat midge adults should continue this week and especially in regions where higher densities are predicted to occur. It is especially important to be monitoring for adults at dusk in regions expected to be at high risk, based on the 2020 survey which is mapped here.

Monitoring: When scouting wheat fields, pay attention to the synchrony between flying midge and anthesis.  

In-field monitoring for wheat midge should be carried out in the evening (preferably after 8:30 pm or later) when the female midges are most active. On warm (at least 15 ºC), calm evenings, the midge can be observed in the field, laying their eggs on the wheat heads (Fig. 7). Midge populations can be estimated by counting the number of adults present on 4 or 5 wheat heads. Inspect the field daily in at least 3 or 4 locations during the evening.

Figure 7. Wheat midge (Sitodiplosis mosellana) laying their eggs on the wheat heads 
(Photo: AAFC-Beav-S. Dufton & A. Jorgensen).

REMEMBER that in-field counts of wheat midge per head remain the basis of the economic threshold decision.  Also remember that the parasitoid, Macroglenes penetrans (Fig. 8), is actively searching for wheat midge at the same time.  Preserve this parasitoid whenever possible and remember insecticide control options for wheat midge also kill these beneficial insects who help reduce midge populations.

Figure 8. Macroglenes penetrans, a parasitoid wasp that attacks wheat midge, measures only ~2 mm long.  (Photo: AAFC-Beav-S. Dufton).

Economic Thresholds for Wheat Midge:
a) To maintain optimum No. 1 grade: 1 adult midge per 8 to 10 wheat heads during the susceptible stage.
b) To maintain yield only: 1 adult midge per 4 to 5 heads. At this level of infestation, wheat yields will be reduced by approximately 15% if the midge is not controlled.
Inspect the developing kernels for the presence of larvae and larval damage.

Wheat midge was featured as the Insect of the Week in 2021 (for Wk07). Be sure to also review wheat midge and its doppelganger, the lauxanid fly, featured as the Insect of the Week in 2019 (for Wk11) – find descriptions and photos to help with in-field scouting!  Additionally, the differences between midges and parasitoid wasps were featured as the Insect of the Week in 2019 (for Wk12).  Remember – not all flying insects are mosquitoes nor are they pests! Many are important parasitoid wasps that actually regulate insect pest species in our field crops OR pollinators that perform valuable ecosystem services!

Information related to wheat midge biology and monitoring can be accessed by linking to your provincial fact sheet (Saskatchewan Agriculture or Alberta Agriculture & Forestry).  A review of wheat midge on the Canadian prairies was published by Elliott, Olfert, and Hartley in 2011.  

Alberta Agriculture and Forestry has a YouTube video describing in-field monitoring for wheat midge.  

More information about wheat midge can be found by accessing the pages from the new “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and Field Guide”.  View ONLY the Wheat midge pages but remember the guide is available as a free downloadable document as both an English-enhanced or French-enhanced version.

Predicted wheat midge development

Wheat midge (Sitodiplosis mosellana) overwinter as larval cocoons in the soil. Soil moisture conditions in May and June can have significant impacts on wheat midge emergence. Adequate rainfall promotes termination of diapause and movement of larvae to the soil surface where pupation occurs. Insufficient rainfall in May and June can result in delayed movement of larvae to the soil surface. Elliott et al. (2009) reported that wheat midge emergence was delayed or erratic if rainfall did not exceed 20-30 mm during May. Olfert et al. (2016) ran model simulations to demonstrate how rainfall impacts wheat midge population density. The Olfert et al. (2020) model indicated that dry conditions may result in:
a. Delayed adult emergence and oviposition
b. Reduced numbers of adults and eggs

This week, wheat midge model simulations indicate that the majority of the larval population has moved to the soil surface (Figure 1). Dry conditions in the Peace River region have resulted in delayed development of larval cocoon populations. Pupae should now be occurring across most of the prairies (Figure 2). First appearance of adults is predicted across Manitoba and most of Saskatchewan (Figure 3).

Figure 1. Percent of the wheat midge (Sitodiplosis mosellana) larval population that has moved to the soil surface across the Canadian prairies as of June 27, 2021.
Figure 2. Percent of wheat midge (Sitodiplosis mosellana) population that is in the pupal stage, across the Canadian prairies as of June 27, 2021.
Figure 3. Percent of wheat midge (Sitodiplosis mosellana) population that is in the adult stage, across the Canadian prairies as of June 27, 2021.

The model was projected to July 13 to determine potential development at Regina (Fig. 4), Lacombe (Fig. 5), and Grande Prairie (Fig. 6) over the next two weeks.

Figure 4. Predicted development of wheat midge (Sitodiplosis mosellana) and wheat development near Regina, Saskatchewan as of June 27, 2021 (projected to July 13, 2021).
Figure 5. Predicted development of wheat midge (Sitodiplosis mosellana) and wheat development near Lacombe, Alberta as of June 27, 2021 (projected to July 13, 2021).
Figure 6. Predicted development of wheat midge (Sitodiplosis mosellana) and wheat development near Grande Prairie, Alberta as of June 27, 2021 (projected to July 13, 2021).

Compared to Lacombe and Grande Prairie, Regina has been warmer and wetter for the period of May 1 – June 27, 2021, resulting in advanced development of larvae and pupae (Fig. 4). In the Regina and Lacombe areas, initial oviposition is predicted to occur this week (Figs. 4 and 5). Emergence patterns for southern Manitoba are predicted to be similar to Regina. Cooler and dryer conditions in the Peace River region are expected to have impacted the movement of larvae to the soil surface, resulting in reduced adult emergence and later appearance of adults. Oviposition in the southern Peace River region is predicted to occur during the first week of July (Figure 6). Wheat crops near all three locations may be susceptible for the next 14-17 days.

If not already underway, scouting for wheat midge adults should begin this week and especially in regions where higher densities are predicted to occur. It is especially important to be monitoring for adults at dusk in regions expected to be at high risk, based on the 2020 survey which is mapped here.

Monitoring: When scouting wheat fields, pay attention to the synchrony between flying midge and anthesis.  

In-field monitoring for wheat midge should be carried out in the evening (preferably after 8:30 pm or later) when the female midges are most active. On warm (at least 15 ºC), calm evenings, the midge can be observed in the field, laying their eggs on the wheat heads (Fig. 7). Midge populations can be estimated by counting the number of adults present on 4 or 5 wheat heads. Inspect the field daily in at least 3 or 4 locations during the evening.

Figure 7. Wheat midge (Sitodiplosis mosellana) laying their eggs on the wheat heads 
(Photo: AAFC-Beav-S. Dufton & A. Jorgensen).

REMEMBER that in-field counts of wheat midge per head remain the basis of the economic threshold decision.  Also remember that the parasitoid, Macroglenes penetrans (Fig. 8), is actively searching for wheat midge at the same time.  Preserve this parasitoid whenever possible and remember insecticide control options for wheat midge also kill these beneficial insects who help reduce midge populations.

Figure 8. Macroglenes penetrans, a parasitoid wasp that attacks wheat midge, measures only ~2 mm long.  (Photo: AAFC-Beav-S. Dufton).

Economic Thresholds for Wheat Midge:
a) To maintain optimum No. 1 grade: 1 adult midge per 8 to 10 wheat heads during the susceptible stage.
b) To maintain yield only: 1 adult midge per 4 to 5 heads. At this level of infestation, wheat yields will be reduced by approximately 15% if the midge is not controlled.
Inspect the developing kernels for the presence of larvae and larval damage.

Wheat midge was featured as the Insect of the Week in 2021 (for Wk07). Be sure to also review wheat midge and its doppelganger, the lauxanid fly, featured as the Insect of the Week in 2019 (for Wk11) – find descriptions and photos to help with in-field scouting!  Additionally, the differences between midges and parasitoid wasps were featured as the Insect of the Week in 2019 (for Wk12).  Remember – not all flying insects are mosquitoes nor are they pests! Many are important parasitoid wasps that actually regulate insect pest species in our field crops OR pollinators that perform valuable ecosystem services!

Information related to wheat midge biology and monitoring can be accessed by linking to your provincial fact sheet (Saskatchewan Agriculture or Alberta Agriculture & Forestry).  A review of wheat midge on the Canadian prairies was published by Elliott, Olfert, and Hartley in 2011.  

Alberta Agriculture and Forestry has a YouTube video describing in-field monitoring for wheat midge.  

More information about wheat midge can be found by accessing the pages from the new “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and Field Guide”.  View ONLY the Wheat midge pages but remember the guide is available as a free downloadable document as both an English-enhanced or French-enhanced version.

Alert: Predicted wheat midge development

Wheat midge (Sitodiplosis mosellana) overwinter as larval cocoons in the soil. Soil moisture conditions in May and June can have significant impacts on wheat midge emergence. Adequate rainfall promotes termination of diapause and movement of larvae to the soil surface where pupation occurs. Insufficient rainfall in May and June can result in delayed movement of larvae to the soil surface. Elliott et al. (2009) reported that wheat midge emergence was delayed or erratic if rainfall did not exceed 20-30 mm during May. Olfert et al. (2016) ran model simulations to demonstrate how rainfall impacts wheat midge population density. The Olfert et al. (2020) model indicated that dry conditions may result in:
a. Delayed adult emergence and oviposition
b. Reduced numbers of adults and eggs

Wheat midge model simulations indicate that the majority of the larval population has moved to the soil surface (Fig. 1). Dry conditions in the Peace River region have resulted in delayed development of larval cocoon populations. First appearance of pupae should be occurring near Winnipeg, Brandon, Regina and Edmonton areas (Fig. 2).

Figure 1. Percent of the wheat midge (Sitodiplosis mosellana) larval population that has moved to the soil surface and is preparing to pupate across western Canada, based on weather conditions up to June 20, 2021.
Figure 2. Percent of wheat midge (Sitodiplosis mosellana) population that is in the pupal stage, located near the soil surface across western Canada, based on weather conditions up to June 20, 2021.

The model was projected to July 6 to determine potential development at Regina, Lacombe and Grande Prairie over the next two weeks. Compared to Lacombe and Grande Prairie, Regina has been warmer and wetter for the period of May 1 – June 20, 2021 (Fig.3). The first appearance of adults in the Regina area is expected to occur this week and initial oviposition is predicted to occur by the end of June. Emergence patterns for southern Manitoba are predicted to be similar to Regina.

Figure 3. Predicted development of wheat midge (Sitodiplosis mosellana) populations near Regina, Saskatchewan as of June 20, 2021 (projected to July 6, 2021).

Cooler temperatures at Lacombe are predicted to result in slower development of larvae and pupae (relative to Regina) with the first emergence of adults predicted to occur during the last week of June (Fig. 4). Cooler and dryer conditions in the Peace River region will impact the movement of larvae to the soil surface, resulting in reduced adult emergence and later appearance of adults; adult emergence is predicted to occur during the first week of July (Fig. 5).

Figure 4. Predicted development of wheat midge (Sitodiplosis mosellana) populations near Lacombe, Alberta as of June 20, 2021 (projected to July 6, 2021).
Figure 5. Predicted development of wheat midge (Sitodiplosis mosellana) populations near Grande Prairie, Alberta as of June 20, 2021 (projected to July 6, 2021).

Based on predictions for adult emergence, monitoring for the appearance of wheat midge adults should begin this week in Manitoba and Saskatchewan and later next week across Alberta in areas where wheat midge is expected to occur. It is especially important that adult monitoring be prioritized in regions with high risk based on the 2020 survey (Fig. 6).

Figure 6. 2021 Wheat midge forecast map which represents regions at risk of damage to cereal crops due to wheat midge, based on the number of un-parasitized wheat midge larval cocoons in soil samples collected in the fall of 2020.

Monitoring: When scouting wheat fields, pay attention to the synchrony between flying midge and anthesis.  

In-field monitoring for wheat midge should be carried out in the evening (preferably after 8:30 pm or later) when the female midges are most active. On warm (at least 15 ºC), calm evenings, the midge can be observed in the field, laying their eggs on the wheat heads (Fig. 7). Midge populations can be estimated by counting the number of adults present on 4 or 5 wheat heads. Inspect the field daily in at least 3 or 4 locations during the evening.

Figure 7. Wheat midge (Sitodiplosis mosellana) laying their eggs on the wheat heads 
(Photo: AAFC-Beav-S. Dufton & A. Jorgensen).

REMEMBER that in-field counts of wheat midge per head remain the basis of the economic threshold decision.  Also remember that the parasitoid, Macroglenes penetrans (Fig. 8), is actively searching for wheat midge at the same time.  Preserve this parasitoid whenever possible and remember insecticide control options for wheat midge also kill these beneficial insects who help reduce midge populations.

Figure 8. Macroglenes penetrans, a parasitoid wasp that attacks wheat midge, measures only ~2 mm long.  (Photo: AAFC-Beav-S. Dufton).

Economic Thresholds for Wheat Midge:
a) To maintain optimum No. 1 grade: 1 adult midge per 8 to 10 wheat heads during the susceptible stage.
b) To maintain yield only: 1 adult midge per 4 to 5 heads. At this level of infestation, wheat yields will be reduced by approximately 15% if the midge is not controlled.
Inspect the developing kernels for the presence of larvae and larval damage.

Wheat midge was featured as the Insect of the Week in 2021 (for Wk07). Be sure to also review wheat midge and its doppelganger, the lauxanid fly, featured as the Insect of the Week in 2019 (for Wk11) – find descriptions and photos to help with in-field scouting!  Additionally, the differences between midges and parasitoid wasps was featured as the Insect of the Week in 2019 (for Wk12).  Remember – not all flying insects are mosquitoes nor are they pests! Many are important parasitoid wasps that actually regulate insect pest species in our field crops OR pollinators that perform valuable ecosystem services!

Information related to wheat midge biology and monitoring can be accessed by linking to your provincial fact sheet (Saskatchewan Agriculture or Alberta Agriculture & Forestry).  A review of wheat midge on the Canadian prairies was published by Elliott, Olfert, and Hartley in 2011.  

Alberta Agriculture and Forestry has a YouTube video describing in-field monitoring for wheat midge.  

More information about wheat midge can be found by accessing the pages from the new “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and Field Guide”.  View ONLY the Wheat midge pages but remember the guide is available as a free downloadable document as both an English-enhanced or French-enhanced version.

Predicted wheat midge development

Wheat midge (Sitodiplosis mosellana) overwinter as larval cocoons in the soil. Soil moisture conditions in May and June can have significant impacts on wheat midge emergence. Adequate rainfall promotes termination of diapause and movement of larvae to the soil surface where pupation occurs. Insufficient rainfall in May and June can result in delayed movement of larvae to the soil surface. Elliott et al. (2009) reported that wheat midge emergence was delayed or erratic if rainfall did not exceed 20-30 mm during May. Olfert et al. (2016) ran model simulations to demonstrate how rainfall impacts wheat midge population density. The Olfert et al. (2020) model indicated that dry conditions may result in:
a. Delayed adult emergence and oviposition
b. Reduced numbers of adults and eggs

Based on averages across the three provinces, 56% of the wheat midge population is predicted to be in the larval cocoon stage (in the soil) and 44% of the larvae have moved to the soil surface. As a result of suitable temperature and rainfall, wheat midge model simulations indicate that more than 70% of the larval population has moved to the soil surface in central Alberta and northwestern and southeastern Saskatchewan (Fig. 1). Dryer conditions in Manitoba and the Peace River region continue to delay the movement of larvae to the soil surface.

Figure 1. Percent of the wheat midge (Sitodiplosis mosellana) larval population that has moved to the soil surface across western Canada, based on weather conditions up to June 13, 2021.

Information related to wheat midge biology and monitoring can be accessed by linking to your provincial fact sheet (Saskatchewan Agriculture or Alberta Agriculture & Forestry).  A review of wheat midge on the Canadian prairies was published by Elliott, Olfert, and Hartley in 2011.  

Alberta Agriculture and Forestry has a YouTube video describing in-field monitoring for wheat midge.  

More information about wheat midge can be found by accessing the pages from the new “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and Field Guide”.  View ONLY the Wheat midge pages but remember the guide is available as a free downloadable document as both an English-enhanced or French-enhanced version.

WHEAT MIDGE: TINY PESTS CAN CAUSE BIG PROBLEMS

Wheat midge larvae (AAFC)

This week’s Insect of the Week is the wheat midge. Found around the globe where wheat is grown, these small insects can pose a big problem for producers. Sizeable crop damage has been attributed to wheat midge populations across the Prairies, where it feeds on spring, winter and durum wheat, as well as triticale and spring rye.

Crop damage occurs when the wheat midge is in its larval stage. Once hatched, the wheat midge larvae eat developing wheat kernels, causing shrivelled, misshapen, cracked or scared kernels. This damage isn’t apparent at a glance and developing seeds must be inspected within the glume. Losing wheat kernels will lower crop yield, while damaged kernels will impact the grade given to the harvested wheat. The Canadian Grain Commission allows midge damage between two and five percent prior to impacting the assigned grade.

Wheat midge adult (AAFC)

Adult wheat midges are delicate orange flies that grow to 2–3 mm long, with large black eyes and long legs and antennae in relation to their otherwise small size.  Mature larvae grow to 2–3 mm long. Young larvae begin as translucent white maggots and turn bright orange during the maturation process.

Biological and monitoring information related to the bertha armyworm in field crops can be found on our Monitoring page as well as on provincial Agriculture Ministry pages (ManitobaSaskatchewan and Alberta). For more information, visit the wheat midge page in the Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and Management field guide. (en français : Guide d’identification des ravageurs des grandes cultures et des cultures fourragères et de leurs ennemis naturels et mesures de lutte applicables à l’Ouest canadien).

Predicted wheat midge development

Wheat midge (Sitodiplosis mosellana) overwinter as larval cocoons in the soil. Soil moisture conditions in May and June can have significant impacts on wheat midge emergence. Adequate rainfall promotes termination of diapause and movement of larvae to the soil surface where pupation occurs. Insufficient rainfall in May and June can result in delayed movement of larvae to the soil surface. Elliott et al. (2009) reported that wheat midge emergence was delayed or erratic if rainfall did not exceed 20-30 mm during May. Olfert et al. (2016) ran model simulations to demonstrate how rainfall impacts wheat midge population density. The Olfert et al. (2020) model indicated that dry conditions may result in:
a. Delayed adult emergence and oviposition
b. Reduced numbers of adults and eggs

As of June 6, 2021, wheat midge model runs indicate that recent rainfall in central Alberta and northwestern and southeastern Saskatchewan has resulted in movement of more than 30 % of the larval population to the soil surface (Fig. 1). Dryer conditions in other parts of Saskatchewan, Manitoba and most of the Peace River region continue to delay movement of larvae to the soil surface. If dry conditions persist, this should result in delayed pupation and adult emergence.

Figure 1. Percent of wheat midge larval population (Sitodiplosis mosellana) that has moved to the soil surface across western Canada, based on weather conditions up to June 6, 2021.

Information related to wheat midge biology and monitoring can be accessed by linking to your provincial fact sheet (Saskatchewan Agriculture or Alberta Agriculture & Forestry).  A review of wheat midge on the Canadian prairies was published by Elliott, Olfert, and Hartley in 2011.  

Alberta Agriculture and Forestry has a YouTube video describing in-field monitoring for wheat midge.  

More information about wheat midge can be found by accessing the pages from the new “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and Field Guide”.  View ONLY the Wheat midge pages but remember the guide is available as a free downloadable document as both an English-enhanced or French-enhanced version.

Field heroes

The Field Heroes campaign continues to raise awareness of the role of beneficial insects in western Canadian crops. Check the recently updated Field Heroes website for scouting guides, downloadable posters, and videos. Learn about these important organisms at work in your fields!  

Two NEW Field Heroes resources for 2021 include:

  1. The NEW Pests and Predators Field Guide is filled with helpful images for quick insect identification and plenty of tips to manage the pests AND natural enemies in your fields. Claim your free copy at http://fieldheroes.ca/fieldguide/ or download for free to arm your in-field scouting efforts!
  2. Real Agriculture went live in 2021 with Season 2 of the Pest and Predators podcast series!
    NEWEpisode 10Good bugs relocate for work (June 1, 2021)
    Episode 9Secret agents in the stubble (May 18, 2021)
    Episode 8Good vs pea leaf weEVIL (May 4, 2021)
    Episode 7Powerful parasitoids: Better than fiction (April 20, 2021)
    Recap of SEASON 1: Episode 1 – Do you know your field heroes? Episode 2 – An inside look at the Prairie Pest Monitoring Network. Episode 3 – How much can one wasp save you? Episode 4 – Eat and be eaten — grasshoppers as pests and food Episode 5 – Killer wasp has only one target — wheat stem sawfly Episode 6 – Plentiful parasitoids

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Predicted wheat midge development

Wheat midge overwinter as larval cocoons in the soil.  Soil moisture conditions in May and June can have significant impact on wheat midge emergence.  Adequate rainfall promotes termination of diapause and movement of larval to the sol surface where pupation occurs.  Insufficient rainfall in May and June can result in delayed movement of larvae to the soil surface. Elliott et al. (2009) reported that wheat midge emergence was delayed or erratic  if rainfall did not exceed 20-30 mm during May.  Olfert et al. (2016) ran model simulations to demonstrate how rainfall impacts wheat midge population density. Our wheat midge model (Olfert et al. 2020) indicates that dry conditions may result in: (a) Delayed adult emergence and oviposition, (b) Reduced numbers of adults and eggs.

Wheat midge model runs indicate that, where wheat midge are present, pupation is occurring across Alberta, northwest Saskatchewan and southern Manitoba (Fig. 1). Simulations suggest that, though still less than 15%, adult emergence has begun, most notably across Alberta (Fig. 1). Females lay eggs on developing wheat heads. This typically occurs in evenings when winds are calm. Wheat midge monitoring protocol suggests that wheat fields should be inspected for adults in late June and early July as wheat heads are emerging. The next three weeks are very important for monitoring wheat midge populations for the purpose of making management decisions.

Figure 1. Predicted percent of population of wheat midge (Sitodiplosis mosellana) at adult stage across the Canadian prairies (as of July 5, 2020).

Simulations were run to July 21 to assess population development over the next two weeks (Figs. 2-4). The first graph illustrates development of wheat midge populations near Saskatoon (Fig. 2). Adult emergence has begun and should peak next week, suggesting that monitoring fields for adults should begin in the next few days. Oviposition has just started and larvae will occur soon after.

Figure 2. Predicted wheat midge (Sitodiplosis mosellana) phenology at Saskatoon SK projected to July 21, 2020.

The second graph compares synchrony between wheat midge and wheat for fields near Lacombe (Fig. 3). The graph indicates that adult emergence and oviposition may occur this year when the crop is most susceptible.

Figure 3. Comparison of predicted phenology of wheat midge (Sitodiplosis mosellana) and wheat at Lacombe AB projected to July 21, 2020.

The last graph compares phenology of wheat midge adults near Saskatoon with the phenology of Macroglenes penetrans, a parasitoid of wheat midge (Fig. 4). The parasitioid wasp lays is eggs inside wheat midge eggs. The graph shows that the timing of emergence and oviposition of wheat midge adults is similar to the emergence and oviposition timing of M. penetrans. All of this information can be used as a guide to determine when fields should be monitored.

Figure 4. Comparison of predicted phenology of wheat midge (Sitodiplosis mosellana) and its parasitoid, Macroglenes penetrans, at Saskatoon SK projected to July 21, 2020.

Information related to wheat midge biology and monitoring can be accessed by linking to your provincial fact sheet (Saskatchewan Agriculture or Alberta Agriculture & Forestry).  A review of wheat midge on the Canadian prairies was published by Elliott, Olfert, and Hartley in 2011.  

Alberta Agriculture and Forestry has a YouTube video describing in-field monitoring for wheat midge.  

More information about Wheat midge can be found by accessing the pages from the new “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and Field Guide”.  View ONLY the Wheat midge pages but remember the guide is available as a free downloadable document as both an English-enhanced or French-enhanced version.